Hello Everyone,

First off I would like to thank you for clicking on this thread and reading about my issue.

Now onto the story..

This is Fuel Pump Relay # 3. From my understanding, It is responsible for supplying the 12 V voltage that our fuel pumps see at boost. At idle, our fuel pumps see around 8V voltage to keep from overrunning our stock fuel pressure regulators. In other words, our fuel pumps are smart enough to not use more power than they need.





What we have here is a variably labeled wire harness that plugs into relay #3 since the colors are very faint to identify.



Finally, here is the corresponding male end of the relay labeled as well for the matter of identifying.




Now, my questions to everyone is this.

Which one of these wires in the harness that goes to and from the relay is responsible for providing 12 volt power directly to our fuel pumps ?


Where does the white wire we see at the fuel pump directly connect to before the fuel pump ?

I am a bit thrown off because the color of the power wire at the Pump end is actually white. So at some point between the front and rear of the car there must have been a change in wire color or transfer to somewhere else because all I see is 2 reds on one side, one larger than the other and 2 red whites on another side, again with one larger than the other.

I tried using a multimeter on wires A and B at the harness using the white fuel pump wire as my grounding point and both of them check out continuous ! Both have a direct connection to the fuel pump power white wire when the engine is off with nearly no resistance.

Gentlemen, I am completely stumped

Any information is greatly appreciated. After searching the forums and service manuals, I could not find anything that told me directly what these wires do.

Thank you all for your help .

 

The big all red wire A is the 12v supply to the pump, It changes color to white on the way back at one of the connectors not really sure where though.

At relay 3, The two red and white wires should be hot (12v) with the engine running. Once the engine reaches a certain load, the ecm grounds the small red/black wire, which sends power on the big red wire to the fuel pump.

You should also have 12v at the red/white wire on the fuel pump resistor, and with the engine at low load the you will get 9v out of the resistor on the red wire, and this wire splices into the Big red wire from the relay 3, and then to the fuel pump.

 

Now thats a high quality answer!

Thank you very much for the informative response sir. This delemna was bugging me for a while now.

-pal215

 

No Problem glad I could help

 

WHere is this relay located at please send me a photo

 

Its in the engine bay on the firewall. Look behind the passenger side of the intake manifold. It sits to the right of the fuel injector resistor pack.

 

Where can i Buy a Brand New one Because my car stall and when try to start it again i didn't hear the fuel pump. It cranks but doesn' start before all this happen the car was giving me trouble with the A/F ration over 18. I will apreciate some help. Thank you

 

Old topic but I have a question!!

I have many misfires under 7psi.. Very lean mixture.. Maybe the problem is the fuel pump relay..

Can I connect a 12V battery wire to the A-Red wire without the relay to check if the problem will fix?

 

Anyone??

 

Based on the description above, if it's correct, it sounds like you could. Although if it were me, I would use a fused power source, such as jumping the relay, and not direct battery voltage.

Having said that...

Would I do it? Hell No! Not without a wire schematic to verify that I wouldn't fry the computer.

The possibility of frying up the ECU would create more problems than it would be worth. Especially considering that you can purchase another relay and swap it out to check if your hunch is correct.

Good luck.

 

Some good info in this thread. Wish the pictures were still up

 

Seems like some very good information indeed.
Also wish the pictures was still up.

Im currently dealing with a Lean issue thats driving me insane, i have no boost/vacuum leaks, no exhaust leaks, brand new Walbro 255 pump, brand new fuel filter, cleaned and tested injectors.

Pretty sure it has to do with the relay not kicking in and giving my fuel pump full voltage.

 

If high voltage is not working, then the car will fall completely on its face when boost hits, or tries to hit.

 

Thanks for the answear!

How do you mean falling on its face?
As soon as i get into boost it starts to missfire and runs leaner and leaner
Got new plugs, gapped to 0.60, pretty sure thats like .024inches

 

Hard to say how strongly it would stop making power. I think its a bad idea to keep testing though. My first thought would be for you to verify that the pump is correctly installed (sealing gasket is properly seated and not split), and then if that's ok, then try another Walbro 255 because I have not heard of any other cases where high voltage has failed to work.