avhart

Hi everyone, my question today is can anybody tell me what may cause a low voltage of about 0.5v at the B+ on the Diagnostic connector in the engine bay? I swapped the EFI relay already but that didn't make a difference.

I am trying to bridge the B+ and FP connectors to get my fuel pump to run. This has been an intermittent problem (the worse type of problem) for some time now and only happens when the car has not being started for three or four days. Once started, it runs and starts up from then on just fine. So I decided to do some trouble shooting today and found this low voltage on the B+ connector terminal.

Thanks in advance.

LeX2K

Don't have a wiring diagram for your car but the circuit is basically this.

Using a test light with incandescent bulb (volt meter can fool you) check for power at the EFI relay.

avhart

Right! I think this diagram will be a great help. I haven't seen it before but it seems a very simple and direct circuit to the B+ on the connector. I will work with it and post my results.

Thanks very much..

avhart

Well, well I swapped the horn relay with the EFI relay and guess what - started up right away. I had another old relay in my stock that I had used initially but that one didn't work as I mentioned above.

I'll give it some time yet to make sure the problem is really solved but it sure looks good at the moment.

Thank you LeX2K

LeX2K

Nice. Guess what, I had the exact same problem with my '87 Camry. Intermittent start would fail maybe every 2 months and always in warmer weather. I got stranded once but luckily had some wire in the car so ran it directly to the circuit opening relay and could drive home. When I examined the EFI relay it looked cooked meaning it was obvious the thing had been powered for a very long time in this case about 300,000 miles. Got one from a salvage yard under the dash same relay but not on all the time.

I wonder if it's exactly the same relay in your car, could be.

avhart

Very well could be - they are both 90987-02004 pretty common. The car uses more than one of them as well.

LeX2K

Same relay. I think the actual problem with the relay in my case was due to heat the terminals were oxidized they looked much darker than other relays. Instead of cleaning I replaced because I don't like getting stranded. Car never stalled once started it only failed to start.

avhart

Well good show all round I'd say. What you did made a lot of sense.

avhart

You know, on re-reading your post about the terminals on your relay being dark and oxidized I realized that's exactly how the terminals looked on my problematic relay. The terminals on the horn relay were pristine. So it all made a lot of sense to me.