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Stalling: Ground locations on 6.5 1997 Express van

11K views 86 replies 6 participants last post by  CampVan 
#1 ·
New to the forum, spent an evening going through the wealth of informative postings to find help with the latest phenomenon in my new-to-me 6.5 1997 Chevy Express van. I'm not very mechanically gifted and on a steep learning curve with this van project; Previous owner made many mods, including computer delete, DB2 injection pump, vacuum delete/spring loaded waste gate, 4WD, manual transmission, 2 electric fans instead of stock fan, custom instrument cluster with pyro and boost but no rpm gauges, relocated all fuses from 2 panels in engine and driver foot panel to one in passenger side dash, ...

The coolant temp gauge went off after the needle 'danced' for a couple hours on a road trip last weekend that also included some bumpy dirt roads. A few hours later after taking off from a fuel stop the engine stalled at a red light.

Starts and drives fine but stalls now every time the rpms go down to idle. Except if I manage to shift down and decelerate very carefully and bring the van to almost a stop in first gear. At least a couple of times the idle then held without stalling.
I read on this forum that the two events (engine stall and temp sensor turning off) could be related to a faulty ground, and that there are several, that should be cleaned. Happy to do it as maintenance, but also would like to avoid a goose chase, open to other guidance to get back on the road and home ;-)

I only found one engine ground cable so far, going from the van's passenger side battery under the hood behind the lights down to the engine, and to the frame. Hard to reach but I'll try. (The other battery is on frame under the van, a little behind driver door.)
Where are other ground locations, seems different on the van?
 
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#3 · (Edited)
The factory coolant gauge sender is on the driver's side head located above the #1 cylinder injector. I would check the connector and the wiring.

Check the Fuel Shut Off Solenoid to make sure it is working correctly. Worth downloading the 6.5L Turbo Diesel DB2 Student Handbook. A link to this Handbook is in HeavyChevy95's signature above.

Gotta wonder how the PO has the lift pump wired to run. Is there a fuel pressure gauge in the van?
 
#4 ·
Thanks Heavy, I was just reading your excellent writeup on fuel system checks you posted to tpetty a moment ago. If it helps diagnosis: this van has 2 fuel tanks, 1 stock and 1 aux, each with independent lift pumps. Lines meet just before the IP. So for roadside diagnostics' sake I start looking for other clues as the supply up to the T-solenoids before the IP, and the respective returns would be surprising to fail or have a blockage on both sides at the same time.
I'll look for kinked lines next.

I feel this issue is a little different from a fuel supply problem I had recently. The supply fitting at the IP did have a loose connection a couple of weeks ago drawing in a little air over night so it would stall after the first cold start in the morning but fine when starting warm later.
 
#5 · (Edited)
Thanks Freddy,
I looked at the coolant temp sensor yesterday evening and the red wire and connection seem stock and fine. I only followed the wire a foot or so until it merges a wrapped bundle of wires as I hesitated to unravel all these, what do you think?
This sensor only had one wire. A sensor on the rear passenger side corner of the engine visible when opening the doghouse inside the cabin has two wires; I assume it is the oil pressure sensor, that gauge works fine. That's why the ground fault theory made sense to me which I read in a posting.

I downloaded the DB2 handbook and will try to read, a little tight on my phone screen.

I am not sure how the stock lift pump is wired, I do hear/feel a pump from the inside of the stock tank if that makes sense.
Perhaps unrelated: there is a 'minor' fuel supply issue in the stock tank, as I noticed in the past twice it cannot start when parked facing uphill with less than 1/3 diesel in the stock tank. It's fine when flat/downhill, I keep this tank more than 1/3 full for now and was planning to ask a question when I get home about dropping that tank and looking for possible clogged sock or delamination. Thoughts?

I did change the stock diesel filter and cleaned out the aux tank, lines and filters last week before starting on my first road trip.
 
