Fool Pump

[sloopjohnrb]

1962, 4 door, 948 cc

The fuel pump seemed to be operating below normal, so I suspected the fuel filter needed cleaning.

I took the pump off, and cleaned the filter (it really needed it!) and replaced the diaphragm.

I have refitted the pump, but have the following problems.

1. On ignition circuits first turn, the pump doesn't click away like normal, rather it is making a BUMPING sound.

2. Engine will start, but fades away quickly.

I have checked the connections and they are clean and tight.

This is a strange one, any ideas most gratefully received.

[MarkyB]

When you replaced the diaphragm did you do it according to the instructions?
There needs to be some pull on it before you do the screws up otherwise it's too tight for the mechanism to pull it.

[bmcecosse]

As above - strip and rebuild following the instructions EXACTLY......

[sloopjohnrb]

hello,
Thank you for your reply.

I don't understand what is meant by, needs pull on the diaphragm?
If you could elaborate I would be grateful.
By, "Diaphragm", I mean the gasket/diaphragm as in the pic attached.

I used the Haynes manual as reference and followed the instructions, is it the case that there are other steps to observe?

Many thanks again,[frame][/frame]

[MarkyB]

Your picture is of the gasket, not the diaphragm which is black with a brass piece connected to a rod in the middle.
You may have screwed the rod in too far.
Or the diaphragm has no slack in it.

[sloopjohnrb]

hello
yes, the gasket is what I replaced.

What is "the rod" and the gasket is obviously new, so how to put play in it?
Thanks again

[MarkyB]

From here;

http://www.mg-tabc.org/library/fuel_pump/supump2.html

Assemble diaphragm spring with the large diameter towards the coil. Position the impact washer onto its groove in the armature on the diaphragm assembly. Insert spindle into coil assembly and position the 10 armature guide rollers into their locating groove (or fit plastic guide clip on later units). Screw the diaphragm assembly spindle into the contact rocker assembly.

Hold the magnet assembly horizontally and press the diaphragm firmly with the thumb and check to see if the contact rocker throws over.
If the rocker throws over, screw the diaphragm assembly in until it just ceases to throw over under thumb pressure. Back of until it just throws over, then unscrew by 4 holes. Continue unscrewing a little until the diaphragm lines up with the holes in the magnet assembly. Check that the rocker still throws over under thumb pressure. This adjustment must be made with the contact blade removed.

Have another go at it and check that it works using the battery before you refit the pump.

[sloopjohnrb]

Thank you, that's very comprehensive.
I will start tomorrow and let you know how I get on.
John

[sloopjohnrb]

I made a start and decided to examine the fuel pump again.
I suspect it is on it's way out as not only are the points and contacts pitted but there is a devil of a small red wire that is loose and may be broken internally. I don't want to trust to a re soldering, and replacing the points and so forth so I will go for a recon /new fuel pump and take it from there.

[sloopjohnrb]

I fitted a recon fuel pump (MMOC spares) and the difference is astonishing.
Immediately there was an improvement in just about everything.
I did some fine tuning of fuel mixture and idle speed and it now seems to be ideal.
Many thanks indeed for your advice