I have been following much advice from previous posts, but am now in a hole. New fuel pump and new FP relay. Still no gas. After another check with the volt meter, I only have 4.7 volts at the FP relay, terminal E. I was thinking there should be full battery voltage. According to my shop manual, the diagnostic steps say to now check circuit 340. I would like to try to do that, but where is there information on ciricuit 340? All I can find out so far from my manual is that C340 goes into the plug at the ECM.

Can anyone tell me where circuit 340 goes? Or, maybe, tell me what the heck would make it have only 4.7 volts?

Thanks,
Buddy

 

E is the orange lead right??? If so, it should be 12V indeed. it's the same orange lead shared by the oil press. switch. It comes from the junction block in the battery compartment if I'm not mistaking. It's a direct lead from the junction block to the relay and to the press. switch. The junction block gets power from a red wire (thick one) that comes from the battery and the alternator also hooks up there. It's right next to the battery, right under the lid. Check if the connection is not corroded, also check if the orange lead on the press. switch (next to distrbutor w/ the large rubber plug) has 12V on it. Circuit 340 consists of the connection points where the orange lead spltis to the relay and the pressure switch.all the way to the ECM plug where the 2 orange wires come in (they are directly opposite of each other in the ECM plug, it's the #1 plug, has 3 orange wires in total..the other has just 1)
The orange wire is shared by both the press. switch and the relay and both switch to a tan/white wire, that is split between the 2, this wire is the final feed for the fuel pump (when you turn ign. on the relay primes it but the press switch supplies the power when the engine is running and there's oil pressure)

the orange wire has an inline fuse, you might want to check if that is okay and makes proper contact.

 

Thank you very much, Twin Turbo!!! It is late here now, but I will follow your directions tomorrow and let you know how it comes out. I really appreciate the information. This thing has had me going in very near circles now for about 2 weeks (but part of that time was waiting on parts).

Thanks again and will post how it comes out.

Buddy

 

Check the fuse mine was corroded and the caused the same low voltage back to the fuel pump.

donald