I'm having problem starting my car after I've already got her nice and warmed up. If I need to stop for 10 minutes, when I return to the car she's hard to get started. Cold starts are not a problem. My mechanic tells me that it's the hot start problem is normal, and that I need to push down on the gas pedal as I turn the key, after a few seconds it will start. Then he said to run it for another few seconds before driving.
It just doesn't sound right that pushing the gas while starting is a really "sound" solution.
I've searched for Hot Starts, but don't find anything difinitive for 1979 911sc.

Thanks for the suggestions.

rosco28

 

Hi Rosco,

Is this true? does it start after that?

If it's a CIS engine the problem may be the fuel accumulator. Cranking with the throttle down allows the sensor plate to be lifted and makes the fuel pump run (at least it does on mine) this repressurises the system again to make up for pressure lost due to a faulty accumulator.
When cold the mixture is enriched with the cold start valve. When hot I think it relies on the accumulator to give proper pressure.
Also the “warm up regulator” may not be working correctly or it may be partially blocked.

You could start with measuring Cold control pressure and when warm, warm control pressure. This testing procedure also allows you to check the accumulator to see if it’s holding pressure.
I’d check the accumulator first, but I’m not a mechanic.

Someone else here will know. Guys?

Good luck.

 

Fuel accumulator,definitely.
Ask me how I know!

 

psychoideas - It takes a while to get started, which of course is humiliating with a crowd around, but eventually she does start. But is this common, do I need to worry about fixing something if she does start with the gas pedal down?

 

No, it's not common.
If the accumulator is holding pressure it should start without pedal or too much cranking.
I'm not exactly sure but I imagine that too much pedal on warm start up could put excessive fuel into the intake runners and leave you open for an "Airbox Accident" like the Iceman had.

I'd look into it and get it sorted out.

 

I would change the fuel pump check valve first.

Easy and cheap.

Just make sure it comes with new sealing washers.

John

 

accumulator .....

 

I have this issue as well, especially at tracking events in the CA deserts. When the engine is really hot, it's difficult to start.

My mechanic says it's "very common" in SC's and is related to the fuel accumulator and the need for fuel pressure, as mentioned. Replaced check-valve in the fuel pump, or replacing accumulator may fix it. Personally, I wouldn't depress the throttle. You could get a fairly good backfire/missfire pop, as mentioned. Without a pop-off valve you could be in for trouble. Ask TheIceMan about that :-(

For now, I just practice patience: try to start. Wait a few seconds, try again. It usually kicks over after two, three or four tries. No throttle used. Just my personal experience.

Good luck!

 

When the problem occur, does the starter crank or it's all quite?

 

+1

+2

i was actually at a tech session on saturday and this is one of the probs they covered

 

The engine turns over, but doesn't catch...

JV911 - Did they recomment pushing the throttle during ignition if this problem occurs? Did they offer other solutions?

 

base on my reading, reference sensor and speed sensor also create the same problem. I am not sure how to measure/test them. You might want to search on "reference sensor and speed sensor".

 

if i understood right the easiest fix was to install a one-way valve on the outlet side of the fuel pump which would prevent the loss of pressure in the system

looked like a simple, and cheap, solution

 

yup either the fuel pump check valve or the accumulator. The check valve is a very messy job because there is no good way to block the fuel from flooding you. You have to pinch the fuel line at the tank and its usually old and dried out and should be replaced while your down there. Theres no good way about it while theres fuel in the tank.

 

I did not lose much gas changing my check valve since it's on the outlet side of the pump. Gas won't flow with the pump off.

I just kept a small bucket under the car.

John