How to diagnose no fuel in the injector rail on a 97 TJ 4.0


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LennartfromAustria
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There is a fuel pump wire connector just forward of the tank on the drivers side, you can pull the connector apart and test for a momentary 12V source while you have someone turn the key.

The pump can be hard to hear, typically there will be a humming noise that lasts for about 2 seconds before shutting off.
Hey thanks for the advice, which pin should receive 12 Volts at the connector?
Best regards Lennart
 

TJ4Jim

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Hey thanks for the advice, which pin should receive 12 Volts at the connector?
Best regards Lennart
There will be 3 conductors at the plug, 1 Black which is the common ground and a dark green/white that is the fuel pump power and the third is for the fuel gauge. Test between the black and dark green. If at first there is no power try the dark green to the frame.
 
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LennartfromAustria
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There will be 3 conductors at the plug, 1 Black which is the common ground and a dark green/white that is the fuel pump power and the third is for the fuel gauge. Test between the black and dark green. If at first there is no power try the dark green to the frame.
Because I can see my fuel gauge needle rise when I power up the jeep. Does this mean the connection is good?
There will be 3 conductors at the plug, 1 Black which is the common ground and a dark green/white that is the fuel pump power and the third is for the fuel gauge. Test between the black and dark green. If at first there is no power try the dark green to the frame.
So I ground the black prong to the frame and check with the red the black and dark green is that right?

Thanks for your help
 

TJ4Jim

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Because I can see my fuel gauge needle rise when I power up the jeep. Does this mean the connection is good?

So I ground the black prong to the frame and check with the red the black and dark green is that right?

Thanks for your help
The wire for the sender has nothing to do with fuel pump operation, put your test leads across the dark green/white pin and the black pin and turn the key to run, if no reading then try the dark green/white pin to any body/frame ground . If your system is functioning properly there will be a momentary 12 volt reading if not we will have a few more steps.

Question: have you been able to confirm proper spark on a plug.
 
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LennartfromAustria
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The wire for the sender has nothing to do with fuel pump operation, put your test leads across the dark green/white pin and the black pin and turn the key to run, if no reading then try the dark green/white pin to any body/frame ground . If your system is functioning properly there will be a momentary 12 volt reading if not we will have a few more steps.

Question: have you been able to confirm proper spark on a plug.
Yes, ther are sparks on my plugs.
 

TJ4Jim

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Yes, ther are sparks on my plugs.
That's a good sign, it means the computer is receiving the correct signals which allows the engine to actually start once the fuel issue is addressed.

Talk to your local auto parts guy and see what is available to flush your fuel tank out, it's definitely going to need it eventually. Not sure what products are available to you.
 
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Wtrask

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So did you get a 12v signal at the plug on the pump wire? If you did then your fuel pump may be dead. If you get yourself a power probe it will help a lot.
 
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LennartfromAustria
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So did you get a 12v signal at the plug on the pump wire? If you did then your fuel pump may be dead. If you get yourself a power probe it will help a lot.
I am going to check today, so I put red positive on the dark green/white pin and the black negativ prong on the black pin? is that right?

Thanks in advance for your help
 

Wtrask

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I’m not sure the color wires. That sounds correct. All you need to know is that there is a momentary 12v signal on one of the wires.
 
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LennartfromAustria
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The wire for the sender has nothing to do with fuel pump operation, put your test leads across the dark green/white pin and the black pin and turn the key to run, if no reading then try the dark green/white pin to any body/frame ground . If your system is functioning properly there will be a momentary 12 volt reading if not we will have a few more steps.

Question: have you been able to confirm proper spark on a plug.
Hey TJ4jim,
Today I checked the connection, I received for about 2 Seconds about 12 V at the dark green/white and black pin. I checked then the dark green/white with the frame as the ground but I got just 0.534 Volts not alot.

Then I tried to start the engine, sprayed some starter fluid directly into the throttle body, it startet up for 2 Seconds but died even if I continued to spray.


Best regards Lennart
 

TJ4Jim

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Hey TJ4jim,
Today I checked the connection, I received for about 2 Seconds about 12 V at the dark green/white and black pin. I checked then the dark green/white with the frame as the ground but I got just 0.534 Volts not alot.

Then I tried to start the engine, sprayed some starter fluid directly into the throttle body, it startet up for 2 Seconds but died even if I continued to spray.


Best regards Lennart
Good news, looks like you may be down to replacing the fuel pump and flushing the system. Time to drop the tank.
 
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LennartfromAustria
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Good news, looks like you may be down to replacing the fuel pump and flushing the system. Time to drop the tank.
That's a big relief,
do you have any advice on a fuel pump and what should I change and do also. Is it possible to clean out the fuel lines, maybe with compressed air?
Thanks again
 

TJ4Jim

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That's a big relief,
do you have any advice on a fuel pump and what should I change and do also. Is it possible to clean out the fuel lines, maybe with compressed air?
Thanks again
For the fuel pump at first I would pull and check the original, it may just be gummed up and still operable since I believe they are thermally protected from damaging itself. A good soak may get it going. I have little faith in blowing the lines clear but at minimum it will tell you if the line is free flowing or plugged up. If you have a local parts store see what they have available for soaking the components to remove any gumming or varnish.

As previously stated the Bosch pump assemblies are not available (just the actual pump) so Delphi is a go to assembly.
 
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LennartfromAustria
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For the fuel pump at first I would pull and check the original, it may just be gummed up and still operable since I believe they are thermally protected from damaging itself. A good soak may get it going. I have little faith in blowing the lines clear but at minimum it will tell you if the line is free flowing or plugged up. If you have a local parts store see what they have available for soaking the components to remove any gumming or varnish.

As previously stated the Bosch pump assemblies are not available (just the actual pump) so Delphi is a go to assembly.
So I have to buy new lines or is there a way to clean them, and the injectors.
 
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LennartfromAustria
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No reason to buy a new line, it is a stainless tube that if necessary can be removed and flushed, same with the pump if not damaged (just soak it) along with the fuel rail and injectors.
I took out the fuel pump tested it not working, not a single sound. So i disassembled the pump, clean everything with a ultra sonic parts cleaner. Dryed the pump off tested again no sound. So the pump is dead, today i searched for the whole assembly and found two types one for the 15 Gallon Tank and one for the 19 Gallon Tank. My question now is, will the 19 Gallon Pump Assembly fit my 15 Gallon tank, its way cheaper than the 15 Gallon Tank Assembly, what i dont understand....

Best regards Lennart
 

OldGuyOutdoors

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I took out the fuel pump tested it not working, not a single sound. So i disassembled the pump, clean everything with a ultra sonic parts cleaner. Dryed the pump off tested again no sound. So the pump is dead, today i searched for the whole assembly and found two types one for the 15 Gallon Tank and one for the 19 Gallon Tank. My question now is, will the 19 Gallon Pump Assembly fit my 15 Gallon tank, its way cheaper than the 15 Gallon Tank Assembly, what i dont understand....

Best regards Lennart
I found that the only difference (in most cases) in the 15 and 19 gallon tanks is the length of the vent tube next to the filler tube. I thought I had a 15 gallon tank and after a little research and replacing the fuel pump, I cut the vent tube to within 1.5" of the tank entrance and I now can fill upwards of 19 gallons in the tank.

Like all input, do the research yourself and double check all facts! Good luck!