Hope somebody might be able to point me in a likely direction here. I have this 1988 4runner (22re) with 240K miles that my son normally drives around town now. He pulled up the other day, complaining of the lights flickering. Then it wouldn't start. I jumped it with my Tundra. It started up pretty easy. However, after a few mins I pulled the cables and within maybe 5 more minutes it started to lug and then died. I cleaned the batt terminals (2.5yr old) and went back and jumped again. This time I left the cables on and left for a while. Came back, was running totally fine, apparently as LONG as the cables were attached and my Tundra was running. I suspected the alternator maybe, even though I recall replacing it 20-30K miles ago. Pulled it and tested it (I know you can test it in place, which I should have put more energy into), it tested fine. Now I have to put it back in and refill w/ coolant (eghh). Anyways, seems odd, I could see how it could be fuel delivery maybe but the fact that when it has continuous electrical power, it runs fine, seems like it might check that off as possibility? Sort of seems like it *must* be electrical in nature? Does anybody have any suggestions for places to look ? I might give my self a couple days before I haul it in to somebody. I get the sense that the problem could be a bit subtle and I might have problems finding it.

 

Since it runs fine with the jumper cables, I'd eliminate the charging system? At least the simple stuff. Did you have the battery load tested? Is the alternator belt slipping? I'd put a volt meter on the battery posts after you get it running and pull the jumpers off. See if you have charging voltage and it's steady. Should be 13.5ish to 14.5ish volts and not pulsating or flickering like the lights were. Try it with lights on and off. You can turn on other loads such as the blower for the heater and A/C. A good charging alternator should handle that and maintain proper voltage. (Amp output will increase, but that's not what your checking with the volt meter set on DC voltage on the positive and negative battery posts.)

Usually when your alternator isn't charging ,you get a battery and brake light on the dash.

Good luck with it and please follow up.
Scott in AZ.

 

Battery tested fined. My neighbor mentioned maybe an issue w/ grounds. I cleaned terminals, which didn't seem *that* bad and got the battery fully charged. It seems to run and *maybe* hold charge, not sure how to test that? maybe w/ multimeter over a few days? I'm replacing the negative terminal and ground wires and cleaning connections to body/engine today. It does sort of seem like that kind of thing. I'll respond again here in a few days if that seems to check out. Thanks for the reply.

 

Forgot to conclude this, sorry. I handed the 4runner back to my son and he said it died a few days later. I returned to the place where I had the alternator bench tested and they retested. Said they had never seen the weird results they got from the automatic checker tool, or whatever. Finally, w/ really high rev/rpm, it failed. Hard to tell where/why/what, etc. Anyhow, I did ... what I should have done up front and just went w/ my gut and installed a new one when the old one was out. After a new install, it is working fine. Alternator had 25K on it .. in 21 years. Autozone was where I bought it and tested ... they replaced the 20+ year old alternator for free. Pretty amazing. Anyhow, all good now, thanks for the feedback from folks. Got a bit more practice w/ the multimeter, which was probably good : )