Fuel pump

Technical advice Q&A
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max-it-out
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#1 Fuel pump

Post by max-it-out » Sat Sep 25, 2021 3:15 pm

Tried to start the car yesterday and it coughed and spluttered without starting . Then I realised there was no ticking noise from the FP . After a few sharp taps with a small hammer , normal service was resumed and the car ran ok .
My question are - what`s wrong with the FP ? Why does tapping it cure the problem ? Lastly , is this a long term solution , or do I have to buy a new pump , and if so what type ? ( original or cheapo alternative ) . Thanks a lot in advance . :salute:
Mark

1968 series 1.5 roadster

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Robbiee
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#2 Re: Fuel pump

Post by Robbiee » Sat Sep 25, 2021 3:34 pm

It append on my MGs sometimes when they’ve not run for a bit…doesn’t mean the pump’s knackered. It just sticks and the solenoid isn’t powerful enough to overcome the friction😂
Robbie 1962 3.8 Coupe OSG 1962 OTS ODG

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mgcjag
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#3 Re: Fuel pump

Post by mgcjag » Sat Sep 25, 2021 5:49 pm

The points are on a rocker that flip flop.....open it up and clean it and inspect the points ....i wouldnt buy a cheap one i would get an SU pump with electronics.....Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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christopher storey
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#4 Re: Fuel pump

Post by christopher storey » Sat Sep 25, 2021 6:11 pm

Sticking is not uncommon with disuse, and once it's been in operation for a while it should be good to go . However, if this trouble recurs, spares for these pumps are readily available ,( I got them from SNGB but Burlen Fuel Sysyems are the primary source) and indeed I've just changed the points and rocker assembly on one of mine - it was a bit fiddly but following the instructions in my SU manual it was not that difficult. If you need instructions, I can always e mail you

I'm afraid I do not share Steve's ( mcjag) enthusiasm for the new pumps with electronics having seen more than one example at Hutson's ( admittedly of the V12 type ) which had suffered internal fires!! :sad:

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mgcjag
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#5 Re: Fuel pump

Post by mgcjag » Sat Sep 25, 2021 6:31 pm

Just done a search of the forum and only one report of a fuel pump fire.....on a standard points pump......however it really depends what type of fire we are talking about....an electrical burning insulation type.....or fuel igniting.......if your going to do some work on your pump it pays to insert a fuse in the pump feed.....the standard electrical cct isnt fused.....Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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Series1 Stu
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#6 Re: Fuel pump

Post by Series1 Stu » Sat Sep 25, 2021 7:30 pm

The series 1 have a dedicated 5 amp fuse. Fuse 4. I take mine out when working on the car to avoid unnecessarily raising fuel.

Maybe other series don't?

Regards
Stuart

If you can't make it work, make it complicated!

'62 FHC - Nearing completion
'69 Daimler 420 Sovereign
'78 Land Rover Series 3 109

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max-it-out
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#7 Re: Fuel pump

Post by max-it-out » Sun Sep 26, 2021 9:55 am

CS - I`m sure this problem has occured before , so it looks like a rebuild kit might be the best idea . Is getting the pump out difficult ? It looks like access might be difficult .
Mark

1968 series 1.5 roadster

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angelw
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#8 Re: Fuel pump

Post by angelw » Sun Sep 26, 2021 11:04 am

Mark Wrote:
Is getting the pump out difficult ? It looks like access might be difficult .
Hello Mark,
Not difficult, just a little awkward. Probably half an hour job to remove and replace, including boot area trim.

Regards, Bill

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MarekH
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#9 Re: Fuel pump

Post by MarekH » Sun Sep 26, 2021 12:21 pm

I assume you are talking about a standard SU pump.

The SU pump works as a lift pump, the same as the nodding donkey oil well rigs that go up and down continuously. Every time it lifts fuel, it draws ~3amps and this is switched on and off by the points cradle over and over again. This is quite a high current and the points corrode a bit due to electrical arcing and eventually the pump contacts corrode and stick. Cue the big hammer.

This is exactly what I made the fuel pump circuit board for (see classifieds section). This works by diverting the big ~3amp current away from the points and this switches through a transistor rather than through the points directly. The life of the points cradle is extended as it never sees high switching currents any more. Essentially anyone with a semi life-expired points cradle should fit one.

You should, as a minimum, clean up the contacts of the points cradle using emery paper or this will keep coming back whenever the car is left standing for any period of time.

kind regards
Marek

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