3.1 MPFI problems

[creepin_olds]

hey everyone,

 

I have a 90 Grand Prix with a 3.1 MPFI. I have a problem. My battery light comes on on my instrument panel and will not go off. The battery terminals are tight, the solenoid seems ok, I have not found any loose wires, and the car starts up time after time ok. Does anyone have any clue what this could be? I am wondering if it could be something minor if it might be something worse than I think, I need any and all input here please!

 

Thanks in advance guys.

[THe_DeTAiL3R]

Well, on my 88 GP the batt light came on. I let it go for about 3 days, then all of a sudden it wouldn't start... ALTERNATOR!

[creepin_olds]

Thats kind of what I am thinking also, but I really really hope not. I just had it rebuilt about a year and a half ago

[THe_DeTAiL3R]

At least they are damn easy to change... unlike a 3.4DOHC or a LIM gasket

 

I would keep an extra alt in the trunk and a tool box

[jeremy]

http://www.w-body.com/forum/viewtopic.php?t=39164

[dman]

check the open terminal voltage of the battery using a voltmeter without the car runing. you should see about 12.5 volts DC. if it is at least 2 volts low you probably have a dead cell in the battery. one dead cell for every two volts low. if the battery checks ok, proceed with checking the alternator by starting the car and checking for voltage at the battery again. you sholud see at least 14.5 volts or so. if its much less than 14 volts the diodes in the alternator are going out one by one. a tell tale sign is if the light comes on than goes off for a while and comes back on. good luck.

[95oldsVan]

I agree,when my 91 3.1 Lumina Euro had that same problem,the alternator was dying.Do be sure theres no other problems in your pulley/serpentine belt system,say if one of the other pulleys were slowing down and grinding and wont let the belt spin fast enough.

 

Also be sure your battery gets a full charge before changing out alternators if needed.

 

[3pt1lumina]

My alternator shit the bed 1 day after the battery light went on. I bet that's probably it.

[92LuminaRS]

In my '92 I caught the alt before it died. Battery light never came on, I just happened to notice my voltmeter not as far up as it use to be. It normally charged around 15v, and it was in fact charging at about 13v... Battery light never had the chance to come on. As soon as I noticed it I put in a different alt.

[cutlass1991]

my 91 batt light came on. It was the alternator.

[5speedz34]

Autozone and most of the other "chain" auto parts stores should be able to test your alt for free.

[1990lumina]

My alternator shit the bed, and the batt light came on after the engine wouldn't turn over stupid pos car lol.

 

I'm gonna say alternator as well, it's cake to change on the 3.1 - I have minimal hands on mechanical knowledge and changed mine out in around 45mins...but could do it much quicker now that I know what to remove in what order.

 

Damn you guys with your volt meters.....though I like mt oilp ressure guage too....GM should have made the Lumina cluster with a volts guage and oilp ressure......put something under the gas guage would have been fine.

[92LuminaRS]

Get an aftermarket voltmeter, their like $3

[creepin_olds]

Thanks for all your replies guys. I took the car by a local alternator shop yesterday and sure enough, he tested the battery and everything and said the alternator was not charging, so I paid him to rebuild it. but he told me he just slapped a new one on it today while i was at work because they were pressed for time so i basically got a new alternator for a hundred bucks!!!!!!!!!!!!!! Sure enough, when I got the car back today, the battery light was off.