#9 ·
Thanks Freddy,
I looked at the coolant temp sensor yesterday evening and the red wire and connection seem stock and fine. I only followed the wire a foot or so until it merges a wrapped bundle of wires as I hesitated to unravel all these, what do you think?
This sensor only had one wire.
That is the right sensor. And it only has one wire. The sensor grounds via the engine block.

A sensor on the rear passenger side corner of the engine visible when opening the doghouse inside the cabin has two wires; I assume it is the oil pressure sensor, that gauge works fine. That's why the ground fault theory made sense to me which I read in a posting.
.

6.5L blocks have the Oil Pressure Switch on the drivers side behind the head or located in the back of the valley below the lower intake manifold.

If you can post some pictures of what you are seeing that might help us.

I am not sure how the stock lift pump is wired, I do hear/feel a pump from the inside of the stock tank if that makes sense.
Perhaps unrelated: there is a 'minor' fuel supply issue in the stock tank, as I noticed in the past twice it cannot start when parked facing uphill with less than 1/3 diesel in the stock tank. It's fine when flat/downhill, I keep this tank more than 1/3 full for now and was planning to ask a question when I get home about dropping that tank and looking for possible clogged sock or delamination. Thoughts?
That is a sign the tank sender may have holes in the pick up or it is broken off. Make sure to get an AC Delco TS1012 tank sock. New senders come with gasser socks on them.

I did change the stock diesel filter and cleaned out the aux tank, lines and filters last week before starting on my first road trip.
Can you tell if it runs better from the aux tank?
 
#6 · (Edited)
Whats the 8th character of the VIN, not that it makes a difference but it may tell us if this is a complete conversion of just a DB2 conversion.

Thoughts..... All the diesel models use an externally mounted lift pump ACDelco EP 158 just forward the fuel tank. Usually mounts where the fuel filter would normally be located on gasoline models. If its still has the gasoline filter and fuel pump in place, might explain a few things..

If your liftpump is inside the tank, its likely the wrong one and its got the wrong strainer(sock) on it most likely.
 
#7 · (Edited)
8th VIN character is an F
Yes it has a small cylinder that could be a liftpump mounted on the forward edge of the tank protective cover. I did not feel/hear vibration from it when I familiarized myself a bit with the van after purchasing it a month ago. At least it sounded like coming from inside the front of the tank but I could be wrong. I can clearly hear it even inside the cabin when turning ignition on.
The aux tank lift pump looks similar. It is wired to a switch that turns either the stock pump or the aux pump on and the other off, and seems to change the flow at solenoid Tjunctions before (and probably aft of) the IP.

Sorry for challenging y'all with the PO's mods, thank you for goodwill helping regardless; in the last month I already suffered the glare and rejection by standard mechanics, most of whom seem to be capable to swap stock parts but refuse to try helping with common/mechanic's sense.
Just as a word of context: I bought this van and thus entered your Chevy6.5 world coming from the scary underworld of the Ford6.0. As I plan on doing a South America road trip some time next year, this van, which the PO whizzkid so craftily simplified, appealed to my layman's eyes as I thought it could be more easily troubleshooted in countries where none of the US-made vans were ever sold and thus computer diagnostics would be hard and parts unavailable. So my local road trips are testing that thought right now ... ;-()
 
#8 · (Edited)
Took too long to double check so exceeded the time the forum seems to give for editing my above post, so posting a correction:
The stock lift pump IS in fact the one working outside forward of the stock tank, I must have misheard the sound as coming from further back inside as the vibration travels on the plastic tank shield. It is alive and pumping.
Will now start taking off the doghouse and report later if I find kinks.

FWIW regarding the grounds theory: seems the starter battery(ies) were a little weak to start this morning. That's the first time. It did start after 10 sec cranking (normally she starts right up on the first crank since I changed the glow plugs and relay last month and replaced the manual momentary hold switch the PO installed instead of the gp ignition key position) with the help of the 4 deep cycle camper batteries in addition switched in series.
Still same idle dying, except if I bring the idle down gently in first gear to a halt using the handbrake (I know I know, that handbreak's another mod ;-)
 
#14 ·
Only sensor I can recall that would remotely be 'above and aft of the last glowplug' on the passenger side would be the ECT sender, turned around... opposite of the drivers head..

