My car is a '74 with a 2.5L JDM Subaru motor and stock 914 tranny.

Background on the issue: (sorry for length.. want to give the full picture)

I used the original 914 starter motor when I finished the conversion which failed within a few months. (This was expected as the compression in the subie is much much higher)

I then switched to the 911 starter motor which worked for ~2 years no problem. I took a trip down the coast to LA and ended up driving through a pretty serious rain storm (this could be coincidence or a possible cause of the problem) - this is when my problems started.

The starter motor felt like it no longer had enough 'juice' to turn over the subie motor (I would get maybe 1 or 2 cranks at a time). Thinking it was just a failed started motor, I switched to the 'Hi-Torque' starter motor. This worked for a few weeks then failed and had the same symptoms I experienced with the 911 starter motor. I decided to switch back to a new 911 starter motor and same thing... worked for a few weeks then failed.

The weird part is, is that if the car has sat for a bit (more than a few days), it generally starts right up - or if i use jumper cables (i.e. 2 batteries) with another car. But, if i drive it, then park, then try to start it again, it most likely wont start.

I've tried different batteries, different starter motors, replaced possible faulty cables and nothing seems to have changed.

At this point, I'm really lost on solving this issue. Hoping you guys can help.

Thanks in advance,
peter

Starter switch or you need to add a relay. Sounds like the "Dreaded Hot Start Problem". Have you tried adding a Ford relay to the starter circuit?

Check the starter relay? If you aren't using one, that may be your problem.

I am using a starter relay. But I will check it. I thought a relay was a pretty much on or off type of system? How do I 'check' it?

Also, what is the Ford relay?

-peter

Relays fail. Check for voltage at the output terminal on your relay when the switch is turned to "start". Be sure it is in neutral.. Then pull the yellow spade connector from the circuit and measure the voltage at the end of the wire when in the start position. The Bosche solenoid requires 9.3v to energize the starter. Our old switches may or may not supply enough voltage because of old connections or the old switch itself. Ron aka Slits was selling Ford relay for $10. The Ford relay only requires about 3v to energize so a "big" load is removed from your starter switch. You say you have a starter relay. Is it a Bosche? If so I'd switch it to a Ford relay. IMHO

It is a Bosch relay. Just to confirm my test... on the input terminal on my relay I get 12.3v (coming from the battery)... On the output terminal in the 'start' position, I get ~10v. Shouldn't this be 12.3v?

My understanding of a relay is that once you activate the relay with the ignition switch, it just connects the two other terminals.. if one side has 12.3v, shouldn't there be 12.3v coming through to the other terminal?

Measure the voltage on the starter battery cable as you try to crank it. If less than 8V, you may have a bad cable or ground.

NOTE: this take 2 people to accomplish

Thank you, Mike!

I tested and only got 3-5 volts. The ground strap from the tranny to the car was loose. I thought I had checked this before, but I guess i never got a wrench on it. This also makes sense why the starter motor worked right after installing it - having to disconnect and re-connect the ground cable.

All is good!

Thanks again.

Nice work.