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Discussion Starter · #1 ·
My friend has a 1992 4.0/auto YJ. Ever since he bought it it has had a intermittent really long cranking problem. Some times it will fire right up other times you have to crank on it for quite a while and he told me sometimes it fails to start.

I have done a lot of work on this jeep but i cant do all of it and most of the time im not anywhere near the jeep and he messages me about it and what could be wrong.

So far we have done a complete basic tune up. plugs, wires, cap, rotor and we replaced the fuel pressure regulator and fuel filter and none of it has helped. So i started thinking maybe it is the capacitors in the computer so i told him to check it out and he ended up replacing all 3 of them. It seemed to fix it at first but now it is back to cranking forever before it starts.

When we had the tank off it had a newer Bosch pump on it so we left it alone. The tank and the sock on the fuel pickup were clean. So i am thinking it must be a fuel problem either a defective pump bleeding off pressure or a injector leaking intermittently. I have told him to rent or buy a fuel pressure tester and see if it bleeds off but he dont seem interested in doing it and he seems to be getting burnt out on working on this jeep.

If you were to take a guess as what was wrong here and just wanted to throw parts at it would you buy a new fuel pump or have the injectors cleaned or maybe even throw a new crank sensor in it? I am leaning towards fuel pump, he ran a can of seafoam in the gas last spring and didn't seem to do anything for the injectors.
 

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check valve in the sending unit (fuel pump) leaking so you have to fill the fuel line all the way from the tank every time. just a thought
 

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Discussion Starter · #3 ·
check valve in the sending unit (fuel pump) leaking so you have to fill the fuel line all the way from the tank every time. just a thought
That's what i am thinking. I told him to rent a fuel pressure tester and see if it bleeds off. He said it has pressure i think he check it by pushing the valve on the fuel rail but not with a gauge. But it is intermittent so you never know if your going to catch it while it's holding pressure or if it's not. It's just one of them problems that is kinda hard to pin down.

The Bosch pump was put on shortly before he bought the jeep. Bosh is supposed to make the best fuel pumps but this pump dont know it is supposed to be the good one. I dont know if i will tell him to try another Bosch or buy something else like a Denso.
 

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I bought an injector harness for $8 and made my own injector cleaner. The tube is the cone thing you get with rtv, a piece of 1/2" hose, some clamps, black tape and carb cleaner hose.

Taped the ground to the battery post and tapped the positive wire against the positive battery post while I sprayed carb cleaner through it.

ALL of my injectors were gummed up to some degree. Less than 15 seconds each, they are all shooting a nice clean pattern.

One great thing is I can go out once or twice a year, or anytime that I feel, and run through and check them.

Also check his vacuum hose that supplies vacuum to the fuel regulator. I replaced my elbow on mine due to it being spongy, didn't like that. And the nipple that it attaches to may need to be cleaned out.

Throw money at it with a fuel pressure regulator, who cares? Keep the old one in the box in the jeep as a backup.
 

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Had this problem for a bit on my TJ, I could solve it by turning the key to "on" for a few seconds before turning it to "ignition". It started after I jammed my tank bad on a ledge, and fixed when I removed the tank and reinstalled it with a steel skid. I figure a line or something that prevented back drain of fuel line had crimped a bit.

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I have 92 xj 4.0, it has long crank problem, solution is bump starter momentarily first then start right up. This works every time but ignition cycle doesn't help. My guess is electrical. Some day it will fail to start but it has gone on a long time.
 

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Welcome to the Wrangler Forum wllrdmoor,

For your starter situation, I suggest cleaning your battery cables and posts. Then clean the negative cable where it bolts to the block. Reassemble all connections with dielectric grease or Vaseline.
If that doesn't cure the issue, make sure the starter grounds properly to the block and that all the connections are clean and tight. Use dielectric grease on the starter connections too.

Good Luck, L.M.
 

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If I were faced with the decision of whether to throw injectors or fuel pump or some other part at it....
I absolutely would not. I would diagnose the problem and then repair it. He needs to check the fuel pressure when cranking and not starting. He needs to check spark/ timing when cranking and not starting.
 

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90% of long cranks are due to worn out brushes in the Starter Motor. You might want to crack it open and take a look.
 

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90% of long cranks are due to worn out brushes in the Starter Motor. You might want to crack it open and take a look.
Uh noooo that would be slow cranking...
 
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