At a total loss, 2 injection pump, NEED HELP!

[ryno]

Here goes
First it's a 1995 6.5 TD 240,000km. 3" Exhaust, Power Chip, K&N. The truck began quitting on me randomly a while back until I could hardly go 30 seconds without a stall.
I replaced the fuel filter twice
The injection pump twice
Lift Pump and added a second after market one
Replaced two fuel lines that looked old
Tested fuel pressure (7psi)
The first time the truck acted up it left a grocery list of codes. The first replacement injection pump it ran fine for about 500km, then began stalling with no codes. The second pump had a few misses right away and then lasted about 100km before it began quitting and then it went into a limp mode with little power. This time with codes 18, 36, 54, 98.
I don't know where to go now. Would lake of proper timing cause this?

[ 10-31-2003, 06:54 AM: Message edited by: ryno ]

[ucdavis]

You can rule out fuel filter (assuming the second filter was a clean filter).
You can rule out the lift pump if the 7psi is when engine is running.
Sounds like first IP w/list of codes was bad, but that 2nd IP w/out codes may have only needed a new FSD (coulda been the pump but replacement of FSD only woulda been the prescribed step B4 R&R'ing the pump).
What you have now could be the pump or just the FSD, but you've narrowed it down to those assuming the first two items above are as described. And I'd say the 54 & 98 are sort of phantom codes. I got those randomly when 17, 18, 35 & 36 were coming up at random (my trouble was the old blue-tag IP) and the 54/98 never meant anything; I think PCM gets confused if it starts getting multiple codes and it could be that limp mode helps confuse the issue. The GM techs know to record & clear the initial smorgasbord of codes, then try to replicate the trouble & compare new & orig. sets of codes.
Try:
A) Ohm-check all grounds & disassemble, clean & reinstall any that give even a hint of resistance (top of IP, block to batt, frame to batt...)
1) clear codes & run it to see what you get starting w/a clean slate; check codes immediately when you get trouble (B4 the confusion sets in & phantom codes get set).
2) If you get 17, 18, 35 &/or 36 you have to suspect the IP, but try replacing just the FSD first.
3) If you get only the 17 and/or 18 & new FSD doesn't fix it, that is the "optical sensor" on top of IP (small black bakalite box w/harness connector & circlip). You can R&R just the sensor w/EXTREME CARE FOR CLEANLINESS as you will have the central IP cavity open & will contaminate the pump & high pressure injection section if you let dirt in; Stanadyne will sell you the part, look under yellow pages for "diesel injection" and you should find authorized Stanadyne rebuilders who sell parts.
4) If you replace the FSD & still get 17, 18, 35 and/or 36, it is the IP, unless
5) it is the PCM. There is always a default possibility that electronic trouble is the PCM, which has no method of diagnosis either by setting codes or by scantool. Proof is by R&R if trouble goes away. If you are able to scare up a spare PCM unit for your year (ya gotta reuse the prom chip from your current PCM in the new one) this is a much easier test than R&Ring the IP. New PCM for a '95 is about $212 + $200 core charge @ your local friendly GM stealer. FYI, the PCM is a low probablity trouble spot; problem w/probability is that if you have the 1:100 shot example under your hood, you have what you have & not the average situation. I R&R'd my PCM to no avail, then did the IP R&R; oh well.
Hope this helps. Good luck.

[ 10-31-2003, 10:35 AM: Message edited by: ucdavis ]

[ryno]

Thanks For all your help.

I am hopping that the injector pump and the pdm are good as I have replaced them both twice within 500kms. I am going to replace the lift pump again. I have a second fuel lift pump in the engine bay and my thought is that the frame mounted lift pump has failed or is plugged. This would cause the second pump in the engine bay to suck hard enough to draw air into the system. Therefore causing the random misfire and then eventually such poor running conditions the computer goes into a limp mode and occasionally sets codes? As the truck will run fine after it sits for a while. I really do not know where else to go as I really do not want to replace the pump or pdm again. Are there any other grounds other than the ones that come from each battery?

[moondoggie]

Good Day!

You may want to look at DTC 35 - Help! (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=004386#000000). It probably doesn't apply to your problem, but the ground locations are listed.

Blessings!

Brian Johnson, #5044

[ucdavis]

If you are getting code 17 or 18 (I forget which one is the "high resolution" circuit) that can be air bubbles in the pump causing hard to read internal pump timing.
Did you read the actual codes being set? When I finally did that I kicked myself at how simple it was, how much it improved my reading of the situation, and how long I had put it off.

[ryno]

I did read the codes, via crossing the terminals under the dash and reading the SES light flashes. I replaced the lift pump again yesterday and got much higher fuel pressure than before. But as usual the truck drove great with the exception of the odd miss fire and then tonight it died again. It began to stutter as the rpms increased during acceleration (like it was out of fuel) and then the SES light came on and it seemed to go into it's limp mode, running fine but with very little power. The codes this time are 18, 35, 54. Are there any common areas that these fuel systems suck air into themselves? I really am not sure what to fix next?

[ryno]

It would seem that I may finally solved the problem. Two injection pumps, pdm's, lift pumps and hours of trouble shooting, it would seem that I had a plugged fuel line. I dropped the tank Friday, cleaned it and the filter in the tank. Saturday I removed all fuel lines including he filter canister and forced 110psi through all. Put everything back together and I now run 7 psi with just the lift pump and no fluctuations while driving. Oh I also replaced all the small o rings on all line coupler fittings. It's been three days and no problems, figures crossed!