Got a car in the shop that we installed an in-tank dual Bosch 044 setup on. Ran a hot feed from the battery to the pump through a relay that is switched by the stock fuel pump feed. So the new pumps should work just like the stock single pump. Come on when the key is on to prime the system then shutoff until the engine cranks. Problem is the pumps are on at all times with the key on and the engine not turning. I've traced the stock circuit back through the stock relay, etc and turns out the output signal from the ECU is on at all times with the key on. In other words the system is doing what the ECU tells it to do but the ECU isn't working as it should. The ECU is an Apexi PFC. Has anyone seen this before and/or have a solution other than a new PFC?

 

Actually, I have. And this is weird and may not apply at all to your situation. I've got a 2nd gen with a Power FC using the Banzai Racing adapter harness. Very occasionally I get the whole "click-click-start" deal, and I had read that you could run a relay triggered by the stock thin starter wire to pull more juice to the solenoid. Basically I cut the stock wire, and had it trigger the coil in the relay, and when the coil engages it sends juice straight from the battery to the starter.

Well as soon as I hook that up and put the key in the "on" position, the fuel pump was running constantly (I never tried to start the car). But this never happens on a stock 2nd gen ECU. I'm not sure why this happened, and I decided it wasn't worth the trouble of tracking it down, so I put it back to stock and it worked like normal. My guess is something is confusing the PFC into triggering the circuit opening relay, the same way it was on my car.

Hope that helps somehow.

 

Check the diagnostics box for a jumper wire. then make sure the FP wire is not gounding out to anything.

 

The diagnostic box is clear. And there are no shorts. You can unplug the relay and still get positive voltage out of the ECU on the fuel pump trigger pin. The issue lies in the ECU. I am under the impression that the only thing that can make the pump spin up when the key is turned to ON is the initial prime and then a signal from the crank sensor. True? Or is there another input that may cause the pump to run?

 

Are you using the right channel? The ecu also regulates the speed of the pump with an output connected to a resistor.

 

Install a stock ECU, if it runs all the time it is an electrical issue, if it primes normally then it is a PFC issue

 

Finally got back to this today and solved it. Wasn't the ECU. Figured that out when I removed the ECU and the fuel pump still ran with the key on and I still had continuity to ground on the pin. Someone has done some fancy wiring to circumvent the resistor as best as I can tell. The ground side of the relay that is supposed to be triggered by the ECU was wired straight to ground. At any rate, thanks for the suggestions.