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Fuel pump service kit.

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supercass
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Fuel pump service kit.

Postby supercass » 24 Feb 2019 13:57

I have a service kit for my original fuel pump purchased from a specialist. My car is over fuelling and I am pretty certain the fuel pump diaphragm is past the sell by date. I thought this would be a nice easy job and that I could do it with the pump in situ. I have got the section off containing the gauze filter and a rubber ring seal but silly though it may sound|I am lost as to how the rest separates and I don't want to damage it by forcing it. It is the original pump on a latish convertible. I have had a look on line and am non the wiser nd unfortunately my workshop manual is elsewhere. Any one help? supercass

dursleyman
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Re: Fuel pump service kit.

Postby dursleyman » 24 Feb 2019 16:48

Much easier with the pump off the car. I remember you could buy those kits back in the day, the valves were staked in the housing as I recall so will need a punch or drift to replace them, but its a very long time since I did one.
Russ

1981 TR7 Sprint DHC
Dursley
UK

http://tr7russ.blogspot.co.uk/

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saabfast
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Re: Fuel pump service kit.

Postby saabfast » 24 Feb 2019 18:22

If the car is over fueling it sounds like the fuel pump is over pressurising if it is the pump? If the fuel pump diaphragm was bad would that not have the opposite effect, ie low pressure. Assume you have standard SU's? You could try a thickness or two of card as a shim in gasket to the block to reduce pressure. Have you checked the float shut off needle valve in the float chamber, although the overflow pipe tends to run with fuel if that is bad.
Alan
Saab 9-5 2.3t Vector Auto Estate Stage 1
Saab 9-3 2.0 SE Turbo Convertible
'81 TR7 DHC
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supercass
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Re: Fuel pump service kit.

Postby supercass » 24 Feb 2019 18:57

Thanks for your reply saabfast. Wouldn't a holed / damaged diaphragm deliver lots of fuel at low pressure rather than a smaller amount of fuel at high pressure. The fuel pump is the original one and with ethanol fuel it must be in need of a service. Any one got a pic of a disassembled one? supercass

saabfast
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Re: Fuel pump service kit.

Postby saabfast » 25 Feb 2019 19:30

From memory the diaphragm is moved by the arm riding on the cam to suck fuel in from the tank through one one way valve and then pump it out through the other one way valve into the carb float chambers. I would have thought if the diaphragm was badly damaged or holed it would not work well at all.
Alan
Saab 9-5 2.3t Vector Auto Estate Stage 1
Saab 9-3 2.0 SE Turbo Convertible
'81 TR7 DHC
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Hasbeen
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Re: Fuel pump service kit.

Postby Hasbeen » 26 Feb 2019 06:42

The fuel is actually pumped by the spring in the pump. The spring is compressed by the leaver riding on the cam lobe. The more the spring is compressed the higher the pressure produced by the pump. Our SUs should not be asked to handle above 2.0PSI.

The replacement pumps supplied in Oz come with a couple of spacers in the box to allow you to space them off the block to give the 2.0 PSI. They have a 3/16" & a 1/4" with the last pump I bought some years ago. They are hard to find today, but there are a number of different spacers available.

I gave one 1/4" spacer to a mate restoring a Dolly Sprint, when it had a flooding problem. He required the addition of 3 thicknesses of a kellogs cornflakes packet, spacing to stop his SUs flooding.

I found it most helpful to fit studs to the block, to make fitting the pump around the steering column much easier. It is easy to get the arm off the cam lobe while mucking around fitting the second bolt. This usually results in a bent or broken arm.

Hasbeen

Cobber
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Re: Fuel pump service kit.

Postby Cobber » 26 Feb 2019 12:31

Hmmmmmmmmn! How many thicknesses of Aldi cornflakes packet equal 3 thicknesses of Kellogs cornflakes packet? :lol:
Yes I know that only Kellogs cornflakes packets are factory genuine parts! :lol:
"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"

'80 Triumph TR7, '73 Land Rover (Ford 351. V8),
'97 Ford Falcon Longreach 'S' ute,
'98 MG-F, '69 Ford F250.

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