Fuel Pump/No power to relay area

[mattsplat72]

Help!! I pulled car into my garage and shut her off. Go to start and nothing. Opened hood and Neg terminal was off. No fuel pump when cranking over.

Checked Fuse Good
Checked EFI Main Good
Checked Fusiable Link Good
Checked Fuel pump Good
Replaced all Relays and Resistors with different ones No Change
Checked wiring harness to Fuel Relay and there is no power going to it .:aigo:
I opened the ECU and nothing looked bad of burnt.
No Codes

I spent all day trying to track down what is going on . Tried searching and didn't find anythin conclusive.
Did the TSRM checks and didnt get anywhere with those either.
I even went as far as having two of my Navy Buddies who work on the wiring for the EA6B Prowlers at Whidbey Island N.A.S. and they were stumped.

Could this be an issue with the theft deterrent system ?
Is there a Fuel saftey cutoff like in case of an accident?

Thanks for the Help.

 

[mattsplat72]

Bump

 

[jetjock]

Hmmm. Glad I'm not flying Prowlers outta Whidbey...

 

[mattsplat72]

LOL Butthole I think I may have found it . Could it be the Circut open relay? pulled it and it was shot ?

 

[jetjock]

It could be, especially if there's no juice at the FP relay when cranking. As long as the clutch switch is closed and the key at start power supplied by the ST1 section of the ignition switch energizes the starting coil in the Circuit Opening Relay. The COR then passes power from the EFI fuse to the FP relay, which sends it on through the normally closed contacts to the fuel pump. Assuming a good ground the pump then runs.

Why normally closed contacts? Because the FP relay remains de-energized until engine start so the pump can run at high speed during cranking. After start the ECU energizes the pump relay (using the FP output) to switch power over through the resistor and run the pump at low speed. At the same time the ECU brings low (grounds) the holding coil of the COR via the FC output pin so everything keeps running. FC remains low as long as the ECU receives CPS pulses. Therein lies the safety function you were asking about. However if there's no power during cranking all that can be ignored. Lastly, if the engine cranks the theft system can't be involved in the problem.

Assuming you haven't done the 12 volt mod all this is shown on the schematic. Butthole doesn't know of anything more conclusive than it

 

[mattsplat72]

Thank you very much. This makes total sense to me. This would be the only thing left I believe. So tommorow I will go get a new one and hopefully everything will work out. Again thanks for the time and help.

 

[A70BoosTFienD]

what was your conclusion to your problem? im having the same problem and it is killing me. i did change the COR and didnt help much but i continue to have the problem that there is no power goin to the fuel pump relay. i wired a direct 12v line to the fp and grounded it and the car runs.

 

[mattsplat72]

It was the Circut open relay, I dont know what it would be otherwise. Have you searched the forum? Try looking in this.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/ save this link in your fav's it is a God send.

 

[bis_1315m]

Hey this post mIght pertain to my problem aswell so heres my story I've done the 12v. mod to my new walbro and my mods are as follows hks f-con, fcd, fmic, 60-1, 2.5in piping.

Alright so basically my car will start right up until I start driving not right away but after it warms up my afr guage will be super lean between the red and yellow unless I floor it or somthing but out of know where my guage will drop off no red nothing and I will lose power momentarily and then the light will blip back up and power will return and keep bogging all the way home.

I've checked connections everwhere and have drop the fuel tank more than anyone wants to in a life time. oh and for some reason the first relay I used on my 12v. mod blew somehow but I've sinced replaced and problem still occures but I know with mods I should be running super rich.

someone please help.

thanks
Michael

 

[A70BoosTFienD]

It was the Circut open relay, I dont know what it would be otherwise. Have you searched the forum? Try looking in this.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/ save this link in your fav's it is a God send.

lol o yea ive searched all over that. ive looked into the tsrm and tested for resistance and all connection are under 2oms and all the relays work from the efi realy to the pump and the pump works 4 sure. i went as far as twed and traced the wires and everythings stright. im thinkin ecu at this point

 

[A70BoosTFienD]

Hey this post mIght pertain to my problem aswell so heres my story I've done the 12v. mod to my new walbro and my mods are as follows hks f-con, fcd, fmic, 60-1, 2.5in piping.

Alright so basically my car will start right up until I start driving not right away but after it warms up my afr guage will be super lean between the red and yellow unless I floor it or somthing but out of know where my guage will drop off no red nothing and I will lose power momentarily and then the light will blip back up and power will return and keep bogging all the way home.

