So I usually run my car on a chipped obd1 ecu. I’m trying to pass NYSI this spring and I bought a obd2a conversion harness and matching p75 ecu.

the car runs fine on the obd1 ecu. Only “problem” would be once every like 20 times I try to start it, the starter won’t engage. The dash lights dim and no click, no nothing. It’s never really bothered me because it always starts the second try. At worst, 3rd

so now when I plug in the obd2 ecu, the fuel pump
never turns on. The car will start and run for a few seconds until the rail runs dry

im thinking the obd2 ecu uses a different ground than the obd1 one and it’s causing the pump not to prime.

Aany suggestions?

 

Either your adapter harness is bad or the ECU is bad. Try known good examples of each and see which is the culprit.

 

I’ve tried multiples of both with no change.

 

Bad harness, never had this problem. Use ffsquad ecu pinouts to make sure its correct, the harness that is.

 

How would the engine harness be bad if it works with an OBD-1 ECU and conversion harness ?

 

The jumper harness. If you look at ffsquad they tell you which wire needs to be moved in order for the fuel pump to run, or something to do with the difference between the obd2b integras and obd2b civic ecu pinouts. It was one wire I believe.

 

I’ve looked into that and the fuel pump power wire is different- on my conversion harness the 2 possible locations are merged.

I really only need this thing to run for a little bit on this ecu just to pass inspection. Any other suggestions?

I even just went as far as cutting the “empty slot” wire and making it so the conversion harness was only connected to the civic fuel pump pin. Still no change. Car will want to start but fuel pump still isn’t turning on. Car runs perfect on the obd1 ecu with matching conversion harness.