I went through the checklist - hopefully the results will help somebody point me in the right direction.

0. Describe in detail the problem you are having. Please be as descriptive as possible.
96 Chevy 1500 truck, 350k miles. Bought truck at 323k miles and it has used about a quart of oil every 3-5 thousand miles since I bought it but it has started and driven normally. About 3 weeks ago it got hard to start. I figured out that I could let the glow plugs cycle 2 or 3 times by turning the ignition off for 15 seconds between cycles and get it to start normally, albeit with a small but noticable amount of white smoke from the pipe. About a week ago it started stalling while driving down the road, always well after being warmed up (15+ miles down the road). The first time it did this was when I came to a stop sign; I was able to get it to start again by double-cycling the glow plugs. About 10 minutes later it died 4 or 5 times while driving about 50 MPH; sometimes it fired back up on its own, others I was able to start by shifting to neutral and cranking it while still rolling.

It seems to be getting progressively harder to start and stalling at freeway speeds more frequently and getting harder to start when it does die at speed. I changed both fuel filters a few days ago (the previous owner installed a second canister filter next to the brake fluid reservoir); the factory location filter had about 25k miles on it, the aftermarket filter had about 5k miles on it. Certainly noteworthy is the condition of the secondary fuel filter - it was covered with some sort of rust-looking sediment. I've attached some pictures.

1. Does the engine crank, or 'turn over'?
Yes, it cranks normally.

1a. Does the engine start and run?
Yes, but only with several glow plug cycles, and even then it requires several seconds of cranking. This is more pronounced in the morning at 50 deg F than the afternoon at 70.

1a1. If the engine does not start - Crack injector line: do you have fuel? Yes/No


1b. Do you have a Wait To Start Light & the amount of time (seconds) lit.
Yes, about 4 seconds on cold start.

1c. Ambient Condition (temperature outside indicate F or C) _____ °
Usually about 50 deg F in the morning.

1d. Engine Cranking speed (if you have an accurate tachometer).
Dash tach doesn't read while cranking

1e. Are you experiencing stalling?
Yes.

1f. If Stalling, describe (upon startup only, down the road, hit a bump etc)
Always 10+ miles down the road. Doesn't seem to be affected by bumps, corners or stopping.

1g. If Stalling, do you notice loss of dash or instruments?
-note if experiencing stalling,you must indicate PMD location in #24.
I haven't paid attention. Will note next time it stalls.

1h. Check turbo inlet and air filter for obstructions. Cone filters have lost disk and stopped air to turbo.
Appears clear.

1i. In a no-hot start, pour a bottle of room-temp water on the injection pump. Does it start now? yes/no


1.1 Lift pump test - describe results
Opened T-valve, steady fuel (not spurting or anything) came out, but not full volume of the hose or very high pressure. Closed T-valve and opened bleeder valve on fuel filter, got steady fuel there.

2. Service Engine Light while running?- on/off/intermittent
Off.

2a. Service Engine light does glow during start/cranking/bulb check: Yes/No
No.

3. Model year
1996

3a. Odometer reading (indicate if in miles or km)
350,000 miles

3b. Miles on major engine components if been replaced (example Injection pump)
Unknown. Truck previously driven by sewing machine salesman and seems to have been well maintained, but I have no documentation.

3c. Indicate the model number on the Injection pump (starts DS4 or DB2......)
I looked for this, but not sure where to find it.

4. Have you scanned for engine codes? (varies by pre/post 96) yes/no
It doesn't want to start now, but the next time it starts for me, I'll take it by the parts store to get the codes read.

5. List exact results on engine codes:


6. Air Filter condition (visual check)
Clean. Changed maybe 10k miles ago

7. Fuel filter condition (freshly changed/condition unknown/mileage since changed)
Two filters. Factory location filter just changed when problems started. Previously changed when I bought the truck (27k miles ago). Aftermarket filter also just changed, previously changed at 345k due to leaking water bleed valve.

8. Condition of Battery terminal connections (removed, cleaned and tightened)
Look good, didn't remove since cranking isn't a problem. Should I do this?

8a. Known condition and age of the batteries.
Both new in Sep 2007

8b. Are batteries of differing age or are they a matched set?
Matched set.

8c. Condition of Major Grounds. (same drill as batt - removed, cleaned, retightened)
Is there a diagram available showing where these are?

9. Upon cold start, does the radiator hose get hard quickly? Yes/no
No, it doesn't get hard at all.

10. Upon cold start, do you have excessive white smoke? Yes/no
Not nearly enough to obscure the neighbors house. Small but noticeable amount, I'd say.

