madmax94

I've got a 94 GSR with a B18C1 just put in. The check engine light comes on, but the main relay doesn't click when the light goes off. I put in a new main relay, but no joy. The fuel pump still won't prime, so the engine only turns over.

There is no voltage at the fuel pump connector when the main relay is connected. Jumping the main relay connector does give the fuel pump power, and it primes. The only way that I can get the car to start and run is to jump the main relay connector.

So far, I've triple checked the fuses and grounds. I'm thinking maybe it's the ECU? It throws codes and the check engine light turns off though. I came across a post by FCM on here that mentioned something about the ECU's fuel pump relay control output.

Anyone have ideas?

N/A

Try a different relay or try the ecu

*JDM*Ej8*

main relay ecu or fuel pump. double check grounds and fuses

fcluddington

have you checked for power to the ecu? and yes the ecu does control the fuel pump turning on for 2 second prime then after a certain engine speed turns pump on.

N/A

He is getting power to the ecu, it starts when he jumps power to the pump.

fcluddington

is the ecu making the ground to relay at ko. NA do u know what conditions must be met so ecu to allow 2 sec prime? also the check eng. light should go out after 2 sec.

fcm

There are two things to check, [easy].

The green/blue lead at PGM-FI Main Relay is the ECU/ECM control lead, use a jumper lead and jump from the black ground lead, [or any ground point] to the green/blue lead, if car starts the ECU/ECM is the problem.

Turn ign. on and check for power at the ECU/ECM, [IGP1 and IGP2] they are the only two yellow/black leads, [injector relays output] going to the ECU/ECM, both must have power, [12V+] for ECU/ECM fuel pump relay control, [green/blue] to work.

The fuel injector relay itself must be working and all 3 fuses for the PGM-FI Main Relay must be good or car would not have started when you jumped the fuel pump relay, [supplied power directly to fuel pump power lead, yellow/green] so either the ECU/ECM is N/G or there is a connection problem between the PGM-FI Main Relay, [injector relay] and the IGP1 & IGP2 inputs to the ECU/ECM. 94

fcluddington

Damn well said ol fart. i am betting on IGP1 and IGP2 inputs No good.

madmax94

Ok, so jumping the green/blue lead to chassis ground at the main relay connector didn't let the car start. The fuel pump still did not prime.

The yellow/black lead on the largest ECU connector (connector A?) has 12v with ground to chassis and ignition on. But the yellow/black lead on the smallest connector (connector B?) has nothing. So I guess my next step is to retrace the dead yellow/black lead and check for shorts?

fcm

You can test it by running a jump from the one that has power to the one that does not, just make sure the yellow/black without power is not shorted to ground before you connect the jumper to it, if it is shorted to ground, cut it and make the jumper permanent, pull enough of the yellow/black lead without power out of the harness to reach the yellow/black with power. 94

madmax94

I was looking for shorts and found that one of the leads on the IACV connector snapped. I've got a Skunk2 IM, so the GSR harness wires were too short. Oops. Anyway, I fixed that and tested again.

With the main relay plugged in, jumping from the green/blue ECU control lead to chassis ground primes the fuel pump. Without the jumper, the fuel pump doesn't prime like before.

Before fixing the IACV connector, IGP2 had power, but IGP1 didn't have any. They both have power now.

NassTeaNa8-1993

did you ever fix it?

madmax94

It turned out that it was the old ECU. I plugged in a new phearable ECU and the fuel pump primes. The main relay clicks when the check engine light goes off upon startup. Everything works now!

fcluddington

kick azz. did you send in your old one or do you think you fried it with the first way you jumped wires. cause it worked before this build correct?

madmax94

The old one never worked. I hadn't touched any wiring when I first put it in and the fuel pump wouldn't turn on, so the old ECU was probably bad the whole time. It was an ebay special that was pretty rough looking. The phearable ECU is much better.