Electrical problems- No Fuel

[thedude]

Hi guys,

I'm new to supras, so bear with me!

I just inherited a late 86 MKIII non turbo (M7whatever engine). It will run on starting fluid, so I know the ignition system works. I am not getting fuel. I unplugged the banjo bolt to the fuel rail, and didnt get any flow. I tested the leads to the pump. (under the cover by the spare tire) with the ignition on, and i get nothing. So obviously I have no power. I supplied direct 12v to the pump and heard nothing and got nothing through to the fuel rail. So obviously the pump is shot as well. Any ideas as to why it wasn't getting power? What is the most common problem you've heard of? Fuel pump relay? All fuses look ok. I couldn't see any fusable links, but I'm sure they are somewhere, so obviously I haven't tested them yet.

If anyone knows how to get ahold of some free wiring diagrams online, that would be cool. In the meantime, I'm off to drop the fuel tank...

Thanks for any and all help!

[Bill UK]

These may help Link

[Cameroonski]

With key in on position, short out B+ and Fp... this should supply power to the pump to check pressure or operation or whatever while car is off.

I had a hell of a time figuring out a problem with mine once... heres a couple things i remember off the top of my head.

EFI main relay should make an operation noise when key is turned on... check first.. then see what your power is at the EFI fuse... i think thats what its called.

Something else to check.. does check engine light come on when key turned to on? if not, theres a couple things it could be. That was what my problem was, ended up being a loose (number 15?) fuse on driver side kick panel. Wedged some paper in there to fix a problem i was trying to solve for two weeks... lol

[thedude]

ok, so i've got the new fuel pump in, but still no power to the pump. i've checked all of the pins on the "fuel pump relay" on the passenger side under hood. none are reading any voltage whatsoever in relation to ground while the key is on. any idea what would cause this?

thanks for the link, bill.

cameroonski, where is the efi relay? i can't locate it on the diagrams or on the vehicle.

the check engine light does come on. the fuses in the drivers side kickpanel all look good save for the two 7.5A fuses. (the one for the gauges went out, and when i tried to pull the one for the dome lights, i dropped it. lol.

also, the EFI fuse in the under-hood fusebox is getting 12V, and is good.

[thedude]

ok. i actually shorted +B and Fp on the diagnostic port and it runs now. so, i guess the fuel pump relay works? is the problem in another relay then?

[Bill UK]

This is an UK right hand drive, so it could be slightly different,

[Cameroonski]

That picture is correct. The fuel pump relay is on the passenger side, and the EFI relay is a gray relay in the fuse box under the hood. There should be a diagram on your fuse box cover, but maybe not. What should happen is with the key turned on, the EFI relay should click (and so should the fuel pump relay i think). So if it does not do this you do the short Fp B+ Since you said that made it work, then.... well honestly i need to look in my book b/c i dont remember. haha.

So check to see if the EFI relay clicks with key on. And if not if it clicks when those two terminals are shorted. And I will take a look at the schematics and get back to you, if someone else doesnt first.

good luck

[Supra_Freak_7m]

I am pretty sure the fuel pump does not turn on at all until you turn the key to start, so that relay should be dead until you turn the key to start. Another thing you can try is to go through the steps to disable the theft deterrent system as i think this disables the fuel pump...