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No start

X

XJeeper87

NAXJA Forum User
Location
FL
I have a no start problem.
The jeep cranks over good but it doesnt fire I have fuel at the rail.
I havent been able to test if i have spark bcus I didnt have anyone to crank it while i wached spark plug but I just found the starter relay wire :)

Anywas I my tach does NOT move when cranking wich suggests CPS/CMP/ECU troubles right??? i have tried 2 different CPS's with no avail.
And i replaced the CMP(WICH WAS!! BAD) it had the little magnet thingy broke off still nothing.
I heard that the CPS and or the CMP going out can fry the ECU is this true??
Is there a way I can check the ECU? where is the ECU??

1987 XJ 4.0L 5speed 4x4

Its been almost a month I wanna get this beast back on the road cus if i dont I might have to drive a minivan :(

I WILL die from embarissment
lol
 
Fuel at the rail doesn't say alot. What is the pressure?

Try and confirm spark.

You could try ether starting fluid in the intake and see if it will start that way to confirm spark or fuel issue.

Use a noid light (about $3 tops at the parts store) to confirm if the injectors are firing.

Is the fuel pump PRIMING? If it isn't priming, you may have a problem with the Latch relay (later models ASD relay). Try swapping the relays around. It is usually the third relay moving away from the firewall.
 
ive tested all relays all work. yes the fuel pump is priming. and i have tried starting fluid in intake nothing at all. im 99% sure it is spark issue. where is the ECU located???
 
The ECU is mounted on the inside fender in the engine. Later models it is on the drivers side, but don't know on renix (like yours) You can check some inputs and outputs, but can't hardly check out fully yourself. Look for other stuff first. Do you have 12V going to your coil when cranking?
 
If i jump the Ignition threw the test for MSD ignition Box the jeep will run but u gotta keep jumping the wire and my CPS/CMP/ECU seem to be fine cus it runs but i still have NO tach and gauges dont work right and it wont run on its own any ideas???
 
Start from scratch.

Go to the MSD sight and download the installation instructions for use with the Cherokee and follow them. Something may be wired wrong or have come apart.

The tach feeds from the coil, the gauges have a fuse and I think there is a ground up under the dash, probably have to pull the cluster to see it.

While thinking of grounds, check the strap from the rear of the head to the firewall, and the grounds at the dipstick tube. Renix era XJs gotta have GOOD grounds.
 
IDK about the newer XJ's but the Renix Tach does NOT run of the coil it runs off the ECM/CPS/CMP but all those are functioning properly so it has to be wiring right???
i checked the MSD site and made sure everything was conected correctly something between the ECM and the C101 is bad but i cant seem to find what it is
 
XJeeper87 said:
IDK about the newer XJ's but the Renix Tach does NOT run of the coil it runs off the ECM/CPS/CMP but all those are functioning properly so it has to be wiring right???
i checked the MSD site and made sure everything was conected correctly something between the ECM and the C101 is bad but i cant seem to find what it is
Click to expand...

Strange... Page 8E-2, Instrument Panel, 1990 FSM, "Tachometer The Tachometer displays the engine speed, (RPM). With the engine running, the tachometer receives an engine speed signal from the negative side of the ignition coil (values shown in chart)."

I added the bold, italics, and underline for your edification. And in case you are wondering, yes, the 1990 is also Renix.
 
i rent stoopid i know 1987-1990 is renix 1991 threw 1996/7 is OBD1 and 1997 thew 2000 is OBD2 lol ive done soo much research on the XJ's its dispicable
 
well it worked b4 and the coil is conected to my MSD box and that is conected to the battery and the ECM POS/NEG to batter and a white wire and a red wire goes to the ECM where I think the origanal coil atached
 
So lets get the knowns clarified here. Please correct or clarify the following assumptions of knowledge.
1. Jumping a hotwire from the positive side of the battery to the positive side of the coil will let it run.
2. Even when it runs like this, the tach does not work.
 
well u dont jump the coil u jump the MSD box and it activates the coil. But yes when you do this it will run

No the tach and other gauges dont work at this time
 
Don't know why the gages don't work, but you have a bad connection or wire break between the PDC and the MSD box. Trace the wire to the big fuse box under the hood. Check for continuity after disconnecting both ends and you will most likely see that you don't have it. If you do have 12V exiting the Power Distribution Center, you could just run a new wire from PDC to MSD. Another thing you could try is just bypassing the MSD box. It doesn't seem like that is the real problem, but you don't need it anyway. Do you have a wiring diagram to see which wire that is at the PDC?
 
winterbeater said:
Don't know why the gages don't work, but you have a bad connection or wire break between the PDC and the MSD box. Trace the wire to the big fuse box under the hood. Check for continuity after disconnecting both ends and you will most likely see that you don't have it. If you do have 12V exiting the Power Distribution Center, you could just run a new wire from PDC to MSD. Another thing you could try is just bypassing the MSD box. It doesn't seem like that is the real problem, but you don't need it anyway. Do you have a wiring diagram to see which wire that is at the PDC?
Click to expand...

His is Renix, so the PDC is the starter relay.

If none of the gauges work it could be as simple as the fuse in the fuse block by your left foot.
 
OK, I'm going to make a suggestion, please keep an open mind.

I went to MSD website and looked up your application, i.e., 87 XJ, and they sell the control box, and a wire adapter set. Nothing else is available--specifically NO coil.

So here is what I suggest. Lose the MSD coil. Follow the directions for installing the MSD box with the stock XJ coil and ignition control module. Here is the link: http://www.msdignition.com/uploadedFiles/MSDIgnitioncom/Products/Accessories/8813_instructions.pdf

Here is my reasoning: it ain't working now. Follow the manufacturer's directions and use what they say to use, wired the way they say to wire it, and see if it runs.

Other than that I don't have anything further, constructive wise, to say. I hope you do get it figured out, and I sure as H*ll can understand your frustration. Good luck.
 
Ok i dont have the STOCK coil cus i got the jeep with the MSD stuff in it BUT cant i just disco the MSD box and use the MSD coil inplace of factory???
 
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