Hey Fellas,

This started as a sort of like mis-timing sort of thing on a gasser. Driving along at any speed, use slight pedal pressure and engine acts like it jumps timing for a few seconds, rattles or pings, then levels off until next time you push the accelerator, then it rattles again. It doesn’t seem to have the power on acceleration it once had, and pours black smoke on hard acceleration. I suspect a boost problem of some kind, probably the waste gate solenoid or maybe the waste gate accuator, however they both check out. One question I have is about the accuator. Does the spring in the accuator push the waste gate open/closed and then the vacuum pulls it closed/open? At engine off, my accuator doesn’t seem to open/close much more than 1/2 way. Running, the vacuum pulls it in hard.

Diagnostic Checklist:

0. Describe in detail the problem you are having. Please be as descriptive as possible.

1995 Chevy C1500 ext cab, 6.5L Turbo Diesel, Vin-S, completely stock, 126K miles. Cranks, idles and runs. On acceleration slight shudder and sounds like a gasser that is mis-timed or jumping time for a couple of seconds then levels out. Pinging noise. Seems to have loss of power. On hard acceleration blows a lot of black smoke Throwing no codes. On cruise control, it dosen’t seem to have the jumped timing thing.

1. Does the engine crank, or 'turn over'? Yes
1a. Does the engine start and run? Yes
1a1. If the engine does not start - Crack injector line (http://www.dieselplace.com/forum/showthread.php?p=2188140#post2188140): do you have fuel? Yes
1b. Do you have a Wait To Start Light & the amount of time (seconds) lit. 5-10 seconds
1c. Ambient Condition (temperature outside indicate F or C) ____90_ ° F
1d. Engine Cranking speed (if you have an accurate tachometer). No problem
1e. Are you experiencing stalling? On acceleration, but more of a shudder than a stall.
1f. If Stalling, describe (upon startup only, down the road, hit a bump etc) Down the road.
1g. If Stalling, do you notice loss of dash or instruments? No`-note if experiencing stalling,you must indicate PMD location in #24.

1h. Check turbo inlet and air filter for obstructions. Cone filters have lost disk and stopped air to turbo. New air filter no obstructions
1i. In a no-hot start, pour a bottle of room-temp water on the injection pump. Does it start now? yes/no N/A
1.1 Lift pump test (http://dieselplace.com/forum/showthread.php?t=39350)- describe results New Lift Pump less than 100 miles
2. Service Engine Light while running?- on/off/intermittent Off
2a. Service Engine light does glow during start/cranking/bulb check: Yes/No Yes – at switch on – off while running
3. Model year 1995
3a. Odometer reading (indicate if in miles or km) 125,978
3b. Miles on major engine components if been replaced (example Injection pump) Nothing replaced except Lift Pump, PMD, and Oil Sending Switch
3c. Indicate the model number on the Injection pump (starts DS4 or DB2......) I can’t find number on pump, but it looks like a DS-5521
4. Have you scanned for engine codes? (varies by pre/post 96) yes/no Yes, none showing
5. List exact results on engine codes (http://www.dieselplace.com/forum/dtc.php): N/A
6. Air Filter condition (visual check) Clean, new less than 100 miles
7. Fuel filter condition (freshly changed/condition unknown/mileage since changed) New- changed 400 miles ago, but will check and let you know
8. Condition of Battery terminal connections (removed, cleaned and tightened) Removed, cleaned and tightened this morning,
8a. Known condition and age of the batteries. Batteries matched pair, new two years ago
8b. Are batteries of differing age or are they a matched set? Matched
8c. Condition of Major Grounds (http://www.dieselplace.com/forum/showthread.php?t=157085). (same drill as batt - removed, cleaned, retightened) Need to check this
9. Upon cold start, does the radiator hose get hard quickly? Yes/no Yes
10. Upon cold start, do you have excessive white smoke? Yes/no No smoke
11. Do you have excessive cranking time before the engine starts? Usually starts in less than 5 turns.
12. Have you used the block heater, and does this effect engine starting?(only try for starting problems) No Block heater
13. During hard acceleration, do you have excessive black smoke? Yes/no Yes, very excessive
14. Do you have any unusual exhaust smoke issues? Other than the black smoke, none
15. Turbo check out (http://dieselplace.com/forum/showthread.php?t=39368)- pass/fail – Vacuum is good all over, everything seems to be in working order wit 25/hg off pump, 22/hg off wastegate accuator, and 22/hg off waste gate solenoid.
16. Do you have an EGR on the engine? (An F or an S engine code 8th VIN digit) Yes, it has EGR and is a Vin-S engine
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 #1
18a. If running a VO (Veggie Oil fuel) setup, indicate details of your conversion (homemade, or packaged system) N/A
19. Are you using any fuel additives? If so, please list. No
20. Please indicate geographic region you are in: (example: Texas or Canada) Mississippi
21. Do you have any service history available that might pertain to the problem you are having? No. changed out PMD about 5-months ago after intermittent starting and stalling, and finally dead, but put it back in valley.
22. Please indicate any modifications to the vehicle that might help us diagnose better.
23. Upon unscrewing the fuel cap (http://dieselplace.com/forum/showthread.php?t=42338), do you have a large vacuum formed in the tank? yes/no
24. Location of PMD/FSD (http://www.dieselplace.com/forum/showthread.php?t=39436)? On the pump/remoted over intake/remoted out of engine bay (please specify placement specifically) On the pump in the valley
24a. If remote mounted, describe wiring harness (homemade or purchased from a vendor?) N/A
24b. Indicate the location and condition of the FSD/IP grounding wire. Top of the pump
25. Are ALL glow plugs in proper working order as per this thread (http://www.dieselplace.com/forum/showthread.php?t=39182)? They appear to be.

