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Bob uk
Unregistered guest
Posted From: 94.197.122.81
Posted on Sunday, 03 August, 2014 - 10:21 am:   Edit PostDelete PostView Post/Check IP

All makes.
The fuel pressure is just enough to unstick the needle valve when the float drops.

This preassure is controlled by springs and the.springness of the diaphragm

The mechanism is wrist watch delicate
SU pumps suffer from lack of use
The points plaque causes high resistance

Someone cleans the points. This is the start of problems. Next new points. Then total strip down and stretch the springs for stronger action.

Instead of damaging the pump
Disconnect both pipes and place in liquid. Start pump with a tap.with a hammer and run pump for 10 mins. When the points make and break they slide first to self clean
And with luck the pump will be ok.
The pumps expensive because it is precision kit
The pumps attracts meddlers.
If it doesn't work plan B is sarcasm
Plan C is.find expert on web and follow the pictures.
Burlington carbs ate SU Weber who have parts
Cheapest way is solid state.

(Message approved by david_gore)
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Jan Forrest
Grand Master
Username: got_one

Post Number: 590
Registered: 1-2008
Posted on Tuesday, 05 August, 2014 - 09:28 pm:   Edit PostDelete PostView Post/Check IP

If a precision unit like the double fuel pump can continue to work for 3 or more decades while hanging in the air and continually being bombarded by dust, dirt, stones, rocks, rain, sleet snow and ice then I'd hardly consider them to be delicate.

Even when they do ... fail to proceed new sets of contacts and condensors are available - although not particularly cheaply compared to similar contacts used in other applications.

There's nothing in them that's too sensitive for the average DIYer to fix with a little patience and attention to detail. I've had mine stripped down a few times so that I could stone the old contacts flat again. I'm too cheap to spring for a new set, but I'm 'old school'. Why replace if I can refurbish?

Admittedly I'm replacing the door mirrors (Jag units) and all the speakers (3-way coaxial 6" units), but I see these as upgrades from a later era.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 936
Registered: 6-2009
Posted on Wednesday, 06 August, 2014 - 12:07 am:   Edit PostDelete PostView Post/Check IP

Jan,

I'm with you.

The dual SU pump on my Shadow II ran from 1978 to 2009 with what appeared to be zero maintenance and with one half having been invaded by water and becoming non functional.

Rebuilding the thing was not a particularly complex or tedious process, two EPK300 kits:

EPK300 SU Fuel Pump Rebuild Kit

and off I went.

I sealed things up using a tape that's far more robust than what had been used way back when. Getting the thing back on the car such that the various vent tubes both stayed in place and would not get ripped out by the drivetrain right next to them was tricky, though, and involved cable ties.

Of the many adjectives I'd apply to the SU fuel pump, delicate is not one of them.

Brian, who stayed with contacts and replaced the included varistors with diodes, so the contacts should have a "virtually eternal" service life
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Bob uk
Unregistered guest
Posted From: 94.197.122.74
Posted on Wednesday, 06 August, 2014 - 06:19 am:   Edit PostDelete PostView Post/Check IP

I agree with you but you are an expert. What I have found is that some do not completely understand which is why I said follow the pictures. Because if springs are stretched and I have seen people do that then the pressure maybe wrong. Some carbs such as SU will not accept a small increase in pressure and overflow. Others the excess pressure raises the fuel level and the extra buoyancy of the float shuts the valve. In fixed jet carbs the mixture will be rich.
In SUs when the pressure is high but not enough to cause flooding the fuel level in the main jet will be higher but this can be compensated by raising the jet a tad.

Diy pump rebuild is 100% do able.

The over centre points mechanism is delicate. A wind up wrist watch will work in adverse conditions but take the back off and start poking around with screw drivers to clean points most likely bend something.

Of course owners on this site are savy about SU pumps. But the previous owner maybe a meddler.

Pumps mistreated so can easily be put right but can result in high fuel pressure. So I always check fuel pressure.

(Message approved by david_gore)
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Randy Roberson
Prolific User
Username: wascator

Post Number: 278
Registered: 5-2009
Posted on Wednesday, 06 August, 2014 - 10:12 am:   Edit PostDelete PostView Post/Check IP

Reworked my Car's pump and it works fine. Quite a lovely and admirable mechanism, in my opinion.
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Bob uk
Unregistered guest
Posted From: 94.197.122.92
Posted on Thursday, 07 August, 2014 - 05:51 am:   Edit PostDelete PostView Post/Check IP

Good once done the pump will be good for 100,000 miles and 15 years on average. Did you tape up the plastic covers or use push bike inner tubes or both.

I put a clear plastic cover over mine and used office staples to clip the bag together and left a gap for any water to get out.

Because I use lpg only. I run the pump empty for short time to keep points clean. 40 years old never been touched.

(Message approved by david_gore)

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