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Banned
Join Date: Apr 2004
Location: Portugal
Posts: 1,513
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Is it the check valve ?
Today I went for a longer drive than usual, weather was hot, and as a result the engine did get hotter than it used for some time.
When I stopped it, oil temp was about 100C, about 30m later, when I returned, it wouldn't start. After much cranking without any signs of life, I decided to try that old trick - lifting the measuring plate 1-2 times with the ignition on... and presto, it started cleanly ! Question: Could this be a faulty pump check valve, or is it another sign of bad WUR ? From what I read, I'm suspecting the check valve although I can't really understand what effect heat has on it. As I understand, the valve just prevents gas from re-entering the tank. Am I right ? Sorry for the longish rant. Hope any of the CIS-Xperts can chime in ! |
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09-23-2009, 06:41 AM
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Band.
Join Date: Dec 2003
Location: Denver, CO
Posts: 13,324
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Your fuel pump is located on the left rear trailing arm, right where hot exhaust gas exits the "flapper box". Even with a good check valve and accumulator, CIS cars (up to '76) have problems with hot starts because of all the heat in this area. In 1976 they moved the fuel pump up by the fuel tank to alleviate this problem.
You did the right thing by lifting the sensor plate!! To fix the problem pretty much the only thing you can do is relocate the fuel pump to the front crossmember by the fuel tank. You need new high-pressure lines in the tunnel, but otherwise, it's pretty easy to do. 
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1983 SC Coupe 1963 BMW R60/2 1972 Triumph Tiger 1995 Triumph Daytona SuperIII |
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09-23-2009, 07:05 AM
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Designer King
Join Date: Mar 2004
Location: Toronto, ON Canada
Posts: 5,499
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It could also be your fuel accumulator.
If you have the CIS fuel gauge you can check your warm control pressure. The WUR is certainly a likely candidate for the cause of this problem. 100C isn't really too hot for a 911 engine.
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Paul Yellow 77 Sunroof Coupe/cork interior; 3.2L SS '80 engine/10.3:1/No O2; Carrera Tensioners; 11 Blade Fan; Turbo tie rods; Bilstein B6; 28 tube Cooler; SSI, Dansk; MSD/Blaster; 16x7" Fuchs/205/50 Firestone Firehawk Indy 500s; PCA/UCR, MID9 Never leave well enough alone |
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09-23-2009, 07:40 AM
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Banned
Join Date: Apr 2004
Location: Portugal
Posts: 1,513
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The fuel accumulator was changed a few months back, so I guess it's ok.
The temperature is a good point. My car was held up in a rebuild for more than 2 months, so I kind of forgot what were the normal temps... And, during the rebuild I added a 44 row Mocal cooler, so I expect it to run cooler. Anyway, during a fast road drive (no start-stop) in hot weather (30C) what typical oil temps are reasonable to expect ? |
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09-23-2009, 07:54 AM
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