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Functionista
Join Date: Jul 2011
Location: CO
Posts: 7,717
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I am running the stock setup minus the thermo time switch because that’s how the engine came to me. I’m not sure I could go without the t-stat and warmup hose here in 20F temps. I know the t-stat is fully pushing in on the linkage at 113F per factory service manual but I recently tested the temp with a temp gun and it was only about 80F at its hottest point after climbing 2000ft in 20 miles. Measuring the outlet temp would’ve been a better test. My heat exchanger is in good shape too.
I sort of embrace the Rube Goldberg mousetrappiness of the thing anyway.
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Jeff 74 911, #3 I do not disbelieve in anything. I start from the premise that everything is true until proved false. Everything is possible. |
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02-11-2019, 07:03 PM
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Registered
Join Date: Nov 2001
Location: Bucharest, Romania
Posts: 41
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Just wanted to share my experience with our 1972 911 T with MFI. It always started only after cranking for about 10 seconds, when it finally fired up it ran just fine for the rest of the day.
I researched the cold start issue a little more and found out that all components in my car were just fine with one exception: the temperature/time cold start switch. It provided ground to the cold start relay just fine but as soon as power was supplied via the starter motor solenoid cable (yellow), it opened up within a split second. Therefore the cold start valve on top of the fuel filter was never energized. I temporarily disconnected the yellow cable and wrapped the contact with some electric tape, just to see if there was any difference. Hand throttle full up, key in and after letting the fuel pump buzz for a couple of seconds, I gave it a try. The cold motor started with this test setup within 2 seconds and ran immediately stable like it did before after 10 seconds of cranking. Ordered a new switch (911 617 117 01) for the vent cover on top of the engine. Somewhat expensive but after installation the car starts like never before! Conclusion: if your MFI motor starts like mine, check the following: 1. relay function and connecting cables 2. electric valve on top of the fuel filter 3. thermo/time switch (does it still provide ground to the relay and check the time function by applying 12 volts briefly to the contact where the yellow cable connects to. Time delay is normally around 9 seconds. Important! Disconnect the yellow cable first otherwise you'll crank the starter!)
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1991 944S2, Kobaltblau, sold 1972 911T Targa, Geminiblau 1992 928GTS, Amazonasgrün It's not the speed that kills you, it's the sudden stop 
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05-15-2020, 01:28 AM
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