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Strange problem after installing new fuel pump

oldskoolsleeper

NAXJA Forum User
Location
North Carolina
Hello everyone,

This is my first post, Ive been all over this forum lurking just never registered.

I have a 1987 XJ with the 2.5L. :tear:

It wouldn't start one day after a few good years of faithful service. I traced it to the fuel pump crapping out. I had 12V at the connector, no noise, and no fuel when the key was on.

So I replaced the pump, the sock filter thing on the bottom, and the canister fuel filter, too.

Now the jeep acts like it has no power. I can BARELY get it moving in first gear. It bucks and sputters and wants to die. Also idles pretty bad.

So, whats the deal here guys?

Thanks...
 
few things you can check...
1. fuel pressure
2. tps-throttle position sensor

never had a 2.5 only the 4.0's so not sure what other sensors it may have.

2 dumb questions but I have to ask them, sorry
1. you filled the tank back up correct?
2. not sure if it is possible(like I said never had a 2.5) but when you put the lines back on the fuel pump sender did you put them(is it even possible) on backwards i.e.-return on the send line and send line on the return line?
 
few things you can check...
1. fuel pressure
2. tps-throttle position sensor

never had a 2.5 only the 4.0's so not sure what other sensors it may have.

2 dumb questions but I have to ask them, sorry
1. you filled the tank back up correct?
2. not sure if it is possible(like I said never had a 2.5) but when you put the lines back on the fuel pump sender did you put them(is it even possible) on backwards i.e.-return on the send line and send line on the return line?

Thanks for your reply,

yes the tank is full.
and I checked tps -- its got the 5V with key on, although I couldnt find an easy way to check it while its plugged in and moving the throttle at the same time. I understand I'm looking for something like 0.8V at idle.

1. I havent got around to checking fuel pressure yet because I thought the parts stores rented them out, and they dont around here. But if I were to check the fuel pressure I understand I should look for around 50lbs all the time.

2. Trust me, I've been going nuts over this myself. I distinctly remember the two lines being different sizes along with the sizes of the hoses. So I'm 99% sure thats not what I did.
 
Seems to me that the 87 2.5 was TBI injected, the 88 is still that way per FSM.

Pressure on the TBI 2.5 per 88 FSM would be 14.5 psi. Fuel pressure is also adjustable at the fuel pressure regulator.

Ok, so you had zero issues until the pump wouldn't run. Replace pump, now you have issues. Logic tells me to go back over what you did, confirm that everything is Ok.

Any chance the fuel filter is in backwards?

Any chance the new pump was Airtex? Some reports that those pumps are easy to wire up to run backwards.
 
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Seems to me that the 87 2.5 was TBI injected, the 88 is still that way per FSM.

Pressure on the TBI 2.5 per 88 FSM would be 14.5 psi. Fuel pressure is also adjustable at the fuel pressure regulator.

Ok, so you had zero issues until the pump wouldn't run. Replace pump, now you have issues. Logic tells me to go back over what you did, confirm that everything is Ok.

Any chance the fuel filter is in backwards?

Any chance the new pump was Airtex? Some reports that those pumps are easy to wire up to run backwards.

Nah, I double checked before I installed the filter. I did take what looked like a set screw out of the throttle body, near the top, when I was looking for fuel pressure. It was an allen screw and I don't think its important but maybe I screwed the fuel pressure?
 
Yeah, I would get a fuel gauge on it and drive it. Duct tape it to the windshield so you can observe it while driving.

The fuel pressure regulator is attached to the throttle body and has a torx adjustment screw that you have to come at from the bottom.

Was there much contamination in the tank when you changed the pump?

Also, did you replace the rubber fuel line from the top of the pump to the tank flange--if you re-used the old one it might have split during reassembly.
 
Was there much contamination in the tank when you changed the pump?

Also, did you replace the rubber fuel line from the top of the pump to the tank flange--if you re-used the old one it might have split during reassembly.

It was surprisingly clean, really. Although the fuel filter was FULL of crap. I'm starting to think I should take apart the throttle body and clean it out plus blow some compressed air through the lines.

I'll have to find a buddy to borrow a tester, I try not to buy something I'm gonna use once :farmer:
 
I haven't figured this out yet but I wanted to share a link for anyone dealing with this TBI system on their XJ.

***DELETED LINK TO COPYRIGHTED FSM MATERIAL***

This link contains an AWESOME troubleshooting flow sheet, along with sensor info and everything.
 
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