Failure of Petrol Supply

Steve Welton · Joined: 17 Oct 2013 Posts: 105

Out yesterday in the heat!!
The petrol pump begins to tick in an agitated fashion and then the car hesitates............
Blow me I have run out of petrol ........get to a garage and the tank will only take £25 so I have not run out of petrol plenty there.
Refer to Technical manual and I see a cause could be vaporization in the filter if the ambient temperature is high. Well I guess it could be that and will check the other potential causes.

Question 1. Is there a fix (other than moving it) that will prevent vaporization in the filter?
Question 2. Reading the section on Fuel and Carburation B/P/5 I noted the info on leaded and unleaded fuel. What fuel do Derby Bentley owners use? Do they use additives as suggested? I have been using unleaded fuel................

Christopher Carnley · Posted: Mon Jun 19, 2017 5:54 pm Post subject:

The only total fix is to mount the pumps at the rear of the car, and replace the filters with modern in-line filters.

Yours is a 3 1/2litre car?

Steve Welton · Joined: 17 Oct 2013 Posts: 105

Thanks Christopher, Yes it is a 3 1/2 Litre car.
What a shame there is no other fix if I mount the pumps to the rear will that work? Are they not pulling rather than pushing pumps?

Did you have advice on the petrol?

David Cocking · Posted: Mon Jun 19, 2017 9:49 pm Post subject:

I had exactly the same problem yesterday, pumps ticking away furiously in vain each time I came to extended inclines. I happen to have a spare pump pair and am thinking of fitting it by the fuel tank and leaving the existing pumps where they are. One pair suppling fuel to the engine bay, the second pair finishing off the job. I figure that should leave me with plenty of redundancy onboard Very Happy

Chris Card · Guest

Have just returned from a trip to France together with a friend in his Derby 3.5L. He also had the same problem - a partial "get you going again" remedy is to Leave the bonnet open for a bit and put a wet rag over the pumps and associated Pipework to cool them off.

By all accounts, it does seem to be a 3.5L Derby problem. Peter's pumps clicked away and then stopped, indicating that the float chambers should be full, but the engine still died as if from fuel starvation. I don't think that the 4.25L cars have the same problem so, presumably, there is a fix.

Chris

Christopher Carnley · Posted: Tue Jun 20, 2017 9:11 am Post subject:

Apart from the later 4 1/4Litre just having the single filter and only the main delivery,no overdone reserve and switch over, it is similar to the 3 1/2litre.

The filters are situated at the top of the rear body arch and this collects the heat from the entire exhaust system, so you could fit a little fan or lag the exhaust pipe work.
Moving the pump to the rear was a modification that was offered at Derby on request, and you will note this revision in the Green Book, for a pusher pump.

You also get rid of the machine gun under the bonnet!

Donald Jack · Posted: Sun Jun 25, 2017 5:39 pm Post subject: Fuel vaporisation

Disconnect the water heating from the inlet manifold.

Christopher Carnley · Posted: Mon Jun 26, 2017 8:43 am Post subject:

Not really a practical proposition, assuming that the typically blocked jackets are allowing circulation. It would involve removal of the "Y" pipe and capping off the 3 off connections.
Then the heat from the cylinder head would again take over.

This water jacket idea was never resolved until the 1955 4.9 litre engine.

Donald Jack · Posted: Mon Jun 26, 2017 5:44 pm Post subject:

Have you tried it?

Christopher Carnley · Posted: Tue Jun 27, 2017 8:45 am Post subject:

No, and I don,t intend to.
When the heat wave passes, so do the vapourisation problems.

Donald Jack · Posted: Tue Jun 27, 2017 5:28 pm Post subject: Vaporisation

That doesn't add to the reservoir of human knowledge and assumes that global warming is a fallacy.
I had fuel vaporisation on a 4.5 mark 6 special and eliminated it by disconnecting the water heating to the manifold.

Christopher Carnley · Posted: Tue Jun 27, 2017 6:25 pm Post subject:

Donald,

What you are saying does,nt follow, and makes no sense.

The Pre-War Derby engine, a development of the R-R 20 engine differs greatly from the Early Post-War cars, more than a generation in design,and I suggest that you examine the differences in water supply to the carb jackets before applying a generalisation.
I really can,t imagine that the cause of the vapourisation in the big bore engine was due solely to inlet manifold overheating.

Donald Jack · Posted: Thu Jun 29, 2017 5:42 pm Post subject:

Consider the formulation of modern petrol compared with that of the thirties and forties. Why did we require water heated manifolds? We don't need them now and in my opinion they are the main cause of the current problem.
Don't buy petrol from supermarkets and always use premium. It has less ethanol in it's formulation.

David Cocking · Posted: Fri Jul 07, 2017 8:06 am Post subject:

Update on mine - I went ahead and fitted my spare pumps near the fuel tank. Long, spirited run yesterday, very hot day, ran one rear and one front pump, no sign of problems. Looking promising.

