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Bad fuel pump?

murfs66

NAXJA Forum User
Location
So Cal
Well I just picked this cherokee 88 4.0 A/T up a few month ago and have replaced just about everything on it.

New MAP,o2 sensor, new temp unit, new Fuel injectors, new plugs, new cap and rotor, new fuel filter, new battery, new battery cables,new strap, and then some.

The only thing I didnt change was the fuel pump. When I bought hhe jeep It sat for aa few years. I had about 1/4 tank of gas thaat I should have drained, but just topped it off. I chnaged the filter and it had sutt and other white film.

Well I was going out of the drive and it just died. I checked the fuel rail for pressure and nothing. I pulled the fuel line off and tried to start it , not a spit of gas. I can hear the pump, but dont see any fuel. I can hear the fuel in the tank making noise when pump is on.


What is it.
 
I also have no dash lights from day one, but that is another can of worms I HAVE TO TACKLE. It ran great until today. I have only put about 40 miles on it since I bought it and tons of parts.
 
Get yourself a cheap fuel pressure checker and test it at the sharader valve on the fuel rail.
The fuel pump can still make a noise and not pump fuel.
 
Get some test results with a fuel pressure gauge. But if you have NO pressure at the rail and you can hear the pump energize and run for about 2 seconds when you turn the key to the ON position (the way it is designed), then it almost assuredly is the pump itself.

With an 88, you should have 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approx. 39 psi. Good to verify all of this with that gauge to confirm proper fuel delivery.

If you buy a pump, don't buy an Airtex. No lack of reliability threads about them. I specifically seek out Bosch when I am shopping for a fuel pump. They make excellent pumps.
 
I have no pressure at the valve. I'm doing the fuel pump this weekend.

My neighbor works for Jeep , so he's hooking me up at cost.

Thanks guys
 
there is zero need for a fuel pressure gauge... ::facepalm:: if you pull the fuel line and nothing comes out, is it 26psi? noooooo its 0psi ::facepalm::


check the lines, ive had crud clog up the lines. start by pulling the fuel tank side of the fuel filter, then prime. if it flows to this point, your leak is upstream. if not, downstream.
 
If your tank has any rust in it from sitting with a 1/4 tank then get a new one. It is a loosing battle to try to knock that rust out and keep it out. I went through two pumps before i got a new tank. Plus one on the bosch. I had two airtex that the rust took out. Kept the sending unit and replaced the pump with a bosch with a new tank and it is quiet and strong.
 
Checking Fuel flow is a good idea, look for the fuel filter just forward of the rear axle on the driver’s side.
If fuel is not even getting to the inlet side of the fuel filter it will never make it to the fuel rail.
Keep us posted of progress.
I also have a ‘88 and live in West Covina
 
I had that issue on my 89 DD. Turned out that it was shorting out. The power wire on the pump itself was up against the body of the pump. I bent it back off the pump body and has been fine ever since.
 
My bet is the short hose from the pump to the mounting bracket inside the tank.

By the way, if you are pulling the pump, I recommend the factory large Oring on the mounting and the anular ring hold down. They have had enough problems with them leaking that they redesigned it and the new design works much better.
 
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