11. Do you have excessive cranking time before the engine starts?
Increasingly, yes. When problem first started, not so much.

12. Have you used the block heater, and does this effect engine starting?(only try for starting problems)
I haven't tried this, but can if it might help diagnose. Is 45-50 degrees F overnight cold enough for the block heater to make any difference?

13. During hard acceleration, do you have excessive black smoke? Yes/no
Yes, but this has been the case since I bought the truck.

14. Do you have any unusual exhaust smoke issues?
Aside from heavy black smoke during hard acceleration and steep hill climbs, no. And these are problems before the hard starting/stalling.

15. Turbo check out - pass/fail
Vacuum to the WG solenoid, none out of it.

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

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

18. Indicate fuel that you are using: Bio-diesel, #2 Diesel, #1Diesel, SVO/WVO, other
I generally use commercially purchased biodiesel blend, I think the pump says 5-20% or something like that. I do sometimes use regular diesel from other stations though.

18a. If running a VO (Veggie Oil fuel) setup, indicate details of your conversion (homemade, or packaged system)


19. Are you using any fuel additives? If so, please list.
No.

20. Please indicate geographic region you are in: (example: Texas or Canada)
Central Alabama. Previous owner was southern Alabama but was traveling salesman so drove who-knows-where.

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

22. Please indicate any modifications to the vehicle that might help us diagnose better.
Secondary fuel filter (screw-on, oil filter looking thing) added by previous owner. I removed the decorative engine cover the first time I changed the fuel filter and never put it back. Other than that, none that I know of.

23. Upon unscrewing the fuel cap, do you have a large vacuum formed in the tank? yes/no
No.

24. Location of PMD/FSD? On the pump/remoted over intake/remoted out of engine bay (please specify placement specifically)
Factory location.

24a. If remote mounted, describe wiring harness (homemade or purchased from a vendor?)


24b. Indicate the location and condition of the FSD/IP grounding wire.
Factory location, I assume. Not sure where that is to check condition.

25. Are ALL glow plugs in proper working order as per this thread?
The four on the driver's side check out OK with Ohmmeter. I found what appears to be the wires going to the passenger side plugs - how the heck do I get to those things though without pulling the turbo?

350K and the PMD is still on the IP......Thats got to be a world record......(Stalling?)

You can scan for codes with Key On position...."Not running"

The location of all the grounds should be in the FAQs. Grounds are VERY important on these trucks. That spin on fuel filter looks nasty. You may want to drop the fuel tank to see why that filter looks like that. Also check all the fuel lines. It has to be getting water in it some how to rust a fuel filter[possible flood or hurricane truck]. The filter sock in the tank could be plugging.
Definitly check for codes.

If you have fuel at the t-valve, then it sounds like PMD. Get a new one that is relocated outside the engine compartment.

May want to measure the fuel pressure at the t-valve.

Additional issue may be GP or GP controller, with 50 to 70F, GP should not have any trouble starting but then if PMD is bad, you will have problem starting.

Since I was having so much trouble getting it to start just now, I decided to try...

1i. In a no-hot start, pour a bottle of room-temp water on the injection pump. Does it start now? yes/no

Poured a bottle of water behind waterpump and in front of intake (this is the IP, isn't it?). Started up with minimal protest.

The codes are:

P0231 Fuel Pump Secondary Circuit
P0236 Turbo Boost Sensor A
P0251 Injection Pump Metering Control
P0370 Timing Reference Hi Res Signal
P0404 EGR Flow
P0406 EGR Flow Signal A Circuit

Sounds like your turbo wastegate vacuum solenoid or vacuum pump isnt working. That would cause all your black smoke on acceleration, and you would have less power than you should.

I would clear the codes and see if they all come back.

Also looks like your Optical Sensor (OS) on the Injection Pump (IP) might be faulty. The OS is the black stubby harness on top of the IP. The first thing you need though is a remote mounted PMD, with a new PMD.

For the turbo vacuum issue I would get a manual turbo wastegate actuator, block off the EGR with a plate and swap the serpentine belt for one removing the vacuum pump.

Shop around for IPs or shops around your area that may know how to work on the 6.5TD. Most shops don't unless they are a Stanadyne dealer and actually rebuild these IPs. Beware because mechanics really screw people with 6.5s. Its best to just hand them in writing what you want them to do.

When it wont start, try unplugging the OS and see if it will start. If a faulty OS is plugged in and you unplug the crankshaft position sensor (CPS) the engine should crank smooth and not even try to turn over. Might be another good way to see if OS is functioning. the CPS has a wire tail that comes up by the thermostat next to the IP and you can unclip the harness.

