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vapour-lock Daimler V8 2.5

Warsash 2
Posts: 332
Joined: Sun Feb 28, 2016 1:53 pm
Location: Southampton

Re: vapour-lock Daimler V8 2.5

Post by Warsash 2 »

Hi
I meant to mention I was driving at 4000 to 4500 rpm. I can't give the speed as the speedo is a bit erratic like the owner.
Regards
Colin

Soundmike
Posts: 76
Joined: Thu Mar 17, 2016 8:54 am

Re: vapour-lock Daimler V8 2.5

Post by Soundmike »

An open circuit capacitor in the ignition system can cause similiar symtoms. Bridging it will soon confirm, even a radio suppression cap can be used as a "get you home" senario....

Chris_R
Wise Man
Wise Man
Posts: 662
Joined: Wed Feb 10, 2016 12:48 pm
Location: Twickenham

Re: vapour-lock Daimler V8 2.5

Post by Chris_R »

First off, my Daimler (Majestic Major) is not yet running but I do run a Jensen Interceptor, supposedly renowned for "overheating". I have no special insulation on pipes, pump or carburetor. It still has the original electric radiator fans with no extra radiator shrowding. Last weekend I drove from Derby back to London on Sunday afternoon when the temperature was over 30c. I didn't do anything special on the drive and from Banbury back to Beaconsfield on the M40 drove at "standard" motorway speeds. Getting stuck in traffic queues didn't cause any problems.
The reason for all that is that I don't think 30c is an excessive air temperature. If your car is running at 85c then the ambient air temperature under the bonnet will also be about that temperature and the cars have been designed to operate with those sorts of conditions. You will reach an equilibrium state quite soon after starting on a long journey when the heat conditions under the bonnet have reached a maximum and if you are going to get a vapour lock it is likely to be sooner rather than later in my opinion.
All other Daimler V8 2.5's will be operating similarly so I am more inclined to go along with Tony's suggestion that there was a problem of the breather or perhaps some dirt in the tank being sucked up and blocking or partially blocking the pickup pipe. I had something similar on a tour of Germany after driving from the UK I was in the Eiffel area when I lost power and the engine died going up a slight incline. The car restarted immediately but died again. Fortunately near the top of the incline was a petrol station so I added some fuel to the tank which was only about 1/4 full so to make sure there was enough in there and then pulling out of the petrol station it died again. Restarted it yet again and then drove another 800 miles on that trip and another 5,000 miles since with no recurrence. I think there was a bit of dirt that was sucked up and blocked the pipe which dropped off when I stopped and added fuel freeing the supply again.
On another continental trip we had two Interceptors fail with similar symptoms, first loss of power, then stopping altogether. Both initially thought to be electrical, one with the coil overheating and the other a faulty ignition module. In fact in both cases it was neither. In one there was a problem in the (original) fuel pipe and in periods of high demand it didn't quite allow enough fuel to flow leading to a gradual starvation and loss of power and in the other a faulty new vapour separator in the emissions control system was starving the carburetor of fuel.
The Rover P6B 3500 was also mentioned in this thread. I used to run one of those, when they got hot the fuel in pump bowl could vaporise resulting in no fuel supply to the carburetor but this only happened at idle, so you could be at a set of lights for a few minutes perhaps and then when you finally got through accelerated away only to conk out 100 yards down the road when the carburetor chambers finally ran dry. That happened to me twice, both times after sitting at idle. This was a vapour lock but it never happened during normal driving. What makes Simon's case different is that it happened during normal driving.
Simon - you don't say what happened next after you parked in the safety lane. Did you wait a while and then carry on? If you were able to restart quite soon after stopping I think it indicates more a problem like Tony suggests or perhaps some dirt blocking than it does a vapour lock.

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