The OPS should be in the valley towards the back on the drivers side, or on the back of the block atop the trans mounting flange just behind the drivers head. IIRC theres another option down by the oil cooler lines...

Theres an 'oil pump drive' in the back where you'd expect to find a distributor on a small block. On EFI models, it has no wires. The manual models with automatics, had wires and acted much like a CPS for the TCM.

CPS still there, disconnected?

Yea, pics would help alot.........
 
#18 ·
Here the sensor pics (not sure when it's called a sender?):
- Dual blue/black wire sensor in the rear passenger side of the engine block (behind an unrelated single silver sensor that could be your EGT sensor),
- Red single wire sensor in the front passenger side.
 

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#21 · (Edited)
I'd say yes to that.
Attached is a pic from the passenger front a little further out.

To Heavy's question, I cant really see much of the engine valley. As you probably know there is virtually no space to get into some of this through the little hood opening or doghouse in a van. The turbo and intake sits on top of the engine in the rear and the intake air hose, AC compressor and fat coolant hose block the view from front.
 

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#23 ·
OK, so on truck/suburban engines, the Engine Coolant Temperature sensor (two wires) mounts in the coolant cross over. This sensor sends coolant temp info to the PCM.

The Coolant Temperature Gauge sender (1 wire), located on the drivers side head near the #1 cylinder, sends the signal to the dash gauge. On a van this might be different, but :confuzeld

Looks like the PO installed some kind of coolant gauge sender in the coolant cross over and wired it to the dash gauge. From your first post I cannot tell if the coolant gauge is factory or aftermarket.

I would direct you to the 1997 Factory Manuals in the FAQs for wiring diagrams (among other things), but I am not sure they would be of any help.
 
#25 ·
Nope, that one on the front passenger side head corner isn't connected and hasn't been in a long time by the way it looks. I'd say ignore it. The PO made most mods in 2012-2014.
Is the engine in the van that different looking?
Do you have a van engine manual? I see no port for a sensor on the driver front corner of the head.

All dash gauges are custom AutoMeter SportComp dial type.
 

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#26 · (Edited)
So, if the single wire coolant temp sender to my dash gauge had a lacking engine ground I could test that, once the engine is hot, by connecting a grounded wire to the base of the sender where it is screwed into the coolant crossover, right?
If it is not coming on then, I'd know it needs to be replaced, right? How would you replace, Will a lot of coolant come out when I remove it?

Now back to the biggest issue, engine stalling. I found a minor leak in the clamp connection of an inline fuel filter and a little bend in the fuel hose between it and the hard pipe going into the IP. But after tightening the clamp and when I smooth the hose out it made no difference, engine idle still dies. Ideas?
 
#27 · (Edited)
So, if the single wire coolant temp sender to my dash gauge had a lacking engine ground I could test that, once the engine is hot, by connecting a grounded wire to the base of the sender where it is screwed into the coolant crossover, right?
The sender grounds through the engine.

If it is not coming on then, I'd know it needs to be replaced, right? How would you replace, Will a lot of coolant come out when I remove it?
My guess is you will have to get a sender that matches the gauge. I would check the wire from the sender to the gauge and also that the gauge ground wire is connected to a good ground point.

You will lose some coolant, but not much.

Now back to the biggest issue, engine stalling. I found a minor leak in the clamp connection of an inline fuel filter and a little bend in the fuel hose between it and the hard pipe going into the IP. But after tightening the clamp and when I smooth the hose out it made no difference, engine idle still dies. Ideas?
In line fuel filter? Can you post a picture? some have tried replacing the in tank fuel sock/strainer with in line filters. They get plugged up and inhibit fuel flow. Just going from memory, I think the factory van fuel filter was mounted somewhere on the frame???

I also think you have to verify the electric lift pump is working. You have to make sure it is delivering fuel.

And you have to figure out how the lift pump is getting power.

