good morning as the title states I have an inconsistent issue wherein my fuel pump is not priming when keyed on. for instance Friday I installed a new fuel pump assuming that was the issue, car starts up on demand all day as I wanted to confirm the issue is solved, no issues, celebrations are had, next day afternoon, nothing has been touched. issue returns and will not prime period. I have done some searching and I can see that this is a common problem however I was hoping to get more recent feedback as methods and information change. Please see the below information on the vehicle. Oh and the issue was present before swapping out the previous James Bond level smoking engine.

1997 Del Sol w/D16z6 block, d16y8 head, using d16z6 manifold, injectors, harness and P28 ECU. so its been converted to OBD1.
ignition fuse = good

ECU fuse = good

battery voltage is being kept in the green with a maintainer/charger.

main relay has been converted using the JDI conversion to a standard 5 pin relay. tested pins on the relay with volt meter and no power, made an ground nearby on the chassis and tests showed power on both legs, mind you the day before I had the car running on this relay and have made no further changes relay =good

fuel pump tested by creating a direct ground at the relay. I can assume that as power is coming through the relay when I create an artificial ground that both the fuel pump and the relay are in good working order so = good

P28 ECU w/fresh capacitors (except the big one) tested in other Del sol this morning and fuel pump primes, the problem car still does not, I also tested another known good ECU on the problem car and the fuel pump no prime persists. ECUs= good

Anyhoo what I'm guessing is that there is some kind of short somewhere on the ground side. where should I look? which pins on the ECU control the main relay? what hidden/related connections might i need to check? your time and help are appreciated thankies!

 

how is your ground to thermostat housing?

 

i went through the thermostat, transmission and the ground on the other side of the engine and sanded them, degreased them and made sure they were snugged up yesterday. the issue is still present.

 

Almost seems like it could be a bad ignition switch. Maybe even try checking for spark when you have the problem with it not priming. If there's no spark it's probably the switch.

 

I have spare I just pulled from my other Del Sol when I installed in the JDI push start. I'll give that a try as it costs me nothing, I'll check on spark as well. thank you for the suggestions. report back when i have news.