bsoccer

Probably a hundred posts on this topic and I think I have read most but want to ask a question or two. Put in a new fuel pump as old one was definitely dead. Still not getting 12 volts to the pump and truck starts but cuts of after a second or two. Checked volts at pump and not even close to 12 volts so I checked continuity on the Relay. Relay failed on continuity between 1 and two so I have ordered one. While waiting I was thinking of running power to pump from external battery but do not want to screw up new pump or blow myself up. Truck sat unused for 3 years so working on getting it back in shape. Am I likely looking in the right direction. Thanks in advance for any advice.

2ToyGuy

Do you mean the COR when you say "relay"?

Did you try jumping the Fp and B+ connectors on the test connector and listening for the fuel pump? If it runs, we can start trouble shooting. If not, you may well have bad wiring between the battery and the fuel pump, or a bad fuse.

If it runs when you jump the test connector, did you pull the test connector, and open the AFM vane, to see if you hear the fuel pump run? If it doesn't, it could be the AFM, or the COR. You can then ohm the AFM to see if the fuel pump contacts close when you open the vane. This will isolate the trouble to the COR or the AFM. If manually opening the vane causes it's contacts to make correctly, it's the COR or the wiring from the AFM to the COR. Get out your multimeter and start checking continuity.

I hope this helps a little...
Pat☺

bsoccer

2TOYGUY you are way above my head but will try jumping between the two. No I tested the EFI main relay relay. The fuse in the same box under the hood is good and not sure if there are any others to check. I have not yet run a wire direct to the pump out of fear of messing up the new pump.It seems to get some fuel now where with the old pump it got none, it cranks for a second or two now and did not at all before the new pump. Your info definitely helps and like I said continuity failed on the EFI main relay so hoping that is the issue. It is like it gets fuel when I turn the key to start but not enough or not continuously. Thanks again.

scope103

Before you swap that EFI relay, measure voltage to ground at B+ with key-on. If you have battery voltage (~12v) your EFI relay is fine. (It probably is; the COR and fuel pump are downstream of the EFI relay, and it has to close for the fuel pump to run for even a few seconds.) 1 to 2 on the EFI relay is the coil, so it should be a few score ohms. Not a dead short.

FP goes straight to the fuel pump, so if you follow 2ToyGuy's advice, then you're just running battery straight to the fuel pump. Without horsing around with the wiring under the truck.

"Runs for a second or two then quits" is the classic sign of a VAF COR problem. 2ToyGuy's plan works straight for that.

PS: And don't throw that old fuel pump away. Since you weren't getting power to the pump, who knows what condition it was in?

bsoccer

I have done some of the trouble shooting and want to report on it and see what you think. I first tried to measure at B+ and got on volts. Don't know what that means because when I jumped between FP and B+ the fuel pump is finally running and the truck tries to run but backfires a bit and never really runs. At least I can hear the fuel pump running with the jumper in place and without that in place it does not run. I still think that the EFI main relay might be fried. I definitely did not have voltage at B+. Not sure what to do next. Any advice would be appreciated.

bsoccer

with the jumper in place the pump is running just fine.What would you suggest.

scope103

Assuming you meant to type "no" volts, that's like looking at your thermometer and saying "I got no degrees."

The fuel pump will not run, jumper or not, if there is no voltage to B+. Make sure you're using your multimeter correctly by measuring the voltage of the battery. Then re-read these posts, follow the advice if you so choose, then let us know what you found.

bsoccer

After going back to the truck this morning and jumping between B+ and FP the trucks cranks and idles smoothly. I definitely feel that the relay is bad.

scope103

Suit yourself; it's your money to waste.

You've demonstrated your problem is in the VAF-COR circuit. 2ToyGuy told you a simple test to confirm and localize it. But it's up to you.

bsoccer

hey dude I qm still very much a novice and learning so I do not understand all of this. No need to be a bit of a jerk with a snippy response. If it pisses you off then don't read or respond.