tech diagnoses stalling

[alberta]

I have a 94TD 3500 crew,162,000mi.that stalls infreqently.My son has replaced the PMD,beefed up the new battery posts,checked all the grounds,repaired all dicoverable wires.Still stalls.Took it to Chey dealer.Tech spent a lot of time on it,reported on test drive it did(luckily) stall.He reports that it didn't code nor did his meter.He rec:replacement of the IP.Also he found a lot of rust in the fuel filter bowl and advises the fuel tank be dropped and the lines be cleaned,price-4200.00.It occured to me that perhaps if the fuel system was cleared of all possible particles mayby the injector would behave. kevin

[Turbine Doc]

Something the size of visible rust is pretty big and would be stopped by 5 micron filter of the filter manager, and also the last ditch screen on the transfer pressure regulator at inlet of IP (I dont know micron rating of it, but it is pretty fine mesh), rust in the bowl is a good thing means it most probably didn't make it to the IP or injectors would have to be particulate less than 5 micron passing, and wear form it would cause poor mpg-idle-hard start, not the problem of cutting out.

Bad however in that your lift pump digested rust so you could be having delivery problems to the IP, do a full diagnostic of lift pump delivery pressure, also dropping & cleaning your tank as a 94 isn't bad idea, there is a pickup sock tube (70 micron) in tank that if stopped up will starve you of fuel, happened in my 98 this summer.

The shutoff solenoid "silver thing" on top of IP needs constant 12V while running if that is dropping out or the solenoid itself is bad that will cause cutoff just like a failing PMD

Replaced PMD with new or ebay "used but good", mounted where on IP or remote mounted;

if remote mounted, remote mounted where, anywhere under hood has not proven out to be the best location for many myself included, 3x underhood fails until I remote mounted out of engine bay. I chose a Heath driver as it carries as warranty for subsequent fail for 7 years, nodoy else in the industry carries a warranty for that long. Before conclusively saying it's PMD ignition switches can als cause same symptom you are describing, also with a 94 your IP may have a RFI filter in the harness that sometimes act up,.

With help of the gang here you can save a ton of money doing the repair/troubleshooting yourself, collective wisdom this site far surpasses that which any GM dealer can offer as their techs no longer see the 6.5 frequently enough to be profficient with them. My advise is to get it home and work on it yourself and become the 6.5 expert with the assist of members here.

[bbudus]

Mine was doing something similiar, so I contacted Bill at Heath Diesel, we decided to replace the filter wiring harness...ding ding ding, we had a winner. But just because I never wanted the truck to stall in the middle of a busy intersection again, I also installed the Heath remote PMD kit and heavy duty lift pump, and the oil pressure switch was replaced.

[RobK]

Did anyone else notice the price tag?!?!?! $4,200?!?!? What are they charging? $500/hr?

[alberta]

Thanks,I'm searching around for method to check the lift pump.If we do drop the tank,do we need to also clear the fuel lines? kevin

[alberta]

In the process of trying to clean out the fuel lines. We removed the fuel tank and inspected the sock. The attached photos show a multitude of silver flakes and a brownish coloration of the sock. The silver flakes appear to be the inner coating of the fuel thank as evidenced by the sctrach marks we made on the inner wall of the tank. Are these unusual findings? Do we need a new tank and sock?

[Robyn]

Wash the tank out as good as you can and install a new sock.

Flush the lines out as well as the fuel manager (filter)
make sure the soft lines on the engine are in good shape. ( the ones that come from the filter to the IP and the drain line under the manifold.

Once this is done install a freshh filter and power up the lift pump and bleed the fuel system of air all the way to the IP.
Once all the air is out there be sure the drain line also is purged of any air.
Once this is done that part should be fine.
The optical sensor on the IP can get hinky and cause an intermitent stall but then restart and not toss a code.
The filter harness to the optical sensor can also go sour. This wiring harness is about 8 inches long and plugs into the top of the IP and then into the main engine harness under the air plenum.
The air plenum must come off to readily access this little creature.
The filter harness was peculiar to the 94-95 models and has a little black box in it that the wires run through.

If no codes are being shown this sort of thing can be agravating.
The oil pressure switch controls the power to the lift pump and if the switch fails it can in some cases cause stalling.

Make sure you have 2-5 PSI at the IP with the engine running (fuel pressure)

Keep us posted

Robyn

[alberta]

Robyn,thanks,we will flush the lines.etc.Did you view the attached photos and the silver flakes that were floating in the fuel,clearly from the coating on the inner wall of the tank?When you state "flush lines",is that done with the diesel?One of the reasons we checked the tank was the tech's finding of a rust coated fuel filter housing,his opinion water had gotten into the system and perhaps the fuel tank. kevin

[JohnC]

How'd the nickle get in there? ;)