Fuel pipe diameter?

[silloyd]

I need to replace my fuel pipe (to remove one of those catalytic lead replacement things that was on the car when I bought is and to insert an in-line fuel filter. Does anyone know what the correct diameter of the braided fuel pipe from the pump to the carb is please?

Also, is it teh same diameter from the copper pipe to the pump?

[bmcecosse]

I think the fittings at each end are 5/16" - avoid the in-line filter, the pump already has a filter, and an extra one can lead to problems in hot weather!

[silloyd]

Thanks for the info.

I thought an in-line filter would help keep the carb safe from dross from the tank but I guess that if there is a (inlet?) filter in the pump then it is fairly pointless, assuming the pump filter is fairly fine. Is it easy to get at and clean the pump filter or is it a strip down job?

By the way, I'm interested to understand why you think the extra filter would cause a problem in hot weather particularly?

[bmcecosse]

The SU pump does indeed have a little filter in the base - it's not difficult to get to it, but don't worry too much - the SU carb is very tolerant of dirt, it doesn't have any small jets to clog up. The pump struggles to lift fuel from the tank to it's high mounted location in hot weather - the fuel tending to vapourise becuase of the reduced pressure as the pump sucks. A filter will just create even more resistance to flow - and the pump has to suck even harder = even more tendency to vapourise, causing the pump to have 'panic attacks' of frantic high speed ticking and sometimes grind the engine to a halt. The real answer of course (if this is troublesome) is to mount the pump lower down - so it doesn't have to suck so hard! It seems to affect some cars more than others - it's never been a problem for me - but then - it's not usually all the warm up here in Ecosseland, which may have something to do with it!

[silloyd]

Thanks for that - another lesson learnt for the newbie!

I'm having some fuel problems (intermittent loss of power and stuttering), which (based on another thread that I read) suggest that the points on the pump are on their way out, so I'll check the filter at the same time.

[bmcecosse]

Just clean the pump points- although - if ~ 40 years old - a new set may be a good investment.

[ferret76]

I think the fittings at each end are 5/16" - avoid the in-line filter, the pump already has a filter, and an extra one can lead to problems in hot weather!

30c+ here all year, never had a problem with an inline filter.

[bmcecosse]

Maybe your fuel is formulated to deal with the conditions! I have never had a problem with this either - but many do seem to have problems - some with filters, some without.

[silloyd]

I took the pump apart and found that the filter (nylon cage with fine gauze) was distorted due to bad fitting and therefore not doing it's job properly, i.e. dirt could get around it. There were quite a few bits of gunk in there and the float bowl but, as you suggested, not enough to cause a real issue.

The points were well shot with only about half of one of the pair of points making contact; the other had burnt our completely - so they got replaced, as it was a breakdown waiting to happen.

After doing all that it was still lumpy and wouldn't fire properly, so the problem had to be electrical, and yes the good old condenser turned up trumps!!

[bmcecosse]

Well done - and I like your notice!

[silloyd]

Sorry! Couldn't resist