Fuel Pump Question On 1984 Jeep Xj With A 2.8

[ICEBOX]

trying to figure out why i keep ruining the fuel pumps. 3 new pump dead. Install it and it will run for a few seconds then fuel gushes out the diaphragm vent hole. .

 

anyone ever run into this. And does anyone know if maybe it is possibly missing a fuel pump spacer ?

[jimoshel]

Thought '86 was the last year for the 2.8 in Jeeps. Assuming that was a typo, or some one did a engine swap, there is no spacer. It's a little bit of trouble but to try and pin point the problem, tighten the 2 mounting bolts to where the pump rod is just contacting the cam. Turn the engine over. Observe the fuel pump, Slowly tighten the bolts while keeping and eye on the pump. It should never get so tight you can't wiggle it. Check the possibility it's the wrong push rod.

[cruiser54]

No kidding. I'm confused...........

[ICEBOX]

@jimoshel . you are right I typed the wrong year . the jeep is an 84.

[Eagle]

Those fuel pumps are mechanical, and they operate by an arm that's activated by a lobe on the camshaft. If the cam pushes the arm too far, it destroys the diaphragm in the pump just because of overtravel.

 

The cure is to space out the pump body from the block so the pump arm contacts the cam lobe at the very tip. If you still have the pumps that self-destructed, take a look at the arms and see if you can find any marks that show where the arm made contact wityh the cam.

[jimoshel]

Jeez,,hate to disagree with Eagle 'cause when I do I'm usually wrong. But in this case, Page B67 FSM 1986 MJ. If I have to I have a couple sitting on the ground. I can go pull one.

 

[jimoshel]

The Jeep manual doesn't show it but the Chevy S10 manual shows where some engines have a block, spacer, between the pump and block and some don't. Something to check. If you want, pull the pump and measure the length of the rod. I will pull one of mine and compare. Also something to think about. The later years S10 V6 has a plate covering the hole where the pump mounts and a electric fuel pump in the line. There is a fuel filter mounted where the mechanical pump was.

[ICEBOX]

Ok guys I will get the pump out and see what length is. and I will get the engine number and make sure is was not swapped out .

[Eagle]

Jeez,,hate to disagree with Eagle 'cause when I do I'm usually wrong. But in this case, Page B67 FSM 1986 MJ. If I have to I have a couple sitting on the ground. I can go pull one.

 

Mea culpa.

 

I confess, I've never seen a 2.8L fuel pump. I know it's mechanical, and every mechanical fuel pump I ever saw, from my 1939 Hudson right up through the 70s AMCs and small-block Chevies, had the same mount and the same arm. So I made the classic blunder -- I assumed.

[88blackpearl]

I don't have any experience on a jeep fuel pump spewing out gas, But on my 75 camaro, I kept having trouble with my fuel pump. While ideling it would work with no problems, but a trip around the block, when I turned the engine off, it would spew gas from the pump and the gas tank would make a hissing sound. Turned out, the gas cap vent had stopped up with years of dust or whatever. I bought a new vented gas cap and it fixed the problem. Maybe this would help.....I dunno.....

[HOrnbrod]

The Jeep manual doesn't show it but the Chevy S10 manual shows where some engines have a block, spacer, between the pump and block and some don't. Something to check. If you want, pull the pump and measure the length of the rod. I will pull one of mine and compare. Also something to think about. The later years S10 V6 has a plate covering the hole where the pump mounts and a electric fuel pump in the line. There is a fuel filter mounted where the mechanical pump was.

 

The rods are the same 84-86. However, the fuel pumps for 84-85 were different than the 86 pump.

 

83500873 for 1984-85

83502715 for 1986

 

Try cross reference the part numbers first to be sure you have the correct pump installed.

[jimoshel]

The rods are the same 84-86. However, the fuel pumps for 84-85 were different than the 86 pump.

 

83500873 for 1984-85

83502715 for 1986

 

Try cross reference the part numbers first to be sure you have the correct pump installed.

 

Well now, that was so obvious I never thought of it.

[ICEBOX]

Ok . I thank everyone for the input. I will check the year and look at both pumps. and I will look into the gas cap as well.

so for now. TO BE CONTINUED...... Dunt dunt DUNNNNNNN.

[jimoshel]

And speaking of obvious. Should have been the first thing to suggest. Do you still have the old pump? was it working at all? Did you place it and the new one side by side and compare them?

[Eagle]

On both my '39 Hudson coupe and my '47 Hudson pickup, I replaced the mechanical fuel pump with a Stewart-Warner electric fuel pump It made life a WHOLE lot easier.