3F-E FJ80 No Power to Fuel Pump?

[TheLoyale]

So yesterday, I drove my truck ('92 FJ80) 40 miles away from my home, arrived at my destination in top shape, running beautiful like usual. Went to leave, and my truck just cranks, check all fuses and the Main EFI relay, everything looks great. I sprayed some carb cleaner in the TB and it sputters a little bit, so it wants to fire up if it had more fuel. Pulled the truck home for further investigation, popped off the main fuel line running to the fuel filter, cranked it over, no fuel came out of the hose. SO, the fuel pump is not getting power, I tested for power on the main fuel pump/sending unit connector, and I didn't find anything. Why?

All the wiring looks good, as its all inside except where it exits the body and runs to the fuel pump. What else would be the cause of no power?

Is there another EFI relay or Fuel Pump relay else where in the truck? Up under the dash somewhere maybe? Kinda running out of ideas at this point.

Just finding it strange that it always started and ran great for the two years and 25,000 miles I've put on it.

Also rust is not an issue on this truck, it came from MO.

Ideas?

Thanks for any pointers,
-Tom

 

[FrankTorres]

Are you getting a

with the key in the ON position?

 

[TheLoyale]

Nope, the only lights illuminated on the cluster are the A/T Oil Temp, Seat Belt, Brake, and the Red square above the Volt gauge.

I also did verify that the pump indeed does work, took it out and tested it. I followed the red power lead on the pump harness further into the truck (Under driver side rocker cover) and I don't have voltage up there either. So its somewhere even further up the line.

 

[FrankTorres]

Your ECU is not powered up.

Check the 15amp EFI fuse and read this link.
Diagnostic Procedure for EFI Related Woe and Strife

Good luck

 

[jynx]

I would check the fusible links at the battery. The fuel system is the little plug kind of by itself. Mine was a pink wire I believe. It had pulled off at the battery. Dumb question, but did you pull the relay and check it? Have you verified that there is power to the relay?

 

[TheLoyale]

Thanks for the link, that really gives me a better idea of where to go from here. I will follow that write-up and post back what I find.

And yes, I did test for power at the Main EFI Relay, One lead is always hot, and another one becomes hot with the key turned to "ON"

 

[jonheld]

Just for laughs, disconnect the plug on the AFM. DON'T REMOVE THE SCREWS, just push up on the spring clip on either side of the connector housing.
With the AFM disconnected, see if you get a CE light with the key in the ON position.

 

[TheLoyale]

Yeah no CEL that way either.

I do have power going to the brass screw in the fuse box, so I have to keep poking around.

Are there are Ohm specs and procedures on testing the MAF?

 

[jonheld]

Yes there are in the FSM, but if you unplugged the AFM and there's still no CEL, then odds are it's unrelated.

 

[TheLoyale]

Finally got a little time today to check out some more stuff.

I checked the diagnostic connector up by the fire wall, with the key ON, if I check terminal +B, it only has 0.5 Volts and so does terminal FP. With key OFF, I have nothing on any of these terminals.

As for the Fuel pump/sending unit side, the only lead that has power with the key ON is the dark red wire that runs to the top of the assembly. When I took the pump out, this wire looked like it was for the Sending unit/Float. As the Power lead for the pump is a Blue wire.

I am going to keep checking things out and see if I can track this down. Just posting this to see if anything rings a bell with anyone.

Jon, I also found this very helpful thread which you posted in.
https://forum.ih8mud.com/80-series-tech/510977-no-cel-help.html

Cheers all!
-Tom

 

[jonheld]

If pin 8 is not +12 with the key on, then the EFI relay isn't closed or something is dragging down the circuit.

On the EFI relay connector with the relay removed, make certain that pin 3 is +12 with the key on. Make certain that pin 1 is a good solid ground. Pin 2 should be always hot.
Once verified, short pins 2-4 and turn key to ON. Pin 8 on the check connector should now read +12 and your CEL should illuminate.

The fuel pump is only energized while the starter is cranking and when the AFM flap opens. It should not run when the key is in the on position with the motor off.

 

[TheLoyale]

Ok, did exactly what you said. Jumped Pin 2 and 4 together after checking voltage (Which checked out great) turned key to ON and voila! CEL is on.

So this points out that the EFI Relay is bad, correct?

 

[jonheld]

Yes, either the EFI relay is faulty or there is a bad connection in the fusebox.
FYI, if you leave pins 2-4 jumped you will drain your battery. It's OK to drive like this, but remember to remove the jumper when you shut her down.

 

[TheLoyale]

Yes, either the EFI relay is faulty or there is a bad connection in the fusebox.
FYI, if you leave pins 2-4 jumped you will drain your battery. It's OK to drive like this, but remember to remove the jumper when you shut her down.

Cool, I will be getting another relay from work and this should be back on the road!

Thank you for the help, its really appriciated.

-Tom

 

[Jez Aga]

Hi Tom, so as I understood the EFI main relay was a culprit? I have eimilar problem with my 92 FJ80.