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Discussion Starter #1
I've had 6.5's for 15 years and have had plenty of issues firing up over the years, but now am completely stumped. Have a 99 Suburban, replaced with rebuilt engine 2 yrs ago and had been very reliable and fast starting daily driver. One day it wouldn't start, only coughs for a few seconds and then nothing. Over 3 weeks of messing with it I can occasionally get it to start but not every time. Replaced glow plugs, tried second PMD, cleaned grounds, verified lift pump - slight improvement but still rarely starts. I appreciate any help and advice you can give. Here's the checklist.

1. Describe the problem you are having in detail: No start. Truck was daily driver and very reliable starting. Drove fine to work one day 3 weeks ago, then when time to go home wouldn’t start and has only started a few times since. Each crank gets a cough for a few seconds, then nothing. If I do this for a while, then charge the battery, I can sometimes get it to start. I have idled the engine for ½ hr to be sure there are no air pockets. If engine is hot it will restart easily. When it cools back down it won’t start again.

2. Year of truck/engine. 1999
3. Odometer reading (indicate miles or kilometers). 165000
4. Indicate the model number on the Injection pump (starts DS4 or DB2......). DS4
5. Indicate if you know if it’s a 1500, 2500, 2500HD, 3500, 3500HD. 2500HD
6. Do you have an EGR on the engine? (An F or an S engine code 8th VIN digit) No
7. Air Filter condition (visual check). Tried with AF removed, no change
8. Fuel filter condition (freshly changed, mileage since changed). New
9. Location of PMD/FSD? (ex. on pump/remote over intake, behind bumper). Top driver side of engine on large heat sink
9a. If remote mounted, describe wiring harness (homemade or purchased from which vendor). Standard harness
9b. Indicate the location and condition of the FSD/IP grounding wire. Top of IP
10. Outside Temperature (C or F). _____ ° 45

11. Service Engine Light while running?- on/off/intermittent None
11a. Service Engine light does glow during start/cranking/bulb check: Yes
12.Have you scanned for engine codes? Yes
12a. List exact results on engine codes. None

13. Condition of Battery terminals (removed, cleaned and tightened). Cleaned and tightened
14. Known condition and age of Batteries. Optima, 2 yr
14a. Are batteries a matched set of same age? No, passenger battery is newer Optima
15. Condition of Major Grounds (removed, cleaned and tightened) cleaned battery grounds and rear left engine grounds
15a Have the batteries been individually load tested? No

16. Does engine crank, or "turn over"? Yes, speed seems normal
16a. Does engine start and run? Rarely
17. If engine does not start- Crack injector line: do you have fuel? Yes
18. Does your Wait To Start light come on? Yes on the first crank, sometimes no on second crank
18a.Number of seconds WTS light is lit. 15-20 on first crank
19. Engine Cranking speed (if you have an accurate tachometer). Seems normal. No tach

20. Are you experiencing Stalling? No
20a. Describe the event (upon startup only, down the road, hit a bump, etc...) N/A
20b. Do you notice loss of dash or instruments? N/A
21. Check turbo inlet and air filter for obstructions. Removed air filter. No change
22. In a no-hot start, pour a bottle of room-temp water on the injection pump. Does it start now? No. Tried new second PMD, no change
23. Lift pump test - Describe results. I have strong fuel stream out of T hose with engine running

24. Upon cold start, does the radiator hose get hard quickly? No
25. Upon cold start, do you have excessive white smoke? No, is grey for a while then clear
26. Do you have excessive cranking time before the engine starts? When it does start it goes quick.
27. Have you used the block heater? Does it affect engine starting? (only try for starting problems). Tried with and without, no obvious difference
28. Are all glow plugs in proper working order? Replaced them all with Bosch fast start and verified 12 v to all

29. During hard acceleration, do you have excessive black smoke? Yes/No Don’t know
30. Do you have any unusual exhaust smoke issues? No
31. Turbo check out - Pass/Fail
32. Indicate fuel that you are using: Diesel
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. Winter additive
34. Upon unscrewing fuel cap, do you have a large vacuum formed in the tank? 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.
a. Mostly stock. Have diy turbomaster, boost fooler, gauges
b. Have clear hose on fuel return. Clear and no air bubbles. Tried removing to make sure no return blockage- no change
c. New fuel sending unit, hose all the way up. No delivery issues
d. Marine injectors, 2 yrs
 

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1995 GMC Suburban
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Do 15a?
 

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It sounds like injectors are pissing, and you have low compression.

1. You have new bosch glow plugs, and verified they are getting 12v

2. Your motor is cranking, and you have fuel to the injectors.

3. When it starts, you have grey smoke.

I would get a compression test performed.

Plug in the block heater to get it warm for morning starts.

A remote possibility is air in the fuel lines, but a filter bleed should show that.
 

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Discussion Starter #4
I'm leaning towards the batteries too, because after a charge I have a much better chance of starting, and after 3-4 cranks they start to slow down. I will have them load tested.

On the injector and low compression theory- this event was like flipping a switch type deal. Every start prior to the "no start" time was within a few seconds of turning the key, almost to the point it sounded more like a gasser than a diesel. I never had extended cranks before it would catch. Even that morning when it was much colder it fired up quickly, then after work nothing. Would the low compression and pissing injectors be so black and white, or would I have seen degradation over time?
 

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Discussion Starter #5
One item I left out. I was low on the tank and the fuel sender was bouncing between 1/4 and empty. It is possible that I ran it dry that day. That would explain the difficulty in getting it restarted. The cough and then not running seems very similar to when I replaced the engine and had to get it restarted after being dry. However, I have run it for 1/2 hr since then, and there are no bubbles in the clear return tube. Is there a chance of air still in the system? Maybe grabbing at straws but wanted aty least to get everything I know out there
 

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Not saying you do not have another problem, just went through the same thing with my 6.2 over the last few days, it refused to crank yesterday, but acted just like you described cranked for a few seconds and died, then once for a few minutes died. Fuel gauge same place, so I pulled the separator/filter and it was filthy, dumped it out then filled it with fresh diesel, cracked injector lines, same results, with very little fuel at the nuts. Today, after thinking about how much trash, dirty fuel and even a little water, I decided to change both filters, switched to the left tank which was full, and purged the air out with air pressure in my tank because I have a mechanical pump. Then once I got fuel to the new separator/filter it cranked right up, didn't even have to crank the injector lines....drove it about 10 miles, restarted fine, just feels like I have lost a little power, so I am going to clean more of the fuel system tomorrow. Just saying mine did the exact same thing low on fuel about 3/8 of a tank, surged a bit, driving home and would not crank back the next day. I was surprised at how much crude and nasty looking fuel that came out of the filter....and it was also only a few weeks old, so I know that I pulled it into the filter by running the tank low. Others have mentioned a sock in the tank off the sending unit causing them to replace ip and many other things only to find out that it was about a 27 dollar sock/strainer that was stopping up. You should be able to find the part number in the forum. I know that am dropping the right tank, cleaning it out and installing a new strainer as soon I a have a couple of free days to do it. Its worth a shot, to check these items too and good luck with it.
 

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1995 GMC Suburban
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make sure there is gas and make sure to bleed the air from fuel.
Did you try a KNOWN WORKING PMD?
 

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1995 GMC Suburban
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Try to tap the starter when you start?
To check if starter is the culprit.
 

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Discussion Starter #10
The winner is.... CRANKSHAFT POSITION SENSOR !!!!

The only way I figured it out is that it finally threw a code.

Thanks to everyone for your suggestions. I couldn't have figured it out without your help
 
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