(SOLVED) XJ Fuel Pressure/Injector Question - JeepForum.com

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post #1 of 31 Old 02-25-2017, 04:23 PM Thread Starter
dan4081
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(SOLVED) XJ Fuel Pressure/Injector Question

Recently my 96 Cherokee Country (Auto) has been hard to start.
After reading here I came to the conclusion it was a fuel issue. It is harder to start after sitting overnight...or after work.
If I put the key in position 2 for a while and then do it a couple of times until I hear the pump go on and off as the line gets pressurized I can start it on the first or second try.
Strange thing...reading other posts they say to put it in position 2 for a few seconds a couple of times. I have to leave it in position 2 for about 2 minutes and then back and forth a couple of times and I can hear the pump finish and then I can start it up.

Last week I changed the fuel pump figuring it is the check valves. No change.
Today I bought a fuel pressure tester and did some experimenting.
Key in position 2 pressure goes above 45
Start truck and at about 49psi.
Turn truck off and it drops to 40....then to just below 30 after one hour.
Almost the same readings with the fuel line clamped just forward of the tank.

Btw,,,cam position sensor less than a year old, same with crank sensor, IAC cleaned, rebuilt PCM within last year. Plugs look good.

Any ideas where to go from here? Injectors??
Thanks


Last edited by dan4081; 03-20-2017 at 04:30 PM.
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post #2 of 31 Old 02-28-2017, 08:32 AM Thread Starter
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Just an update....problem pretty much solved.

Was frustrated after the testing I had done didnt point me to an answer so figured I would start over with testing the fuel pressure.
I hooked pressure guage up and started jeep...pressure at 49. Turn off and pressure drops to 26 within 1 hour.
Tried again but this time clamped fuel line before tank. Even though I had done this before I think maybe I didnt clamp tight enough because this time pressure stayed constant. As soon as I loosened clamp pressure dropped steadily.
No I'm getting somewhere!

Looked like the issue is the fuel pump...which I recently replaced. But, even though I had read warnings I went with an off brand. Swapped it out Sunday morning with a Bosch and its now starting right away.

One issue though...it stalls pretty quickly and I have to start it again...then it smoothes out and runs fine. Not sure why but at least so far its starting right up.
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post #3 of 31 Old 02-28-2017, 01:16 PM
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Quote:
Originally Posted by dan4081 View Post
Just an update....problem pretty much solved.

Was frustrated after the testing I had done didnt point me to an answer so figured I would start over with testing the fuel pressure.
I hooked pressure guage up and started jeep...pressure at 49. Turn off and pressure drops to 26 within 1 hour.
Tried again but this time clamped fuel line before tank. Even though I had done this before I think maybe I didnt clamp tight enough because this time pressure stayed constant. As soon as I loosened clamp pressure dropped steadily.
No I'm getting somewhere!

Looked like the issue is the fuel pump...which I recently replaced. But, even though I had read warnings I went with an off brand. Swapped it out Sunday morning with a Bosch and its now starting right away.

One issue though...it stalls pretty quickly and I have to start it again...then it smoothes out and runs fine. Not sure why but at least so far its starting right up.
Sticky fuel pump relay taking a couple tries maybe? Try swapping it with another relay and see if the behavior changes.

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post #4 of 31 Old 03-01-2017, 08:27 AM Thread Starter
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Thanks...Ill give that a look this weekend.
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post #5 of 31 Old 03-05-2017, 11:23 AM Thread Starter
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Swapped relay...no change. Really confused on this.

The long crank to start issue is really bad.

If I go out to the jeep and put the key in position 2 and leave it and then come in the house for 5 minutes or so the jeep will start up when I go back out.
If I just go out and try to start it it will take forever...cranks and cranks until it finally starts.

Really not sure where to go next. Seems like a fuel issue to me but am open to suggestions.
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post #6 of 31 Old 03-05-2017, 12:04 PM
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So...if you turn the key to on and let it sit for a few seconds and then start is it fine?

If th epump is activating fine and you're losing pressure I'm forced to think the check valve on your new pump is DOA. Did you use a store brand or an airtex or something by chance?

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post #7 of 31 Old 03-05-2017, 03:09 PM Thread Starter
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That's the thing....I cant just let it sit for a few seconds and then it starts. I have to sit and let the pump run for minutes before it starts.
And no...not a store brand.
First, had a Bosch in there that I thought had a bad check valve. Changed it to a store brand and still had the issue. Yanked that and replaced with a new Bosch and again, same thing.

