I'm having trouble diagnosing my 22RE, fuel pump is getting about 10v when the engine is cranking over, it will fire and the voltage will drop to zero and the truck will bog out. I have replaced the Circuit Opening Relay behind the kick panel, it has the same 10v coming off the relay going to the fuel pump when the engine is cranking then nothing after it fires. when i was doing research, I saw something about the air flow meter in the air box which would tell the ECU to send voltage to the fuel pump as needed from my understanding. Any suggestions on how to test the AFM? Any other suggestions on what the issue could be?

 

The contact (pins 1 & 2) of the AFM itself sends power to fuel pump when the flap is open = there is airflow. ECU not involved.

 

A problem well-stated is almost solved. What happened and what did you do before this problem?
My first-gen's COR is behind the glove box, not behind the kick panel. Regardless, I would not suspect the COR first. Toyota components are bullet-proof.
What does your battery voltage read?
You got bare shiny metal tightly against bare, shiny metal on your connections?
There are many posts about checking AFM n the forum. Use "Google" search, not posts / thread search the latter are crap.

With Ign switch ON, jump the +B to FP in "Check Connector". Fuel pump should turn on. Sorry, I do no know what the "Check connector looks like on your generation.
Also, while trying to crank like you did above, measure voltage at B+ of "Check Connector" That would show if you have problem with COR circuit.

 

Here's the manual page for the VAF: http://web.archive.org/web/201209071...33volumeai.pdf As Rad4Runner says, pins 1 & 2 (Fc and E1) are the switch. On the harness side, E1 is ground, and Fc connects pin 4 of the COR to ground.

Start by checking the VAF side (because that's easiest. I wouldn't call this part bullet-"proof," more like bullet-"resistant," so it's worth a few seconds to test it). If the switch works, you can try grounding Fc on the harness side. With key-on, the pump should run.

10v while cranking is a little low, but not low enough to stop the fuel pump. Based on your description, your problem is in the VAF-COR circuit. Now that you've spent the money we can be pretty sure it wasn't the COR component, but simple tests will point to exactly where the problem really is.

 

Yes all of the connections are clean contacts and I will jump the +B to FP and see what it reads. Thanks for your help

 

Thanks for the info on the VAF, I will test it , thanks for the help. I'm not familiar at all with Toyotas. I hope this diagnosing works

 

I had insulation on wire harness connector is under passenger seat goes under body along top of frame then plugs into fuel pump harness. was a massive PITA to find. You can test theory by hot wiring pump to 12v power and ground. If truck runs fine bingo. Then test along electrical path to pump.

Looked like something had hit wire and time led to corrosion that reduced voltage to pump.

 

i was running the fuel pump off a toggle switch to the battery but it was hard to keep running, i think that was because it was running rich with too much fuel, it doesn't have a bed on it so its not bad to get to all the wiring but if it was 10v at COR then i don't think it would be in that section of wiring.

 

10 volts is not ideal so I would still suspect that section.Check it or waste time wondering about it.