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New Fuel Pump won't move fuel

S

Short Bus

NAXJA Forum User
Location
Litchfield Park, AZ
:flame: I have a 1986 XJ that has a 2.5 liter in it. I have been having problems getting it to run properly. It is hard to start and won't give me but 3psi of fuel pressure. i did all the repairs to increase and now forked out the dough to get a new pump.

Pump is in and will turn over for just a second. The book says to go to the ECU. Any ideas??? Is their a fuel cutout switch that won't let fuel get to the TBi?????
 
Start by checking that your getting voltage to the fuel pump. It's not unheard of to get a bad pump, especially if its an off brand. I think on the Renix 4.0 engines one of the pins on the diagnostic connectors goes to the fuel pump wiring. Not sure that's the case on an 86 2.5l though. Does the 2.5l have a ballast resistor or fuel pump relay?
 
Don't forget that most fuel injected models only run the fuel pump for 3 seconds with the key in run position. You say the pump runs for a second. Does it keep pumping with the key in the crank or start position? The ECU has to see the "running" signal from the crank position sensor before it keeps spark and fuel running. Crank position sensor is a common failure (as well as the ballast resistor).
 
The pump runs for about three seconds, and nothings there. Where is this ballast resistor located? Prior to this issue the vechile ran but had no fuel pressure whatsoever. I was doing a dianosgotics on the the pins at the ECU and it pointed to the ECU as the problem. Do you think that it could be the cranck position sensor?
 
If you have voltage at the pump, your ballast resistor and fuel pump relay are good. If you have voltage to the pump (and the ground is intact), the pump should run or else it is defective. You also have voltage to that plug for the gage, right? Two voltage inputs at the plug, one for pump and one for gage.
 
I believe I have voltage at both. The sending unit works showing me a reading in the tank. The pump does run for a couple of seconds. It's just that when i crank the vechile my pressure gauge shows nothing and there is no presents of fuel flowing. I know the lines are clear and not plugged. If i spray a little fuel in the TBI it starts for a second. The fuel pump should self prim right? Could the ECU cause these issues?
 
Fuel in tank, fuel pump pumping, no pressure at rail--check for fuel at inlet and outlet of the filter.
 
I installed a napa pump, it ran, same thing no pressure, I took one wire off and put it in the same position on the new pump as to not mess up. Well its backwards on the replacement pump. silly me
 
I've got fuel and all. I just can't get anything to pump out of the tank. I will try the wires. I hooked it up the same as the old pump. I believe the prior ower might have been wrong. On the pump instructions it shows the + gound to ground. That can't be right ??? Right? If i hook up power toi the pump it should just run? Right? !!!1
 
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