911 engine

[avian2324]

Hello, my 1980 911 sc has a warm restart problem and sometime engine stop when cold first miles. Will replacement of the WYR solve the issue?

[Henry Schmidt]

Originally Posted by avian2324

Hello, my 1980 911 sc has a warm restart problem and sometime engine stop when cold first miles. Will replacement of the WYR solve the issue?

Warm start issues are generally a control pressure problem. Often as simple as the fuel pump check valve. If the system loses fuel pressure during the cool down period, warm restarts a challenging.
Shutdown during cold running sounds like a tuning issue.
CIS injections function entirely on controlling the fuel pressures at predetermined temperatures and RPM demands.
Hook up a fuel pressure gauge and have at it.

[boyt911sc]

Originally Posted by avian2324

Hello, my 1980 911 sc has a warm restart problem and sometime engine stop when cold first miles. Will replacement of the WYR solve the issue?

Avian,

Residual pressure loss is the most common cause for warm start in CIS. For 1980 SC, the most common culprits for residual pressure loss are:

• Defective fuel accumulator.
• Defective fuel pump check valve.
• Defective primary pressure valve of the fuel distributor.
• Etc.

You need a pressure gauge tester to locate and identify the culprit for your warm start problem. This topic has been extensively discussed in this forum. Do a search for residual pressure loss.

Tony

[PeteKz]

avian2324: You are new here. Use the search function to look for "hard to restart warm" problems. I and many others have written extensively on this very typical problem. Also use a thread title more specific than "911 engine," otherwise you may not get much help.

With the CIS system, DO NOT throw parts at the problem! You will waste money and time, and worse, you will complicate your troubleshooting. You must troubleshoot and diagnose first.

How long has this problem been occurring? Did it start suddenly, or is it getting gradually worse over a long time? How many miles are on the car? Has it been sitting for several months or more, or do you drive it regularly? Where are you located? (add your location and car type/miles to your profile too).

The most likely reason for warm restart problems is, loss of residual pressure. (RP) The most likely component at fault for losing residual pressure is the fuel accumulator (FA). The FA in your car is now 45 years old, and with increasing ethanol contamination in the fuel, many rubber fuel system parts are failing. The FA has a rubber diaphragm inside it.

The best way to check for loss of residual pressure, or other pressure related problems, is to use the CIS pressure gauge and valve setup. If you plan to keep your car and do your own work on it, buy a CIS pressure gauge setup. They are not expensive and can be bought on Amazon for $60 or so. See the other threads for recent links to what you need.

However, you can do a quick check for a leaking FA without the gauge, with the following steps:
1. remove the lower "return" fitting from the FA and plug it off.
2. Run the fuel pump and see if fuel leaks out the bottom of the FA. If it leaks, it is bad, and losing pressure, so replace it with a new one. Report your results here.

Note: To run the fuel pump in your car, remove the air filter, turn the key to ON, and push up on the air metering arm. This triggers the safety relay to allow the fuel pump to run. You should hear the fuel pump run when you do this.