My '92 Acura fails to start sometimes. It will work fine for days, then one day it will crank but not start. Later, it will start fine. Research suggests this is a problem with the main relay, except for one thing: all the "bad relay" information I've seen suggests this is a hot weather problem. My problem seems to have nothing to do with the heat. The first time it happened was in late summer when the day was warm but cooler than it had been in a couple weeks (Washington DC summer). The second time was in the morning of a warm but not particularly hot day. Yesterday it was cold and rainy. There have been times when it's been far more hot and I haven't had a problem.

Should I pursue the bad relay diagnosis anyway? Any other suggestions?

Thanks,
-Scott

 

Listen for the fuel pump to turn on for about 2 seconds when you first turn the key to the II position (don't try to start the car). It is a faint buzzing/whirling sound that comes from the back seat, so turn off radio, etc and listen carefully.

 

Thanks for the response. By this do you mean that I should stop and listen for the fuel pump every time I want to start the car, and note whether I hear it when the car starts but not when it fails to start? If I don't hear the fuel pump when I'm experiencing the problem should I assume it's a bad main relay?

At this piont the problem occurs once every few weeks. Since it may take awhile for it to happen again, might it make sense to just go ahead and attempt a repair of the relay (I've found instructions) and hope that solves the problem?

-Scott

 

If you're good with a soldering iron, the repair is EASY. Go for it. If you were gonna spend $50 on a new relay, I'd say do some more diagnosis.

Yes, you want to listen for the fuel pump each time you start the engine. If you ever catch it "in the act" where the pump DOES run yet the engine doesn't start, then you'll know the relay is doing it's job so you should look elsewhere for the problem.

 

I'm fair to middlin' with a soldering iron. I wire electric guitars and such.

Should the fuel pump run every time the switch is put to II? In other words, if I should put the key in and turn the ignition all the way to cranking it, and it doesn't start, and I stop and pull the key out, would I expect the fuel pump to run if I immediately put the key back in and turn it to II again? And if it doesn't run I know the relay is not working?

Thanks all,
-Scott

 

Every time you go from OFF to the II position, the fuel pump should prime. I am not sure if it does it from Start to II.

If you don't hear the fuel pump prime, then it could be either the relay, the ignition switch, or the fuel pump.

One way to verify is to back-probe the blk/yel wire in the 3-pin connector near the back seat in the trunk. Connect a 12V test light to the backprobe then connect the other end to a good ground. The light should turn on when you turn the key to the II position for 2 seconds.

 

For years (maybe mid-'80s?) there's been a US-DOT requirement that the fuel pump stop running if the engine isn't running. (It's about fires after collisions.)

When you first turn the key to RUN (not START) it runs for 2 seconds then stops.
It runs while cranking the starter.
It only continues to run if the ECU sees the ignition-timing signals from the CKP, CYP, TDC sensors.
I think(?) it won't run again unless you turn the key back to OFF & then back ON.