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Hard to change fuel pump?

Hi all -

I own a 1991 Cherokee Laredo with the 4.0L engine. I have been fighting a hard start problem, which I posted earlier to the group and got alot of good feedback. I put an Actron fuel pressure gauge on the vehicle and here are the results. After I turn the key on, the pressure shoots up to about 40 PSI. It then drops rapidly within a few seconds down to almost zero. When running, it holds fairly steady at about 34 psi (the specs say 31 psi, is this a problem). So, I'm assuming from this that the problem is the fuel pump. My question is, how hard is this to replace? My mechanics instructor swears you need to drop the tank to do this, but according to my Chiltons manual you do not. Is there enought room to pull the entire pump assembly out with the tank still mounted? Also, when reinstalling, the picture shows a rubber stopper on the pump that needs to mate into a cup on the bottom of the tank. Forgive my ignorance, but since you can't see inside the tank, how in the world do you know if the stopper is sitting inside the cup? Do you just go by "feel".

Thanks so much, Bud

Reply to
Bud
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This sounds normal. The pressure should drop to zero, within a few seconds, if the engine is not cranking. What you want to find out, is the fuel pressure while cranking.

Earle

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Reply to
Earle Horton

That pump sounds like it might be working ok. I would be suspecting the anti drain check valve or regulator.

Once running at the 34 psi, you shut it down and watch the pressure. After 1/2 hour it should still be holding 19-39 psi.

My book then says to pinch off the return line with the engine running. When the pressure reaches 95 psi, shut down the engine and take a reading. Then wait another half hour. If the pressure drop is about 20 psi, suspect a bad regulator, if it a much bigger drop, the check valve is bad. Both are independent parts.

You are correct about changing the pump, you don't have to drop the tank. Just observe the placing of the lines so you can put it or another in the same way, but I believe it is keyed or only fits when it mates up inside.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

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Reply to
Mike Romain

Hi, Mike is correct, the pump can be easily changed without dropping the tank. It's a 30 minute job at worst. Spdloader

Reply to
Spdloader

Take digital pictures of it from as many angles as possible before you start so you don't need to depend upon remembering correctly. Tomes

Reply to
Tomes

Reply to
philthy

Park it on an incline, so the front is higher than the rear.

Spdloader

Reply to
Spdloader

I believe the lines are two different sizes, and the pump/sender combination only fits one way. You'd have to be a dufus to mess this one up.

Spdloader

Reply to
Spdloader

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