Help for dad.

[brianblack138]

I got a call from my dad this evening. He's been having some problems with his 1994 GMC Suburban 2500 4X4. For background info, my father bought the truck 5 years ago right after it had a brand new injection pump put in it. After just a few miles, he had to have a rebuilt engine installed (To be honest, I can't recall why). All in all, the truck probably only has 150k on it and less than 50k on the new IP and engine.

So my mom called me about three weeks ago and told me that my father had taken the truck into the shop after starting issues. The truck had been really hard to start and impossible to start on cold days and eventually it went into limp mode and he was barely able to make it to the shop (a shop that claimed to have expert diesel mechanics and to know the 6.5L TD very well). They told him he needed a brand new injection pump. Because he needed it for work and knows very little about mechanics (and for some reason didn't want to bother me) he agreed to pay the $2300 the mechanics wanted for it. As soon as my mom told me this, I called him back and tried to get him to let me fedex him a new PMD to try before paying for a brand new IP. I told him that I could even get him a new IP for about $500 less than the shop was claiming it cost. All to no avail... my father is the type of guy who would rather pay more money to have something warrantied.

So after a bit of discussion, he told me that he was willing to pay the $2300 even though I told him it was steep.

Last weekend he drove from their house on the Delaware shore to Baltimore for Easter. I drove down from WV to meet him and he told me that he was still having terrible problems with the truck. My immediate thought was the lift pump... if the lift pump had gone bad, it could have caused the premature IP failure and unless they replaced the lift pump along with the IP, he still would have fuel pressure issues which would cause the hard starts and stalling that he was reporting. I crawled under the truck and sure enough, the lift pump looked like it was 10 years old. The compression fittings were rusted shut, and it didn't sound or feel like it was running at all. I told him that the lift pump was probably a $100 part and would take only an hour of labor to install. He took it back to the same shop and gave them my diagnosis. At first they insisted that the lift pump was inside the IP. It wasn't until he crawled under the truck and pointed to the lift pump that they finally admitted that they hadn't thought of it and would test it to see if it were working. They tested it once and it didnt work, and another time and it did (which indicates a possible bad ground to me... but again, my dad didn't want to bother me, so he paid them the $350 they wanted to replace it), So by now he has put about $2800 in this truck. Unfortunately, it is still having a hard time starting and is frequently stalling out. The shop wants him to send it in for 3 days of diagnostics (because it didn't have any error codes they could read...) and quoted him $700 for the diagnostics alone. They also told him he has a small exhaust leak, but since the truck was so old, they couldn't buy him an exhaust so he would have to pay them to custom build him one (bull$#%t, I can get him one from SSDiesel Supply for $350).

He loves the suburban, but is just about ready to ditch it for a newer gas pickup. Do any of you guys have A) an idea what the problem could be and B) a recommendation for a GOOD diesel mechanic (who knows 6.5L's) in the eastern shore area?

[Robyn]

Its easy to check the lift pump. Open the fuel water drain on the front top of the engine.With the engine running fuel should run out the hose and fill a pint jar in less than 30 seconds or so.

If there is little to no fuel or the engine stops the lift pump is not working.

With a non op lift pump these can be tough to start.

No codes also suggests that its a simple support system issue rather than anything frantic.

The lift pump can be easily heard from under the rig. It should run during cranking and all the time the engine is running.

The oil pressure switch on the LH rear of the engine right back of the head is a likely culprit.

These switches close under pressure to power the pump and also run the gauge.

The switch can and does fail and when this happens things get hinky.

Easy to remove and replace. Takes about 15 minutes. :)

What you describe is typical symptoms of fuel starvation.

Fuel lift pump and fuel filter will do this.

Check the drain with the engine running. No fuel, No pump working , that simple.

The relay and the fuse for this are located in the little black plastic cover by the RH cowl above the AC housing.

The fuse is in the liitle box like thing and just clips in.

Good luck and keep us posted.

Robyn

[ronniejoe]

Make sure that no air is getting into the system. A faulty lift pump and an air leak will cause the problems that you are describing. Check the fuel filter, too.

[brianblack138]

I wasn't able to fully test the system when I saw it last on Sunday because I didn't want to get diesel all over the driveway where he was parked (we weren't at home).

I completely forgot about the OPS. I usually test the LP the same way I prime my filters after a change by opening the T and then shorting the fuse under the little black box to force the LP to run, but I didn't do that on Sunday.

I had suspected poor grounding, but as the LP was so rusted and corroded that the fittings were starting to crumble, and since we ran the truck and I couldn't hear or feel any vibration on the LP, I thought that could be the culprit as well.

Sounds like the best thing to do is what I did to my 1994 K1500. Install a sight valve before the IP to check for air bubbles and install a pressure guage there as well to test the fuel pressure for 7psi under load. Also clean the ground contacts and test the LP. I guess we could also use a multimeter to check the OPS but probably wouldn't be necessary because if the OPS isn't working, the LP won't work.

[rustyk]

Check the battery grounds on the engine block.