rare stall leads to many questions

[Simzie]

Was out today replacing brakes on my boat trailer,when I was done decided to take it for a quick run to see if it was ok. When I pulled over briefly to check something, my truck stalled, and had some minor difficulty in restarting it, cranked over but no fire, finally restarted and was fine. I decided then it was probably over due for a filter change. That went fine until I tried to prime the new filter, I could hear the lift pump run briefly, cycled the switch several times, but couldn't get fuel out the bleeder. I finally removed the fuel pump relay and jumped the terminals, bingo! fuel. Truck started fine, went to bleed the fuel at the brass fitting...nothing, :confused: didn't even stall, just a brief trickle of fuel.I dont have access to a fuel pressure gauge, but my gut feeling is the lift pump going bad,I hear it cycle at start up and at shut down so that tells me the rest of the circuit should be good,BTW, I now have about 59,000 miles on the truck, about 20,000 on a new fsd and cooler, Im not ruling out the fsd yet, but the priming issues definetely has me concerned. any feed back would greatly be appreciated, thanks Simzie

[Dan Nicholas]

Simzie,

You maybe on the right track with the lift pump. Diaphram could be worn. If the diaphram is worn, typically you'll have hard starting symptoms if the truck sits a couple or 3 days. The worn diaphram allows fuel to drain back to the gas tank leaving air in the lines after the lift pump. This is what happened to my truck. Do you have any starting symptoms? Lift pump cost me $149 from NAPA.

[Andy Chesek]

Do you guys have any Advance Auto Parts stores up your way? What people pay for lift pumps at NAPA makes me cringe.

Down here in York, PA, NAPA wanted $113 for a lift pump with a 1-year warranty. Advance Auto Parts wanted $53 with a lifetime warranty. Obviously I went with Advance.

[Simzie]

Ok, update time....Hasn't stalled since my original post, but since then I have done some poking around. While the truck was running I checked voltage at the lift pump, steady 13.8 volts, I cound feel the pump running, felt warm to the touch,while the fuel lines were cool. Hard to say if the pump was running smoothly while as the engine noise overrules all other noise around
Got a question though, Does my vintage truck still use a oil pressure switch to control the fuel pump? I only have two wires to the fuel pump and really could not locate the OPS with a quick visual glance at the rear of the motor, tons of wiring, fuel filter and glow plug controller, Is it under the fuel filter or off to the side?
I have done a search on the OPS and all that I have seen are earlier model trucks. I was hoping to check the voltage across the terminals, or possibly install a relay to relieve the OPS terminals, but guess I have to know if my truck still uses this type of system or not.
Im moving soon so all my manuals are all packed away, its guess work time
Thanks Simzie

[MTTwister]

Sim.. - I'm sure it does. The actual OPS is burried in the valley under the Intake, next to and in from of the Fuel Filter housing on the drivers side.

I did a thread on doing the OPS relay, with some hints on how to find the wires. Can't say for sure I ever saw the actual OPS down in there!

http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=007116

[rjwest]

NO 96 and later do not use the OP's for lift pump primary control.

The OP's sw is a Fail safe on 96 and latter:
IE If Lift pump realy does not power lift pump., Cranking eng will cause oil pressure to apply 12 volts in parralrl to the lift pump.

Normal operation The lift pump relay is controlled by the PCM. It will turn on lift pump for a few seconds when ign is turned on. Than turn on lift pump when eng rpm is sensed.

ALSO: There is a jumper connector under the hood
to allow 12v to be applied to the lift pump
for test and bleeding....


Look under hood, driver side , next to hood hinge.
find a wire bundle. look closely at bundle where it
bends down to firewall.

there is an open ended conector ( nothing attached.)
jumper to 12v to run lift pump.....

Again only on 96 and later ( obd2 )...

[Simzie]

Another update, Stalling got progressively worse, to the point where it would not restart.Had it towed home where I replace the lift pump,got much improved fuel pressure and steady stream of fuel out of the water drain.Took it out for a ride and all appeared to be fine until I restarted an hour later, drove 50 feet and died completely, would restart and go another 50 ft. Its at the dealer now, they got a code for the shut off solenoid on the pump....why do I have my doubts that this is really the problem? I think I need some ammo for attempting to get a new i.p. for Im sure its another failed FSD. The tech seemes to think GM will kick it back as I have installed a FSD cooler remotely mounted.The original failed FSD is still mounted to the pump so I will probably tell him to reconnect that one and try again.
I'll post again as the saga continues...Simzie

[rjwest]

I had a fuel shut off solenoid fall ,
same symptoms, hard to tell if IP or Fuel solinoid.
If there is really a code that points to Fuel solnoid.I would think they are correct.??????
That use to be considered part of the IP, ( replace IP )don't know what latest Service leter states.

Are you sure the code is not a IP code.
Fuel control solenoid ( FSD driver pulses it ), the part that controls injection duration and timming....

You should have reconnected the pump mounted FSD,
before it went to dealer,
Ask them if you can restore to Original,
and rediagonose.

The Fuel shut off Solenoid cost about 43 bucks and no more than 1 hr to replace.....

[norm]

My local NAPA lift pump was $97.99 a couple months ago. It was made by Carter. Two Pep Boys pumps before that one (supposedly Borg-Warner?) failed too fast (at about the same price).