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Old September 19th, 2020, 12:48
Spencer0428 Spencer0428 is offline
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1990 XJ. Will not start - please help

So, Iíve got a 1990 XJ 4.0 that Iím about to light on fire.

The Jeep will turn over, it has spark, and it is getting fuel. It was just running a few weeks back and now it will not fire up anymore. After I try to start it, when I turn the key back from the ďcrankĒ to the ďrunĒ position, the injectors start to fire uncontrollably.

Iíve checked the CPS, (stator/camshaft position sensor), and the ECU.

I have 10 Xjís here at the house and have never had this issue. Starting to think there is a short somewhere.

Iíve got a video if the injectors pulsing but canít figure out how to post it.

Any help would be greatly appreciated
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Old September 19th, 2020, 12:50
Spencer0428 Spencer0428 is offline
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Re: 1990 XJ. Will not start - please help

Also, the only light that comes on in the diagnostic/idiot light panel is the “BRAKE” light. It is only lit up while the key is switched to the “crank” position and the starter is turning the motor over.
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  #3  
Old September 19th, 2020, 14:00
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Saudade Saudade is online now
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Re: 1990 XJ. Will not start - please help

So what happened during the "few weeks back and now"? Did it just sit? Did you do any other work?

How did you test for fuel? Did you just depress the schrader and get a spurt of fuel? You need to use a fuel pressure gauge.

Please explain further "when I turn the key back from the “crank” to the “run” position, the injectors start to fire uncontrollably". How do you know this?

And how did you check the sensors?

Here's a link to testing the RENIX sensors:

http://www.lunghd.com/Tech_Articles/...iagnostics.htm

Also check Cruiser54's tips #1 to#5 at:

http://cruiser54.com/
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Old September 20th, 2020, 09:13
Spencer0428 Spencer0428 is offline
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Re: 1990 XJ. Will not start - please help

Quote:
Originally Posted by Saudade View Post
So what happened during the "few weeks back and now"? Did it just sit? Did you do any other work?

How did you test for fuel? Did you just depress the schrader and get a spurt of fuel? You need to use a fuel pressure gauge.

Please explain further "when I turn the key back from the ďcrankĒ to the ďrunĒ position, the injectors start to fire uncontrollably". How do you know this?

And how did you check the sensors?

Here's a link to testing the RENIX sensors:

http://www.lunghd.com/Tech_Articles/...iagnostics.htm

Also check Cruiser54's tips #1 to#5 at:

http://cruiser54.com/
No work was done. I pulled the battery a few weeks back, it sat outside in the rain, went down there yesterday and put the battery back in.

Iíve tested for fuel in multiple ways, no pressure gauge though. After attempting to start the Jeep, The spark plugs are wet with fuel when I pull them. Iíve also sprayed starting fluid in the intake. Canít even get it to act like it wants to start. So Iím not sure how a lack of pressure would cause it to not even try to bust off.

I know the injectors are firing uncontrollably because I can hear them after I let off of the key. Itís just loud clicking noises coming from each injector.

Iíve got another running remix that I have swapped sensors from. They all worked on that engine so Iím not sure why they wouldnít work on this one. The CPS ohms out at .23. But again, it worked on the other running motor so why wouldnít it work on this one?

Thank you for the links, I am going to read them now
Also thanks for your input.
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Old September 20th, 2020, 11:07
Spencer0428 Spencer0428 is offline
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Re: 1990 XJ. Will not start - please help

Going to get a new ECU. Will update after I try that
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Old September 20th, 2020, 12:48
Spencer0428 Spencer0428 is offline
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Re: 1990 XJ. Will not start - please help

Tried the new ECU. No luck. Still have injectors firing rapidly after the attempt to start it.
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Old September 20th, 2020, 13:08
Spencer0428 Spencer0428 is offline
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Re: 1990 XJ. Will not start - please help

Tested the CPS and I’m only getting .2 AC volts. So I’m hoping that’s my issue.
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Old September 20th, 2020, 14:21
Spencer0428 Spencer0428 is offline
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Re: 1990 XJ. Will not start - please help

3 different CPS sensors are all reading .2 volts AC. I tested our other Renix 4.0 in the yard and it’s reading .6 volts AC. Going to try to get it to move a little closer to the flywheel and see if I can get a little higher reading. Thanks for the help Saudade
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Old September 21st, 2020, 15:53
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Re: 1990 XJ. Will not start - please help

Checking the OBD1 ECU for any codes as a start. Expect a code 12 for sure if you've disconnected the battery since it last ran.
https://www.fixjeeps.com/jeep-check-engine-codes.html
This can point you in the right direction to find out which sensor, or sensor wiring needs attention.
Also trying starting it while holding the throttle down a bit. If it starts it may be a dirty IAC. Here is a relevant older post. When one of mine XJ's don't start. It's usually IAC.
https://www.naxja.net/forum/showthread.php?t=67091
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Old September 22nd, 2020, 06:42
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Re: 1990 XJ. Will not start - please help

Quote:
Originally Posted by XJCreeper View Post
Checking the OBD1 ECU for any codes as a start. Expect a code 12 for sure if you've disconnected the battery since it last ran.
https://www.fixjeeps.com/jeep-check-engine-codes.html
This can point you in the right direction to find out which sensor, or sensor wiring needs attention.
Also trying starting it while holding the throttle down a bit. If it starts it may be a dirty IAC. Here is a relevant older post. When one of mine XJ's don't start. It's usually IAC.
https://www.naxja.net/forum/showthread.php?t=67091
Renix is before OBD1.

OP, take a close look where the injection harness travels from the firewall to engine. That harness can chafe near the rearmost head stud.
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Old September 22nd, 2020, 12:29
Spencer0428 Spencer0428 is offline
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Re: 1990 XJ. Will not start - please help

Quote:
Originally Posted by Spencer0428 View Post
3 different CPS sensors are all reading .2 volts AC. I tested our other Renix 4.0 in the yard and itís reading .6 volts AC. Going to try to get it to move a little closer to the flywheel and see if I can get a little higher reading. Thanks for the help Saudade
Took a burr bit to the CPS and got it a little closer to the flywheel. Itís reading a steady .6 V AC now. Still no start.
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Old September 22nd, 2020, 12:30
Spencer0428 Spencer0428 is offline
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Re: 1990 XJ. Will not start - please help

Quote:
Originally Posted by cruiser54 View Post
Renix is before OBD1.

OP, take a close look where the injection harness travels from the firewall to engine. That harness can chafe near the rearmost head stud.

Checking that now. Thank you
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Old September 22nd, 2020, 12:53
Spencer0428 Spencer0428 is offline
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Re: 1990 XJ. Will not start - please help

Replaced the coil pack and it started up. Thanks for the help guys.
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Old September 22nd, 2020, 13:57
Spencer0428 Spencer0428 is offline
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Re: 1990 XJ. Will not start - please help

What would be the reason for me having 4 quarts of gasoline in my oil?
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Old September 23rd, 2020, 09:37
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Rob Mayercik Rob Mayercik is offline
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Re: 1990 XJ. Will not start - please help

The injectors are flooding gas into the cylinders. Left unchecked, that'll wreck the cylinders and put you into an engine rebuild/replacement.

I'd change the oil immediately, and monitor it closely to see if it's getting gas in it again. If it does (and at the same rate), you should probably stop running the engine until the injectors can be checked or replaced with known good units.

Are these injectors original to the truck?
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