Manuals: a link to the FAQs is in my signature below. Go to post number 2 for the links to the factory manuals. But the student handbook I mentioned earlier is going to be more helpful, since you have a DB2 injection pump. It appears you do not have any of the factory wiring or engine management systems that will be covered in the factory manuals.
 
#31 · (Edited)
That mr gasket glass fuel filter needs to be removed completely NOW.
Its unsafe and its worthless as a site glass to check for air bubbles which again, needs to be checked just before entering the IP via clear tubing..
Snap a pic of your FFM or filter set up, and lets see the lift pump. It may have the model stamped on it. Mostly truck guys here, its all the same ****, different packaging really...
Grab a cheap mr gasket fuel pressure gage (0-15psi), avail at most autoparts store for less than $20.00. Grab a brass Tee, 2- 24" lengths of clear 1/4" ID tubing to run between the FFM and IP, a handful of clamps and what ever else you may need to make it happen (see my set up below)..


This looks like a coolant temp switch. I'd think thats for the GPRController but you said it has electric fans. Are the fans thermo controlled, on all the time, or :confuzeld



But so does this one.... possibly for the I/P gage err cluster Censored?



And Im guessing this is the old MAP and AIT (circled)..



How many pins does the GPRController have? It it manually activated, does it even work?


Take several more pics..........


As for measuring fuel pressure between the FFM and IP. Install a 'Tee' and run a long hose to a gage that can be routed to and zip tied to the windshield wiper blade, visible by the driver or better yet the passenger who can read the gage so you can pay attention to the road whiles stickin' your foot in 'er ass. Safety first..
If you look next to my windshield wash reservoir, you can see where I have my gage temporarily stashed away..

'Pay no attention to that new Stanadyne PMD mounted to the firewall' comes a squeeky voice from behind the curtain...
 

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#32 ·
GP relay has 3 pins, is manually activated with a momentary hold switch on the dash, yes it is new and works well.
The sender with the silvery braided single wire is in the first inches of the exhaust pipe, I'd assume it goes to the pyrometer.

Does the sender with 2 wires behind it look like your oil pressure sender for the gauge?
I don't find another oil pressure sensor that by the book would interact with the stock lift pump. So my guess is the lift pumps are simply wired from the switch in the dash as mentioned in my earlier posting above.

I'm pretty sure the sender with single red wire is coolant temp.
 
#36 · (Edited)
The sender with the silvery braided single wire is in the first inches of the exhaust pipe, I'd assume it goes to the pyrometer.
That looks like the Pyro sender

Does the sender with 2 wires behind it look like your oil pressure sender for the gauge?
On an older model 6.2L diesel, that is the location for the GP relay temperature inhibit sensor.

On these engines, the heads are interchangeable. So coolant temp sensors/senders are located on the drivers side front and the passenger side rear.

Based on the picture, that location in the head would not have oil pressure present.
 
#39 ·
Note optional OPS port used for turbo oil feed on truck engines.
Check opposite corner at the back of the engine block for the normal OPS location for pre efi models..
 

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#41 ·
So, the good news:
The ECT gauge sender works again. The little red wire was broken right behind the crimped and soldered ring terminal. It was not noticeable as the shrink-wrap held on firmly. I noticed it after checking conductivity a couple of times ...
I did clean up the ground from battery and frame to engine, but it was surprisingly clean and obviously not the problem.

Back to the main problem: stalling.
Small improvement in returning to/maintaining idle after I replaced the rubber hose that showed signs of minor kinks from the past but it did not pose a restriction, between the hard pipe from the fuel tank switch solenoid T and the hard pipe going into the IP and cleaned the MrGasket glass filter, it also had a tiny air leak at high pressure
It got a little better, i. e. A little easier to gently ease the rpms into idle without stalling, and then idle holds. Must do it very slowly. But if I ever just lift the foot off the accelerator pedal the engine shuts down again.

I'll now be offline hiking til Tuesday, but feel free to continue coming up with solutions.

Thanks !!
 
#42 ·
'tiny airleak' here, tiny air leak there,, one is all it takes...


