1977 911 won’t start please help

[C3s]

Hello DDK people, it’s been a while. My 911 starts briefly and immediately cuts out. Can’t hear the short ‘’buzz / whining noise’ when switch notion on before starting so presuming a fuel problem, some fuel gets through but not enough to keep the engine running. Can anybody help please?
Thanks in advance,
Paul.

[C3s]

Auto-correct got in the way, should read ignition instead of notion

[C3s]

Update, the horn has also stopped working, would it be the same fuse that controls both?

[neilbardsley]

Sounds like your fuel pump isn't pumping. I'm guessing the horn and pump aren't on the same fuses but the fuses are easy to check. My guess is you have a short somewhere but try applying 12v directly to the pump and see if it runs

Sent from my 22081212UG using Tapatalk

[Guy]

You should be able to hear a constant high pitch noise from the transistor unit with the ignition on.

To test the pump remove the straps from the air box and remove the top half complete with the filter. With the ignition on reach inside the air box and lift the air flow sensor lever. You will hear a very distinctive noise if the pump is working and fuel is flowing through the injectors.

[C3s]

Thank you so much Neil & Guy for your replies. The car is in another garage which makes quick texts awkward. Will be going tomorrow evening to try these. Will report back, thanks again, Paul.

[Jonny Hart]

On the top of the fuse panel connections, there's an external red wire that links between fuses 11 and 16 to power the fuel pump. Check this is present and in good order.

Fuses are numbered from front of vehicle to back - e.g. Fuse 1 is on the RIGHT as you look at the fuse panel.

[C3s]

Thanks Johnny, appreciated.
Yo add context, the car’s been in storage there for 5 years on a battery optimiser and was regularly (ish) started and one day a few months back this problem occurred. Garage is dry & car always fired up immediately.
Will report back tomorrow,
Thanks for your input,
Paul.

[Mike911scrs]

Hi C3s
I take it you still have the Carrera 3 engine and K-jet injection fitted?

go under the front bonnet and push the RED relay back in and if it still do's not run,

go into the engine bay and put your hand behind the Large rubber boot on top of the engine where you will find a electrical socket, pull this off and the pump should run,

it is the fuel cut off incase of a issue with the driver and a R.T.A.

report back

regards mike

[C3s]

Hi Mike,

Thank you for taking the time to help.

Car is stock with original engine rebuilt by PCT back in the day and yes has K-jet which looks similar to the system on a 924 l had years ago.

Haven’t removed any relays, the car just wouldn’t start on a random visit so absolutely baffled.

Will give all suggestions a go this evening.

Does anybody know if the fuel pump is fused?

Thanks again and to everyone with input so far,

Paul.

[Jonny Hart]

Yes, fuel pump fed from fuse 16. Should be a 25A fuse.

[C3s]

Result! Took air filter top off with ign on, pressed the flap upwards and heard the buzz/pumping noise that’s not present when ign is first turned on. Got car running and was happy when warm.
Just need to solve the lack of buzz/pumping noise that’s not present when ign first turned on, was only for a second or so which l presume primes the system?
Thought l’d stop when l heard the engine running sweetly.
Presumably fuel pump is working to a degree?
Does anybody know where to tackle next please?
Really appreciate your help so far guys.
Thanks,
Paul.

[Jonny Hart]

That's normal. Certainly on an SC, the fuel pump only runs when cranking and when the engine is running so you won't hear it with the ignition on prior to cranking. Pretty sure it is the same with the C3.0. If the engine stalls it is shut off by the air metering flap. I think it is also shut off if the car ends up on its roof .

On earlier cars you DO hear the pump when the ignition is on.

[911hillclimber]

The 3.2 engine on stock Bosch management has no pump activity until the engine is cranked over for starting.