wiring from scratch, need help with fuel pump
 

Hey, long time creeper first time poster here:

I have a 64 Fairlane that I am dropping the engine from an 86 Crown Viccy the computer from a 89 GT (A9P, got a racing AOD behind it) and the wiring harness from a 92 (i think, based on the fuel pump relay I had to get from autozone) Cobra. Now, with that out of the way...

I am piece by piece bringing this abomination online. I am now working on the fuel pump.

I wired up this fuel pump http://www.autozone.com/autozone/acc...er=244642_0_0_

Now turn the key... nothing. Which I always kind of expect.

So here is the evidence I have at this time.

The blue and orange wire (the EEC ground) is showing 10.2v (so is the red wire, thus the relay isn't opening). When I use the self test pigtail and ground out blue and orange the pump runs wide open.

At the computer, I've hooked up a multimeter between blue and orange (the infamous pin 22) and constant power. key off: I get 12.2v. key on I get 2v. this happens instantaneously and doesn't change.

I have successfully hooked up to the computer with a tweecer and it seems to be running right but I haven't changed anything or written a new tweec.

I also haven't hooked up any of the other sensors.

My question is: how does the computer decide weather or not to let the fuel pump run? e.g. could it be that the computer is preventing the fuel pump from running because it is freaking out about not having feed back from any other sensor?

My initial solution to this problem is to bypass the relay by hooking pink and black (the constant power for the fuel pump) up to a switch or grounding blue and orange via switch and then manually operating the fuel pump like that. I know this increases the chance of flooding it, but what other problems might this cause? I will do this as a temporary fix until i bring all of the other components online just in case it starts operating normally when something else gets hooked up.

Based on the trouble shooting guides I am at the point which seems like a bad computer, but there are sooo many other variables going on, i'm hesitant to blame the computer just yet, especially when tweecer is reading it ok.


thanks

Hate to be the bearer of bad news, and it's totally irrelevant to the thread, but a 86 Crown Vic motor isn't HO. You'll need an HO camshaft or the engine won't run with that computer.

That's true the motor I have doesn't have the HO firing order, therefor I either need to replace the camshaft or reprogram the injector firing order. That's why I have the tweecer. If you go that route ( I am now speaking for the benefit for any fool who follows my path), if you reprogram the injectors you need to switch the distributor gear from the steel one that goes with the TFI distributor to an iron one, because the steel one will chew up the cam shaft that is currently in crown vic motor. There also seems to be an active debate/rumors on the interwebz about this, some say it will run even with the wrong firing order you'll just loose a couple horse power less than a mpg and it will stumble ever so slightly at idle.

thanks mattdel, I apprecieate you trying to warn me of potential pit falls, and I'm sure there is one I have over looked that will inevitably be my doom.

any ideas yet on potential downside to a manual fuel pump via grounding out blue/orange via switch? also, why doe dk green/yellow go back into the computer (and to the pump) is the computer monitoring that the fuel pump is on? I generally get about 2 volts coming out of dkgreen-yellow from the computer side.

Ah, didn't see the tweecer part. Also, in answer to your question: The ECM fires the FP relay for 3 seconds after initial ECM power up. Then afterwards it triggers the relay when it receives a PIP signal from the pickup coil in the distributor.

Awesome! Thank you!