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'87 stock 4.0L MJ Starts, Runs Well, Then Won't Start, Repeats


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The truck was starting and running fine until about a week ago.   I went to Lowes, parked, came out and it would crank but would not start (not even a burp).  Did the under hood check for loose wires, vacuum hoses, odd smells, etc.  Nothing looked, or smelled out of order.  After about 5 minutes, it started like nothing was wrong and ran all the way home with no issues. 

 

Since then I have driven it several times, and it has refused to start several more times, but always starts eventually.  I wore out the battery trying to restart it when it refuses...and replaced the battery yesterday.  It started right up.  Shut it off.  Would not restart.  Cranked fine but again, not even a burp.  Started fine a while ago.

 

I've done most of Cruiser 54's Renix tips, and all seemed good until now.  If the fuel pump is going out, would the engine run so well when it does start?

 

Any and all advice appreciated,

 

Thanks in advance.

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As stated, CPS.

 

I don't know if this has been stated before elsewhere on this forum, and it doesn't make any sense...

 

but when mine was going bad (1989 XJ), when it wouldn't start, I would simply unplug the CPS connector (its on the intake manifold, towards the firewall) and plug it back in.  That would usually cure a no start.  I've done it for other XJ owners at gas stations, on the side of the road... always worked, to their (and my) amazement.

 

I would then suggest an immediate CPS replacement and drive off into the sunset with Superman cape waving behind.

 

True story.

 

Better advice would be to do Cruiser54's tips.

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Yes, I would check the CPS too as others have said, but I would also check your fuel injectors. If they are leaking, then it will make it hard/impossible to start after you have reached operating temperature (at Lowe's) since there's too much fuel to ignite. After waiting for that extra fuel to evaporate, that's why you can then start right up and it runs normal. What's your gas mileage like?

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Yes, I would check the CPS too as others have said, but I would also check your fuel injectors. If they are leaking, then it will make it hard/impossible to start after you have reached operating temperature (at Lowe's) since there's too much fuel to ignite. After waiting for that extra fuel to evaporate, that's why you can then start right up and it runs normal. What's your gas mileage like?

Gas mileage is around 13.5 to 14.5 mpg.  Injectors have been cleaned about a year ago, but I will also check them out as well.  Thanks.

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Currently waiting for new CPS and new starter to arrive.  It was a bear getting the old CPS out.  Not sure how I'm going to get the new one in (very tight squeeze between the bell housing and the floor board).  Hopefully this will solve the problems.  If not...I will surely follow-up on all other suggestions.  Thanks

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