'Lift pump pumps pretty much exactly 0.25 liter in 15 seconds, measured after the stock fuel filter before the hard line going to the IP.'


• If more than 0.24 liters (½ pint) in 15 seconds, refer to Fuel Lift Pump Pressure Check.
• If less than 0.24 liter (½ pint) in 15 seconds, refer to Fuel Lift Pump Suction Line Check.



IMO, thats a tail err fail, definitely a sign. It should be nearly double that with a healthy unrestricted lift pump receiving full voltage.

Stalling and other symptoms your describing are ALL classic sign of fuel STARVATION. All Im saying..​


Grab a donut and a large cup of coffee, enjoy the show....​


:coffee::coffee::coffee:





Fuel Tank Components

FILLER CAP
The filler cap contains a 2-way check valve. This will allow air to escape during the day when the tank heats up. In the event of a rollover, the valve will prevent spillage. Under pressure, no greater than 2 psi will exist. The valve must also allow air to enter the tank to replace the fuel used by the engine. A vacuum of no more than about one inch of mercury can accumulate in the tank and a slight hissing sound when removing the cap is normal. The fuel system is calibrated with the cap in place and any alterations will effect performance. Diesel fuel tank caps are specific to Diesels. Gasoline tank caps may fit in the diesel tank filler neck but should not be used.​

FUEL PICKUP AND SENDING UNIT
See Figure 4-4. The fuel pick up, commonly known as the “ sock” has three functions:
1. Strain out large solids.
2. Act as a strainer to prevent entry of water.
3. Act as a wick to drain fuel down to the bottom of the tank since all pickup pipes do not reach the very bottom of the tank.
The tank filter is a Saran (Polyvinylidene Chloride) sock and is fastened to the fuel inlet line of the in-tank fuel filter and fuel pick-up assembly.
The fuel tank filter sock has a bypass valve which opens when the filter is covered with wax allowing fuel to flow to the fuel heater.
Without this sock fuel line heater would be ineffective because the fuel would be trapped in the tank. Since the bypass valve is located at the upper end of the sock, fuel will only be drawn into the waxed sock if the tank contains more than approximately 4 gallons of fuel. Therefore, it is important to maintain a minimum of 1/4 tank of fuel when temperatures are below 20 degrees F.
The Saran sock material has a nominal pore size of 130 microns. In addition to acting as a particle filter for the mechanical lift pump, the Saran tank filter acts as a wick to pick up fuel from the bottom of the tank and as a water filter; water is excluded on the basis of the difference in surface tension between the water and the sock material on the one hand and the fuel and the sock material on the other.​

The fuel pickup tube doesn’t reach the bottom of the tank. However, since the sock acts as a “wick” the fuel level can actually be lower than the level of the tube and fuel will be drawn out right down to empty. Also, with this design, the level of water in the tank can be much higher before water enters the fuel system. This is about five gallons. Water that gets into the tank will eventually be absorbed by good fuel and will pass harmlessly through the fuel system. Water will be absorbed at a rate of about one gallon per 1000 miles.​

— IMPORTANT —
If the gas unit is installed on a diesel, it will cause intermittent problems with idle and power loss.


Let me interject this quickly. Emphasis added- Thats why you shouldn't delete the strainer. Going strainer-less allows natural condensation to coaleces into water droplets that collect and stew into a brew of toxic and most corrosive sewage at the bottom of the tank.. Theres a picture of a fuel tank 'round here that clearly shows the end results of going naked. Do be afraid..
Point being.. Make sure the proper strainer is in place. Common for new aftermarket fuel sender to come preassembled with the incorrect 'gasoline sock' aka a diesel choker. Dont asume anything at this point. On with the show..​




[FONT=Arial,Bold]Lift Pump[/FONT]
The lift pump is designed to move fuel under a low (suction) pressure from the fuel tank and deliver it through the filter to the transfer pump inside the fuel injection pump. In order for the lift pump to operate correctly the fuel tank must have fuel, the lines between the tank and pump must not have leaks, and the fuel fill cap must be operating properly.​

