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Warm start issue - Still a problem after accumulator change

Hi,

I have a 1979 911 SC Coupe Manual with a warm start issue. Car starts first go when cold. Can also be restarted easily when warm if restarted within 5min
.
Any longer and it takes some cranking to restart it.

I've changed the fuel filter and accumulator as the symptoms matched what others on this forum had described.

I still have the warm start issue. Other thing I've noticed is that once fully warm, the engine idles up and down. If I give the throttle a blip, it settles back to a normal idle until I come to a stop again.

Otherwise the engine runs beautifully when driving.

Any suggestions would be greatly appreciated.

Cheers,

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I have the same situation. I also replaced the fuel pump.
Thanks.

Residual fuel pressure...........

Quote:

Originally Posted by nadhome (Post 10754020)

Your problem is residual fuel pressure loss due to internal fuel leak. The three (3) most common culprits in a CIS are:
1). Defective fuel accumulator.
2). Defective fuel pump check valve.
3). Defective primary pressure regulator.

You need to test and verify that all these components are all good and working. You will need a pressure gauge to confirm their conditions. Keep us posted.

Tony

Quote:

Originally Posted by boyt911sc (Post 10754054)

...e.
3). Defective primary pressure regulator.

\y

You mean Warm Up Regulator.

Quote:

Originally Posted by yelcab1 (Post 10754086)

You mean Warm Up Regulator.

The primary pressure regulator is located in the fuel distributor that controls the system pressure and the return line to the fuel tank. If the tiny viton o-rings starts to leak, the residual fuel pressure in the system is compromised. You need a pressure gauge to test and confirm if it is the culprit. Same with the other culprits. Test and verify.

While fuel accumulator is the most common culprit for residual fuel loss, the two (2) others are as likely the culprit/s. Stop guessing and perform a systematic troubleshooting. Do not replace CIS parts unless tested and verified defective as demonstrated by OP.

Tony

Hook up the gauges, get the engine hot then let it sit and watch the system pressure. When and if it starts dropping, be ready to block off parts of the system. I realize easier said than done, but that is how you do it. Devise a system to facilitate doing that. Tedious and time consuming. Bob