My 75 914 starts up fine when cold and idles as it should. After a brief warm-up, I drove off and all is fine until the oil temp gets to about 110-120 degrees (after about 7-8 minutes of driving). Then the engine cuts out and re-engages sporadically making it very difficult to drive. After about a minute of this very nerve racking ordeal, it will settle down and all is fine once it gets through this hissy-fit. All vacuum lines are new and all of the components in the fuel injection system have been replaced including a new wiring harness. The car drove flawlessly for nearly 6k miles before this started. Thoughts?

Well I don't remember having that exact problem in my '75 L Jet, but I have had power to the fuel pump interrupted by a bad connection at the dual relay. A loose connection might be causing your problem. It's not easy to tell whether the wires at the dual relay are always making a solid connection. I would pull the plug on the left side of the dual relay; then gently pull on each wire. If one comes out easily, then it's not making solid contact. The relay connector terminal have a little barb that locks the connector in place. I had the fuel pump power wire loosen a couple of times.

I'm sure there are other causes.....

Thanks. I will check this out. I had a problem with the fuel pump and replaced it. The problems with the engine cutting out started after this.

Another thought:

Be sure the fuel pumps ground wire is firmly attached, not easy to reach, but doable; second, the dual relay has a ground wire that attaches to the engine case. I've knocked it loose a couple of time while cleaning the tin.

Lastly, a fuel pressure gauge mounted next to the cold start valve helps. If the fuel pump isn't getting power the gauge goes to zero when their is a power interruption; except when you turn the ignition off. Then the pressure slowly goes down.

And, you might try bypassing the dual relays power to the fuel pump. Attach a ground wire from III on the 4 spade connector ( lower left on your relay board) to ground.

The diagram/picture is for an earlier relay board. On the late cars, pin 12 PN the 12 pin connector goes to the fuel pump, not the AAR.

Did you replace the lines under the gas tank?

I had similar issues after replacing/rebuilding EVERYTHING from stem to stern on my '75 1.8, and the problem ended up being a fuel line that was trapped between the body of the car and the gas tank. After diagnosing everything with the L-Jet, I finally pulled the tank (again) and discovered that the return line was completely smashed. I replaced the line and carefully re-installed the tank to insure that I didn't make the same mistake, and the car is running great again.

If you can get under the car and remove the bottom access panel, you should be able to ascertain if the fuel lines from the bottom of the tank are moving freely to the fuel pump.

Please PM me if you need me to talk you through this process.

Good luck,
Ken

Kinked fuel line is another common issue,,,,

I remember my dad mustang was making that problem, the only thing I do is to put a wet cloth on the coil and it will run again but when it gets hot again, the engine will have a bad idle. I don't know if this can happen on our 914. Mine is also 1975 1.8L F.I.

Just sharing. God Bless!

oops double posting. message deleted.