Some time ago my car decided it didn't like to stay running after starting. This problem just showed up one day. It would die almost immediately after starting, revving up to 2k then down to 500rpm, then up to 1k, then cutting off. Nothing would keep it going. I traced it to the Circuit Relay located next to the EGI Main Relay. I replaced the relay with a new one with the exact same problem occuring. So then I tried bypassing the relay all together with jumpers as seen below. This is the only way the car will run. Obviously something is going on and I need some input as to where to look next to solve this electrical problem. FYI both new and old relays test good per the FSM.

 

Most likely have a break in a wire somewhere in the body harness of the car. I had a customer's car doing the same thing so I ran new wires from the ecu to the relay. It was too much work to diagnose and he didn't want to spend the money on a new body harness.

 

Isnt that the Fuel pump relay?

 

Yes it is...well...one of two fuel pump relays. So what I've come up with is that the wire from the relay to the 1T location at the ECU must be bad. I have 12V at the same sides of the relay when grounded to the chassis. This eliminates the fuel pump wires (as the fuel pump runs) and leaves the ECU side. I think that the wire from the relay to the ECU has broken somewhere in the harness compromising the ECU's ability to close the circuit. I'll take Rotary Experiment Sevens' experience and run a stand alone wire directly to the 1T terminal at the ECU from the relay. I'll post my results.

Steve.

 

So here is what I've discovered.....
I checked the voltages at the four connectors (key to "on" position and relay removed) where this relay plugs in and found that the wire that goes from the relay to the 1T location on the ECU is generating a voltage of .14 volts. I checked this at the diagnostic box at the fuel pump pin and again found .14 volts. Finally, with relay removed again, I removed the wire from the ECU and tested again and got the same voltage. This was with both ends of the wire disconnected. So it seems this wire is making contact with a live wire somewhere in the harness. I'm now adding a stand alone wire directly from the relay to the ECU. Will update again shortly.

 

Check up inside the front wheel fender liners and make sure your tires have not rubbed thru them in a spot and into the front "ring" harness. This has happened before


later

 

Ok, I've wired the relay directly to the 1T pin on the ECU harness. Tried to start it, relay in place, with no luck. I connected a voltmeter across the coil side of the relay plugs and it registers .25volts. Grounding it to the battery I get 12v from the source side so for some reason the ECU is still not closing the circuit. Any ideas why this is occuring? Would this throw the car into limp mode? It still runs if I jump the connections as shown int the picture. Man, I pulling my hair out.

 

I've got some burn thru on the drivers side wheel well up front but no wires are in this location. Keep throwing out the ideas though.

Steve

 

I am a bit tired but so i may have missed it if you posted it. any 4 post relay will have 2 power sides at all times (if it is ground controlled meaning the ecu supplies a ground) one side will go to the load (ie the fuel pump) the other comes from the control.

A. 12v (will power fuel pump) B. 12v (will be used to close relay)
C. wire goes to fuel pump D switching ground (when - relay is active)

that FP relay only closes for a few seconds when you first turn the key to on. It also engages (ecu grounds it) when you crank the car. you do have 2 powers in the socket when the car is just turned on correct?

a good test is to have a test light attached to battery + probe the relay socket (on the ecu controll pin) and have someone turn the key to on. you should see it light up for a few seconds then shut off. then have them crank it and you should see it on steady. this means the ecu control is ok.

with the test light on batt - turn the key to on and you should find two pins with power where the light turns on.

 

Yes, I have tested and both 12v sources are good. I've determined that the ECU is not grounding. Fuel pump runs fine when using the jumper wire. I used a voltmeter instead of a light to determine the ECU was not closing the circuit. Car running or starting, the ECU won't close the circuit.