DDK - Die Deutschen Klassiker

Took my 68 car out today for a run. About 8 minutes in I came up to a roundabout and slowed down which then produced a loud 'slapping' bang. Car didn't stop as I managed to keep going on to a slip road but under acceleration the car was hesitating. 2 further minutes I came off on to slip road and had to stop at roundabout to allow cars to go round.. At this point my car decided to stop and refused to start. I noticed that I had loads of bubbles feeding up back to the fuel filter as though it was boiling. Took about an hour or 2 to get it going again which involved sucking fuel through, filing rotor arm, points (tried everything). Not sure what did the trick.
Not the first time it's happened but not pleasant when sat at the end of a slip road. Any ideas?????
Got a video of bubbling fuel filter but can't upload it to site.

Mechanical or electric fuel pump?
When was the last time it was serviced
When did you last check the timing?
When was the last time you checked the valve clearance?

Sean

Hi Sean,
Mechanical fuel pump
Serviced last year
Timing checked when serviced
Valves checked prior to taking out and all good

So after it got started again did it run OK (as normal) or still with hesitation?

Thinking outside box.
Could the fuel tank vent be blocked?
Try running without a fuel cap?

Collapsed fuel lines

Nick you sound like you have experience of this. Which lines collapse?

I had a 912 many years ago that kept loosing power, the old lines were collapsing. I replaced all the flexible lines

When the car restarted it ran ok without hesitation but was only a 2minute blast back.
All fuel lines were replaced at the last service apart from the line from the fuel tank. I did look at this yesterday and it's an old braided one so may be worth replacing anyway- is this straightforward?
When it had conked out I released the fuel cap to see if there was a vacuum etc but nothing.
Could an electric fuel pump help??
Thanks for all the help so far.
Dan

Replacement is pretty straight forward

Do you have a fuel filter? When was it last changed

How clean is the tank? If i remember rightly there is a mesh filter in the the tank outlet

HAve you tried tanking the fuel line off from the pump outlet and getting someone to crank the car over whilst you catch the fuel in a suitable container to prove the pump is pumping?

Sorry I can't offer any mechanical advice that would help with your situation and apologies for a bit of a hijack, but for the sake of collective knowledge on this issue, some of what you are experiencing sound very much like the symptoms that I have (and which required emergency help from Sean, Paul & Martyn on my way to Stanford Hall on Sunday).

For some reason I have a mechanical fuel pump feeding into an electrical fuel pump and I was experiencing the stuttering & hesitation under load and the near cutting out at junctions etc (needing to try and catch it before it died) that you mentioned. The problem came to a head at Newport Pagnell when the car wouldn't start after a shortish stop and we could see there was no fuel in the filter so the guys kindly diverted the fuel away from the electric fuel pump as that failing was the initial diagnosis, so I just relied on the mechanical. This got me started and enabled me to get to Stanford Hall and back home afterwards, but still with the juddering and hesitation when putting it under load and needing to catch it before it died at junctions.

Could anyone shed light onto why someone would have both a mechanical & electrical fuel pump? Could any carb blockages contribute to the issues (just thinking about the thread over on the early 911 page where there was a carb issue)?

Thank you for any thoughts.

Marcus

Marcus- your issues sound very much like mine. Only difference is I don't have two pumps.

Hi Sean P,
New inline fuel filter.
Haven't checked the fuel quantity by doing as you mentioned but will do so and report back.
Not aware of a fuel mesh from the tank but that's not say there isn't one. Something else I will have to check.

Seven wrote:Sorry I can't offer any mechanical advice that would help with your situation and apologies for a bit of a hijack, but for the sake of collective knowledge on this issue, some of what you are experiencing sound very much like the symptoms that I have (and which required emergency help from Sean, Paul & Martyn on my way to Stanford Hall on Sunday).

For some reason I have a mechanical fuel pump feeding into an electrical fuel pump and I was experiencing the stuttering & hesitation under load and the near cutting out at junctions etc (needing to try and catch it before it died) that you mentioned. The problem came to a head at Newport Pagnell when the car wouldn't start after a shortish stop and we could see there was no fuel in the filter so the guys kindly diverted the fuel away from the electric fuel pump as that failing was the initial diagnosis, so I just relied on the mechanical. This got me started and enabled me to get to Stanford Hall and back home afterwards, but still with the juddering and hesitation when putting it under load and needing to catch it before it died at junctions.

Could anyone shed light onto why someone would have both a mechanical & electrical fuel pump? Could any carb blockages contribute to the issues (just thinking about the thread over on the early 911 page where there was a carb issue)?

Thank you for any thoughts.

Marcus

You had an electric pump feeding into a mechanical pump. We simply took the mechanical pump out of line once we had confirmed that the electric pump was working correctly.

Let me know when you are free to bring the car over to have a proper look.

Regards

Sean

dlampard wrote:Hi Sean P,
New inline fuel filter.
Haven't checked the fuel quantity by doing as you mentioned but will do so and report back.
Not aware of a fuel mesh from the tank but that's not say there isn't one. Something else I will have to check.

https://www.rosepassion.com/en/cat/pors ... -mm/P12948

This is the in tank filter I am on about. If the tank is not clean, (sediment and rust in the bottom), as the fuels passes through it can drag the sediment onto and block the filter, hence the fuel starvation issues

Regards

Sean