Intermittent No Start

[krustyballer16]

Question!

Got an 87 xj 4.0, bought it, it started great. Had lots of new sensors on it cuz the previous owner was having problems with it starting. He put a new throttle position sensor on it and that worked.

 

So after a few months it's gone down hill to the point of not wanting to start at all. So we put 2 crank position sensors on it. First one we thought was defective (from o Reilly's) , second one tested defective too (from napa).

 

BUT, after the 1st CPS, we pulled a plug wire to test spark and sparked it off the AC housing. It sparked and started instantly then the next day, nothing. So put the 2nd CPS on it, same issue. Pulled plug wire and put it on the AC, started instantly and will start a few times after, until the next day...

 

What is the issue here? Has a new coil too.

 

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[cruiser54]

Completed Tips 1 through 5 yet? 

[krustyballer16]

Not yet, will be starting monday. We have wiggled all connections.

I just wanted to make sure I wasnt overlooking something simple and stupid. This is the hardest jeep I've worked on! I think its cursed!

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[krustyballer16]

The o Reilly's cps read .29v and the napa one reads .22v....

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[krustyballer16]

I'm just wondering why itll fire instantly when the spark plug wire sparks onto the AC (or anything probably)

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[cruiser54]

Get the Tips done..........

[DJHeath]

Hi, cruiser54. 89 cherokee crank, no start condition, replaced cps (.5vac), refreshed grounds, tried new ecu, replaced cap, rotor, coil. Checked all sensors. I had a spark from coil to cap than from cap to plugs. Have sprayed starter fluid and still no start. I believe I'm not getting fuel injector pulse.

Was driving fine. Coming home one day it just died. Would crank but no start. 

[krustyballer16]

Update: sorta
Havent messed with electrical yet cuz we had an overheating issue BUTTTTTT.... we havent done anything to it since I made this post. And now all of a sudden it starts quickly EVERY time we try it. And runs as well as it ever could. CPS still reads .26v....
Weird

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[cruiser54]

1 hour ago, krustyballer16 said:

Update: sorta
Havent messed with electrical yet cuz we had an overheating issue BUTTTTTT.... we havent done anything to it since I made this post. And now all of a sudden it starts quickly EVERY time we try it. And runs as well as it ever could. CPS still reads .26v....
Weird

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STILL do the Tips!!!!

[cruiser54]

On 9/18/2019 at 5:33 PM, DJHeath said:

Hi, cruiser54. 89 cherokee crank, no start condition, replaced cps (.5vac), refreshed grounds, tried new ecu, replaced cap, rotor, coil. Checked all sensors. I had a spark from coil to cap than from cap to plugs. Have sprayed starter fluid and still no start. I believe I'm not getting fuel injector pulse.

Was driving fine. Coming home one day it just died. Would crank but no start. 

Test for pulse on any colored wire on any injector plug.

 

Wiggle wires near the back of valve cover while cranking. Those wires were prone to abrasion.

[DJHeath]

I'm getting .2 vdc from injectors while cranking

I wiggled the harness behind the valve cover and no difference.