Pull off the belt, and check the vacuum pump - mine sounded
like it had steel marbles in it when it went out, no vac pump,
no boost

My 6.5 has similar symptoms. It only happends as I ease on the throttle, and only under no load. Accelerate slowly and as you get to an easy cusing speed even if I don't move the throttle it will start to rattle, as soon as I give it more throttle I get a puff of black smoke and it clears up an accelerates. It only seems to happen as I ease on the trottle under no load, or as it attains a crusing speed and I keep the throttle in the same place-it pings/rattles, move the throttle and it goes away.
I will check the wastegate vacume and see what I come up with. I was thinking IP. Hope it is turbo related- that would be less expensive and something I can deal with

Mine does basically the same thing. I have good vacuum at waste gate. Only thing I found is that if waste gate accuator is susposed to be spring loaded, mine only goes back about 1/2 way when vaccuum or engine is off. Maybe a bad spring?? It pulls in and can't be moved under vacuum. I hope it is vacuum related too. I'm retired and don't need to have IP problems.

Pull off the belt, and check the vacuum pump - mine sounded
like it had steel marbles in it when it went out, no vac pump,
no boost

I checked this. No problems.

Mine does basically the same thing. I have good vacuum at waste gate. Only thing I found is that if waste gate accuator is susposed to be spring loaded, mine only goes back about 1/2 way when vaccuum or engine is off. Maybe a bad spring?? It pulls in and can't be moved under vacuum. I hope it is vacuum related too. I'm retired and don't need to have IP problems.

No spring in the wastegate, your wastegate system is fine. Is it by chance getting slowly and progressivly worse?

Yes Mine has gotten slowly progressively worse. Waste gate vacume is good - air filter clean. I figure it is related to IP, but don't really know what.

No spring in the wastegate, your wastegate system is fine. Is it by chance getting slowly and progressivly worse?

Nope! It seems to be about the same. Runs awhile, then pings on accelleration or may just ping like it is out of time for no apparent reason. Best I can explain it would be like a bad vacuum advance in a gas burner.

crank shaft position sensor going south ?

crank shaft position sensor going south ?
Tell me more-crankshaft position sensor- where is it what does it do? My problem is getting worse quickly. I now notice a lot more black smoke than I had before- but less power.
I will go research crank sensor. Thanks

I thank you too. The crankshaft position sensor makes sense. I'll check that sucker out tomorrow and see what I can find out.

I Have ben watching this thread. Mine is doing the same. It was never that bad until I give it some juce or pull something. I had it in the GM shop here. They had it for two days and threw up their hands and said they couldnt get any info from the trucks computer. If anyone knows of a good diesel mechanics in Portland Oregon that may be better than the dealer? Well thanks to you guys for this site!!

I just re-read gmctd's explaination of how the turbo and waste gate operates in the Faqs, and I am confused. He mentions that the waste gate accuator is spring loaded (probably, I guess to open or close the gate), and is vacuum pulled to either open or close the gate - I don't know which. My accuator doesn't appear to have any spring loading. It is locked tight with vacuum at idle, but with engine off it only moves about 1/2 way back. My questions are -

(1) is there susposed to be a spring inside the accuator cannister that pushes it back opposite the pull of the vacuum?

(2) I also understand that the accuator solenoid is susposed to buzz at idle - mine has good vacuum at idle but doesn't buzz. Pulls 17" vacuum at idle, which pretty well remains constant under load (acceleration in drive with brakes on) but drops off to about 10" when I let off the pedal and goes back to 17".

(3) Which way is the waste gate closed? When it is pulled up under vacuum or when it is the opposite way?

I have good vacuum, and accuator checks out, but waste gate doesn't seem to move because of the vacuum holding it in. Without vacuum (engine not running) it moves freely. I am trying to understand what pulls it open (or closes it, whatever the case)against the vacuum - spring action, exhaust blowby suction, or what?

I'm trying to find out what is wrong with this thing without throwing a bunch of new parts at it without ever knowing what caused the problem.

Vacuum holds it closed, exhaust pressure pushes it open

AFAIK the only time there is a spring is when someone made or bought and installed a turbo master which bypasses the factory vac system and uses a spring to operate the wastegate.

I drove it out to a mechanic that was an IP tech for 15-years and his conclusion was that the IP was going south. Something about a screw loose or broken in the "C" whatever. Anyway, he recommended replacement of the IP. I didn't like that diagnosis and thought i'd experiment first before dropping big $$ on a pump.

I ordered a wastegate solenoid and changed it out. That eliminated most, but not all of the rattling or pinging, and the surging it had developed lately. I now hear the turbo spool up, but it is blowing smoke like a locomotive at most any acceleration. It rattles some on hard acceleration, but not as bad as it was.

My next guess is either the MAF or the ERG. Vacuum on ERG is good, but it could be stuck. I think it might also be the pressure relief valve on the reurn line causing the overfueling.

Any opinions?

OK, took it for a test drive. Little smoke on acceleration. No rattling. Punch it hard, rattles loud, lots of grey smoke, slow to downshift to passing gear. Now what?