84 Carrera Starter Questions

motogman · 05-19-2018, 10:42 AM

I have done a bunch of searching and diagnostics on my car and I am looking for additional input/support.

The starter does not turn over but the solenoid operates. I have checked the voltage to the starter and it is measuring 10.7 volts at the starter. The battery checks out at 12.65V. I ran a set of jumper cables from batter to starter to see if higher voltage would make a difference but the voltage drop over the jumper cables was about the same with about 10.8 volts with the jumper cables. Besides the trouble shooting guide on the porscherepair site suggests 7.5 volts at the starter is sufficient.

https://www.porscherepair.us/porsche-911-1984-1989/starting-system-troubleshooting.html

So I don't think it is a solenoid, battery or voltage problem.

I have owed this car about 5 years but have been around it with the previous owner for 22 years. They had replaced the starter a couple of times with a Bosch unit the last time bing about 6 years ago and there are not that many miles on the car since. What is the likelihood that the starter is bad? It seems that the Bosch units are rebuilt units and maybe prone to problems - what is the community experience?

What else could be causing this? Any other ideas or things to check before I replace the starter?

darrin · 05-19-2018, 11:19 AM

what happens if you try jumping the battery? (e.g. jumpstarting the car) -- A battery's resting voltage doesn't give much of a picture into its amperage/capacity? another "old school" way to test would be to try starting with headlights on (without trying to jump)-- if they go dark when the solenoid click, good chance your battery's shot.

uwanna · 05-19-2018, 11:21 AM

Buy one of these and your troubles will be history! Been using one for the last five years on my 3.6 transplant with no problems.

https://www.ebay.com/itm/323234225978?ViewItem=&vxp=mtr&item=323234225978

motogman · 05-19-2018, 12:25 PM

To Darren's post --- I forgot to mention that I pulled the new battery from my BMW and hooked it up to check and there was now difference.

I have just taken the starter out, not as bad as I feared.

With the starter on the bench, I put jumper cables between the + battery and the battery post on the starter and then - to the starter mounting flange. When I jumpered 12 V to the solenoid - nothing. Not even solenoid action which I had when the starter was in the car. That doesn't seem right to me.

When I put the 12 volts directly to the terminal post with the wiring going into the starter motor (i.e. on the other side of the solenoid from where the battery power normally comes in) I expected if it was OK for the motor to spin, but again nothing.

Is my thinking on the starter tests correct here or am I doing something that doesn't make sense.

Seems like voltage to the input to the motor should make it spin if it were working.

BTW... I am on the verge of ordering a new starter from our host unless someone has a better idea...

Tremelune · 05-19-2018, 01:42 PM

You sure you're grounding it correctly on the bench? No click? Seems weird that the solenoid would suddenly fail coming out of the car, or that both would fail together completely.

I'd blame the transmission ground strap, but I think you'd at least get something if it was just a weak ground.

motogman · 05-19-2018, 06:23 PM

So here is the end result...

Car back on the road and all working fine. Hopefully this can be a thread that others with this problem will find and maybe forego some of the extra work I endured.

As can be seen in the earlier posts, my starter was not engaging but the solenoid was activating. The battery measured good voltage, and connecting another known good battery to the battery in the 911 with jumper cables did not result in the starter operating properly. After removing the starter from the car, it did not function on the bench when powered from the battery in the 911.

After ordering a starter off of PelicanParts, I thought to try powering the starter from the battery in my BMW. Low and behold, it worked as expected. With jumper cables connecting the starter to the battery and jumping the solenoid it engaged, whirled etc. as expected. Damn.

So I pulled the battery and had it tested and ... YES - the 5-6 year old battery was no longer doing it's job - a bad cell (or two). Even with this the voltage read correctly at 12.65 volts.

So the morale of the story is... don't necessarily jump to the worst conclusion. Start with the easier things. Oh... and a 12.6 volt reading on your battery does not mean it is good.

So after installing the starter back in the car and putting a new battery in, I had a nice drive this afternoon. Figured it would be good to fully charge the new battery.

DRACO A5OG · DRACO A5OG's Garage

AAA or FLAPS will give you a reading on state of the CCA. I wish there was a cheap tool for that out there.

Glad you got it taken cared of, Enjoy!