Fuel Shut off...

[samgm2]

I have a 749 installed into a supercharged chevy cavalier (Z24). I've been told that this is the computer to run for forced induction applications.

Not sure why people think that because I can find very little in the way of documentation for use of this ECM in ANY OTHER Vehicle.

In any case, the car is electronic ignition (no distributer). The car starts and will run if the fuel pump is bypassed. If the fuel pump is not bypassed, the ecm shuts it off.

Does anyone have ANY idea why this might be happening?

I've already tied MAP and MAP2 together and ESTHI and EST2HI (J2-D8 and J2-C5) together.

Any help would be appreciated. I am very uncomfortable running the car with the power to the fuel pump bypassed.

Sam.

 

[turbodig]

Re: Fuel Shut off...

I have a 749 installed into a supercharged chevy cavalier (Z24). I've been told that this is the computer to run for forced induction applications.

Not sure why people think that because I can find very little in the way of documentation for use of this ECM in ANY OTHER Vehicle.

In any case, the car is electronic ignition (no distributer). The car starts and will run if the fuel pump is bypassed. If the fuel pump is not bypassed, the ecm shuts it off.

Does anyone have ANY idea why this might be happening?

I've already tied MAP and MAP2 together and ESTHI and EST2HI (J2-D8 and J2-C5) together.

Any help would be appreciated. I am very uncomfortable running the car with the power to the fuel pump bypassed.

Sam.

Sounds like an issue with a fuel pressure interlock on your Cav.

A11 and A12 drive the fuel pump relay on the Sunbird app. I'd check the wiring up to your
fuel pump relay, then validate that the relay drive goes high when the vehicle is running.

ftp://ftp.diy-efi.org/pub/gmecm/manuals/1227749/749sunbird2.jpg

Other possibilities would be an anti-theft system of some kind that came with the Cav.

Is this a Quad-4, or another motor?

Hope it helps...

 

[samgm2]

Re: Fuel Shut off...

That helps a LOT. I think you are right.

It's a 3.1 Liter V6.

Sam.

 

[turbodig]

Re: Fuel Shut off...

That helps a LOT. I think you are right.

It's a 3.1 Liter V6.

Sam.

Interesting. Do you have the 3-coil pack with the crank sensor that fits in the block,
or do you have a cam sensor?

There's a whole set of pinouts for the '749 and should be for your native ECM there as well...
you should be able to do a pin for pin comparison of the two and check to make sure
every wire has a home.

One thing to note... some '730 based apps used different IAC wiring from the '749.
That'd be something to watch for once you get it running steadily... IAC steps moving, and the
numbers make sense.

Later,

Dig

 

[Mike V]

Re: Fuel Shut off...

Hi Dig, Hi Sam.
I know I might be a wet diaper for bringing this up, but if you have a
7730 (do you?) car, a switch to the TurboGranPrix code and a map sensor
swap is all you need. From there, it is a few tweaks to the fuel & spark
tables. I did it to a 3.1 in a 90 Beretta a couple years ago.
Mike V