j.kenzie@sbcglobal.net

Hi guys,
As Winter draws down, I'm looking to get my 84 US supercharged car ready to drive. I have started to develop difficult cold starts. This has been coming on for a year or so. I will be addressing that, but it is basically a crank, no start, where I smell gas after start attempts.
Because the car is supercharged, during install by myself, I could not find clearance for the wiring connector of the thermotime switch on the front of the engine. ( The thermotime switch is basically a temperature and duration sensitive switched ground that operates the cold start valve while the starter is running.) My solution was to ground one connector terminal so it energizes the cold start valve whenever the starter is running, regardless of temp and without a time limit. This has worked fine, for years, if the car starts promptly, which had always been the case, but with prolonged cranking, it can presumably flood the engine. So my idea is to relocate the thermotime switch so that it functions at least partially. If I mount it in the open in the engine compartment, it should give me a first start function similar to being mounted exposed to engine coolant. I could also try to find a coolant hose to splice in a metal mount to thread for the switch. Not sure it's worth trouble and leakage risk, also not sure upper or lower hose.
Besides the obvious suggestion not to redesign the Porsche system, any suggestion or ideas?
Thanks very much,
John

j.kenzie@sbcglobal.net

I moved the TT switch to a position just above the radiator on the cold side of the intake scoops. I grounded it, and will make an extension cable to connect. It will react to its internally heated bi-metal strip as well as ambient engine area temps. Hopefully it will be enough to give me cold start injector function but no flooding. BTW, since I have a mini-starter, I am using the TT switch (+)trigger to activate a relay sending battery voltage to the .6 ohm resistor (bypassing the .4 ohm), then to the coil during cranking only.
I'll finish all the hookups tomorrow, and report back.
Thanks,
Dave

PorKen

If you are not starting in extreme cold then I found I could run without the cold start injector on my old '81.

I used the thermo-time-switch to add 20K to the Temp II sensor via a 12V reed relay.
https://rennlist.com/forums/928-foru...ete-2-0-a.html



I reckon the TTS could be bypassed as well and just using the starter voltage. (Maybe use a thermistor instead of a resistor?)

Petza914

Dave, does your supercharger setup have a liquid cooled heat exchanger (washer fluid)? When I did my AOS, I tapped into that plumbing to introduce heat from that fluid to the back of the AOS chamber. It keeps the oil from becoming think and sludgy so it can return back to the oil pan.

Maybe you could hook a temperature sensor into that line. The heat exchanger fluid isn't critical to vehicle operation, so a failure there doesn't strand you, which is why I went this route instead of connecting into the coolant lines.

j.kenzie@sbcglobal.net

Hi Pete. Very clever idea. I must admit that I do have a air/water intercooler, but I often drive with the pump fuse pulled, for normal city traffic. I will add your thinking into my scheme. Right now it's an air-cooled thermotime switch.
Thanks,
Dave

hacker-pschorr

Losing the thermotime switch is similar to having a CIS car with a WUR "broken" in the "full warm up" side, the cold start injector will not operate.

The temp fix on those cars is to simply jimmy rig a momentary button to manually fire the cold start injector. It works like a charm and the car will fire right up. No reason why the same idea won't work on an L-Jet car. Just need power / ground and put the button in-between one of the two circuits.

I remember following your lead on that one back in the day since eliminating all those parts sure cleans up the engine. My experience wasn't the same or just our perception of what we wanted was different. Even on a hot July day, my 81 would crank longer than I was comfortable with without the cold start injector.

j.kenzie@sbcglobal.net

Nice idea, Hacker. I might use it.
Thanks,
Dave

PorKen

But. It. Did. Start.




I probably won't delete the bypass air system on my new-to-me '80. Would have to push the pedal a little while starting. Horror!

hacker-pschorr

Well sure, eventually

Actually it's really a moot point since due to where we live, even summer nights can be in the 50's and spring / fall in the 30's.