Front carb problem
Discussion
As I'm away on a Scottish Borders tour at the weekend now my '73 Midget decides to play up!
Serviced it a bit early two weeks ago (annual 12,0000) to make sure it was ready and allow a couple of weeks just in case (previously serviced Oct '08 6,000 6 months)
Overflow (on front carb) comes into operation sometimes when stopping for traffic light ect.
I've had it professionally looked at and (personally, twice) blown thro' fuel pipes from tank outlet thro' to both carb float heads
I can't get hold of any other float carb heads at the moment (Sod's Law)
I've had the float needles and seats changed and cleaned out debris in both float chambers/bowls
Anyone any other suggestions please as we don't want to go on tour and be smelling petrol I had enough of that with the GT6
ETA: checked (electronic) pump, pressure wasn't fantastic but adequate, the pump was fitted new by me in Set '07 (a couple of months after getting the car even tho' the old seemed to be fine but looked outwardly possibly old so I took no chances)
Serviced it a bit early two weeks ago (annual 12,0000) to make sure it was ready and allow a couple of weeks just in case (previously serviced Oct '08 6,000 6 months)
Overflow (on front carb) comes into operation sometimes when stopping for traffic light ect.
I've had it professionally looked at and (personally, twice) blown thro' fuel pipes from tank outlet thro' to both carb float heads
I can't get hold of any other float carb heads at the moment (Sod's Law)
I've had the float needles and seats changed and cleaned out debris in both float chambers/bowls
Anyone any other suggestions please as we don't want to go on tour and be smelling petrol I had enough of that with the GT6
ETA: checked (electronic) pump, pressure wasn't fantastic but adequate, the pump was fitted new by me in Set '07 (a couple of months after getting the car even tho' the old seemed to be fine but looked outwardly possibly old so I took no chances)
Edited by SB - Nigel on Wednesday 22 April 10:50
At least you know that the overflow isn't blocked....
Happy to stand corrected, but from what you say, there's only two reasons that petrol comes out of an SU's overflow.
Notwithstanding replacing the float needle and cleaning out of debris etc, it can only come out of the overflow because either the float needle is not seating properly, because of debris coming up from the tank via the supply pipe (fit a fuel filter), or the float is not pushing the needle up into the housing fully because it leaks or is not adjusted.
Assuming that the float itself is airtight and doesn't leak, make sure that the float fork arm is adjusted correctly - try these clearances:
http://www.7ent.com/images2/sucarburetorschematic....
All the best
MG Mark
Happy to stand corrected, but from what you say, there's only two reasons that petrol comes out of an SU's overflow.
Notwithstanding replacing the float needle and cleaning out of debris etc, it can only come out of the overflow because either the float needle is not seating properly, because of debris coming up from the tank via the supply pipe (fit a fuel filter), or the float is not pushing the needle up into the housing fully because it leaks or is not adjusted.
Assuming that the float itself is airtight and doesn't leak, make sure that the float fork arm is adjusted correctly - try these clearances:
http://www.7ent.com/images2/sucarburetorschematic....
All the best
MG Mark
Hi Mark thanks for your reply
I fitted a filter soon after I got the car despite most saying I didn't need it, of course now they're saying that could restrict the flow!
My float doesn't have the fork fingered arm
At the moment I don't have the problem but is it solved or just dormant?
I favoured the groove worn in by grit myself but haven't checked and I've now been given by a friend a set of carbs as spares so I'm happy now to sit and see - but I smell petrol all the time now, paranoid!
ETA : despite having a filter (changed every 12 months) and Q-tip cleaning out the float bowls before debris was back in so I cleaned it out again this week
I think possibly, maybe and fooling myself the new needle may have need to seat itself inthe old float bowl cap (?????)
I fitted a filter soon after I got the car despite most saying I didn't need it, of course now they're saying that could restrict the flow!
My float doesn't have the fork fingered arm
At the moment I don't have the problem but is it solved or just dormant?
I favoured the groove worn in by grit myself but haven't checked and I've now been given by a friend a set of carbs as spares so I'm happy now to sit and see - but I smell petrol all the time now, paranoid!
ETA : despite having a filter (changed every 12 months) and Q-tip cleaning out the float bowls before debris was back in so I cleaned it out again this week
I think possibly, maybe and fooling myself the new needle may have need to seat itself inthe old float bowl cap (?????)
Edited by SB - Nigel on Friday 24th April 00:46
Hiya,
Sounds odd that, although you have a filter, debris is still raching the float chamber after cleaning it all out. If you have rubber fuel piping between the filter and the floats, if it is old or been replaced at some point with the wrong type of pipe, the rubber may be degrading inside the bore, which would be the only source I can think of for debris still appearing after a good clean of the system. Might be worth replacing unless it's relatively new with "fuel hose" written all over it!
MG Mark
Sounds odd that, although you have a filter, debris is still raching the float chamber after cleaning it all out. If you have rubber fuel piping between the filter and the floats, if it is old or been replaced at some point with the wrong type of pipe, the rubber may be degrading inside the bore, which would be the only source I can think of for debris still appearing after a good clean of the system. Might be worth replacing unless it's relatively new with "fuel hose" written all over it!
MG Mark
MG Mark said:
Hiya,
Sounds odd that, although you have a filter, debris is still raching the float chamber after cleaning it all out. If you have rubber fuel piping between the filter and the floats, if it is old or been replaced at some point with the wrong type of pipe, the rubber may be degrading inside the bore, which would be the only source I can think of for debris still appearing after a good clean of the system. Might be worth replacing unless it's relatively new with "fuel hose" written all over it!
MG Mark
Hi Mark, I cleaned out debris it looked like very small bits of a house brick so I don't think it's the rubber fuel pipe degradingSounds odd that, although you have a filter, debris is still raching the float chamber after cleaning it all out. If you have rubber fuel piping between the filter and the floats, if it is old or been replaced at some point with the wrong type of pipe, the rubber may be degrading inside the bore, which would be the only source I can think of for debris still appearing after a good clean of the system. Might be worth replacing unless it's relatively new with "fuel hose" written all over it!
MG Mark
Very good piont about rubber fuel pipe - I've had a few encounters with rubber fuel pipes that last only a very short time and even a brand new factory-build Westie with rubber fuel pipe that wasn't petrol resistant!
Other problems have taken priority for now and I don't think I've smelt petrol again so perhaps the clean out worked (yeah, I am wishing)
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