Scaytale

iTrader: (3)

Good Day all

Just getting time to play with the car again, got the new fuel system in, ID 720 Primary and ID 1000 secondary new fuel lined in the engine bay and an automotive regulator and a new fuel pump. I have a Power FC, and the car was running well before I started this.

I used the DataLogit to reduce the fuel map by about 23% overall as a starting point for tuning A/F. This seems to have worked well, the car started right up and my idle A/F was about 13.2 before it was 13.5. All was going well until I took the car for a short drive. After about 5 min I pulled into a parking lot and was idling fine and the car died, at first I didn’t think anything of it and just tried to start it, no go. So I popped the hood and no fuel pressure on the gage. Luckily I was semi prepared, jumped the Diagnostic and still no FP, OK since I did the rewire I checked my fuse (now located near the battery, all is well, in fact I can hear the fuel pump relay click but no pressure. I open the panel to the Fuel pump and no Voltage. Sad Panda. I put it back together and think about how to get the car home and then of course try starting it again and it starts right up. Good FP Idles fine revs good and 7.05 VDC at the pump so OK at idle. I drive the car home and leave it ideling in the Driveway and it dies again, no FP. Sad Panda, I hate intermittent electrical issues! I do a little searching, lots of info about how to and how not to rewire the fuel pump, but not my issue, as far as I could tell. I started checking the manual (notice I checked here first, ). I remember reading somewhere on the forum that the PCM controls the fuel pump after the engine starts. So page Z-28 table B1a Engine control system, fuel control system, ignition system, looks like the ignition switch provides power to the EGI main relay and closes it, with a direct path to Ground also providing power to the fuel pump relay, with what seems to be a ground at the PCM 1T terminal. Once this is grounded the relay should close and the fuel pump should run on voltage provided through the fuel pump resister. Please correct me if I am wrong about how this circuit works.

I have a few issues with this;

1. If the PCM ground were the issue, shouldn’t the jumping of the Diagnostic ground to the FP bypassed this and I should have gotten FP?

2. If the fuel pump relay is the issue the pump shouldn’t run at all, is this true?

So I am stuck, I don’t want to spend 50 bucks on a relay I might not need, and I don’t know for sure how the Power FC provides a ground for the fuel pump relay, or what might trigger the Power FC to stop providing that ground.

Any troubleshooting help out there?

Thanks for your time

vrx8

iTrader: (18)

Can you post a diagram of your fuel pump rewire?

Scaytale

iTrader: (3)

vrx8, sure here it is and the info is from Chuck Westbrooks tuning notes.

HOW TO REWIRE THE STOCK FUEL PUMP SYSTEM FOR INCREASED FUEL CAPACITY

When I rewired mine, the voltage at the pump went up by 2 volts from 11.8 to 13.8 with the engine running. This equates to an increase of power to the pump by 37%. Use 12 gauge or larger wire. We are creating parallel paths for current flow which reduces resistance and increases voltage. Look at pages F-95, F-110 and F-238 of the 1993 manual for the FP wiring which are located below.

If you do this after AFR tuning, your AFRs may will be richer - especially for boost, and you will need to retune. Some people have seen duty cycle reduce as much as 10% at the high revs.

Step1: At the fuel pump connector in the trunk, splice in a wire from the ground black wire to one of the studs protruding from the trunk floor close by. Use a clean washer and clear away paint around the stud. This creates an improved grounding circuit. This gave me an increase of .5V to the pump.

Step2: At the fuel pump connector in the trunk, splice in a wire to the HOT 12 V white wire with red stripe. Run this all the way up to output side of the FUEL PUMP RELAY which is located in the front of the engine compartment. It has the same color wire; white with red stripe.

Step3: Look closely at the CIRCUIT OPENING RELAY for the FP. The HOT 12V side (upper right corner of the relay) is the heavy solid blue colored wire which goes through a fuse to the ignition switch, through other fuses to the battery +12V terminal. We bypass this path and go directly from the relay through a new fuse to the battery +12V terminal. This relay is located on the left hand side of the engine compartment near the strut tower where some other relays and main fuses are. Some people have used one of the unused fuse holders to place the new 20amp fuse, or place it inline near the battery. Cut the heavy solid blue wire about three inches from where it connects to the circuit opening relay. The end going back to the original fuse needs to be fully insulated so that it can't ground/short out. You can remove it's original fuse from the panel inside the car, it is no longer used. From the three inch wire going to the relay, attach your new wire and fuse holder and run the wire directly to the +12V terminal of the battery.

Some racers place the battery in the trunk with a new locally placed relay providing direct full power from the battery to the pump/pumps. They use the original pump power wire to trigger this new relay.

Scaytale

iTrader: (3)

Really? No help? OK I will try to figure it on my own. Must be a Ground issue, maybe the PFC isn't well grounded.

Evadrepus

iTrader: (3)

I had what sounds like the same problem. It turned out to be the connector to the fuel pump inside the gas tank. I deleted the connector to the pump by soldering and shrink wrap. Hope this helps.

Scaytale

iTrader: (3)

Thanks for the feed back, I also have eliminated that connection point. My issue is that I loose voltage to the pump. I check it at the connecter.

vrx8

iTrader: (18)

that how i have mine and there is no problem.