I've been fighting the demons for a while and here's what I got. before i became wise and started checking the forum, my truck was fishbiting occasionally, then 3 weeks ago, it just quit. I put a good used pmd on a cooler remote mounted in the bumper last week. It started and ran fine for a few days. Now, I can start it, sometimes, and it will run for a few minutes and shut down like someone turned the key off. I've put in a new ignition switch on it and removed the filter harness from the OS. I'm leaning towards the OPS or the fuel stop solenoid. Is there a test for either one of those parts?

My Check engine light has not been working lately, so i'm not getting any codes right now.

'94 GMC 6.5 TD, "ss" engine



Here's the check list:

1. Does the engine crank, or 'turn over'? YES
1a. Does the engine start and run? SOMETIMES
1a1. If the engine does not start - Crack injector line (http://www.dieselplace.com/forum/showthread.php?p=2188140#post2188140): do you have fuel?
1b. Do you have a Wait To Start Light & the amount of time (seconds) lit. YES/NORMAL 7-10 secs
1c. Ambient Condition (temperature outside indicate F or C) __40° F
1d. Engine Cranking speed (if you have an accurate tachometer). CRANKING NORMAL
1e. Are you experiencing stalling? NOT stalling, just shuts down
1f. If Stalling, describe (upon startup only, down the road, hit a bump etc) N/A
1g. If Stalling, do you notice loss of dash or instruments? NO START
-note if experiencing stalling,you must indicate PMD location in #24.


1.1 Lift pump test (http://dieselplace.com/forum/showthread.php?t=39350)- describe results OK
2. Service Engine Light while running?- NO
2a. Service Engine light does glow during start/cranking/bulb check:NO
3. Model year 1994
3a. Odometer reading 330,000 M
3b. Miles on major engine components if been replaced :185K on engine, pump has been rebuilt, i think(green tag on the front, but before I got the truck. I got it 110K ago)
3c. Indicate the model number on the Injection pump (starts DS4 or DB2......)DS4
4. Have you scanned for engine codes? (varies by pre/post 96) yes
5. List exact results on engine codes: NONE
6. Air Filter condition (visual check) NEW
7. Fuel filter condition (freshly changed/condition unknown/mileage since changed) NEW
8. Condition of Battery terminal connections (removed, cleaned and tightened) CLEAN AND TIGHT
8a. Known condition and age of the batteries. 6 MONTHS OLD
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) CLEAN AND TIGHT
9. Upon cold start, does the radiator hose get hard quickly?
10. Upon cold start, do you have excessive white smoke?
11. Do you have excessive cranking time before the engine starts? SOMETIMES
12. Have you used the block heater, and does this effect engine starting?(only try for starting problems) BLOCK HEATER IS WORKING STILL NO START
13. During hard acceleration, do you have excessive black smoke? NO START
14. Do you have any unusual exhaust smoke issues? NO START
15. Turbo check out (http://dieselplace.com/forum/showthread.php?t=39368)- PASS
16. Do you have an EGR on the engine? YES
17. Indicate if you know if it’s a--> 1500
18. Indicate fuel that you are using: PUMP DIESEL
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.
20. Please indicate geographic region you are in: OKLAHOMA
21. Do you have any service history available that might pertain to the problem you are having? REPLACED PMD, REMOTE MOUNTED FROMT BUMPER 2 WEEKS AGO, NEW IGNITION SWITCH LAST NIGHT
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? NO START
24. Location of PMD/FSD (http://www.dieselplace.com/forum/showthread.php?t=39436)? MOUNTED IN FRONT BUMPER ON A COOLER
24a. If remote mounted, describe wiring harness (homemade or purchased from a vendor?) PURCHASED
24b. Indicate the location and condition of the FSD/IP grounding wire.STOCK LOCATION GOOD CONDITION
25. Are ALL glow plugs in proper working order as per this thread (http://www.dieselplace.com/forum/showthread.php?t=39182)? YES/NEW

Maybe a not so "good" used PMD.

IIRC wouldn't there be NO WTS light if the OPS is bad?

Tank sock plugged to the MAX! Maybe?

I thought about all of the fuel issues, but would it just shut down, just like that, if it was a filter or fuel sock? I checked the lift pump and it is getting fuel to the filter, but I haven't checked the amount of pressure on it. I would think it would stumble a little bit if it was fuel related. I haven't toatlly ruled that out though. I am going to see if I can get a pressure guage to see how much fuel pressure I have at the lift pump.

On the OPS, I wans't sure on the wait light issue. I saw where someone else had mentioned that, but I think it was in regards to a 96 model. Didn't know if it applied to the 94's also.

