Fuel pump related problem

96 2.7 4x4

Hey guys.
So my fuel pump will not run with ignition on or while cranking motor.
All fuses and relays have been tested and are good. I can remove the COR and put a jumper wire in which will turn the fuel pump on. Truck starts right up and runs fine like this... I have no codes to help trouble shoot unfortunately, however when I have the truck running with the COR bypassed, I can see engine RPM readings, MAF readings and "fuel system status" which says open loop?

I have read a lot of posts on this form and others and can't seem to find a solution to my problem, although some similar sounding situations seem to have been fixed with new ECM?

Originally I thought it was the pump. I could smack the tank with a block of wood and the pump would come on, but stay running non stop with key turned "on" truck not running.... So I replaced the pump and the new pump would turn on right away but same thing, pump would run non stop. Then quit altogether. Now only runs if I bypass COR.. Iv cleaned the MAF sensor and tested all other sensors I can see within the circuit with OHM meter and they all seem to be ok.

This is what iv replaced so far:
-fuel pump
-fuel filter
-cap and rotor
-plugs and wires

Hopfully this is enough info for someone to help point me in the right direction. If not please let me know.

Thanks on advance!

 

Since I can bypass my COR with the jumper wire and the tuck runs fine, I feel like I should have it narrowed down to whatever it is that tells the COR to open and close? I just can not figure out what it is that dose this. Feels like I'm close to a resolution here but I'm having a real hard time pin pointing the issue.

Anyone have any ideas at all?

 

I had an idea once, but it died of solitary confinement.

This might help, if you don't have it already. It's just the fuel pump control and does not show other associated stuff like EFI circuits. It is from Toyota.
The ECM grounds the COR coil (FC), closing the contacts when it sees a signal from the crank position sensor "NE" and 12v from the starter "STA" (cranking). The 12v source for the COR coil and contacts comes from the EFI relay.




These 2 are the whole enchilada, I don't remember if they are from a 99 or 03 (V6) factory service manual but things should be very similar.

 

Thanks for the reply dirtypool,
I'm gona head out now and see if I can verify the 12v is coming from the starter or not. I have ohm tested the crankshaft sensor and it is good according to that test. Is there any other way to test it that I'm missing?

 

Dose anyone know what a proper "signal" from the crank sensor would look like on a voltmeter? I'm getting 0.24 v on "NE" while cranking... Not sure if it should be higher or not?

 

I should also add that The truck will start but dies after 2 or 3 seconds every time.

 

Just did engine and trans swap. Got exact same issue. Was told could be in ecu pinout. Don't know much about that. Let me know if you figure it out. I will do same. G.L.

 

Sounds good. I'm heading to the wrecker tomorow to try a new ECM. Everything elce tested seems to be working so hopfully this is the issue and not a waste of $$.

 

I'm still searching for a ECM...

Have you made any headway on your end Andy G?

 

No luck yet either. I'm gonna figure it out eventually. Got to be something small I'm missing. Still driving it though. I will stay up with you on it.

 

Ok sounds good I'll do the same.

 

Hey Busby! Did you diagnose prob. yet? I'm still running hot-wired.!

 

Unfortunately no, I'm in the same boat as you. Iv givin up until I can find another computer to try...

 

I have a 1999 3.4l and it wont start...i dont hear the fuel pump turn on when i turn the key to the ON position which has led me to believe it is the fuel pump. I have seen a few other posts on here saying it could be my ECM also. Which worries me cause i would hate to replace the fuel pump on my own and it still doesnt work. I have hardly any knowledge at all about working on vehicles other than what i have taught myself or learned off of TW and following tutorials. My question has to do with my Check Engine Light....When i turn my key to the ON position the Check Engine Light doesnt illuminate and turn off like it is supposed to. I think i saw on here that should be a clue that it is actually the ECM that is bad...Can anyone confirm this possibly for me? My truck is flawless and my pride and joy and since i have moved to Grants Pass oregon from Colorado my frame has rusted all to crap and i think it is gonna fail the Rust Campaign through Toyota....The only catch is i only have a couple more weeks of eligibility left before my 15 years from Date of Purchase exceeds 15 years on the dot. Any help would be greatly appreciated, not to mention if it gets bought back from Toyota i have a lot of goodies on it that i would be selling on here to anyone...Ie 882+Nitro Charger Sports, Dakars, ARB Bumper, Brand New TRD Locker, Brand New Cooper STT 32x11.50x15's....I just gotta get it started so i can drive it to Toyota....Heck i will even buy beers and offer a Free Wild Turkey hunt on my property here in Grants Pass if you have a tag...they are everywhere...... Jonathan

 

Did you try to bypass circuit opening relay?

 

No, not familiar with how to do that...i did check the relay under the hood in the main fuse box but that is the only thing i did pertaining to a relay.

 

Did anyone every figure this out?