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Ok folks, here's the problem. We've got a 1986 2wd Comanche with a rebuilt 2.5L V4 and a 5 speed manual. We have replaced just about everything you can replace on this thing and it will start (turn over and crank) but will not run. The problem seems to be electrical/fuel delivery related but we're not sure. New fuel pump, new fuel tank and everything else. With a noid light attached to the TBI connector when you go to crank the engine the light on the noid gets bright for a moment then goes dim. We were told that once the engine cranks the niod light should flash. It's doesn't. It just goes dim and we have no fuel pressure in the TBI. The ECM has been replaced along with every other electrical component associated with the fuel delivery system, when we bypass the fuel pump relay we get good fuel pressure but when we plug the relay back in - nothing. We've replaced the relay three times and still the same issue. What I need to know is if this is a wiring harness problem or a ground problem. Any additional info you might need please ask but we're not sure where to go from here. Any "actual" help would be greatly appreciated!   

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1986 2.5 4cyl was the first renix era Jeep. Does it have a CPS (crank position sensor) on the bell housing? If it does this can cause no start conditions.



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ECM controls fuel and spark. 

 

If the ECM receives no signal from the CPS it will shut down fuel and spark. 

 

Your problem is likely the CPS. 

 

 

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Did you use the correct fly wheel when this motor was Installed?

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Don't guess .....confirm.... 2 eazy tests before removing cps....check for spark.... either remove a plug or take an extra plug hook it to a plug wire and set it against the block to ground...have a helper turn it over....do you have spark? If no start looking at Cps..... if yes then try pouring or spraying a bit of fuel down the throttle body and turn it over....if it fires then it is fuel delivery related....if still nothing... again cps

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12 hours ago, wclegere said:

Ok folks, here's the problem. We've got a 1986 2wd Comanche with a rebuilt 2.5L V4 and a 5 speed manual. We have replaced just about everything you can replace on this thing and it will start (turn over and crank) but will not run.

 

Turning over is the same as cranking -- the engine is being turned by the starter motor. That is NOT "starting."

 

If you dribble a little raw gas into the throttle body, or use starting fluid (ether), will it start and run for a few seconds? Have you checked for a spark at the spark plugs?

 

BTW -- the 2.5L engine is an in-line 4-cylinder, not a V4.

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On 2/9/2019 at 11:15 PM, Green Mesa XJ said:

1986 2.5 4cyl was the first renix era Jeep. Does it have a CPS (crank position sensor) on the bell housing? If it does this can cause no start conditions.



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Crank positioning sensor has been replaced.

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On 2/9/2019 at 11:24 PM, JMO413 said:

Are you getting spark at the plugs?

Yes, getting spark, new distributor, cap, rotor, wires, plugs, ignition control module and coil. 

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On 2/10/2019 at 8:20 AM, Jeep Driver said:

ECM controls fuel and spark. 

 

If the ECM receives no signal from the CPS it will shut down fuel and spark. 

 

Your problem is likely the CPS. 

 

 

CPS is new

 

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On 2/10/2019 at 10:42 AM, jdog said:

Did you use the correct fly wheel when this motor was Installed?

Same fly wheel that was on the truck when the motor was rebuilt! 

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On 2/10/2019 at 11:02 AM, yxmj said:

Don't guess .....confirm.... 2 eazy tests before removing cps....check for spark.... either remove a plug or take an extra plug hook it to a plug wire and set it against the block to ground...have a helper turn it over....do you have spark? If no start looking at Cps..... if yes then try pouring or spraying a bit of fuel down the throttle body and turn it over....if it fires then it is fuel delivery related....if still nothing... again cps

Why are you guys so sure it's the CPS. It's brand new! 

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On 2/10/2019 at 11:38 AM, Eagle said:

 

Turning over is the same as cranking -- the engine is being turned by the starter motor. That is NOT "starting."

 

If you dribble a little raw gas into the throttle body, or use starting fluid (ether), will it start and run for a few seconds? Have you checked for a spark at the spark plugs?

 

BTW -- the 2.5L engine is an in-line 4-cylinder, not a V4.

Engine has plenty of spark. Yes it will fire when gas is dumped into the TB but that really doesn't help much with the solution, does it? 

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1 minute ago, Jeep Driver said:

You replaced it with what? What brand?

O'rielly's I don't know... does it really matter?

 

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Just now, wclegere said:

O'rielly's I don't know... does it really matter?

 

Yes, it matters. 

 

Find a Mopar.

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7 minutes ago, Jeep Driver said:

Yes, it matters. 

 

Find a Mopar.

I have a crown that I've been using for a year and its doing great. that being said, I do agree with Jeep Driver. Most CPS are crap out of the box since the French company Siemens is not making them anymore to my knowledge. But he is getting spark and right now its not the CPS but it sounds like a fuel delivery issue he is having.

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We have replaced the ground wire at the fuel pump. We've also replaced the ground connection at the ECM. EVERYTHING that we could replace has been changed but we still get no fuel pressure through the fuel pump relay. The only thing we haven't been able to do is kill the Gremlins that seem to be running amok all over this truck! One thing I will add is that after we replaced the ECM we were able to drive the truck (It idled and ran fine for about 10 minutes) for about 4 miles then it started surging, sputtering and eventually died and would not restart. I am at a complete loss as where to go from here. 

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On 2/10/2019 at 12:05 AM, wclegere said:

With a noid light attached to the TBI connector when you go to crank the engine the light on the noid gets bright for a moment then goes dim.

 

 

This is what the OP states. 

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1 minute ago, wclegere said:

What is OP?

 

You. Original Post or Original Poster. 

 

Put a fuel gauge on it so you can see what it's doing. 

 

tPmaNAF.jpg

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I’m not sure someone isn’t having a laugh. Fuel pressure from the relay?


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