Fuel pump blowing the pcm/tcm 30a
CF Veteran


Joined: Jan 2017
Posts: 3,413
Likes: 400
From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
That looks like Fuse 8 but that's OK.
Is that the 1996 manual?
What means this?
Did you check the length of A22 Red for shorts? And the length of DK GR?
Did you try a new relay? Not usual, but turn over all the stones.
Is that the 1996 manual?
What means this?
The fuel passmore are for an 89.
Did you check the length of A22 Red for shorts? And the length of DK GR?
Did you try a new relay? Not usual, but turn over all the stones.
I think the was supposed to be "fuel pump". Lol
My friend that owned this before found that schematic, then promptly lost it.
CF Veteran


Joined: Jan 2017
Posts: 3,413
Likes: 400
From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
How about bypassing the PDC. Run your new line directly to the battery. Use a fuse inline. Start out with like a bulb, test lamp, or multimeter so you don't fry the pump.
If that works then try the pump.
If that works then try the pump.
Red ohms out perfectly to the pcm. Green/ white was also good, but went ahead and already ran a new line. Brand new relays for the fuel pump and the ASD.
I think the was supposed to be "fuel pump". Lol
My friend that owned this before found that schematic, then promptly lost it.
I think the was supposed to be "fuel pump". Lol
My friend that owned this before found that schematic, then promptly lost it.
I know the short is happening behind the fuel pump relay. I know the power and ground to the fuel pump are good. I know the lines going to the pcm are good. The fuel pump started when hooked up outside the tank. I'm beginning to suspect it could be grounding out on the tank if that makes sense. Here's a pic of the wiring inside the pump.
Red is power, black is ground, blue is to the fuel gauge. I'm curious why it is going back to the cap and grounding there too. Interesting thing to note, if I only have the power connected, the ground disconnected, and I run voltage down the hot line, it is grounding. I don't understand that, as the brand new line I ran is perfect. It must be also grounding out at the tank.
CF Veteran


Joined: Jan 2017
Posts: 3,413
Likes: 400
From: Connecticut
Year: 2000
Model: Cherokee (XJ)
Engine: 4.0
CF Veteran
Joined: Dec 2015
Posts: 2,139
Likes: 93
From: Syracuse, NY
Year: 1996
Model: Cherokee (XJ)
Engine: 4.0L
Red is power, black is ground, blue is to the fuel gauge. I'm curious why it is going back to the cap and grounding there too. Interesting thing to note, if I only have the power connected, the ground disconnected, and I run voltage down the hot line, it is grounding. I don't understand that, as the brand new line I ran is perfect. It must be also grounding out at the tank.
You refer to black being ground (singular) but I think in your setup you have 2 separate ground wires. One for level sensor, and one for pump. The one for the level sensor is coming from the PCM (according to the information you have provided. I have a 96 which is wired differently).
I think you will find that the black wire that goes by itself out to the edge of the fuel module "cap" (mounting face plate) is the ground for the pump motor. The black that comes into the module with the other wires is the ground needed by the blue wire for detecting the voltage provided by the fuel level sensor.
You refer to black being ground (singular) but I think in your setup you have 2 separate ground wires. One for level sensor, and one for pump. The one for the level sensor is coming from the PCM (according to the information you have provided. I have a 96 which is wired differently).
You refer to black being ground (singular) but I think in your setup you have 2 separate ground wires. One for level sensor, and one for pump. The one for the level sensor is coming from the PCM (according to the information you have provided. I have a 96 which is wired differently).
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