tbi harness question

[j20m715]

I have a 91 v3500 with a tbi 350/4l80/205.

My problem is I have a burnt harness & missing ecm.

From the searching I have done, The ecm should be 1227747. Is this correct ?
My next question is where can I find a replacement harness (fuse panel & int wiring) ?



Great site, I have been doing a lot of reading.

[Six_Shooter]

If it has a 4L80E, the ECM won't be a 1227747, it will likely be a 16147060. The '7747 doesn't have trans control capabilities, the '7060 does, though it is not a very common PCM.

There is the 16197427, that can control the TBI, and with the right code, control the 4L80E. The 16197427 is a more common PCM than the '7060.

[j20m715]

If it has a 4L80E, the ECM won't be a 1227747, it will likely be a 16147060. The '7747 doesn't have trans control capabilities, the '7060 does, though it is not a very common PCM.

There is the 16197427, that can control the TBI, and with the right code, control the 4L80E. The 16197427 is a more common PCM than the '7060.

Thanks for the info. I am continuing to search.

I do know this was a ONE year only setup which is making finding parts even harder.

[j20m715]

Well, I removed the complete harness & fuse panel from the truck today.
Its not as bad as I thought it is.
The ecmb wire melted from the fuse panel to the junction block at the firewall (between fuse panel & junction block).
It looks like it took out a couple other wires (4-5) with it when it melted.
I plan on replacing the burnt wires & giving it a try.

I am also cleaning up the harness of all unwanted wiring (seatbelt buzzer, ect) while I have it apart.

Wish me luck & I will post up as I have progress.

[Six_Shooter]

Make sure you don't remove any legally required circuits. Some places requure the seat buzzer and dash light to work, to pass safety. Check your state/provincial laws.

[j20m715]

Make sure you don't remove any legally required circuits. Some places requure the seat buzzer and dash light to work, to pass safety. Check your state/provincial laws.

Thanks for the heads up. Its a 91, I dont think I have to worry about it.

Im still cleaning & replacing wires, hope to have the harness done today.

[gregs78cam]

WOW, you actually have a 4L80E with a NP205, that is one rare animal.

[j20m715]

WOW, you actually have a 4L80E with a NP205, that is one rare animal.

Yeah, 1 year only in the crew cabs

[JeepsAndGuns]

I thought the 4L80E didnt come out till like 93? But I know very little about chevys too.

[j20m715]

I thought the 4L80E didnt come out till like 93? But I know very little about chevys too.

Also in 3/4 ton burbs in 91 but they got a np241 t-case.



Well I got the harness finished up & halfway put back in.

Now chasing wiring issues for dual tanks & fuel pump relay (some people should not be allowed to work on wiring ).
The p.o. did some very interesting fixes. Looks like the whole reason they fried the wiring is they tried bypassing the tank switch.

[EagleMark]

That tank switch also switches fuel pumps and return lines...

[j20m715]

That tank switch also switches fuel pumps and return lines...

I have fixed most of the harness, I still have one issue with the tank wiring (only getting 9.65 volts) not enough to power fuel pumps.

I can supply 12+ to it & get it to work, but its not right.

Did get truck to start today but need to relplace all fluids (ALL fluids were drained including brake & power steering fluid).

I used a 16147060 pcm to start it but havent driven it YET.

Lots of little things to do, but im getting there.

[EagleMark]

Fuel pump grounds could also be the voltage issue.

[j20m715]

Fuel pump grounds could also be the voltage issue.

Got everything worked out except one issue.
I was having low voltage to my fuel pumps (one at a time).
I replaced my oil pressure switch & now my fuel pump wont shut off.

Can someone explain what turns the fuel pumps on BEFORE the oil pressure switch closes ?

Btw this a 91 chevy 1 ton 4x4 (square body) v3500 with a tbi 350.

Thanks in advance.

[EagleMark]

I think your old oil pressure switch was better then the new one?

The fuel pump relay is what controls the fuel pump power, the relay is triggered on by ECM when key on. Oil pressure is redundant. Check the wiring diagram.
http://www.gearhead-efi.com/Fuel-Inj...8&d=1331599730