Whats up guys new to the forum and have a problem I just can't figure out. I recently replaced the head and head gasket on my 2000 xj and after trying to start it after everything was put back together the injectors were not pulsing. upon further examination I discovered that the Fuel Injectors/Coil Rail fuse #18 under the hood kept blowing. I tried replacing it with a bigger fuse but still the same thing. my guess is a wire broke/tore during the installation of the new head and something is being shorted out somewhere in the harness. I did a check of the wires I could see and they seemed ok. I was wondering if there was an easier way to go about this or if there was a way I could jump the fuse to the injector wiring to attempt to bypass whatever may be broken or shorting out. Any help would be greatly appreciated THANKS!!!!!!

 

You have to fault find, no getting away from it, or have an auto electrician do it

you need to free download the FSM, and see whats on Fuse 18

it also has a list of the connectors, which you should be able to disconnect to help isolate the fault

you can then systematically check each pin, and see if any that are not supposed to be ground are

you have to look at the wire colors and pinouts from the circuit diagrams

its likely to be where the harness goes behind the head

definitely dont try to bypass the fuse, you must isolate the fault

does it always blow straight away ?

do you have a multimeter ?

 

1st thing is to check all the wiring that you had to move . also check to see if it not pinch under anything or any wiring that the insulation is coming off and shorting .

 

In particular the wiring where it goes from the back of the head across the injectors. Bad motor mounts and back routing can cause it to chaff and wear through the insulation inside the loom.

 

Never. Never. NEVER do that!

 

But it makes finding the short easier. Just look for the melting wiring and smoke.

Stick a test light across the fuse socket. go wiggle the wiring until it goes out.

 

Sorry everyone I appreciate the help just been super busy but I bought a test light and tried the wiggling wire technique but the light didn’t even turn on at all. Upon further examination I found that the pcm fuse would not light up whatsoever. I’m assuming the issue lies within the pcm maybe I need a new one or something really not sure what to do here.

 

I would suggest you may have a short circuit in a wire would be more likely.

If you disconnect the PCM connector, does the fuse still blow ?

What else, if anything is on the same fuse as the PCM ?

 

Pinched a wire somewhere when you did the head. Check front where it goes to the CTS and the O2

 

so the pcm fuse isn’t blowing it just isn’t lighting up with the test light. However I noticed the o2 fuse keeps blowing as wel I don’t know if the two correlate.

 

circuit diagram bro !

 

I think you misunderstand the test. If the circuit has a short to ground it will try to pass a lot of current and pop the fuse. By substituting a test light in place of the fuse, the test light will light brightly up instead. Not lighting up or barely lighting up is normal. Using a test light also limits the current that can flow while testing so that you don't melt the wiring or waste fuses. This is an old school trick for working on electronics too. I even have a jig that puts a standard light bulb inline with a power cord to limit the current along with a variac to alter the voltage.

My money is on a damaged wiring harness along the fuel rail or right where is crosses from the firewall to the rail and goes down to the 02 sensor

 

looks more and more like that my clue was when he said he had the head off and everything was fine until he put it back on

 

If there is no power to the PCM fuse then your problem is that there is no power to the PCM fuse. That doesn't point to a PCM problem, that points to a problem with the power to the PCM.