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Renix Not starting. Fuel pump not priming. only 7v at pump.

T

tayman

NAXJA Forum User
Location
Niceville, FL
Well, like the title says, my renix 4.0 is not starting... it'l crank and stumble and pretend like it's starting but won't catch. I have pretty much zero fuel pressure and the pump isn't priming. so I'm sure it's related to the pump SOMEHOW. But the pump was just replaced about 4,000 miles ago. Measured voltage at the connector and I'm only reading about 7v at the pump.

Battery is at 12.5v
Ballast resistor is bypassed.

Which wires do I need to check for power/continuity?
Is it my starter relay?
The stud on the relay is getting full Battery voltage.

What else should I check for?
 
(Sorry for the double post. I'm using my phone)
 
You can rule out the wiring and limit the failure to the pump, just take the point where you were measuring the supply voltage for the pump and get a long length of wire and run it from there up to the battery. Then check the fuel pressure.

Another thing can cause low fuel pressure, the fuel pressure regulator. Clamp off the return line and measure the pressure.
 
'90 XJ 4.0L renix

That's not a bad idea. I'll try the long wire.
 
Don't forget to measure the voltage from the body to the negative wire at the pump as well. Either could be causing problems.
 
Do you mean resistance? Aka check the ground? Do you know the spec on it? Should it be 0 ohms or just a low number?
 
Just tried the hot wire directly to the pump, and nothing. Even used a wire for ground. Nothing. Looks like pump.
 
Yup, that too.
 
Still need to see 12v at the pump connector though, right? Maybe that's why the pump went bad in the first place?
 
tayman said:
Still need to see 12v at the pump connector though, right? Maybe that's why the pump went bad in the first place?
Click to expand...
Wrong. The ballast resistor is there to drop the voltage on the pump and allow it to run more quietly.
 
Can you hear the pump at all? If so, your problem may be the short hose between the mounting assy and the fuel pump.
 
No, pump isn't running at all. And the ballast resistor is bypassed.
 
Do you know what the voltage is supposed to be at the pump?
 
Thanks for replying without an intelligent answer.
 
Alright, so 7v is still low. I think my battery is a bit low, so that may have something to do with it.
 
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