Starting problems in 911 SC MY80

[WP0ZZZ]

I had some starting problems today on my euro-spec 911 SC MY80.

The car didn't start straight away when I went to start the engine after two weeks sitting in the garage. I cranked the engine twice for 5 seconds and the engine hesitated but did not quite start. At the third attempt, though, it started after a few seconds.

I drove the car for five minutes and parked it. An hour later I returned to the car and it wouldn't start. After a few attempts I thought the battery could be weak and connected an external battery to help. It didn't improve things: cranking the engine in 5 second bursts didn't work. When I was about to give up I decided to try again and after some hesitation the engine started! This is a video I took after about a minute, idle sounded like it oscillated although the tachometer was quite steady at 700 rpm:



After driving a few miles the idle sounded much steadier and the tachometer showed 800 rpm:



As you can imagine I'm a bit concerned about this unpredictability. I feel that I cannot trust the car to go anywhere since it could leave me stranded. Any help to diagnose the problem will be much appreciated!

[75 911s]

Sounds like it needs some maintenance.

First thing I would do is check the date on the battery. Here in the wild west, because of the heat, batteries are good for about 2 years. Extreme cold could have a similar effect.

You have cold start issues. Have you replaced the fuel filter recently or when? Accumulator?

Check your fuel pressure using a CIS gauge.

Take the air filter out/ replace, make sure the box is on snug and seated. Remove the gas cap when running and check for idle drop.

Pull the plugs and inspect.

Is it old gas?

Idle should be 950. In the first vid, it's barely hanging on.

Just throwing some ideas out to get you started.

[gomezoneill]

Possible CIS pressure or cold start valve issue.

[WP0ZZZ]

Thanks very much for the troubleshooting leads!

Amazingly, today it started first time. At the beginning the idle was at about 1300 rpm which slowly went down as the engine warmed up.

Idle when warm is about 800 rpm so if you say it should be at 950 I'll try to adjust it up a bit.

You both mention CIS pressure. I noticed that the fuel pump can be heard from outside the car. Is it normal for it to be so noisy?

[boyt911sc]

Originally Posted by WP0ZZZ

Thanks very much for the troubleshooting leads!

Amazingly, today it started first time. At the beginning the idle was at about 1300 rpm which slowly went down as the engine warmed up.

Idle when warm is about 800 rpm so if you say it should be at 950 I'll try to adjust it up a bit.

You both mention CIS pressure. I noticed that the fuel pump can be heard from outside the car. Is it normal for it to be so noisy?

Even a good running FP could be heard in and around the car. Noise level is all relative and very subjective. If you want to be technical, measure the current draw (amperage) and pressure delivery of the FP. This will give you a measurable yardstick for evaluating the condition of the FP. Regarding fuel pressures, what are your control fuel pressures (CCP and WCP)? How many minutes is the transition time between CCP and WCP? Keep us posted.

Tony

[WP0ZZZ]

Originally Posted by boyt911sc

Regarding fuel pressures, what are your control fuel pressures (CCP and WCP)? How many minutes is the transition time between CCP and WCP? Keep us posted.

I don't (yet) have the equipment for measuring fuel pressures. I have never worked on engines before but I'm planning to get the diagnostics equipment as my needs and skills evolve.

I hear a clicking noise on the right side of the engine. Can you identify what it might be from the video?