Car won't start, maybe alternator?

[TRSblader]

Hey guys, I tried doing some quick searching for general "won't start" threads, but wasn't quite finding my particular problem.

Here's the scenario. Battery relocated to the trunk, and no corrosion on terminals. Alternator is what I think it is, but I have no clue. ALL lights (interior and exterior) DO WORK. Radio and stuff is out, so can't check that, but power windows and locks DO WORK. The alternator is getting power, because I went to tighten the screws down where the power wires are, and let go of my wrench and watched a couple sparks fly as it touched my external gate.

My voltmeter in the car reads a solid 12 volts without fan or lights on. When I hook up jumper cables, it will read to around 13.9-14 without accessories. I can start the car, and sometimes it goes to about 750 (stock rev) and dies immediately, and sometimes it goes up to around 2500 then dies. I DO have gas in the tank. Not much, but there is roughly 1/8th of a tank of 91 octane left.

I have not been able to get the battery tested or alternator (that's on the to-do-list, but college is kicking my butt right now).

Any other things it could be, or is it most likely the alternator as I suspected?

Also, if this is a common problem, don't hesitate to tell me what it is so I can search it myself, I am more than capable of doing that. Seemed like no one had the exact problem I did, so with my limited time, I'd like to pinpoint the answer, and not replace a lot of other stuff quite yet.

Thanks in advance for the responses, and sorry for the book I just wrote.

 

[luv2rallye]

Put a voltmeter right on the battery terminals. Should read at least 12.6V with nothing on and battery charged. With engine running (no jumper cables) you should read 14.4V (13.5 minimum) - if not alternator is bad (sometimes can be a really bad battery that is pulling the voltage down but this is rare).

 

[ilco187]

either a bad diode in the alt, or if it mainly happens at cold start could be ecm coolant temp sensor, another way to tell if alt, is bad remove ground on battery while its running if it dies than alt, or bad wires

 

[luv2rallye]

another way to tell if alt, is bad remove ground on battery while its running if it dies than alt, or bad wires

Although this will tell if alt is bad, it can easily damage the ECU and should NOT be done: http://www.dsmtuners.com/forums/pro...-battery-alternator-question.html#post1763645

 

[ilco187]

Although this will tell if alt is bad, it can easily damage the ECU and should NOT be done: http://www.dsmtuners.com/forums/pro...-battery-alternator-question.html#post1763645

ah cool i never knew that could happen but its good to know so i wont be doing tests like that very often, without caution.

 

[TRSblader]

Thanks for the replies. Forgot to say that sometimes before it does fire up and stay running on the jumper cables, it won't stay running if I give it a little bit of throttle (not holding the pedal down the whole time). Not sure if that will change the diagnosis or not, but figure I'd throw it out there.

 

[jdd1231]

Well its gotta have voltage to run too.If the alt is bad,and the battery is discharged,that may be it.

 

[TRSblader]

That's what I thought, but I was just making sure it wasn't a fuel issue then and it was indeed still a charging system problem

 

[John Samuels]

1991 Eagle Talon TSI AWD. I have just replaced my alternator. It was a pig to remove the old one. This is because the pivot bolt, when extracted, grounds out to the engine compartment sidewall.

There is insufficient clearence to extract this bolt fully, without removing the whole side of the compartment.

After much spitting and chewing, I decided to remove the forward splashguard, then drill out a 2"x1" hole, thus exposing the pivot bolt.

It is then simply a matter of grasping the pivot bolt head, though the drilled access hole, and reoving the bolt easily.

Once your new alt is in position, use this same hole to replace the pivot bolt.

Much easier than removing the side of the engine compartment.

See picture (a bit fuzzy, but you can see hole and bolt head)

I hope this tip is useful for someone!

John Samuels