Can't get my 90 Cherokee started

MGWJeep

New Member
Joined
Oct 29, 2011
Location
Germanton,NC
Replaced my fuel pump, fuel filter, and fuel pump relay today. Still can't get fuel to injector rack. Has anyone had a similar problem?
 
Is your pump wired backwards. Are the lines on backwards? Some pumps you can actually wire backwards and instead of pumpin they pull. Ask me how I know.
 
CaverDave is correct. We had a spark . The fuel pump I purchased was an assembly complete with wiring harness. The harness plugged into it's connection in only one direction. I tagged the hoses to make sure that they went back on the way they came off. It is almost as if the pump isn't energized. I will trace the wires back to make sure that I don't have a short somewhere.
 
check for 12v to the pump using the chassis as a ground. if you have 12 volts then id just run a second ground to the body or chassis. did you check the fuel pump relay... theyre pretty common to burn out. if no 12 volts then check at the relay location for 12 V
 
gt500swim said:
check for 12v to the pump using the chassis as a ground. if you have 12 volts then id just run a second ground to the body or chassis. did you check the fuel pump relay... theyre pretty common to burn out. if no 12 volts then check at the relay location for 12 V
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As said fuel pump relay. When you turn the key do you hear the pump come on. You should. As he said check voltage at the pump.

However, a '90 has a ballast resistor on the driver side front fender right next to the air box. The purpose of this is to knock down the voltage to about 6-7 volts. This was mainly done due to the noise of the pump. Ballast resistors are ceramic and are known to crack. This makes the fuel system not function. You can just bypass these, however you'll hear the pump more. Later xj's do not have the resistor.
 
gt500swim said:
did you check the fuel pump relay
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MGWJeep said:
Replaced my fuel pump, fuel filter, and fuel pump relay today.
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hadfield4wd said:
As said fuel pump relay. When you turn the key do you hear the pump come on. You should. As he said check voltage at the pump.
However, a '90 has a ballast resistor on the driver side front fender right next to the air box. The purpose of this is to knock down the voltage to about 6-7 volts. This was mainly done due to the noise of the pump. Ballast resistors are ceramic and are known to crack. This makes the fuel system not function. You can just bypass these, however you'll hear the pump more. Later xj's do not have the resistor.
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Great info brother! I saw the ballast resistor, but wasn't sure what it was for (dang new-fangled Jeeps :lol: )
We're planning to test the FP circuit back to the pump later this week. *IF* it ends up being the ballast resistor, I bet he'd live with a little more pump noise :D
 
FYI... that resistor is bypassed while cranking. I had an '88 XJ that died on the side of the road when the resistor went bad. It would fire up while cranking but as soon as I let go of the key it would die.
 
I had the same problem, I found it to be the pressure regulator. Does any fuel squirt from the test port on the fuel rail. if it just a trickle thhen replace the regulator. you should have between 35 and 50 psi at the rail.
 
He called earlier to say after several attempts to hear the pump prime, he finally heard it. After a re-charge on the battery, it fired right up!

Unfortunately, the 2 dead injectors I diagnosed 2 years ago are still dead! He's headed to PaP later in the week for late model set and should be back on the road after a fluid change...
 
hadfield4wd said:
So all this and it ended up being a dead battery?
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No... tried to crank multiple times until battery went dead. Wiggled connection (was secure, but...) and finally heard the pump prime. A couple of priming cycles and he had fuel on the rail, but battery was dead (earlier cranking/priming). Fired up as soon as the battery was charged...


hadfield4wd said:
I recommend biting the bullet and buying new injectors.
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Where's the fun in that? :lol:
 
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