Fuel pump not running

[Meadowlark]

Hi,

I have a 1961 Moggy but having a few issues. The fuel pump works off the car but when connected up it wont run. I changed it (the garage put in very fast running new pump) to get it going and now the new pump wont go. I checked it and it runs when putting current through it with a charger but when I reconnect it does nothing, Any help appreciated. Thanks

[oliver90owner]

Does the pump have a reliable power supply - not just voltage, while not operating, but also adequate current carrying capacity?

[Meadowlark]

Not sure how I measure for that - when it runs it runs very fast and doesn't stop running - I think its too high pressure for morrie maybe its for a mini. I have been through the manual and started to learn about the regulator and fuses. Interestingly I took out the lower (30 amp) of the two fuses and when I tried to put it back I touched the upper fuse clamps and the fuel pump started running - even though the ignition was turned off!!! I did some cleaning of fuses and clamps and the pump intermittently ran on and off - very confused now! It must be something to do with the fuses being loose or the wires around there - I'll check again tomorrow night.

[geoberni]

From the sounds of it, the car is suffering from wiring neglect, which is very common symptom of the age of the vehicles and the lack of understanding of the care and maintenance that previous generations applied to these vehicles.

The fact that the pump runs when off the car, is 100% an indication that poor electrical circuitry between one battery post and the other are the problem.

Typically people concentrate on the 'supply' side, but the earth return must also be good.

You said you've got a Workshop Manual; I'm assuming at this point that you either haven't looked at the wiring diagram, or you can't understand it (some people just can't for some reason, but then I was an aircraft electrician ....).

The Fuel Pump, and the Ign Coil, are not connected to the output of a fuse.
Subject to the caveat "Unless a past owner has been messing with the wiring" there are 3 White wires connected to the input side of one of the fuses.
Those 3 white wires are the supply to the fuse from the Ign Switch AND the other 2 are the outputs to the fuel pump and Ign Coil. So not going through the fuse.

when I tried to put it back I touched the upper fuse clamps and the fuel pump started running - even though the ignition was turned off!!!

That's because you shorted across to the other fuse with the Brown input wire and the 2 Purple outputs.

That Brown is a direct supply from the battery, the 2 purple ones going out to the Horn and Interior light.

So in case you haven't realise, the vast majority of electrical stuff on the car is all via just 1 of the fuses, the one with the Green wires coming from it.


These comments :

I changed it (the garage put in very fast running new pump) to get it going and now the new pump wont go.

when it runs it runs very fast and doesn't stop running -

Don't make clear whether you have a correct SU Fuel Pump, or some nasty modern constantly running cheap replacement.

Please confirm what you're dealing with, just a photo will do.
If it is an SU Pump, and it has a small tag fitted between a couple of the case screws, that will have the part/model number.

[Meadowlark]

Thanks. I think its a cheap one

pump.jpeg (49.54 KiB) Viewed 75 times

[geoberni]

That is definitely in the OMG category.
I can't speak about any particular manufacturer but as a generalisation that sort of pump are rarely suitable for a Classic with a carburettor.
They just spin like crazy and usually deliver far too high a pressure for the Carburettor float valve to deal with.
Some are OK, if they have an internal pressure switch to cut them off, but they are pretty rare and it's difficult to sort wheat from chaff.
As you identified your one just runs and runs.

If something like that isn't working when fitted you've got a supply or an earth problem.
There's nothing you can do other than check all the wiring for loose or corroded cconnections.
I'm guessing electrical work is not your thing, as we wouldn't be having this discussion.
There's plenty of YouTube videos about basic fault finding with a multimeter; some can be too basic while others are too complicated. Find one that you can understand and invest in a cheap multimeter.. it'll soon pay for itself in the hours it will save you on little issues like this.

Do come back and let us know how this is resolved, or if you have other questions on this or anything else.

[les]

I expect I’m missing something here but maybe not. Why don’t you fit a standard Morris Minor fuel pump ?