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1995 Tahoe
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Discussion Starter #1
Hi, I'm new here. I'm having some problems and looking for expertise.




The Diagnostic Checklist:
Please fill out to best of your knowledge.​



1. Describe the problem you are having in detail:
Long cranking time when cold. Have to press the accelerator a little. (I did not have long cranking time until after replacing a bad lift pump, but the following still occur and occurred prior to replacing the lift pump.) A little white smoke on cold start. Check engine light goes on and off when accelerating depending on how much you depress it. Feels like there is some hesitation, unless fully depressing the accelerator.

2. Year of truck/engine.
1995 Tahoe 6.5 Turbo

3. Odometer reading (indicate miles or kilometers).
270000

4. Indicate the model number on the Injection pump (starts DS4 or DB2......).
Don’t know.

5. Indicate if you know if it’s a 1500, 2500, 2500HD, 3500, 3500HD.
1500

6. Do you have an EGR on the engine? (An F or an S engine code 8th VIN digit)
S

7. Air Filter condition (visual check).
New

8. Fuel filter condition (freshly changed, mileage since changed).
NEW

9. Location of PMD/FSD? (ex. on pump/remote over intake, behind bumper).
New FSD Kit mounted remote over intake

9a. If remote mounted, describe wiring harness (homemade or purchased from which vendor).
Purchased wiring harness with kit from accuratediesel.com

9b. Indicate the location and condition of the FSD/IP grounding wire.
Ground on pump (Original location)

10. Outside Temperature (C or F). _ °
50 to 90 F

11. Service Engine Light while running?- on/off/intermittent
On after initial starting then goes off after a few minutes of idling. Comes back on when accelerating lightly. Light goes off after a few seconds if you let off the accelerator pedal or if you press it all the way down and accelerate hard it goes off.

11a. Service Engine light does glow during start/cranking/bulb check: Yes/No
Yes

12.Have you scanned for engine codes? Yes/No
Yes

12a. List exact results on engine codes.
35 and 36.


13. Condition of Battery terminals (removed, cleaned and tightened).
Clean and tight

14. Known condition and age of Batteries.
Few years old.

14a. Are batteries a matched set of same age?
Yes

15. Condition of Major Grounds (removed, cleaned and tightened)
???

15a Have the batteries been individually load tested?
No

16. Does engine crank, or "turn over"?
Yes

16a. Does engine start and run?
Yes

17. If engine does not start- Crack injector line: do you have fuel? Yes/No
Yes, Engine starts and runs

18. Does your Wait To Start light come on?
Yes, if you mean the the glow plug light.

18a.Number of seconds WTS light is lit.
Around 7

19. Engine Cranking speed (if you have an accurate tachometer).

20. Are you experiencing Stalling?
No.

20a. Describe the event (upon startup only, down the road, hit a bump, etc...)
20b. Do you notice loss of dash or instruments?
No

21. Check turbo inlet and air filter for obstructions.
No obstructions

22. In a no-hot start, pour a bottle of room-temp water on the injection pump. Does it start now?
23. Lift pump test - Describe results.
Just replaced the lift pump. It was dead. Problem still persists. I also replaced the fuel tank, fuel sending unit, blew out fuel lines from fuel filter back, replaced fuel filter. The fuel tank sock was clogged and was drawling fuel through the bypass. A lot of junk in the tank it looked like shredded aluminum foil. I’m guessing that killed the lift pump. The fuel filter had some in it also.

24. Upon cold start, does the radiator hose get hard quickly? Yes/No
25. Upon cold start, do you have excessive white smoke? Yes/No
A little white smoke after cold start.

26. Do you have excessive cranking time before the engine starts? Yes/No
Yes

27. Have you used the block heater? Does it affect engine starting? (only try for starting problems).
It has one, but I have never used it.

28. Are all glow plugs in proper working order?
?

29. During hard acceleration, do you have excessive black smoke? Yes/No
No

30. Do you have any unusual exhaust smoke issues?
No

31. Turbo check out - Pass/Fail
32. Indicate fuel that you are using: Bio-Diesel, #2 Diesel, SVO/WVO, other
What ever is at the gas station. Ultra low sulfur???

32a. If running Veggie Oil fuel setup, indicate details of your conversion (homemade or packaged system).
No

33. Are you using any fuel additives? If so, please list.
34. Upon unscrewing fuel cap, do you have a large vacuum formed in the tank? Yes/No
No.

