Fuel Pump advice needed

[MinorTC]

Hi,
I recently purchased a 1965 Morris Minor 2-door saloon fitted with a Fiat 2.0-litre twin cam and five-speed 'box.

I have jury-rigged the engine wiring to get it up and running, though it needs some tweaks to get it properly on song; problems I currently have are that the block-mounted mechanical fuel pump doesn't appear to work (I tried swapping it for one off a Fiat 1800TC block and that was the same) so I've had to use a Moprod SU-type electronic one (in the engine bay, in place of the mechanical pump) which tends to cause flooding and intermittent starting.

Does anyone know what may be causing the fuel pump problem? When I took the mechanical one off, it appeared to suck OK when operated by hand, and I could feel the cam on the auxiliary shaft. Would a Facet type pump be best, and would it need an adjustable pressure regulator - it's just for road use, not race application.

Thanks for any pointers,
Maurice (Kent, UK).

[MinorTC]

Well, I perservered with the mechanical pump and it does work after all, after a fashion: I installed a transparent section of pipe between the pump and carb (a Weber 34ADF54/250) and when the engine is running, the fuel can be seen to be spurting in what appears to be an aerated form (i.e., not a smooth flow of fuel), and when the engine is switched off, the fuel drops back in the clear pipe to half way or less between carb and pump. Is this to be expected, or does it indicate a fault with either the pump or carb?

Thanks,
Maurice (Kent, UK).

[Guy Croft]

This is normal, yes. The acid test of the effectiveness of a mech pump is to run the motor for a minute or so and take the top off the float chamber. It should be full to correct level (according to float setting).

It is a good idea a return line to the tank from the carb with a mechanical pump, this keeps the fuel circulating cool. Many carbs have dual connections on the top cover for this. Mechanical pumps - which are mounted on-engine and 'sucking' the fuel rather than pushing (as a rear mounted electric pump does) can cause boiling of the gasoline at even modest altitude (low pressure) and on hot days because of the depression they cause in the fuel line betw tank and pump. This shows as chronic power loss..

GC

[MinorTC]

Thanks, Guy. I shall look into getting a Facet rear-mounted electronic pump, as the mechanical one just isn't going to cut the mustard I feel.

[MinorTC]

Bit the bullet and splashed out £50 on a Facet 40105K 'Road kit' electronic pump. This pumps the fuel through effectively (if somewhat noisily!), more so than either the Moprod electronic SU-type or mechanical pump. However, the car now runs ridiculously rich, even with the idle mixture screw screwed most or all the way in :/

I have taken the top off the Weber 34 ADF 54/250 carb and cleaned out the float chamber, removed the jets/emulsion tubes and sprayed them through with carb cleaner, and removed the automatic choke mechanism, jamming the choke flap open (i.e., choke completely off), all to no avail. It rapidly soots up the spark plugs and emits black exhaust smoke aplenty.

I also tried an 1800cc twin cam Weber 32DFM carb, with manual choke, which briefly ran fairly well but kept cutting out.

Is the problem likely to be a worn carb, and would a rebuild kit be worthwhile, or should I look for a new carb, or fit a fuel pressure regulator?

Thanks for any advice,
Maurice (Kent).

[Guy Croft]

If it it's flooding with that pump it is likely:

1. Worn float needle
2. Float height too high
3. Faulty pump jet circuit - dripping fuel into barrels while running


The standard float needle can easily cope with the line pressure.


G

[4v6]

Guy beats me to it.

The information in Haynes ( isbn 185010784X) states 6mm float height +/- 0.25mm for the 34 adf carbs.

[MinorTC]

Thanks for the info, gents.

I discovered why the the 1800cc carb didn't work; despite having a label on saying "Tested OK January 2000", when I removed the lid, there were no emulsion tubes or jets in it - how it ran at all, I don't know!!!

I shall be taking the original 34 ADF to a local Weber specialist, to hopefully have it sorted out; it appears to have some wear to the float valve needle and a pronounced wear ridge on the slow running mixture screw, so I'm hoping that with some new parts fitted, it may run OK.

[MinorTC]

Well, today I took the Weber 34 ADF carb to the local Weber specialist for an opinion. He now mainly does fuel injection, but in a minute he had diagnosed the rich running problem: the car's previous owner had fitted a hose leading from the base of the carb to the fuel return outlet of the float chamber, so some fuel was being pumped directly into the inlet manifold, bypassing the carb altogether!

Took it home, and reconnected the hose to the air filter housing, and blanked off the fuel return outlet, which isn't required in my application.

Result is a sweet running engine with no more sooting up of the spark plugs - very pleased indeed :D

[Guy Croft]

Great story!

G