Hot Start Problem - 911 '74 (SC engine)

[groovecarrera]

Hi everybody,

I've always had this problem and never solved. The engine is a SC 1982. The CIS is from 1974, original from the car.
Cold start is always OK. Hot start up to 5 minutes is OK.
After that it takes about three or four attempts to start.

I have changed the Fuel Accumulator. Now i have the correct for the engine (1982) , but the CIS is from1974. Could that be the problem?

The mechanic also checked the WUR and is OK. The CIS is in good shape. After start, the car runs fine.

I'd appreciate any advice.

Thanks


Diego

[75 911s]

what fuel pump are you running? Without the check valve, which may have been omitted with a new fuel pump install, you will have hot start issues.

[groovecarrera]

Originally Posted by 75 911s

what fuel pump are you running? Without the check valve, which may have been omitted with a new fuel pump install, you will have hot start issues.

I am running a ''made in Germany pump'', but is not the Porsche OEM. I will check it. The check valve only applies to the OEM Pump?
Thanks.

[75 911s]

It should have come with a check valve fitting. But it probably wasn't put on because you need a cap if you use the stock banjo fitting on the fuel line up to the accumulator. The check valve threads into the pump, then the banjo, then a cap to hold the banjo on. Some will use the included bolt that allows you to put the banjo right to the fuel pump. I think a check valve was inline later on like in 76 but don't quote me on that.



On the left is the bolt that allows you to connect the banjo fitting directly to the pump. To my knowledge that is not a check valve. The fitting threaded into the pump on the right shows the check valve and you could see how you would need the cap to keep the banjo on. The cap isn't included in the pierberg parts bag that come with the pump if that's the one you have.



Something about the original pump, and fitting don't have the hot start issuebecause I think there was a check valve built into the original Porsche pump. Hopefully some other expert can chime in.

This seems to be isolated to midyears 74 and 75 as that was rear mounted fuel pump.

Of course this may not be the issue at all but I would start there, especially since you don't have the original pump on.

[groovecarrera]

When i get home, i will take some pics of the fuel pump setup. My car has it in the rear left.


Diego