If a failure occurs in the operation of the lift pump, the customer may complain about a no-start, stall or low power condition. The injection pump must have a continuous supply of fuel without the presence of excessive air bubble in order to operate correctly.​



[FONT=Arial,Bold][FONT=Arial,Bold]Fuel System Related Services[/FONT][/FONT]​


[FONT=Arial,Bold]Fuel Supply System Check

[/FONT]If the fuel supply system is not delivering enough fuel or air is being drawn into the fuel injection system, driveability could be greatly affected or a "Cranks But Will Not Run" symptom could exist. If another diagnosis indicates, or if the fuel supply system is suspected of not delivering enough fuel or drawing air, the following checks should be performed:
• Make certain that there is sufficient fuel in the tank.
• Check for air leaks or restrictions on the suction side of the fuel lift pump.
• Check for restrictions in the fuel return system.
• Check for leaks at all of the fuel connections from the fuel tank to the injection pump.
• With the engine running, check all of the hoses and the lines for flattening or kinks that would restrict the flow of fuel.​

Fuel Lift Pump Flow Check
1. Remove the ECM 1 fuse from the underhood relay center to prevent engine starting.
2. Disconnect the pipe at the lift pump outlet fitting.
3. Install a hose at the lift pump outlet fitting and place a 1 liter (0.946 quart) container at the hose in order to collect fuel.
4. Crank the engine or energize the lift pump and measure the amount of fuel:
• If more than 0.24 liters (½ pint) in 15 seconds, refer to Fuel Lift
Pump Pressure Check.
• If less than 0.24 liter (½ pint) in 15 seconds, refer to Fuel Lift Pump​
Suction Line Check.

[FONT=Arial,Bold]Fuel Lift Pump Suction Line Check
[/FONT]1. Remove the fuel tank cap and repeat the Lift Pump Flow Check.
• If the flow is more than 0.24 liter (½ pint) in 15 seconds, replace the defective fuel tank cap.
• If the flow is less than 0.24 liter (½ pint) in 15 seconds, go to the next step.
2. Separate the lift pump suction line from the fuel sender.
3. Connect the suction line to a source of clean fuel by using an additional hose.
4. Repeat the Lift Pump Flow Check.
• If the flow is more than 0.24 liter (½ pint) in 15 seconds, refer to Fuel System Air Leak Check.
• If the flow is less than 0.24 liter (½ pint) in 15 seconds, Go to Step 5.
5. Check the lift pump suction line for a restriction.
• If a restriction exists, repair it and recheck lift pump flow.
• If no restriction exists, replace the lift pump and recheck the lift pump flow. Refer to Fuel Pump Electrical Circuit Diagnosis.​
6. Attach the lift pump suction line to the fuel sender.

[FONT=Arial,Bold]Fuel Lift Pump Pressure Check
[/FONT]1. Install a tee adapter at the injection pump.
2. Connect a pressure gauge with the dial indication of 0-103 kPa (0 to 15 psi) to the tee adapter.
3. Start the engine and measure the fuel pressure.
• If the fuel pressure is a least 4 psi (27 kPa) continue to step 4.
• If the pressure is less than 4 psi, refer to Fuel Pump Electrical Circuit Diagnosis before replacing the lift pump.
4. Remove the pressure gauge and the tee adapter.
5. Connect the inlet pipe.
6. Clean any fuel spillage.​
7. Operate the engine and check for any fuel leaks.