Weird thing...I have a pressure tester. I can turn the key to position 2 (from cold) and see the pressure shoot to over 40 in a couple of seconds. But the truck still wont start easily until I let it sit and the pump runs for a couple minutes or I repeatedly try to start and let it crank and crank. Once it starts the pressure will read 49.

My next test...after it sits over night...is to hook the pressure tester up, turn to position 2, and see what it reads after a couple seconds. Then leave the key in position 2 and see what it reads after 4 minutes....before its ready to start.
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post #8 of 31 Old 03-07-2017, 04:33 PM
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My son's 96 XJ has a similar issue. However, the fuel pressure drops to zero instantly when the engine is cut off. Probably the check valve in the fuel pump module. The fuel gauge also does not work. My sons has yet to get a replacement fuel pump module. Pretty sure that's our problem.

You sound like you're actually getting fuel. Have you tried replacing the coil yet? That's a pretty cheap try.
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post #9 of 31 Old 03-07-2017, 04:44 PM
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Quote:
Originally Posted by dan4081 View Post
That's the thing....I cant just let it sit for a few seconds and then it starts. I have to sit and let the pump run for minutes before it starts.
And no...not a store brand.
First, had a Bosch in there that I thought had a bad check valve. Changed it to a store brand and still had the issue. Yanked that and replaced with a new Bosch and again, same thing.

Weird thing...I have a pressure tester. I can turn the key to position 2 (from cold) and see the pressure shoot to over 40 in a couple of seconds. But the truck still wont start easily until I let it sit and the pump runs for a couple minutes or I repeatedly try to start and let it crank and crank. Once it starts the pressure will read 49.

My next test...after it sits over night...is to hook the pressure tester up, turn to position 2, and see what it reads after a couple seconds. Then leave the key in position 2 and see what it reads after 4 minutes....before its ready to start.
I'm pretty much stumped. Your symptoms match either a check valve or a leak in the fuel lines. You've covered the pump a few times and it really seems like you should be able to see or smell a gas leak that bad. Best I can say is trace the lines a few minutes after you shut it off and look for drips.

I THINK a UV dye additive exists for gas, if you want to look for it with a blacklight. I could be wrong, but I'm pretty sure I've seen it. Might be worth a Google or a call to a parts store.

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post #10 of 31 Old 03-08-2017, 06:41 AM
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This could be as simple a fix as cleaning the throttle body and IAC thoroughly.

If you own a Renix Jeep, you'll want to check this out.

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post #11 of 31 Old 03-08-2017, 01:03 PM Thread Starter
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This could be as simple a fix as cleaning the throttle body and IAC thoroughly.
Thanks Cruiser (and everybody else who replied)...
I already tried cleaning the throttle body and the IAC.

Im 99% sure it is a fuel related problem...like I said above, if I leave the key in position 2 long enough that I hear the fuel pump run until it turns off, it will start. If I dont wait that long it will take many many tries of long crank before it starts. Also, if I use the truck and turn it off and within a minute or 2 start it it starts right away. If it sits for even 10 minutes or more its hard to start.

This weekend I am doing two things...1, I'm yanking the new Bosch fuel pump I installed and returning it to Advanced and getting it swapped for another. That way I can rule out a defective fuel pump...its under warranty so why not.
2, I ordered a set of refurbished injectors from injectordyne....figured for the price might as well rule them out as the problem.
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post #12 of 31 Old 03-08-2017, 02:39 PM
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I'd do the injectors first.......

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post #13 of 31 Old 03-08-2017, 04:32 PM
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Have you checked for spark at a cold start? Sounds like maybe the coil or other electrical part is failing and leaving the key on "warms" it up.
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post #14 of 31 Old 03-08-2017, 04:37 PM Thread Starter
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Originally Posted by festerw View Post
Have you checked for spark at a cold start? Sounds like maybe the coil or other electrical part is failing and leaving the key on "warms" it up.
Actually, no I haven't. If the injectors and pump don't solve it that's the next road I'll go down!
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post #15 of 31 Old 03-08-2017, 04:40 PM Thread Starter
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I'd do the injectors first.......
Thanks....injectors first!
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