I am having strange things happen to my 1992 SC4 lately. I just passed 108K miles. Last week My fuel pump ECU went out on me. I bypassed it following the instructions on these forums. Everything was great. I changed my battery 4 days ago since my old one died. Yesterday it rained like crazy here and I went to go start the car to leave work and all it would do is crank over.

I checked voltage to the fuel pump - it was good. I checked for spark and it was getting no spark. Also my AFC NEO quit working. It would not illuminate when I cycled the key on. I believe it gets its power from a 12V wire going to the ECU. I was mad and it was raining so I left the car to sit overnight.

I came back to work this morning, opened the car up, cranked it and it fired up the very first try as if nothing was wrong. My AFC NEO turns on now and everything is back to normal.

Any ideas on what would give me no spark one day and then a perfectly running car the next?

 

The beginning signs of a failing ecu. Typical no fuel or spark everything checks out fine and can't find any other cause. Then the next hour or so its starts right back up. If you have your afc neo hooked up to a power wire that controls spark and there is no power coming from the ecu power wire it might be a defective ecu.(long run on sentence I know) It is going to get worse for some reason the capacators in these ECU's crap out and your car doesn't run. ECU's are cheap for these cars like $100 you might want to think about getting one. Models years affected are 92-95 LS and SC400.

 

I figured that was a possible cause. Funny thing, I just went out to try and start the car again, and it wouldn't start. I tinkered with a few things, even checking all the connections going into the ECU.

I opened the big fuse box under the hood and tapped on the top on the circular EFI relay. The AFC NEO fired back up and the car started. Wit the key on but the car off, I could tap the top of the EFI relay and hear fuel rushing though the rails. My guess is the EFI relay wasnt pushed down all the way or something on the inside of the relay is bad. I switched the EFI relay with the dimmer relay and everything is fine for now.

Thanks

 

Yeah My brother's SC had that issue a lot of corrosion built up on one since it was near the battery. Corroded inside and it was broken. Find another relay to replace the broken one. Just keep the ECU in mind though in the future if it hasn't been rebuilt already.