[FONT=Arial,Bold]Fuel System Air Leak Check
[/FONT]
1. Install a transparent hose between the filter outlet and the injection pump inlet.
2. Start and idle the engine, observing the fuel for air bubbles.
• If air bubbles are not present, stop the engine and Go to Step 7.
• If air bubbles are present, stop the engine and Go to Step 3.
3. Check the lift pump suction line for air leakage.
4. Check the fuel sender for air leakage.
5. Start and run the engine.
6. Observe the fuel for air bubbles.
• If air bubbles are present, stop the engine and recheck Steps 3 and 4.
• If air bubbles are not present, stop the engine and Go to Step 7.
7. Remove the transparent hose and connect the hose of the filter outlet to the injection pump inlet fitting.
8. Disconnect the return hose at the injection pump.
9. Install a transparent hose between the injection pump and the hose of the return line.
10.Start and run the engine.
11. Observe the fuel for air bubbles. (It is normal to see small amounts of bubbles during snap acceleration.)
• If air bubbles are present, replace the injection pump. Refer to Fuel Injection Pump Replacement.
• If air bubbles are not present, Go to Step 12.
12.Stop the engine.
13.Remove the transparent hose and attach the fuel return hose at the injection pump.
14.Clean any fuel spillage.​
15.Run the engine to check for fuel leakage.


Fuel Return System Restriction Check
1. Disconnect the hose of the fuel return line at the fuel sender.
2. Disconnect the hose of the fuel return line at the injection pump and connect a vacuum pump with gauge to the hose.
3. Apply vacuum to the return line and observe the gauge reading.
• If vacuum does not build and hold, go to Step 4.
• If vacuum builds and holds, repair the return line restriction.
4. Connect the fuel return line at the injection pump and fuel sender.
5. Clean any fuel spillage.​
6. Run the engine to check for fuel leakage.

Note; If excessive water or fungi/bacteria are present at the fuel filter, you must perform a fuel system cleaning. This is a lengthy procedure, but it must be performed thoroughly in order to be affective.​










 
#44 · (Edited)
I showed the problem to two diesel mechanics who owned 6.2/6.5s in the past. They say it is a govenor spring/metering valve issue (either dirt or rusted mechanism) and wanted to replace the Injection Pump.

The problem first occurred after driving for 3 hours and letting the engine idle for 15 min, and taking a 20 min break. When taking off it got fine to the next red light, but then cut out when shifting from 1st to 2nd.

Here a recap; the symptom:
The engine stalls when taking the foot off the throttle pedal in neutral (it is a stick shift conversion, so when approaching a stop or when shifting up or down one steps on the clutch and lifts the foot off the throttle).
I can prevent it from cutting out by keeping the foot on the pedal and release it slowly down to idle. It idles fine and accelerates normally. In short it feels like when it snaps down to idle it overshoots for a second causing the idle to drop too low.
It also doesn't start in idle as it used to. I have to depress the throttle pedal a couple inches when cold, and about an inch when engine is warm.

The symptom occurs no matter which tank I used. The van has two tanks, both have their own lift pump. The van has a DB2 mechanical injection pump like the early 90s vans, the PO removed the electronic IP and all computers about 4 years ago.

I retested:
Lift pumps work fine. About 0.3 liter in 15 seconds after the filters. Should be a little more now that I replaced the fuel filters.
No airleaks in the lines. Replaced some fuel lines for good measure.

Fuel cap seems fine, I hear a hiss when unscrewing it. Engine idles
/revvs unaffected with or without the cap.

The shut off solenoid and the cold start advance solenoid both work. The advance solenoid had voltage when starting cold and the voltage goes away after a few minutes, one can feel a little change in idle when that happens.
The shutoff solenoid has 14.3 V when engine runs and 0 V when turning ignition off.

Transfer pump inside the IP works also on its own without the lift pump:

With a hot engine I hooked up one liter bottle of LiquiMoly DieselPurge (2x 500 ml) directly before the IP, unplugged the LP wire, and hung the return line through a transparent vinyl hose into the bottle. I idled and revved full throttle for maybe 10 minutes. Then drove aggressively for 5 minutes until the bottle was almost empty:

No bubbles in the return line.
No dirt in the recirculating DieselPurge.
No change in performance with just the IP sucking in the fuel.
No change in symptoms.

I read that adjusting the idle screws is not recommended or ever necessary.
However, before spending $1000 or more on getting the IP replaced, I wonder if I should try to adjust the low idle screw on the throttle linkage on the side of the IP. It would be hard to get to in the van. Several hours to remove other stuff above it.
Of course it would be annoying to drive, shift, (and stop) with a too high idle all the time ...

