First off this is not on a Toy - Its a 96 ZJ

I do not have fuel coming to the fuel filter(right next to the tank which has an in-tank fuel pump) - I have disconnected the fuel tank harness which has 4 wires. One should be fuel level sender, one should be power for the fuel pump, and I am not sure what the other 2 do.

Now then, I test what voltages I have on those 4 wires with the key in the run position(so I should have fuel pressure.). To make it easier to understand what I did was went back up front to the fuel pump relay and took the voltages. They are as follows:

30 - 12v
87 - .01v
87a - 0.00v
85 - 6.04v (I believe this tobe pwr wire for the pump)
86 - 12v

Now, when i was testing the wires back by the pump, the only one with any voltage was the 6 volts.

The fuel pump should have 12v to run, correct? Any ideas why i am only getting 6 volts on the 85 pin?

The relay is good, I tested the horn relay and then switched them. Also, all of the other relays are getting 12 volts on the 85 pin - and all other measurements are the same as the fuel pump relay.

Anyone know what the next step is. I was thinking of taking a 12v battery back and jumping the power wire at the tank to see if the pump kicks on; however, what do I ground to?

Kat

 

I tried to jump the fuel pump to start but no luck.

 

If you jumped the pump to no avail I would guess that its a bad pump....

But before you said that my first thought was a tripped relay. This sometimes happens in wrecks, or harsh hits when offroad. I would check to be sure, your owners manual, or a chiltons service manual, should have some info, if the jeep even has one.


Okay looking here...



85 and 86 are your switch power(+ and -; most likly switched with ign). 30 is the power being sent to the fuel pump, and 87 should be the power out to the fuel pump, assuming the relay is working. I doubt you have anything hooked up to 87a. So if you jump 30 to 87 on the wire side you should get the fuel pump to come on. '

I am not sure why you get 6v at the 85 pin, but the relay probably takes 12ish to trip.


EDIT: 85 is most like the ground to switch the relay, check its voltage with the key off and the key on, it probably goes to ground with the key on.

 

I will try again tomorrow -- That would have been a lot easier way to jump things than how I was doing it under the dang car....

Thanks!

 

If its a plug, most likely, you can make a wire with two male terminals, like the ones on the relay, to plug into the appropriate slots in the plug...

good luck

 

Toyota fuel pump test jumper how-to:
http://www.4crawler.com/4x4/CheapTri...shtml#FuelPump

And for troubleshooting, see if the voltage drop is across the relay contacts or is it between the relay and the pump or between the pump and ground.

 

Its A Jeep ... Save yourself the grief and just toss a match at it !