I've checked connections everwhere and have drop the fuel tank more than anyone wants to in a life time. oh and for some reason the first relay I used on my 12v. mod blew somehow but I've sinced replaced and problem still occures but I know with mods I should be running super rich.

someone please help.

thanks
Michael

with that f-con u should know more about afr then yellow and red. and the description of the problem isnt really that detailed. the more info u can give of when it happens at what pressure ect. the better.

 

[bis_1315m]

with that f-con u should know more about afr then yellow and red. and the description of the problem isnt really that detailed. the more info u can give of when it happens at what pressure ect. the better.

Well unfortuanatly I dont have a wideband on the car only an afr guage and my f-con plugs into my ecu with a map sensor and fcd attached.

Basically its as if I'm not getting nearly the amount of fuel I should be I dropped my fuel tank again and I relized it has a good bit of rust in the bottom of it and my strainer is full of it so could this be the problem possibly.

also with the pump out of the tank I jumped b+ and fp and it came right on no problems and sounds good and you can even feel it pushing a slight bit of air aswell so I'm pretty sure my walbro pump is still good but would the rust really cause my car to run super lean and occasionally lose power to the point where it bogs and sometimes the light totally dispears on the afr guage.

thanks
Michael

oh and the thread labeled loss of power is my thread so your more than welcome to check that one out aswell might be more detailed.

thanks

 

[A70BoosTFienD]

Well unfortuanatly I dont have a wideband on the car only an afr guage and my f-con plugs into my ecu with a map sensor and fcd attached.

Basically its as if I'm not getting nearly the amount of fuel I should be I dropped my fuel tank again and I relized it has a good bit of rust in the bottom of it and my strainer is full of it so could this be the problem possibly.

also with the pump out of the tank I jumped b+ and fp and it came right on no problems and sounds good and you can even feel it pushing a slight bit of air aswell so I'm pretty sure my walbro pump is still good but would the rust really cause my car to run super lean and occasionally lose power to the point where it bogs and sometimes the light totally dispears on the afr guage.

thanks
Michael

oh and the thread labeled loss of power is my thread so your more than welcome to check that one out aswell might be more detailed.

thanks

Very very possible. i would recommend most obviously cleaning it out asap lol. that could mess up the new pump. as far as your problem do u have a fuel pressure gauge? that will tell u for sure if there is any pressure in the fuel rail when it bogs down

 

[bis_1315m]

Very very possible. i would recommend most obviously cleaning it out asap lol. that could mess up the new pump. as far as your problem do u have a fuel pressure gauge? that will tell u for sure if there is any pressure in the fuel rail when it bogs down

Alright yeah I plan on cleaning it today I already drained it out and got it out of the car but what should I clean it with. I hooked up the pump out of the tank and it sounds fine and I can see the gears spinning nicely and I can feel a slight bit of air being pushed out of it.

I can go pick up a fuel pressure guage but it only bogs or what not when I drive it so how can I read it and drive at the same time.

Or is there a way I can test the pressure without a guage, I have heard of someway but cant remeber exactly how it was done .

Oh and what do you think about dropping some magnets into the tank do you think that will pull the rust to them or not.

thanks
Michael

the car does sound a little weak at idle now to so if you know how I can test the fuel pressure without the guage let me know
thanks.

 

[yhatzee89]

I'm having a similar problem to the OP, my car died all of a sudden, I checked all the fuses and originally thought it was just old gas clogging the line somewhere (car has sat for several years but fired right up with new batt) but I checked the power at the fuel pump and nothing when I turn the key on. Where else should I be looking?

 

[jetjock]

Like the OP you should be looking at the schematic. There shouldn't be any power at the fuel pump with the key on.

 

[yhatzee89]

Don't know how to read electrical diagrams and I'm colorblind anyways so it probably wouldn't help if I could lol
So should I have power when cranking?

 

[jetjock]

Yes, when cranking and after the engine starts of course. Not with the key on/engine off though. The intent is to help prevent fire after a collision.

 

[yhatzee89]

That makes sense, well I had power back there while cranking, but the pump wasn't working. So I dropped the tank and I'm gonna put in the pump from my 91 (got a Walbro for that one) back in the morning

 

[yhatzee89]

Well I pulled the pump out and it works. but it was never getting power.
When I checked before my helper checked the fuel level sender not the power wire :/
So no power with all fuses good, next I'm goin to replace the COR or do the 12v mod

PS: what is this "B+ & FP" that people jump?