Hi, I recently purchased an 89 IROC 305 TBI... and I am switching to carb. I know all of the opinions on why this is not the best move, but I really enjoy older-fashioned set-ups, and I am in no way concerned with fuel economy, and as far as emissions goes, this is more of a project car than a regular driver or street car. I already have a non-computer controlled distributor, and a new manifold is already installed to fit carb applications. Anways, here is my question:

The ECM, which I have taken out, apparently controls the fuel pump. How can I wire the fuel pump so that it will work correctly? Also, which sensors can I remove (or at least the wiring for) which were previously controlled or monitored by the ECM that are now useless? I am just worried that I will accidentally remove some important wiring. Am I correct in assuming that ANYTHING previously connected in some way to the ECM is useless now? Is there any way I can monitor the temperature on the gauge already installed? (i'm assuming that was previously controlled by the ECM). Thank you all in advance for your help.

 

bump.... any advice? Thanks.

 

The gauges in the instrument cluster use separate sensors.
So you can safely remove all the sensors that the ECM used and keep the sensors for your gauges.

As for the fuel pump, you can keep the FPOP (Fuel Pupmp Oil Pressure) switch which will keep your fuel pump running as long as the engine is turning (and buildinng up oil pressure).
And you can add a pushbutton to just prime the fuel pump before starting. The push button would be sending fused 12V to the green/white wire on the FP relay.

Hope this helps.
Lou

 

Lou,

Thanks a lot for the response. It definitely does help. My only question is, the FPOP switch is not controlled by the ECM? I thought it was, based on figure #41 (wiring diagram) on this website:

http://www.autozone.com/az/cds/en_us...rInfoPages.htm

Also what wiring in that diagram MUST stay with a carb setup, but with no ECM?

I know this is asking a lot, thanks very much for your help. I couldnt have gotten as far as I already have without the help of everyone on this site.

Matt

 

Correct, the FPOP switch is a secondary circuit (parallel to the ECM) that ensures your car can run even if the FP relay fails. It's not fun getting stranded 100 miles from the nearest service station / store because of a $5 relay.

You should be able to remove all the wiring from the computer to the engine (it is routed through the passenger side into the fenderwell and up under the hood). But doublecheck first because I have never done it myself.
Practically anything that the computer controls or a sensor that the ECM reads from can go.

Lou

 

Ok, great. Yea I actually already started removing the wiring, pulled it all the way through across the engine bay already, and when I saw that the FPOP switch was wired to the ECM, I was leary of continuing removing all ECM wiring until I knew that the fuel pump could function without all that wiring. I've got most of the ECM wiring pulled from the passenger side fender, separated up to the driver's side firewall, where it connects to a bunch of relays/connectors over there, and Im just trying to figure out what I can take out and what needs to stay. If you're telling me that most ECM connected sensors can go, then I know I can remove most of the wiring going through the driver's side firewall that was previously connected to the ECM as well. Thanks very much, you've been a big help.

 

just curious if anyone knows which snesors can beremoved for sure when taking out the ecm?