Could it possibly be the Optical sensor? I removed the filter harness, but no difference in the way it runs, when it will start and run.

I thought about all of the fuel issues, but would it just shut down, just like that, if it was a filter or fuel sock?

Yes

There are a few cases of not so "good used PMD". If you are still under warranty, may want to exchange it.

. I put a good used pmd on a cooler remote mounted in the bumper last week.
My Check engine light has not been working lately, so i'm not getting any codes right now.

? YES/NEW
I see two problems right in the question..
1) What is a good used PMD ? If you bought it off that clown on ebay you got hosed. Any PMD that was installed on the pump could be damaged.
2)Why is your check engine light not working ? That would be my first order of business. The check engine light itself will throw a code if not working. Get a scanner, find a scanner go to someone who has a scanner and scan for stored DTCs. Otherwise you are flying blind IMO.

On the PMD, I borrowed it from a buddy who has a 6.5 that got wrecked. Engine was running fine before the wreck. Could still be bad though. I fixed my SES light, burnt bulb in dash, and I am getting a DTC 17, High resolution circuit fault. This is the only code I received. Last night, I spent 3 1/2 hours re-checking all of my grounds, connections at the remote mount PMD, pmd extension harness, fuel stop solenoid, optical sensor, etc. I pulled my fuel stop solenoid out and watch to make sure the piston in it is moving in when the key is switched on. It is. Unless this code 17 throws a flag up to anyone on here, I am going to get a new pmd and see if that fixes it.

I might be in the same boat as you. I've been trouble shooting also. I would say yours and my OPS are bad. I disconnected the Optical Sensor and my truck fired up after a little extra cranking. It was running but in limp mode. It ran rough then calmed down. I could give the engine throttle in park but shift into gear and limp mode kept it from having any power. So now I'm studying the optical sensor change or maybe the whole injection pump. With the OPS unplugged I get codes 17,18,35,43 but that is probably expected sense the computer doesn't see or hear the OPS. Good luck!

OOps I meant optical sensor not OPS

I might be in the same boat as you. I've been trouble shooting also. I would say yours and my optical sensor on IP are bad. I disconnected the Optical Sensor and my truck fired up after a little extra cranking. It was running but in limp mode. It ran rough then calmed down. I could give the engine throttle in park but shift into gear and limp mode kept it from having any power. So now I'm studying the optical sensor change or maybe the whole injection pump. With the OPS unplugged I get codes 17,18,35,43 but that is probably expected sense the computer doesn't see or hear the Optical sensor. Good luck!

If this doesn't sound right to someone chime in please.

Wait up, 94 is OBD-I... may have optical sensor filter harness. If present, remove and bypass around it and see if it works stops fishbiting. See Bill Heath's blog about it. Or do a search on here about it. That would be the connection between the ECM and the optical sensor.... thus the 17 code. A PMD will not fix everything.

Worked on the truck for 4 more hours last night. :( It ran:), but only for about 5 seconds:mad:. I pulled the battery cables to reset the codes in the truck. Pulled the fuel stop solenoid and set it on the intake so I could watch what it was doing. When I turned the key to run, the piston on the end would draw in, and release back out with the key off. I didn't try cranking w/ it out because I didn't want fuel going everywhere, and didn't know if it would hurt anything either. I removed my optical filter harness the other day and haven't put it back in yet. I can't remember 100% for sure if I checked the codes before or after I pulled the fuel shut-off solenoid out and checked it, but now the only code I get is 13. Any ideas?

DTC 13 Engine ShutOff Solenoid Circuit Fault. Yea I got the same code for that. Hey if you want to remove the codes faster without having to disconnect batterys you just have to hold the brake pedal and acceleration pedal down until you get code 12 of course after you get all the codes saved on the computer. Where you able to get the truck going while or if you tried starting with the optical sensor disconnected?

61317

I was looking for info on the optical sensor and came across this info for Carquest techs on the optical sensor and crank positoning sensor. I read it as if you disconnect the optical sensor and can get the truck running then the optical sensor is to blame. If you disconnect the crank positioning sensor instead of the other then you probably have a problem with the crank positioning sensor. Thought you might be interested if you are still working with the same problem . Let me know how it goes when you get a chance.

I could be wrong here but could it be the shutoff soleniod on the IP ?

Still working on the beast. So far, i've replaced the fuel stop solenoid, fuel pump relay, pmd/fsd, and ignition switch. I've removed the optical sensor filter. I can't get it to start with the OS unplugged or the CPS unplugged. As of now, the OS filter is still out. I'm getting fuel to the IP, but nothing at the injectors. Could a bad optical sensor cause this?