1.7 fuel injected won't keep started when hot, Runs great cold; won't hardly run when hot Options

[dknechtly]

Guys I'm stumped. My engine was recently rebuilt in the last couple years and I'm working out gremlins. 1.7 fuel injection runs and drives great but when it gets really hot ( I'm in Dallas area), it starts to run erratic. I have to pump the gas or keep it revved high to make it home. When trying to start it. I have to keep pumping the gas to keep it going. I have...
- fuel pressure about 28-29 lbs.
- Bowlsby FI harness maybe 4 years old.
- rebuilt Bolwsby MPS (I've switched out with others) and get no difference
- swapped CPU's; no difference
- swapped coil; no difference
- new 914 rubber HTS; 2200 ohms cold @68 degrees; 118 when hot
- FI points near zero resistance
- no vacuum leaks
- recent valve adjustments (a couple just to make sure)
- fuel pump relocated to front for over 30 years
- pretty new Pertronix ignition (the previous had failed after 10 years)

Any ideas? Thanks

[dknechtly]

I think I now have it figured out. I was adding resistance to my HTS, but it didn't seem to work in all circumstances. I checked the temp sensor that's under the manifold and got 0 resistance. Since I had no spare, I put in a 220 ohm resistor in between ground and the FI harness lead. Now I have no problem except it takes longer to smooth out on warm up. I guess the CPU wants at least some resistance on it. Now I'll be on the lookout for a spare.

[914_teener]

I think I now have it figured out. I was adding resistance to my HTS, but it didn't seem to work in all circumstances. I checked the temp sensor that's under the manifold and got 0 resistance. Since I had no spare, I put in a 220 ohm resistor in between ground and the FI harness lead. Now I have no problem except it takes longer to smooth out on warm up. I guess the CPU wants at least some resistance on it. Now I'll be on the lookout for a spare.

If that is the thermotine switch you are talking about it has nothing to do with the ECU.

I simply provides a switched ground to the cold start injector on the plenum if the temperature is below around 40 deg. If you get 0 resistance from the spade to ground then it is bad.

Simply disconnect it. More important are the collected grounds there on the multispades that grounds to the case. Those ground wires have a tendency to crack over time with the heat they are subjected to.