Sudden Death and Melted Wires

[Alan C]

Long Story, but here goes.....
I purchased a 1997 GMC 2500 6.5 TD new. My dealer warrantied the fuel pump at 72,000 miles in July 2000. The truck now has 146,000 miles. The current driver of the vehicle had been driving with a failed electric pump for about 6 months. He was experiencing intermittant stalling which I attributed to the failed lift pump. We replaced the pump and he continued to report intermittant stalling that was getting progressively worse. About 1 week ago the truck died completely....crank, no start.
When the hood was opened, the smell of burned electrical something was evident. The only obvious thing I noticed was a blown fuel solenoid fuse. Replaced fuse, turned key....poof! Okay, so it appears we have an electrical problem. Brought in an acquaintance with a bit of 6.5 experience....he figured FSD, so we tow the truck to our shop. Hook up the computer and yep, fuel solenoid driver. Okay, no problem...we tear it apart and run down to the local Stanadyne dealer who happens to have the parts in stock. Now, as we removed the FSD, we noticed that the wiring harness plug was MELTED. I mean, beyond recognition, the resistor is gone!. Anyway, Stanadyne sells us the parts and then proceeds to tell us that there is no way we are smart enough to install the parts and make it run (so much for future business with those guys). So, we install new FSD, replace everything and diagnose with the computer.....no codes. We try to start....and try.....and try.....and disconnect injector lines...no fuel. So, we remove everything and pull the pump and take it to a nicer Stanadyne dealer. He diagnoses and finds that pretty much everything electrical on the pump is burned..Including the fuel solenoid itself. Now he repairs pump no problem....BUT....he is warning me that this is the most severe electrical problem he has ever seen with a 6.5 pump and he is cautioning that there could be additional wiring problems that need to be addressed to avoid frying all my expensive new parts.
So now the questions:
* Has anyone had an FSD fail with severe melting of the wiring plug?

* What is the correct resistor for a '97 6.5 in a GMC 2500 4x4? And does it really matter?

* How many amps does the Fuel Solenoid circuit need to operate? Can I install a smaller fuse to test start?

* Is there any particular section of the wiring harness that I should check for damage?

Any comments or thoughts would be appreciated!

Alan--completely demoralized by diesel pickups

[ucdavis]

re: bullets 2 & 3:
2) "Correct" resistor is based on final electronics of ea. pump according to GM Technical Bulletin, and should be determined by rebuilder. In reality, many here just use a #5 if correct one is unknown, or a #9 is trying to maximize fuel delivery (higher # = very slightly more fuel delivery rate). So it won't matter sufficiently to sweat the perfect #.
3) Use same fuse size. If you have short remaining it will blow the fuse nicely. FSD harness uses tinned wire in high-temp insulation which is high grade stuff, but I believe that's because of the location within engine-heated confines (similar to the orange glow plug wires on #4, 6 & 8 that get heated by the exhaust manifold & turbo pre-housing). The FSD gets quite hot, & if I was you & doing all this work, I'd put it on a remote heatsink. Kennedy Diesel sells the harness & a good heatsink (I think its kennedydiesel.com).

[Alan C]

Oh Boy!!! Even more fun!!!
It seems that the fuel solenoid is on backorder all the way to the factory. So my options now become...Use a used fuel solenoid and pray the thing works or buy a new pump....Of course the Stanadyne guys don't want to buy the new FSD back.

Question:

How would I go about installing a NEW fuel pump (no scribe marks)and get it timed correctly?

Can anyone other than a stealership do the TDC offset thing?

Thanks for the help!

Alan-----now understanding why they still make gas engines.......

[cruzer]

Doesn't Kennedy sell them?

[ucdavis]

Now that I think about your problem, I recall buying a used IP off ebay that had an PMD w/a burn on it. I thought it odd & assumed it was burned from outside by something else. But on removal & inspection it appeared that the fsd had burned up from the inside till it had an exit wound about 3/8" diameter & smelled really obnoxious. I chiselled the connector off the fsd & it is now the engine-end of my extension wire loom for remote fsd. Could have been the same failure as you've experienced; didn't appear to affect anything else on pump, although fuel solenoid could have been TU.
About rotation of new pump w/out a mark- simple: use a caliper & measure distance on old IP from mark to angle on flange by mounting bolt, then scribe mark on new IP in same position. Install new pump w/marks aligned. I did this & TDC offset was 0.2 degrees off when firing up the new IP, i.e.
TDC offset was close enough it wouldn't matter (you have more play than that in timing chain) & you probably won't need to do TDC Offset Learn. If you do or just want it checked, any shop w/a Vetronix Mastertech, Tech2 or Snap-On scanner w/the correct software can do the TDC function. I rented one & checked it myself (had to; the rig was 650 miles south of the US border & no service for electronic diesel injection there).
I would check wiring under the dash along w/under the hood B4 restart. IP communicates w/computer so wiring is partially common. Might even split the large wiring loom in a central spot & see if there's damage in there. Looking for deformed insulation; try following IP wires that cooked for starter.

[Alan C]

A quick update...

Looks like I'll go with a used solenoid
I'll have the pump back tomorrow and hope to get it installed by this weekend. Then we'll see if the scrap iron with wheels runs. Thanks for all of the input and I'll let you know how it turns out.

Alan-- Sell 'em all, I'll walk

[Alan C]

Just a quick update.

New solenoid, new resistor, new FSD, have seemed to cure the problem. Runs good, better power than before. Of course, now it doesn't start good when cold....but nothing a block heater won't cure.

Thanks for the help!

Alan

[ucdavis]

Didja need to retime it, or could you get new pump rotated correctly by above instructions? Or do you know (maybe poor starting could be timing?)?
Also, if you have white smoke on start it could be glow plugs or controller; a few new posts on that now that its good & cold.

[StephenA]

Hi AlanC- still got the old failed FSD? I'd like to analyse it... [img]smile.gif[/img]

[twaddle]

Watch out Turbo Power,
You're starting to look like a vulture hovering above any sickly looking FSD's. hee hee

regards

Jim Twaddle
Biggar, Scotland

[G B Sisson]

I recall seeing a photo on TDP of a homemade right angle torx screwdriver someone had made up for removing FSD off IP without removal of intake manifold. Does this work? If I had one,I'd pull mine and send it to Mr. Ambrose. It was down to stalling about every 10 miles when I abandoned it last week....Gary