Stag fuel pump

Hi

I've just managed to start my Triumph Stag after I've left it 5 months to stand. I took off the fuel pipe to the filter and nothing came out with ignition on. The electrical fuel pump in the boot needed hitting quite hard for it to work! I've known starters to need hitting but has anyone else heard of fuel pumps needing a whack after being stood?? What is the likely thing that was causing it to stick- the diaphragm or sediment in the pump

Also, as I initially thought the problem was electrical/damp related, I checked the coil's voltage which was only 6V with ignition on, as it's a 12V coil is this normal? Thanks to any replies, Jon

Reply to
jayseeblue
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this is very common with SU electric pumps, the points stick, a good few whacks gets them going again. replacement with a modern pump will fix it permanently

Reply to
Mrcheerful

Yup, that's what the ballast resistors for.

Reply to
Duncan Wood

You can also get an electronic conversion kit for SU pumps which replaces the points. Never tried one but it sounds a good idea.

Reply to
Dave Plowman (News)

On ignition the ballast reduces the voltage down to 6V but when the key is turned to the start position the ballast is bypassed giving the coil the full battery voltage that whilst cranking is probably about

10/11 volts and that going into a 6V coil gives a healthy spark and the coil is robust enough to handle the over voltage for the brief time it takes to start the engine. Trevor Smith
Reply to
Trevor Smith

They (SU pump) are basically a solenoid which cause a set of contact points to open at the end of the stroke. If the contacts suffer some oxidation, the solenoid will not pull in to pump the fuel. A good clout used to get them going again, by overcoming the oxidation.

It was common in the days when these pumps were used, to see their owners thumping the body work in the area of the pump :-)

Reply to
Harry Bloomfield

jayseeblue submitted this idea :

They used a coil which normally had a resistor in circuit. When cranking the resistor was bypassed to apply the full 12v across the coil.

Reply to
Harry Bloomfield

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