DDK - Die Deutschen Klassiker

Hello everybody

Having a prob with a vacuum on the 912, it runs sweet for 30 mins and then is starved of fuel. Leave it for 30 mins and it starts again and gets back in a groggy fashion!!!
I originally thought it was a vapor lock on the mechanical pump as it is in a very hot position. I have since fitted a facet electric pump and it is doing the same thing.

So, could this be a vacuum problem with the breather? Or what else ?

Is the breather hole on the 12 in the fuel cap?

Has anyone else had similar probs?

All advice on this is very much appreciated. On the positive side, before this fuel starvation occurs, the car goes very nicely, just this little issue of running out of fuel.

Hope u are all having great times in your lovely motors.

David

The breather is connected to the filler pipe inside the boot - it's pretty large diameter plastic pipe so unless it's kinked that's unlikely to be the problem.

I suspect you have a build up of crud in the bottom of the tank. As the fuel is drawn from the tank by the pump, the debris (rust, etc) is sucked into the gauze filter on the fuel tank outlet. When you stop the car, the debris has chance to settle again...

Hi Keith
Thanks for the reply.
The tank is new and has been emptied and cleaned along with the gauze filter.
Would the electric pump position be causing a prob? I have been told they are for pushing rather than pulling! This is in the engine bay on the floor exhaust side!!!! Possibly gatting too hot ? I did have the same prob with the mechanical so possibly too much of a coincidence it is happening with electric pump!!!

My mechanical pump gave up last year and I have a electric pump in the engine bay on the left as you look in, it's now mounted to the side but has never had an issue of fuel starvation, even with the new demands on it. Have you had the mechanical pump off to see if it's blocking the flow?

Is yours mounted inside of rear wing? Mine is on the floor above exhaust , felt hottish!!!
I haven't checked the mechanical pump as I thought it was a vapor lock so changed to an electric!!!

You can see it in this shot as the engine was being fitted, tucked up in the wing

Cool, thanks for the pic. In fact a bit cooler it there. I will shift mine up there

Another thing to consider - fuel pumps like to push, not suck, so perhaps get it lower down where gravity will move fuel to the pump, and the pump can then move fuel up to the engine.

Mine is mounted on the rear torsion bar and works OK.

My electric pump is mounted in almost the same position as Tom. No issues

Sent from my MotoE2(4G-LTE) using Tapatalk

My electric pump is mounted on the front cross member by a he fuel tank. Gravity fed from the tank and pushing fuel to the carbs. No issues so far.

If mounted in the engine bay it is relying on gravity acting on the fuel in the tank to push the fuel along the pipe to feed the pump. Ok if you have a full tank.

Most pumps prefer to push a fluid rather than try to pull through a system having ng to prime themselves then start supplying

Regards

Sean

My fuel pump is positioned on the left hand side of the engine bay.
Have never had any problems with fuel starvation
Would have thought it is more likely to be problems with the fuel lines

Thanks for all your comments guys , I have moved the pump to the smugglers box and so far so good . After a 40 minute drive, no grogginess !!!! Stopped the car to put it back in the garage AND didn't f ing start again !!!!!!!!
Pushed it home!!!!!!

Thanks again
When are u 12 ers having a little outing?

delkel wrote:Thanks for all your comments guys , I have moved the pump to the smugglers box and so far so good . After a 40 minute drive, no grogginess !!!! Stopped the car to put it back in the garage AND didn't f ing start again !!!!!!!!
Pushed it home!!!!!!

Thanks again
When are u 12 ers having a little outing?

Told you that when you came to pick the wings up!

Why is it not starting now? You know when they are warm the manual suggests that the accelerator pedal is depressed when turning the engine over on the starter. Counter intuitive but it works

Regards

Sean