The AC mechanical oil pump.

SydneyRoverP6B

SydneyRoverP6B

Well-Known Member
Staff member
Of course I am not being serious here, it is afterall a fuel pump, but......why do they leak oil so willingly...... :evil: ?

While transferring fuel from inlet to outlet, these pumps,...certainly from my experience also love to fill with oil and then happily pump it out both from around the edge of the main diaphragm and from the air bleed hole.

Even with an oil seal fitted, sometimes sealed with permatex around the diaphragm shaft, sometimes not, for it makes no difference,..the oil will still infiltrate the top section of the pump, coat the diaphragm and then happily leak as detailed above.

I have tried Leyland P76 fuel pumps, essentially a carbon copy of the AC pump save for a longer actuation arm, thus a thicker gasket is required to space it correctly. These pumps came as standard without an oil seal, so oil would leak from them pretty well right from the off.

Even so, this obsession with leaking oil has never compromised the fuel pumping ability, and as such is very much more of a nuisance than a potential point of failure.

Am I the only one who experiences this problem with the AC mechanical fuel pump?

Have you found a successful means of preventing this problem, should your pump also like to masquerade as an oi pump?

Ron.
 
Ron,

What you want to do is buy a blanking plate and fit and electric pump. Problem solved :LOL:
 
Hello Colin,

In actual fact I do have an electronic pump installed. For the most part it just sits idle, but if the need arises I can switch it on.

I do however like things to work properly, hence my question regarding the mechanical fuel pump.

Ron.
 
Ron,

I thought as much, I never had problems with mechanical pumps on my v8's but did on my 2200, petrol in the sump make me nervous.

Have you looked at what the original American cars had fitted before and after Rover bought the rights? maybe even some of the US MGB v8s might have had something, there is a website http://www.britishv8.org/. There might be something of interest there.

Colin
 
Hello Colin,

Many thanks for the link.. :D

I'll do some more searching and post back if I find something.

Ron.
 
Hi
I don't know what the original Buick V8 used,but most non fuel injected American cars of this era had an AC type mechanical pump The NADA spec V8s had an electric pump under the tank , conveniently located to collect mud and grot fom the rear wheel .
These work well and eliminate the fuel vapourisation problems which plagued the "Practical Comics rebuilt P6B' re commissioning tour" . Although this might be a side benefit from the NADA fuel spill back system , which returned any excess fuel from the carb vents to the fuel tank ??
Cheers
RVW
 
What about making a gasket for where the pump bolts to the engine with a slit just big enough for the actuating lever ?
Might reduce the amount of oil getting into the pump body
 
That's a good idea Dave. Do you think the oil runs down the lever or is it splashed through the hole by the timing chain?
 
Hello Paul,

The chain moves a fair amount of oil, so I would imagine that most would be splashed into the back of the pump. I have used the close fitting gasket design as Dave suggested, but the problem still exists.. :(

Ron.
 
A Rover that doesn't leak oil :shock: you are all children of Satan :twisted:

I must admit that once I sealed up my sump I never had any oil leaks and nothing from the Petrol pump, though now a days with an electric pump and a blanking plate I don't expect to see any more. Have you tried another pump? Maybe yours is just a traditionalist and trying to keep the oil spilling name of all things Rover.

Graeme
 
ripvanwinkle said:
These work well and eliminate the fuel vapourisation problems which plagued the "Practical Comics rebuilt P6B' re commissioning tour" .
Click to expand...
Talking of which I see in last weeks 'Classic Car Weekly' the winners of the car have it up for sale as an "unwanted competition prize". Nice to know it went to a good home considering thats what the original owners let PC have it for. :roll: If they didn't want it, why enter the competition you may ask?
£2500, that's why. And I say that without a hint of sour grapes. :wink: :mrgreen:
 
The Rovering Member said:
ripvanwinkle said:
These work well and eliminate the fuel vapourisation problems which plagued the "Practical Comics rebuilt P6B' re commissioning tour" .
Click to expand...
Talking of which I see in last weeks 'Classic Car Weekly' the winners of the car have it up for sale as an "unwanted competition prize". Nice to know it went to a good home considering thats what the original owners let PC have it for. :roll: If they didn't want it, why enter the competition you may ask?
£2500, that's why. And I say that without a hint of sour grapes. :wink: :mrgreen:
Click to expand...

Just read the the story in PC again, "I can't believe we've won a car, it's the best news ever". Not really the tribute to the previous owner PC were looking for? I wounder if it really was the only cure to the dreaded fuel vapourisation? Might try the same with mine :D
 
Well I suppose it may be the "best news ever" if they get £2500 for it. Let's hope the new owner is more appreciative of it & joins the forum, unless of course a current member is the buyer.
 
An update on my oil leaking mechanical fuel pump.

Upon further inspection I discovered that the cause of the oil leak in this case from my AC mechanical fuel pump was.......the top section of the pump that retains the main diaphragm and actuation arm was warped, both on the underside that meets with the diaphragm and the rear section that sits against the timing cover.

The degree of warping to the rear section, even with the gasket and sealant in place meant that oil could still escape from the timing cover, passing out behind the pump and then travelling around and over the pump, giving the impression that the leak was coming from within.

I can only assume that the damage that the pump body displayed was attributable to both the type of metal used in the construction and the number of heat cycles experienced over 150,000 miles.

I have since replaced the top section of the pump with a another AC spare, refitted, and I am very happy to say that there is not the slightest drop of oil to be seen from anywhere... :D

Ron.
 
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