LT1 Idle problem solved....

[Samckitt]

I haven't posted this problem on here, maybe I should have & saved myself some trouble.

Dumb a$$ parts removed to protect the stupid (me).

Anyway a long time ago I read somewhere to use the fuel tank vent line as the return when putting a fuel injected motor in an 80's G body car. Because that line is 5/16" compared to the stock carbed return line of 1/4". So I did, including using that associated line on the sending unit. So I get the motor running & it doesn't idle for crap, nothing I do changes it. Even reprogramming the PCM for the cam didn't make any difference. Well the other night I had it running again & I noticed a puddle of fuel forming on the floor under the gas tank. ^%$# NOW WHAT! So today I take the tank off & turn the pump on & I notice the fuel is coming out around the return junction. So I take it off, take the sending unit out, thinking somehow the line is plugged. Nope, the vent fitting on the sending unit has a restrictor plate in it, a hole about 1/16" is all that is between the returning fuel & the tank. DUH. It wouldn't idle because the fuel pressure is too high because it can't get back into the tank. Fix that & now it idles great.

[86Cutlass383SR]

I learned my lesson on fuel lines and EFI. I converted my Cutlass to a 383 TPI and re-used the OE main fuel line as the return. I then ran a new 3/8 main for the FI. When I first fired fired it up it wouldn't hardly run and was getting over 100 psi (no... that's not a typo...). Come to find out, my old main line was so plugged that fuel couldn't return back to the tank. Weird thing is it seemed to run good with the carbed V6 in it. Guess they don't need much fuel...

Scot... Do you have any experience tuning an 89 F-body ECM?

Doug

[Samckitt]

I imagine before it is all over with I will replace my feed & return lines with some made for a Buick Grand National.

Doug - Sorry no experience tuning TPI ECMs. When I had a TPI in another Monte I didn't have much mods to the motor so I simply had a Hypertech chip in it. Try John Spears at speartech.com. He reprogrammed my LT1 PCM, he can probably do a chip for a TPI too.

[Ollie8974]

If you want to learn how to tune ECM's, Check out Thirdgen.org

[86Cutlass383SR]

I have been to Thirdgen.org I was basically looking for a base chip to safely start a new engine (highly modded 383) and then work on a chip myself as I could. Probably have PCMforless burn me one.

Doug