Early Six cold-start enrichment question

[MountainRoads]

An intervening owner of my '71 E disabled the cold-start enrichment, because he heard they have a tendency to start engine fires. The result of course, is that it's much harder to get the thing to start up, especially if it's cold weather and/or the car has been sitting for multiple weeks. This was true with the Webers (since they have no chokes) and is only slightly better now that the MFI is back on. I confirmed the engine fire concern with two highly regarded local Porsche mechanics. They gave me some starting tips, but it still takes repeated crankings to fire up.

This car started right up when the enrichment circuit was functional and I've never had a fire scare with this or the other sixers like it that I've owned. Frankly, I'm much more concerned about the starter, battery, and engine wear resulting from excessive cold cranking.

Therefore, I'm seriouisly considering reconnecting the enrichment circuit, but not really into tempting fate, so I thought I'd ask this group for an opinion. What do those of you in a similar situation do? Has anyone had a fire problem from the cold-start circuit or actually know someone who has, or are these just anecdotal stories from an over-abundance of caution? Obviously, I'd much rather the car not catch fire.

[Flieger]

The early system was much more of a fire risk than the later version. I have never actually seen engine fires with either, but the later style is much more elegant in that it squirts fuel into each stack, rather than misting it into the airbox. The later one only works with plastic stacks, though.

I would just make sure yours is in tip-top shape with no leaks or dripping injectors, then run it.

[edmayo]

Agree with Max, the source of most fires was due to the spray tubes in the air cleaner, and then the plastic air horns would catch fire and melt down the ports. We replaced a lot of those to the superceded metal ones. That pretty much fixed the problem, then the 2.4 with the nozzles in the stacks was the real fix. Like you say, the downside is all that wear and tear on the starter. Fix the cold start and make sure you've got the metal air horns

[X-Faktory]

I went through the same thought process as I finished my 71E resto. I left the cold-start disabled, at first, due to the fire risk (based on my research and the fact that I bought this car as a roller....it had been sidelined years ago by....an engine fire.) Difficult to start, when cold, but would fire instantly with a shot of starting fluid. I made sure that my cold-start system was in great shape, hooked it back up...and it works great....starts immediately, regardless of temp.

PS: I keep a fire extinguisher in the car.

Regards,
Al

[Flieger]

By the way, I have the plastic stacks and the standard plastic plenum. I do also carry a fire extinguisher, though it is old.
I have tried to start the car with it disconnected and even on a summer day here in Southern California it would not start, no matter how much throttle pumping I did. I hooked the system back up and it "fired up" instantly.

I think as long as the system is in good shape you are fine. I would be more concerned about the risk of using starter fluid.

I think it was the weekend after I replaced the fuel filter, or maybe the pump, that the car would not start. I could not figure it out. Finally, I had my Dad work the starter while I watched in the engine bay. There was a huge gush of fuel out of the console, from the fitting leading to the T line for the cold start. I had tried it several times before so even gushing fuel out like that did not cause a fire. Lucky, I guess.

[MountainRoads]

Thanks for the feedback and good advice, guys. I'll add rebirthing the cold-start to my winter to-do list.
1) I'm pretty sure I have the metal airhorns, but will confirm. I have spares and prefer the look of the metal ones, anyway, so this is a good excuse to make sure.
2) I do carry a fire extinguisher with. Probably a good time to check it's charge.

- MR

[MountainRoads]

I finally got around to working on this little problem and thought I'd provide a little update that might be useful to others, in case they are doing some troubleshooting. The cold-start enrichment solenoid is only energized when the ignition switch is in the "start" position. Although that makes some logical sense (to avoid flooding the engine), one could also logically conclude that it is energized by placing the hand throttle in the full-on-position. The wiring diagrams I saw did not make it clear that there was any electrical connection with the starter circuit or anything else, other than terminating at the hand throttle.

- MR

[edmayo]

The hand throttle has nothing to do with the cold start, it does the same thing as you pushing on the gas pedal. There is a wire from the starter (only energized during cranking) that feeds power to a thermal switch on top of the engine breather. The thermal switch will ground for a period of time based on engine temp, which then grounds the relay controlling the fuel solenoid to spray fuel in the aircleaner spray bar. Remember, these are the same people that built V-2 rockets,,,,LOL

[MountainRoads]

The hand throttle has nothing to do with the cold start, it does the same thing as you pushing on the gas pedal. There is a wire from the starter (only energized during cranking) that feeds power to a thermal switch on top of the engine breather. The thermal switch will ground for a period of time based on engine temp, which then grounds the relay controlling the fuel solenoid to spray fuel in the aircleaner spray bar. Remember, these are the same people that built V-2 rockets,,,,LOL

Hi Ed:

That's very interesting. Thanks for the additional info. I only saw one wire connection at the fuel solenoid (at the top) and that was +12V, and only when the starter was engaged. Confirmed by a test light with the other lead grounded to engine metal. No starter cranking = no light. Granted, the engine was cold. I assumed that ground was coming though the fuel filter body and to the frame. Strange then, that the wiring diagrams show the lead from the solenoid connecting through the hand throttle/heater/parking brake assembly.

- MR
- MR

[edmayo]

There is a ground wire at the parking brake lever, but that is just for the parking brake "on" indicator light. Maybe this is what you're seeing? That wire is brown with yellow tracer.