Fuel pump.

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Fuel pump.

Postby gibbo » Mon Jun 08, 2015 6:55 pm

hello all, i am road testing my minor (52 split with ohv 948) after a considerable rebuild. It has original fuel tank, new fuel line a clear braided hose from pump to carb and new fuel pump. I wanted to use a new SU pump but everywhere seemed to be out of stock so i opted for a modern replacement from New Zealand of all places. It is a "Fuelflow" LM102 low pressure pump with a flow rate of 1LT per minute at 1-2psi. On my test drive circuit there is quite a steep hill to tackle, its not mount everest but quite steep; the car was quite happy in 2nd gear about 2500 revs until almost at the top when it cut out. I estimate that i only had about 3LTs of fuel and assumed going up hill fuel pick-up was the problem. I put another 5LTS of petrol in and tryed again. Once again the car seemed to suffer from starvation; the clear fuel line to the carb seemed to have a lot of air and not much fuel in it? I turned off the engine then turned on the ignition, after a couple of minutes i started and all seemed well.
The fuel pump seems to chatter away continually no matter the engine revs and theres as much air as fuel in the line?; also after 30 mins or so the pump is almost to hot to touch?. I have checked the power and earth leads and they seem fine.
Is there a fuel pick-up pipe inside the fuel tank and could it have become detatched? Should there be air in the fuel line from the pump to the carb? Should the fuel pump be so hot to the touch and clicking away so continually?
Your opinions would be much appreciated many thanks.
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Re: Fuel pump.

Postby woodywoodchipper » Mon Jun 08, 2015 7:06 pm

re check and tighten all connections, there should be no air in system, can't help re pump don't know anything about them,

http://sucarb.co.uk/

has correct pumps,

A,
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Re: Fuel pump.

Postby Panky » Mon Jun 08, 2015 10:25 pm

It sounds like your drawing air into the suction of the pump through a loose connection or split in the pipe, either that or the diaphragm in the pump is knackered :?
Just a thought, are the connection definitely on the pump the right way round, electrical and pipework?
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Re: Fuel pump.

Postby emjay » Tue Jun 09, 2015 4:22 pm

Is the pump always chatter or just when it starts to starve? If's it's all the time, then it's an air leak. If it's only after some usage and warmed up, then it's vaporisation. The pump will heat up electrically when it chatters.
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Re: Fuel pump.

Postby bmcecosse » Tue Jun 09, 2015 6:15 pm

Put a load more petrol in the tank - sounds like the pick-up pipe has rotted in some way...
 









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Re: Fuel pump.

Postby gibbo » Fri Jun 19, 2015 6:40 pm

Many thanks for the help, it turned out to be a bit of rust blocking the tank pickup. I guess no matter how hard you try to clean a fuel tank there is always goin to be a few bits you cant get out.
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Re: Fuel pump.

Postby mark_dolly » Mon Jul 11, 2016 10:53 am

1964 1096 electric fuel pump.

Normally I hear fuel pump tick about every second or so. I is now fluttering at high speed.
Thinking some kind of pressure demand within but note others saying things about air or pick-up. Ive not had any issues before.

Thought I'd put it out for ideas before i get the toolbox out at the weekend.

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Re: Fuel pump.

Postby Panky » Mon Jul 11, 2016 12:15 pm

Unless there is an open end on the outlet the pump shouldn't chatter away. Look for leaks or blockages on the inlet side, the filter mesh in the pump itself is a good place to start. Also try a flow test into a clean container, should pump a couple of pints per minute.
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Postby FMuscle » Mon Jul 11, 2016 1:46 pm

Hi Gibbo, your setup sounds a lot like mine (53 split w/ 948 and a NZ pump lol). I've had the car for a month now, and I had an issue with fuel twice. It cut off from starvation both time, ten minutes or so after I left work. The previous owner had put an inline filter before the pump, and moving it after the pump solved my issue. I'm keeping the filter until I get a chance to clean the tank, which won't be for a while, it's my daily...
I still get knocking on key on when it primes, then some while driving here and there, without affecting performance.
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Re: Fuel pump.

Postby emjay » Mon Jul 11, 2016 2:08 pm

An occasional spell of rapid pumping, typically stopped on a hot day is vaporization in the inlet line as it rises to the pump. A fairly consistent rapid pumping after some driving may be a crack in the diaphragm. Virtually constant rapid pumping from a cold start is an air leak on the inlet side.
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Re: Fuel pump.

Postby bmcecosse » Mon Jul 11, 2016 9:44 pm

See the other thread on same subject. Throw away any filters and mount the pump as low as possible. Could also be flooding float chamber - check the valve in the chamber lid.
 









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