Died at 70 MPH..no start...don't hear lift pump

[TxBeaux]

I was on the road for maybe 10 minutes yesterday and my 96 Dually just died. No start, then or now. Replaced fuel filter and no fuel at bleed valve. I don't hear the lift pump working when I turn on the key. Lift pump is Delco and less than a year old. OPS (Delco) and relay are perhaps 1 1/2 to 2 years old. New FSD on remote heat sink 6 months ago. Sounds like OPS or relay, perhaps lift pump. What would you do next?????

[HowieE]

When the key is first on the lift pump relay supplies voltage to the lift pump. To check the relay look for voltage on the gray wire coming up from the OPS. If you have voltage there when the key is on and you do not hear the lift pump I would check for voltage at the lift pump, on the gray wire. If you have voltage at the lift pump, on the gray wire, and still no pump I would replace the pump.
If you did not have voltage on the gray wire coming from the OPS apply voltage to the gray wire and check for the lift pump. If jumping out the relay causes the pump to work check and or replace the lift pump relay in the fuse center under the hood. There are 2 relays there that are the same size. The easiest way to check the relay is just swap the 2 and see if the pump works when the key is first on. If jumpering out the relay and or swapping it did not do the trick check the ECM B fuse under the hood. You can check this fuse by checking for voltage on the orange wire at the OPS. That wire should be hot at all time.

[charliepeterson]

I agree with Howie.


I recently went through the same thing with the truck just shutting off and difficult restarting. My Lift pump was fairly new too. For what ever reason I think the Lift pump locked up causing a big fuel restriction. No warning either. New OPS and Lift pump and we're back in service.

[TxBeaux]

No juice at the gray wire coming from OPS. Changed out with spare relay, nothing. Jumpered relay, nothing. Checked ECM B fuse, blown, replaced, engine started right up. Thanks Howie!!!!! Is this good news or bad news???? Why did the fuse blow????

[HowieE]

That fuse supplies the following, fuel pump through the OPS, vechical control module, fuel pump relay, power train control module. All are orange wires circuit # 440. They are spliced in the engine harness about 3 cm. from the brakeout to the RH glow plugs. That will be a tough place to get to but if the problem happens again I would try to in there and sperate the wires and fuse each sub circuit and see which one blows.
In the mean time consider installing a relay across the OPS to reduce the contact current. Details on my web page.

[Billman]

ECM B fuse blown, hmmm...

I recently had the same problem. Died while driving for no reason. After looking it over, I decided top replace the lift pump because it was original and possibly my problem. Put 500 miles on it to verify because I was taking a trip with my trailer. Everything seemed good until the day I left. I was doing 70 with the trailer in tow when all of a sudden--died. I pulled over and told my passengers not to worry, we've got 500 more miles before it happens again. Replaced fuse and got back on highway. Within 2 minutes--died again. I had to turn around because I didn't have enough fuses with me.

I'm still chasing this problem. 2 months later...hasn't happened since.

[rjschoolcraft]

One question,

When you say to check voltage at grey wire with key "on", do you mean in the "start" position? My lift pump will not run with the key turned to "on", but will run when the key is turned to "start".

[TxBeaux]

Ronniejoe....
My ignition works as follows >>>>
Lock...
Unlock/Off...(nothing happens)
On...(Lift pump and all lights come on, Radio works, fan blows, buzzer comes on)
Start...(Starter engages)
I have a 5-speed if that makes any difference.

The OPS, Relay and lift pump are all fairly new and I think they are probably OK. I've been in that wad of wires behind the fuel filter and did the dilectric grease thing to all the connectors about a year ago. I have 220K on this ole gal and she runs strong when she runs and always with a load. If this happens again and it wasn't just a suicidal fuse, I'll get back to the wad of wires. For now, I think I'll just go watch the grass grow for a while :cool: it's my day off....Thanks for all the great advice, Jim