The screws feel firm (not loose) and don't seem to have (been) turned.
Open to suggestions.
 
#45 · (Edited)
FWIW. See page 229 of the DB2 handbook..

Idle Speed Adjustments
1. Bring the engine to operating temperature.
2. Set the parking brake and block the drive wheels.
3. Turn off all accessories.
4. Install a magnetic tachometer.
5. Adjust the low idle speed screw on the side of the injection pump according to the specifications on the vehicle emissions label (refer to Figure 7-80, view A).
6. Remove the electrical connector for the fast idle/cold advance temperature switch and jumper its wiring harness terminals with an insulated wire (see Figure 7-80, view B).
7. Open the throttle momentarily to allow the fast idle solenoid to extend fully.​
8. Adjust the fast idle solenoid plunger/screw on the bracket of the injection pump according to the specifications on the vehicle emissions label (see Figure 7-81).
9. Stop the engine.
10. Remove the jumper wire and install the electrical connector for the fast idle/cold advance temperature switch.
11. Remove the magnetic tachometer and wheel blocks.​











And I would double check all the highlighted items below..​


DB2 Injection Pump Diagnosis



Diagnosis of the fuel injection pump includes the following diagnostic steps (more detail for these checks can be found at the end of this section):
1. Check the fuel supply to the injection pump (refer to Figure 7-47):
- Check that the output of the lift pump is correct:
• Volume of at least 0.24 liter (1/2 pint) in 15 seconds
Pressure of 40 to 60 kPa (5.8 to 8.7 psi)
- Check that the restriction of the fuel filter is not excessive:
• Lift pump volume and pressure should be present at the inlet of the injection pump.
- Check the fuel entering the injection pump for the presence of air, using a transparent hose:
• If air bubbles appear, check the lift pump suction line for air leakage under a vacuum.
- Check the quality of the fuel:
• If necessary, use a fuel with a known cetane rating.
2. Check the fuel return from the injection pump (refer to Figure 7-48):
- Check the injection pump housing pressure:
• If pressure is not within 55 to 83 kPa (8 to 12 psi), do one of these things:
- Check the return line for a restriction.
- Check the housing pressure regulator for a restriction.
- Check the fuel exiting the injection pump for the presence of air, using a transparent hose:
• If air bubbles appear, remove the injection pump for service.
3. Check the injection pump transfer pump pressure (refer to Figure 7-48):
- Pressure while cranking should be at least 138 to 207 kPa (20 to 30 psi).
- Pressure should increase as engine speed increases, and a maximum of over 690 kPa (100 psi) is possible.
4. Check the Housing Pressure Cold Advance (HPCA) solenoid operation (refer to Figure 7-49):
- With the engine at 2,000 rpm, jumper the fast idle/cold advance temperature switch to energize the HPCA solenoid circuit.
- Observe that the engine speed increases, indicating an advance in injection timing.
- If no change in engine speed occurs, diagnose the fast idle/cold advance circuit.
5. Check the injection pump automatic advance mechanism piston for movement (refer to Figure 7-49):
- With the engine at 2,000 rpm, press the lower end of the mechanical light load advance rocker arm toward the injection pump.
- Observe that the engine speed decreases, indicating a retard in injection timing.
- If no change in engine speed occurs, remove the injection pump for service.
6. Check the operation of the injection lines and nozzles (refer to Figure 7-50):
- Inspect the injection lines for external damage and evidence of fuel leakage.
- Replace any damaged injection line.
- Remove and test each injection nozzle for correct opening pressure, chatter, leakage and spray pattern (see page 7-60 for more information).
- Replace any faulty nozzle and install the nozzles with new compression gaskets.
7. If a fuel system fault still exists, remove the injection pump and send it to an authorized diesel injection pump repair shop.



























Good Luck..
 
#46 ·
Remove the check valve fitting where the return line connects to the IP and check it for debris. Worth a shot.
 
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