Starter failing? Guidance sought
 

My 87 911 has picked up an intermittent issue. When I go to start it at times, the starter engages for a millisecond and then nothing, but there is power to the dash, etc. If I turn the key again, sometimes once, sometimes it takes twice, the car turns right over. I changed the DME relay just in case it was weakening, but the issue has remained. Any input appreciated!

Could be bad grounds or dirty battery connections. Check these first. Pay articular attention to the ground to the body next to the battery. This can look nice but still have oxidation. Also check the ground from the tranny to the body. Clean the connections well and see if that fixes the problem.

X2

Had that same problem w/ my '88 but completely cured it by replacing the transmission to body ground strap. That starter pulls a lot of power that a 30 year old ground strap can't always handle. Glad I checked that first before pulliing and replacing the starter.

The DME relay isn't involved with the starter spinning the motor. The starter circuit is pretty conventional. You have a big battery cable that goes to the solenoid on the starter and you have a wire coming from the start position on the ignition switch to the solenoid. No Porsche magic involved. (If you have an alarm system that could be in the middle but that usually isn't setup to inhibit cranking the starter.)

Getting a really long wire with alligator clips on it so you can check voltages at the starter while you are cranking it can help.
- Are you getting reasonable voltage to the solenoid when the starter cranks?
- Are you getting about the same voltage on the solenoid's output wire into the starter?
- Are you getting good voltage where the wire from the ignition switch connects to the solenoid.
- When you try to crank and it fails to turn, are you getting a voltage drop? (When the starter is engaged it draws so much current you should see a voltage drop. Turning on the headlights and seeing if they dim is a quick and dirty check for current going to the starter.)

Also check the connections of the battery cables to see if they are heating when it cranks. Heat means resistance which means problems. (Battery cables will heat up if you crank for an extended period but the connections shouldn't heat more then the cables.)

Going through these should show directly where the issue is.

do you have an aftermarket alarm system

+1 on the transmission ground strap.

Check & clean the connections at the solenoid-starter. It's pretty dirty and oily in there.

If you get to the point where you want to pull the starter to test or replace, I recommend the partial engine drop. You don't have to go that route, but it is easier if you have the setup to do it. Otherwise use multiple extensions and lots of lights. Small hands would probably help too.

First time I put the starter back in the 911, I didn't have it in all the way and it was a little cock-eyed. Cost me a ring gear.

Clean all connections especially grounds

+2 on the ground strap. It happened on my 1973.5T and the new strap solved the problem. If not that, then the solenoid.