Engine/Transmission (1994 - 1998) Bad lift pump?

[Josparkz]

My truck started to lose power and boost one day last week. I figured it was lack of fuel cause my egt's were not getting hot at wot.

I checked the screen, clean. Changed the filter. Stretched the overflow spring. No difference. I rigged up a fuel gauge at the inlet to the p-pump. Neddle oscillated wildly between 22 and 66 psi.

I unplugged the solenoid and cranked it for 30 seconds into a container and got maybe 2 ounces.

I pinched off the return line and fired it up. Zero pressure, died out real shortly. I unclamped it, fired it up, and put the clamp on while running. Pressure started to drop right quick, and truck started to die out.

Does this sound like my lift pump is only going to last 185K miles?

Thanks.

 

[Joe G.]

It's possible that it is a bad lift pump, but unlikely. You probably have an air leak. Since it drops so fast, I would suspect the fuel heater. Remove it and see what happens. Use a 17mm socket to remove the fuel stainer. Remove the fuel heater with an 8mm allen wrench. Put the fuel strainer back on where the fuel heater was. If that fixes it you can leave the fuel heater off if you live where it doesn't get real cold.

 

[Josparkz]

I might as well give it a shot. It's not snowing out and I can't get a pump today anyhow.

I'm curious as to what this snubber device you've hooked up to your fuel gauge is.

Thanks.

 

[Joe G.]

The snubber and needle valve is to damp the pressure spikes so they won't wreck the pressure sensor. A 12 valve lift pump will beat the sensor up pretty bad without those items.

 

[Josparkz]

The snubber and needle valve is to damp the pressure spikes so they won't wreck the pressure sensor. A 12 valve lift pump will beat the sensor up pretty bad without those items.

I guess what I meant to ask is where do you get this snubber, and does it only work on electical gauges?

Thanks.

Joe

 

[Josparkz]

WHOOOOPS.

I guess in the light of day I saw that I had the wrong line pinched off.

The pressure went up this time.

However, it only putting out 2 ounces (filter output) as opposed to 10 ounces(filter input) of fuel in the prescribed time still has me suspecting the pump.

Further searching will continue.

 

[Cooker]

How high did the pressure go up? Did it go up quickly or gradually?

 

[bmoeller]

The rubber fuel supply line could be letting in air as well. Does the fuel drain on the fuel filter canister leak fuel?

 

[Josparkz]

How high did the pressure go up? Did it go up quickly or gradually?

About 80 psi. Fairly quickly, maybe 15 seconds or so.

 

[Josparkz]

Does the fuel drain on the fuel filter canister leak fuel?[/QUOTE]



Nope

 

[Joe G.]

I guess what I meant to ask is where do you get this snubber, and does it only work on electical gauges?

Thanks.

Joe

I got the snubber at Graingers. The needle valve is available at any place that sells fittings. I originally put the snubber on for a mechanical gauge. The needle was banging back and forth so bad I was afraid it would break. The snubber didn't do enough so I bought a needle valve too. It works if it is barely open so the gauge just does work. In fact, I think the snubber is overkill. The needle valve should work without the snubber. I got tired of the ugly mechanical gauge so I changed to an electronical gauge and used the same snubber and needle valve to protect the sensor. There were too many sensors being reported on these forums that were failing because of pressure spikes. In addition to the fuel pressure gauge I have an alarm switch on oil pressure and fuel pressure that will turn on a large red light if either is below 10 PSI.