Stephen Blakey · Posted: Fri Jul 07, 2017 10:26 am Post subject:

Christopher Carnley · Posted: Fri Jul 07, 2017 3:50 pm Post subject:

It all depends on the inlet arrangement. Most if not all of the WO engines have carburettors mounted directly onto the cylinder head, as do the later Lagonda built Meadows engines.
The conservative separate Rolls-Royce arrangement, was not resolved to a semi-direct fitting until the 1955 version of the B60, and the all alloy FB60, as designed by Reg Spencer for the BMC 4 litre car.
The earlier 4 litre "Princess" engine, was an all iron Austin engine.

Ewan Gallie · Joined: 29 Oct 1997 Posts: 184 Location: Italy

https://www.youtube.com/watch?v=tcj0hFthsLM

Very Happy

Up in the high 30s (°c) mid 90s (°f) here in Milan, got a wedding to do at the end of the month, will I make it Question

Ciao,
Ewan

Donald Jack · Posted: Tue Jul 11, 2017 5:07 pm Post subject:

I'm sorry this topic has gone cold. It was just getting interesting. I was under the impression that heated inlet manifolds were to assist in vaporising the petrol. The point about preventing icing sounds good and may well be correct but the current problems were not occurring at 2 degrees C. "Specials" suffer from all sorts of problems because they have been re- arranged and the builders and drivers deserve all they get. I believe that standard vehicles, WOs, Derbys, Mark Six's and R Types are now suffering "vaporisation ".

In spite of all the nonsense about global warming we have had very hot days in the past with no problems. If the weather hasn't changed and the vehicles haven't changed, what has? The fuel! I believe that the fuel vaporises much more readily nowadays because of the addition of ethanol. Is this correct?

Surely there is someone in the BDC who knows, or knows someone who knows the facts. No "pub pundits" please. Only people with provenance should respond!

Christopher Carnley · Posted: Tue Jul 11, 2017 6:21 pm Post subject:

Sorry, I don,t converse with the "Donalds" and David Bellamys,of this world who ignore global warming, as a hoax.

John Murch · Posted: Tue Jul 11, 2017 8:49 pm Post subject:

Do we know that these problems didn't occur in period?
My WO , on an autovac, suffers no vaporisation even with 40° ambient temperature, so I am dubious over the modern fuels argument,

Chris Card · Guest

I have SU pumps near the tank in my 4.5L and, touch wood, have never had vapourisation problems- a friend with a Derby and another, with an S3 have both suffered.

Chris

Donald Jack · Posted: Sat Jul 22, 2017 6:25 pm Post subject:

We've gone cold again on this topic of vaporisation. Does no one know for sure of it is the formulation of modern fuel? Has no one else disconnected their water heated manifold?

It would appear that we must keep the fuel lines and carburettor as cool as possible. Insulating gaskets and heat deflectors have been tried with some measure of success. Let's hear from you!!!!

Donald Jack · Posted: Thu Aug 17, 2017 5:04 pm Post subject: Fuel vaporisation

Whilst I'm delighted that Mr Carnley is refusing to converse with me, I'm disappointed with the total lack of ideas and initiatives to solve the fuel starvation problem. The weather may be cooler at the moment but if Mr Carnley is correct, it will get hot again

Christopher Carnley · Posted: Thu Aug 17, 2017 5:49 pm Post subject:

"Touche" ! or even threeshey.

Some fit a little electric fan under the bonnet to circulate the air, but only on hot days, but there is no definite cure all answer.

Mr Carnley, (Exterminator of climate change and global warming deniers).

Michael Hillam · Posted: Tue Oct 23, 2018 5:50 pm Post subject:

Re the subject of madly clicking petrol pumps and possibly hesitation in the engine I too have only just resolved this problem with my 3.5 Derby EF series. I could not accept that fuel vaporisation in this summer's hot spell was the culprit. On the advice of several experts I fitted a shield to the fuel filter. No difference. Then an auxiliary pusher pump on the chassis. Still no improvement with the costs mounting. My local reliable and helpful repa irer and restorer, AB Classics, fitted, at my persuasion, a new pair of petrol pumps. Disappointed at the result I asked him to find the true cause. 24 hours later he rang me to say that the problem had been identified and fixed. He carried out what he described, I think, as a vacuum check. There were 3 air leaks in the system. Firstly, the large gland nut on the fuel tank, although very tight, was fitted cross threaded and hence drawing in air Another more minor leak on the pipe entering the fuel filter and finally the flexible hose from pumps to carbs was leaking. He fabricated a new pipe, infinitely cheaper than the real McCoy but perfect in operation. Car now 100% and all anxiety gone whatever the weather.

Mike Hillam

David Cocking · Posted: Tue Oct 23, 2018 8:11 pm Post subject:

Thanks for the info Mike. A leak on the tank connection would cause the problem for sure, even with pumps at the back. An update from me - further to my posts (above) from last summer, since installing the rear pumps on my Derby all has been uneventful, recently enduring some very hot runs in Spain and Portugal without skipping a beat.