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Ford Pop 103e fuel pump
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Keith D



Joined: 16 Oct 2008
Posts: 1127
Location: Upper Swan, Western Australia

PostPosted: Sun Jan 02, 2022 5:17 am    Post subject: Reply with quote

Personally I wouldn't replace a mechanical fuel pump with an electric pump ever.

In my experience the AC mechanical pump is usually incredibly reliable. The usual checks, as previously noted, are valves incorrectly installed or having grit inside them, or a damaged diaphragm. Check also for a damaged body that could be letting air in.

Sometimes the operating arm wears or is bent over time and although everything appears to be OK, the movement initiated by the cam is not sufficient to bring petrol up to the carby. In the past I have had to very carefully bend the operating arm so that the cam gives increased movement at the diaphragm. If the pump sucks well on the bench when it is hand operated, then that is probably the problem.

Keith
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alastairq



Joined: 14 Oct 2016
Posts: 1950
Location: East Yorkshire

PostPosted: Sun Jan 02, 2022 10:42 am    Post subject: Reply with quote

Quote:
Personally I wouldn't replace a mechanical fuel pump with an electric pump ever.



Whilst an admirable policy, especially when looking at originality, fitting an electric pump should really be seriously considered if using old technology motors in today's motoring environment.

Aside from the issue of service spares for the mechanical pump increasingly being of inadequate quality [many instances noted of swollen diaphragms, for example], due in part to a laissez faire attitude by those ordering the manufacture of these bits...[I suspect?]...there is the issue of today's petrol not in any way resembling the stuff called petrol used when our motors were first designed, or manufactured.

Today's fuel evaporates it's head-end components at a much lower temperature than would have been the case, for example, back inte 1960's.

Today's fuel also leads our old designs of engine to increase their rates of cyclic variability of combustion, leading to much higher exhaust temperatures.
Hence we see a lot of old designs of motors now suffering from hot-start issues....fuel vaporising creating running issues , especially in traffic.
Now we have increased ethanol content to deal with as well.

All this means, we are in a different motoring world, and must adapt the old engines' technologies in order to maintain a status quo in operation.
We already regularly use specialist lubricating oils...instead of run-of-the-mill normally available stuff....

If our mechanical pumps suffer from the changes in the content of our fuels, then they may need supplanting or supporting, in order to continue with normal driving.
Fitting an electric pump, in lieu of, or in support of, a mechanical pump can alleviate issues with fuel in float chambers 'boiling off'....as just one example?

Of course, we can still buy petrol which has the same constituent components as fuel of the 1950's..but that comes at a relatively huge cost, and precludes, in my wallet, any sort of reasonably useful motoring.

{ I don't go driving just to be 'seen out in an old car']
So, yes, electric fuel pumps really do have a place on our old motors, for today's environment, in my view.
As do Hall effect ignition triggers in distributors.....or different types of coolant [how many use so-called 'wetter water?]
After all, we are all happy to stuff our fuels tanks with all sorts of witchdoctor fuel additives....??
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Keith D



Joined: 16 Oct 2008
Posts: 1127
Location: Upper Swan, Western Australia

PostPosted: Sun Jan 02, 2022 12:23 pm    Post subject: Reply with quote

My dislike of electric fuel pumps has nothing to do with originality.

I spent many years thumping firewalls to make SU's start clacking again when there has been no obvious reason for them not to clack. I am aware that modern SU pumps have electronics in them which may or may not improve them, but over my sixty years of driving I have never been let down by a mechanical fuel pump.

Further, most of the modern car breakdowns are caused by electrical and electronic failures (According to our RAC) so I prefer to stick with mechanical components wherever possible even on my moderns. (And I spent most of my working life as an electrical engineer so I do understand electrical components used in a car!)

As far as fuel evaporating in hot weather causing vapour lock. We have just experienced a week of temperatures in the middle forties which, trust me, is bl**dy hot. I have had no problems with modern ULP in my mechanical fuel pumped Austin A40. Nor have I ever had that problem. I certainly don't intend ever having to put an electric pump in series. My carburettor and fuel pump are properly maintained. And no additive gunk of any sort ever goes in my fuel tank.

Keith
_________________
1926 Chrysler 60 tourer
1932 Austin Seven RN long wheelbase box sedan
1950 Austin A40 tourer
1999 BMW Z3
Its weird being the same age as old people.
You are either part of the problem or part of the solution
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MVPeters



Joined: 28 Aug 2008
Posts: 822
Location: Northern MA, USA

PostPosted: Sun Jan 02, 2022 12:56 pm    Post subject: Reply with quote

Keith
My 'O' level Physics isn't helping, but I'm not sure that an electrical pump in series with a mechanical one would actually work. It seems to me that the pressure from the electric pump would confuse the suck-valve on the mechanical one.
I'm sure somebody knows!
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Ray White



Joined: 02 Dec 2014
Posts: 6284
Location: Derby

PostPosted: Sun Jan 02, 2022 2:30 pm    Post subject: Reply with quote

Wouldn't both pumps be stopped when the needle valve closed?
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Keith D



Joined: 16 Oct 2008
Posts: 1127
Location: Upper Swan, Western Australia

PostPosted: Sun Jan 02, 2022 3:07 pm    Post subject: Reply with quote

Sorry, sorry, sorry guys, Please read parallel instead of series.

It's getting late at night here.

Keith
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1926 Chrysler 60 tourer
1932 Austin Seven RN long wheelbase box sedan
1950 Austin A40 tourer
1999 BMW Z3
Its weird being the same age as old people.
You are either part of the problem or part of the solution
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Sun Jan 02, 2022 3:07 pm    Post subject: Reply with quote

SU pumps that require a thump normally just require backing off another “screw” when setting the rocker throw. Once this is set correctly and the points set, they will run for years. The points on them don’t like not being used, they can oxidise and require cleaning after long laid up periods..

Dave
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peter scott



Joined: 18 Dec 2007
Posts: 7113
Location: Edinburgh

PostPosted: Wed Feb 02, 2022 10:22 pm    Post subject: Reply with quote

The SU pumps with double contacts appear to be more self sufficient and don't require kicking.

Peter
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