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How to perform a correct Fuel Pressure Test?

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The problem that I'm having is that the truck does not start. The truck is being sitting for about 3-4 years, recently about three months ago the fuel pump was replaced and the oil filter o-ring kit, by a mechanic that works for a guy that owned me money of some design work that i did for him, he told me that the fuel pump was replaced but i don't know really it is really hard to start the truck, even if i'm jump start the truck, it takes a while. So started reading about this issue and found that it could be the CPS, so i replaced, for a new from autozone. After i replaced the truck did not started , check the ground connection form the battery and found that there was a voltage drop of approx 3 volts so i clean all the terminals and now i don't have a voltage drop. I want to perform a fuel pressure test could you guys point me in the right direction. Also, where can i get the ballast resistor is broken. Finally is there any local comanche owners?


Thank you for help.

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when I first got my MJ, I had a hard time cranking it but I figured out a trick that works for mine.


turn the key to on but not to crank, you can hear the fuel pump come on, after a couple seconds you hear it turn off (or so it sounds that way). I then try to start it and hold the accel to the floor and it turns over a few times and starts right up.


if i vary the process it takes longer to crank.


i know there are likely some fuel flow/pressure issues but it starts fine and i just haven't checked into them yet.

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Well, i just did a fuel pressure test and i got 34psi, it held the pressure, after approx 20min the pressure drop to about 30 psi. I switch the fuel pump relay with the ac relay to see if that was the problem but it did not made a difference also i jumped the ballast resistor but did not a make a difference, what I'm thinking is to empty the fuel tank and put some fresh fuel. Any ideas?

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  • 2 weeks later...

Finally i dropped the fuel tank to see what the hell whats going on with the fuel pump and the tank is rusted from the inside really bad, and the fuel pump assembly is in really bad shape, i was reading that a radiator shop could clean the tank, but i figure if i can get a new one for less than $150 it might be worth buying a new one, i read that a good place is rockauto or ebay , but what about the fuel pump assembly in rock auto cost $330 where you guys think i can get a better deal? I will post a picture of the pump so you guys give an advice.


Thank for your help.

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