35. Do you have any service history available that might pertain to the problem you are having?
No.

36. Please indicate any modifications to the vehicle that might help us diagnose better.
PT Wiring upgrade lift pump and relay.
FSD PMD with Heatsink remote mount
 

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Administrator
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17,026 Posts
Welcome to DieselPlace
in the OBDI systems, when you change out your lift pump you should change out your OPS as well ( AC/Delco brand only) since the OPS supplies power to the lift pump.
You can perform a lift pump relay mod to eliminate the weak power supply issue the OPS creates. The Mod is listed within the 6.5L FAQ page.

Start by going through all of your grounds: Grounds-Grounds-Grounds The importance of good grounds.....
Remove each ground wire and clean the contact areas then reinstall.
One bad ground can cause a lot of issues in a 6.5L

Install a piece of clear fuel line on the return side of the IP ( as shown here) Question: - 1999 GMC Bluebird 6.5L TD - PMD &amp...
this will help find any air in fuel gremlins
 

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1995 Tahoe
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Discussion Starter #3
I replaced the lift pump with an upgraded model from PT wiring along with the relay that they offer. The lift pump is definitely operating now I can clearly hear it running. So the oil pressure switch should be turning the relay on if I can hear the pump running. I checked the ground wires that I could fine looking around. They all seem to be tight. I checked resistance in reference to the negative battery terminal on each side of the connection point of the ground. I did not have a reading higher than 3 ohms at any point that I measured from that was grounded. I checked the resistance between the frame and the engine also. Everything seems to have pretty low resistance. I did not have any clear fuel line on hand so I will get a piece of that and try what you said. Thanks.
 

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You need a fuel pressure gauge to monitor and make sure it is maintaining correct pressure you may hear the pump running but it may drop off while driving, etc..
Go through the link I provided on grounds it has pics
 

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1995 Tahoe
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14 Posts
Discussion Starter #5
Where is the best place to measure the fuel pressure? Before the filter? After the filter?
 

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1995 GMC Suburban
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For S engine, you may need to check under the intake.
It may be full of soot.
Unless the EGR has been blocked.

Is the DTC comes before or after you did all the changes?
Did you put on the Lift Pump from 93 model year which has slightly better pressure than the one from 95?
That slightly better pressure is needed in the truck.

You also said that you put the new PMD over the intake?
I would move it outside the engine bay like to the bumper or in front of radiator.
 

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Registered
1995 Tahoe
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Discussion Starter #8 (Edited by Moderator)
You need a fuel pressure gauge to monitor and make sure it is maintaining correct pressure you may hear the pump running but it may drop off while driving, etc..
Go through the link I provided on grounds it has pics
For S engine, you may need to check under the intake.
It may be full of soot.
Unless the EGR has been blocked.


After the filter would be best



I checked for bubbles in the fuel return line from the pump today there are none. I plan on installing the fuel pressure gauge this weekend. The amount of white smoke during a coldstart is increasing along with the length of time you must crank for.
636458
 

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Go back through your glow plug system. In the questionnaire #28 has a helpful blue link with info
 

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1995 Tahoe
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Discussion Starter #10
I replaced the glow plugs. I didn’t know how old they were. They measured OK and we’re receiving voltage, but I went ahead and replace them because of their unknown age. While I was working on the vehicle it was sitting a couple days I noticed it developed a air bubble in that clear piece of fuel line. So I would guess that the hard starting is due to this air bubble. I still have error codes 36 and 35. What should I look at replacing to remedy the air bubble in the fuel line or is it normal to develop an air bubble over sitting a couple days not being run.
 

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I replaced the glow plugs. I didn’t know how old they were. They measured OK and we’re receiving voltage, but I went ahead and replace them because of their unknown age. While I was working on the vehicle it was sitting a couple days I noticed it developed a air bubble in that clear piece of fuel line. So I would guess that the hard starting is due to this air bubble. I still have error codes 36 and 35. What should I look at replacing to remedy the air bubble in the fuel line or is it normal to develop an air bubble over sitting a couple days not being run.
From the 6.5L FAQ page:
"Where are the likely locations for air leaks" 1997 Suborban F VIN Hard Start/Air in Fuel?
 

