Which electric fuel pump at rear of car?

mrtask

mrtask

Well-Known Member
I would like to fit an electric pump at the rear of my P6, suitable for a 'warmed up' 3.5 litre engine, initially running on the twin SU carbs but with a view to later fitting an injection set-up from a P38 Range Rover 4.6 donor vehicle. I would ideally like an electric fuel pump suitable for both applications. I currently have a Facet pump mounted in the front next to the windscreen washer bottle, but I don't like the positioning. I can hear the 'tack tack' sound of the pump from in the drivers seat. I have an explanatory text from the previous owner which suggests that the tap for the reserve supply, in the engine bay adjacent and lower than the steering box, is not capable of withstanding the pressure of a 'push' pump at the rear of the car,. Hence his use of a 'pull' pump forward of the reserve tap. I don't want to duplicate this solution on my rebuild. Who can advise what pump is best suitable, and how I might retain the reserve function with the tap also at the rear? Would I then have to run a much longer reserve cable alongside the fuel supply line next to the tunnel?
 
If you want to retain the reserve facilty I'm afraid the answer is yes. You'd have to remount the reserve tap at the rear, upstream of the pump. This is the same arrangement as the NADA 3500S, but I very much doubt you could source a NADA reserve cable! It is possible to have special cables made up, but not sure where to advise bearing in mind you're in Berlin. Pesonally I think this facility is a bit of an anachronism and I'd be inclined to delete it altogether. You then win a switch position free on the central speaker panel. A pull switch similar to the HRW one looks good there - perhaps electric rad fan over-ride?

I'm not at all convinced the type of pump makes a lot of difference. You'll need one with enough pressure to cope with the EFI and therefore a pressure regulator at the engine end. Another solution is to modify the tank to take a RR combined pump / level guage / fuel take off. You will need to replumb the entire fuel system, complete with tank return, for EFI. Best to use at least the next size up tubing to that fitted. I hear tell the size of the standard fuel line starts to be a limiting factor on power output with high power engines.

Chris
 
Hello mrTask,

From my understanding, you will have very real difficulties in fitting the fuel injection/engine management system from a P38 4.6 litre Range Rover onto your 3.5. There were two injection systems employed on the P38, the first by Lucas..the second by Bosch. In both cases the ignition system used runs with coil packs and no distributor. P38 distributorless timing covers incorporate a crankshaft driven oil pump and there in lies a major problem in that there is insufficient space within the P6 engine bay to accomodate it. Crankshaft position is obtained via a sensor screwed into the rear of the block and reading off the flywheel, thus you would need to have the block modified and a P38 flywheel fitted. There are also the knock sensors which are fitted into the block via cast in bosses which your block does not have. For this reason the Lucas GEMS and Bosch Motronic 2.1 systems as fitted to the P38 are known as block specific systems. The thermostats for the P38 reside in the bottom radiator hose and are set to open typically at 96 degrees C. The thermostats are sealed within a plastic housing so changing them for cooler ones is not possible, apart from which the management system operates based on that running temperature.

I would be inclined to say that you will probably have to use an alternative such as hotwire.

Ron.
 
In addition I should mention that even if clearance was not an issue for the crankshaft driven oil pump, the crankshaft is! In order to drive the pump a long nose crankshaft is required and no long nose crankshafts were manufactured for 3.5 litre engines.

Ron.
 
Why not just toss the 3500 in favour of the 4.6 and be done with all the needed hard graft cobbling it together I am quite sure the resultant car would be far better than the origional unit.
As to the clunk or tapping noise from the facet pump why not just rubber mount it for the conducted thump noise and maybe an external housing for the radiated noise (also makes an effective heat shield) this would then retain the reserve function, a function I highly value on my p6 and use very regularly.


graeme
 
Thanks for all the helpful input chaps.
Ron, I ought to have been more specific about my longer term intentions. Initially I will be fitting my 3.5 P6 engine, with which I will be able to pass the strict test that will enable me to register my car as an historic vehicle. Subsequently, as and when funds permit, I would like to replace that engine with a newer unit, based around a newer larger displacement engine, topped off with the Callaway injection set-up that I already have waiting in my garage. The larger displacement engine, be it a 3.9, 4.2, 4.6 or even perhaps more displacement by using a 'stroker' kit, would run on coil pack ignition with Megasquirt and Megajolt in place of the Lucas engine management system.
I had not realised that there might not be sufficient space for the longer more modern crank. I had hoped I would be able to retain the short nose P6 timing cover, blanking off the distributor hole and perhaps replacing the oil pump with a remote unit from Mocal or similar. I would want to retain the P6 power steering pump. I don't want to change to a more modern timing cover. This is all conjecture, I am getting way ahead of myself here, basically just thinking/daydreaming aloud!
 
Hello Mr Task,

Your long term plans do sound interesting!

There is room for the long nose crank as used in the interim 3.9 and 4.2 litre engines and the 4.0 and 4.6 litre engines...all different cranks as far as offset is concerned, and with the latter two larger journals too.

If you had wanted to change to a later timing cover that incorporated the crankshaft driven oil pump, that is when you would have had clearance issues.

There is no issue in fitting a P6 or SD1 timing cover to a later block and the P6 power sterring pump and associated bracket will attach straight to the block in the same way. Fortunately Rover did not change the casting in this area, so the mounting points are still there for the P6 pump in a 4.6 block that was cast in 2002 like mine.

Running a remote oil pump so as to not have an issue once the distributor is removed and the hole sealed over does sound most interesting.

I look forward to seeing how your new big engine will evolve as the time comes. Excellent.. :D

Ron.
 
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