The WTS light should be on for more than 4 seconds on an overnight cold start at 50*F. Might be a glo plug controller issue or a coolant temp sensor (CTS) problem.

When it wont start, try unplugging the OS and see if it will start. If a faulty OS is plugged in and you unplug the crankshaft position sensor (CPS) the engine should crank smooth and not even try to turn over.

When it won't start, it just cranks smooth, as you say, without stumbling/chugging, etc. This is with everything plugged in as normal.

What is supposed to happen if the OS is unplugged?

Can anybody suggest a vendor or two for PMD and heatsink? I PM'd "outriggers" about a PMD he's selling for $25, but I'll still need a heatsink and possibly a resistor.

Have you driven the truck at highway speed recently? With a bad or unplugged OS it would have gone into limp mode and not run well.

It could be that you have had a faulty OS for some time which would cause you to have to crank more for the PCM to reference the CPS for timing. And when it wont work now the CPS could also be going dead, so there is no timing reference to the PCM.

If both are bad it wont start, and you wouldnt get any codes, because they need eachother to set a code for the other. You have the OS codes, so at one time the CPS was working while the OS was not.

Have you driven the truck at highway speed recently? With a bad or unplugged OS it would have gone into limp mode and not run well.

It could be that you have had a faulty OS for some time which would cause you to have to crank more for the PCM to reference the CPS for timing. And when it wont work now the CPS could also be going dead, so there is no timing reference to the PCM.

If both are bad it wont start, and you wouldnt get any codes, because they need eachother to set a code for the other. You have the OS codes, so at one time the CPS was working while the OS was not.

Yes i agree with this also but i would also add in a new pmd and you should be good to go.

Have you driven the truck at highway speed recently? With a bad or unplugged OS it would have gone into limp mode and not run well.

It could be that you have had a faulty OS for some time which would cause you to have to crank more for the PCM to reference the CPS for timing. And when it wont work now the CPS could also be going dead, so there is no timing reference to the PCM.

If both are bad it wont start, and you wouldnt get any codes, because they need eachother to set a code for the other. You have the OS codes, so at one time the CPS was working while the OS was not.

I drove highway speeds yesterday and it was fine, aside from stalling several times about 15 miles into my trip.

I could verify the theory of both being bad by clearing the codes and seeing if I get the P0370 again, right? Or do you think the CPS is working intermittently which would allow it to set the code again?

Sounds like dead vac pump and optical sensor problem to me. Dead pump causes the turbo boost sensor code and the EGR codes. The stalling might be PMD but it might be the OS too. If the OS is bad, someone correct me if i am wrong, but the only real way to fix that is with a new IP. I think the IP has to be removed and taken apart to replace it. I could be wrong on that but i think that is what i remember hearing.

Clear the codes and just see what comes back. There are possible other reasons the engine may crank so smooth, like a PMD not outputting anything to tell the IP to release the fuel.

If you can find an OS you can replace it with the IP still in the truck, but I dont think it costs much more just to replace the whole IP.

Cleared the codes and it is now staying code free. I was only able to drive about 3-5 miles though after resetting it - it kept stalling out. Still no codes even after stalling at least a dozen times.

Pouring water on the IP/PMD seems to be a guaranteed way to get it to start and drive for at least a couple minutes, at this point.

I guess I'll start with a remote PMD and see how that goes. Do we think I'll end up replacing the IP/OS also?

Hard to tell, The PMD is on the IP, so if youre cooling it down with the water it might be the only problem.

Picked up an IP with PMD from a junk yard this morning - figure if the IP ends up being bad, I've got one ready to go. Decided to just swap the PMD out, putting the new one back in the stock location to get running while I look for a heat sink and figure out where I want to put it.

Let me tell you, getting the bottom two screws out of the PMD is a real pain in the butt, even with both intakes out of the way. I ended up putting my T-15 screwdriver into a vice and heating it to bend it into an L-shape. The booger is that you can only turn the screws 1/8 to 1/4 turn at a time this way.

I'll finish putting it together in the morning; hopefully this will have been the problem.

The good news is that the PO included a 3/8" Craftsman ratchet in the price of the truck. :) I found it in the lifter valley, covered in grime.

Finished putting it together this morning and it started right up. It's been idling for 30-45 minutes now without stalling so I guess the PMD was the problem.

Thanks for the help. Now I'll be looking to remote it.

since you now know...IMO you'd be better off buying a brand new PMD and relocating outside the engine bay. theres no telling how much life is left in the used one...

my .02 cents