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1995 Tahoe
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Discussion Starter #12
I replaced the fuel line between the sending unit and the lift pump. Nothing has really changed in the good direction. Had to replace the vacuum pump because the bearing in it was squealing horribly. Just got this that on this week. I am still getting a check engine light code 35 and 36 and also now 78. I’ve also noticed that it seems to have become more sluggish on acceleration. The wastegate actuator on the turbocharger does not have a hose barb for a vacuum line to be attached. So I’m guessing it’s spring actuated. That makes me think it’s not the original Turbocharger because I’ve found the vacuum line that should go over there and it is plugged. I do not currently have a boost gage but I’m going to get one. The amount of time that I have to crank the engine has been increasing and I have to pump the pedal to keep it running once it turns over. Is there anything else I should check or am I kind of getting to the end of the line where the injection pump is the source of my problems?
 

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I replaced the fuel line between the sending unit and the lift pump. Nothing has really changed in the good direction. Had to replace the vacuum pump because the bearing in it was squealing horribly. Just got this that on this week. I am still getting a check engine light code 35 and 36 and also now 78. I’ve also noticed that it seems to have become more sluggish on acceleration. The wastegate actuator on the turbocharger does not have a hose barb for a vacuum line to be attached. So I’m guessing it’s spring actuated. That makes me think it’s not the original Turbocharger because I’ve found the vacuum line that should go over there and it is plugged. I do not currently have a boost gage but I’m going to get one. The amount of time that I have to crank the engine has been increasing and I have to pump the pedal to keep it running once it turns over. Is there anything else I should check or am I kind of getting to the end of the line where the injection pump is the source of my problems?
Since you have replaced the fuel line from sender to pump have you had any more air bubbles in the clear line?
In your checklist, you did not list any fuel additive being used. If you are not using any try adding some TC W3 two-stroke oil ( 1 oz. per every 2 gals of diesel fuel) in your tank and run it.
The additive can sometimes clear up the code.
Have you tried another "Known Working" PMD w/resistor?
 

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1995 Tahoe
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Discussion Starter #14
I haven’t had any more air bubbles, even when allowing it to sit for a couple of days. I have been adding diesel kleen cetane boost injector cleaner and performers improver additive. One of the first things I did was buy a new FSD kit with the PMD and mount it remotely. I bought it new from accuratediesel.com. Are they a reputable place to buy from? I’m assuming if I purchased it new it would be good.
 

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I haven’t had any more air bubbles, even when allowing it to sit for a couple of days. I have been adding diesel kleen cetane boost injector cleaner and performers improver additive. One of the first things I did was buy a new FSD kit with the PMD and mount it remotely. I bought it new from accuratediesel.com. Are they a reputable place to buy from? I’m assuming if I purchased it new it would be good.
The reason I mentioned a "Known Working" PMD is that a PMD can last as little as 2 minutes or 20 years, dependant on any fuel systems or electrical issues...
This is the reason we always recommend that you carry a couple of "Good , known working" spares in your vehicle for diagnostics, when your stranded somewhere.
New doesn't always mean it's good..
 

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1995 Tahoe
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Discussion Starter #16
What’s your recommendation for obtaining a known working PMD?
 

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What’s your recommendation for obtaining a known working PMD?
Known sources are:
Leroy Diesel
Badger Diesel
Quadstar Tuning
RockAuto

Avoid the PMD's from eBay that is labeled "Tested, Known good"
Lastly, avoid the Dorman PMD whenever you can. The China made PMD is known for "Ghost code" issues
The Stanadyne is OEM but are hard to locate.
Flight Systems and DTech are the popular goto brands
 

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1995 Tahoe
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Discussion Starter #18
Ok thanks! I ordered one from Leroy diesel. When I receive that I’ll give it a try and post my results.
 

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1995 Tahoe
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Discussion Starter #19
I installed the new PMD. I don’t see any difference in performance from the other one. Things that I’ve noticed in the last past week before and after installing the PMD are the following. Increased white smoke when starting in the morning. The truck is parked in the garage over night and it stays between 50 and 60°. Long cranking times, which I have to press the accelerator to keep it running once it does start. If I rev it up a couple times the white smoke stops. Once on the road driving, light acceleration causes the truck to shake until it’s been driven for about 20 minutes. The pressing the accelerator completely down causes of the shaking to stop or at idle it stops. What should I try next?
 

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Looks like your still having issues indeed.Any chance we can take a peek at your turbo?I noticed you stated it had no port on the wastegate actuator canister unless it has a early 90s turbo from a 92 or 93.
 
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