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Fuel over pressure


GHILA
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Hello everyone, I'm brand new on here and of course I have a problem with my 1980 Triumph Spitfire 1500. before I bought this car in November 2020 it had a new mechanical fuel pump fitted. I thought  good. But it seems that it is producing too much pressure for the carbs to handle. resulting in fuel being ejected from the float chambers. this even after fitting new needle valves and an in line pressure reducer. Thinking of changing to an in line electric pump producing around 3psi. has anyone any advise please.

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If you still have the old pump there are overhaul kits available. Can be a bit fiddly but that way youd have a pump with the correct internal spring which is what sets its output pressure...

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2.5 psi is about as high as the needle valves will take   3 is pushing it 

has someone managed to fit a long arm 1500 pump without the plastic block spacer ??

the only replacement is generally the std  herald spit pump leave the spacer off and use washers to pack the nuts or fit short studs 

the 1500 had a pump set up of it own which is not really available   so 

whats been fitted ???

Pete 

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Fuel being ejected from the reservoirs may not be down to the pump. A new pump means the system has been "messed around with" quite often disturbed debris jams the reservoir valves open causing flooding. One sort of debris is the dread rubber slivers, bits of disintegrating rubber from the inside of the pipes scrapped off during reassembly. It is quite common and a nuisance, I've had to strip my carbs 3 times in quick succession to get rid of them. It's worth having a look before you start flashing the cash! :)

Doug

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15 hours ago, GHILA said:

even after fitting new needle valves and an in line pressure reducer.

GHILA

If you have fitted a pressure regulator and have it suitably set, the the problem is almost certainly contamination stopping the float valves sealing properly as Doug suggests.

If you are able to remove the float chambers (I'm a Strom man not SUs) you might be able to give the lines a flush out without further disturbing the connections. You can remove the needle valves and clean them out and check that they seal by blowing through them.

If you should decide to go electric, I have been very pleased with my Huco sucker. (fitted because the mechanical pump kept vapour locking, being attached to the hot block).

Ian

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I must say that I am very pleased with all of the replies sent over to me, thank you all. the replacement needle valves are the type with a Viton tip, but as I see it the excess pressure is pushing the valve open, therefore the soft seat is in operative. Am I correct with this diagnosis. I have the in line reducer set to a minimum in theory 1 psi. I do not have the old pump this is in Edinburgh where I bought the car from. I will lift the top of the float chambers again, but as I have messed about with the system there could well be most debris around. I have also cleaned the tank out which was another story.

Thank you all again.

 

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GH,

You cleaned the tank out, that would be because it was full of crud? Sounds like it's still floating about! :lol: Have you a fuel filter? Best fitted just before the pump, goes a long way to keeping the fuel clean. I have a clean tank, but I have to clean the filter every couple of years, quite a build up of nasties.

Doug

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Both needle valve housings had slivers of rubber in them, this afternoon ran the engine for 30 minutes, all ok. I expect to do it again in the near future.

Sorry about the photo quality.

IMG_20210325_145052.jpg

IMG_20210325_142718.jpg

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Hi. Don't know how old or how good quality (lot's of crap about) your rubber hoses are?. This can produce the slivers.

Also, when fitting or refitting hoses, smooth down any bure/sharp edges on the metal pipes and smear a bit of vasaline on the pipes. If pos, push the hoses square on. All helps to not shave into the rubber.

Edited by daverclasper
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members dont believe us that these little sods breed in the fuel system 

well done  dont you just love cheap fixes especially ones that give maximum grief   Ha 

Think we will need a seperate post for Rubber sliver syndromes   

so easy to form but you can chase your tail getting rid of them  and the more you mess around the more you make   ...great  its a classic 

Pete

 

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