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Pedal Faster
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2,658 Posts
Discussion Starter #1
Allllllll right. This could probably go in the 5 liter forum, but the wiring is pretty much the same for all '93 and under cars (maybe the others, too.)

I am doing a 5.0L swap in to my 3.8 Bird. Donor car is a '93, got all of the wiring harnesses from the dashboard forward (swapped to auto climate control, too.)

Here's what's going on: everything works beautifully. Except that the ECM will NOT ground the wire to turn on the fuel pump. I have checked every fuse, every bloody wire, made sure that the ECM's grounds are grounded, that the power pins are getting power, everything is cool.

If I jumper the test connector to ground, the fuel pump runs. Thinking that maybe I pinched/cut the length of wire that goes between the ECM and the test connector, I pulled the harness connector off of the ECM and grounded pin 22... fuel pump ran. SO, all the damned ECM has to do is ground pin 22 and the fuel pump will run. But it won't. It won't ground it in Run, it won't ground it in Start.

IF I force the fuel pump on with the ground jumper, the car starts and runs like a dream.

WTF is going on here? The only possible answer that I can come up with has to do with something I did before I was getting ready to start the car. I turned the ignition switch to Run and noticed that I was getting no fuel pump, and that the Check Engine light wasn't on. After poking around a little, I saw that I hadn't reconnected the gray 8-pin connector at the right-front of the car (C156, main ECM power). I shut off the ignition, made the connection, and since then things have been fine with the exception of the fuel pump. Is it possible that turning on the Run power without C156 connected could have damaged the ECM?

I have been staring at the '90 and '93 EVTMs so long that I'm going blind, the fuel pump circuits are the fscking same between the two, this is driving me nuts.

I also have a secondary question: if I can't get this solved soon, what's wrong with driving it with the fuel pump jumpered? The fuel pump relay doesn't energize unless the ignition is on, anyway, and I don't sit around with the ignition switch on and the car not running... good idea? Horrible idea? What say ye?
 

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Premium Member
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1,371 Posts
Check and make sure the pin on the ECM didn't get bent over when you connected it and also make sure it's crimped tight enough.
 

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5oh Transformer
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1,085 Posts
Hmm. I'm doing a similiar swap but mine is on a 96 with the 93 wiring. Did the donor run and everything? I'm between the fence with Clint and with a bad pcm. Thinking of this I should probably run to the garage and see if mine is grounding since my pcm is a yard pull.

Zero
 

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Pedal Faster
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2,658 Posts
Discussion Starter #5
Right now I am suspecting the PCM but can't really know for sure without knowing the PCM internal schematic. But the way things sit:

-All PCM ground and power wires at the harness connector are verified good
-PCM will not ground pin 22.
-PCM will not output speedo signal (though I haven't verified that the PCM is getting a VSS signal)
-Had a Check Engine Light when I first started driving it, but cleaned the -very dirty- MAF and it hasn't come back since.
-The car will spit and sputter if you try to suddenly apply more than about 1/2 throttle. THIS one is pissing me off. I am going to check the TPS, but also am going to replace the fuel filter and get the fuel pressure checked. My fuel pump makes crappy sounds, and always has, but now I'm wondering if it's had diminished capacity that I never noticed with the V6. While I like to think that I'll get out there and the TPS will be crap, the car will rev as far as you want it to in neutral.

There's just so much to think about and I don't have a lot of time to dicker with it. If the TPS is good and the fuel pressure checks out okay, and the new ECM doesn't do anything for me, I will have to put a timing light on it and make sure that is good. Also, I moved a plug wire the other day while it was running and got a little shock, so those probably need to be replaced (but I was smart enough to replace the plugs before putting in the engine). Just lots of nickel-and-dime crap like that that eats up time and money.

For what it's worth, the donor DID run, but it had been wrecked and all I could really do with it was listen to it and drive it up on the trailer. I swapped every piece of wiring from the dash (including the dash wiring because I swapped to automatic climate control) to the very front of the car. For the most part it went smoothly, save for my interior lights and power mirrors (same circuit) not working (and I narrowed that down to one wire at the fuse box.) Oh, and I discovered after I sent the donor car to the scrap yard that they changed the cruise control design some time after '90, so I have to get a new cruise servo. Whoopee. :)

Thanks for the feedback, guys,
 

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Premium Member
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1,371 Posts
Oh, and I discovered after I sent the donor car to the scrap yard that they changed the cruise control design some time after '90, so I have to get a new cruise servo. Whoopee. :)

Thanks for the feedback, guys,

You will also need the speed control amplifier from a 91-93 mn12 to get the cruise control working.

I have an extra ECM that I could let you barrow to verify if yours is working, just pay shipping + please return it after you're testing process.



Here is my thread on the cruise control wiring. CLICK HERE
 

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Pedal Faster
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2,658 Posts
Discussion Starter #7
Thanks for the offer on the ECM. It looks like I'm going to win the one that I've bid on over at eBay, but if it doesn't work out, I'll gladly take you up on your offer.

As for the cruise control, I have the amplifier hardware and the all of the wiring is there, I just still have the old '90 servo in place in the fender well.

Went to the grocery store tonight, on the way back I put it in manual 1st from a light and just pulled out as I normally would, but didn't upshift. As long as I didn't go more than about 1/2 throttle, it gladly wound up to 4 grand. Hoping the TPS test reveals something, but I suppose it could still be fuel pressure-related.
 

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Premium Member
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1,371 Posts
Isn't it sad when OEM part's are an upgrade?

That's what I was thinking when I did my 5.0 swap,

LOL
 
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