M20 super rich-help!

[Natman61]

Hi, my winter project was renewing a 90 325 I cab. I deleted the cat, replaced the O2 sensor, replaced the original injectors with 19lb 4 pintle Ford 5.0 style, in anticipation of adding a Conforti chip soon. Starting it up, it is full rich, like the regulator is doing nothing. Fuel pressure out the return is 70-90 lbs! I ohmed the temp sensor, replaced the regulator, have good vacuum to the regulator…is my ecm not happy with the changes? Any feedback is appreciated

[digger]

probably address the fuel pressure. The fuel pressure should be 3b for m20b25 (43psi w.r.t reference, so depending if idling ~37psi due to vacuum or 43 psi @ WOT ) and this is the pressure as measured on the feed line not the return line post FPR. you might have a blockage on the return line or have mixed up the feed/return lines (which can damage the FPR) but install the pressure gauge on the feedline

Ideally you should use the stock injectors for diagnosis purposes because bigger injectors will run rich until the compensation kicks in (O2 sensor) and there could be some ECU learning involved

[Natman61]

Hi, I did the fuel pressure test at the rail and got just shy of 40 psi, blew through the return line and it was clear. Tried disconnecting the O2 sensor, and no change, still full rich. Kinda stumped, thanks for knowledge

[digger]

How do you know it is full rich ?

put the stock injectors back in

[Natman61]

I will do that, when running heavy, sooty smoke, doesn’t want to idle

[82eye]

run the stock injectors. you need more supporting mods than just a chip for the ford injectors imo. if you want better, smoother power go to an open pintle 4-hole compatible 16lb injector.