Fuel pump not delivering

[Mark McCombs]

Now that I think I have my oil pump issues behind me I am moving on to try and actually Run the car for an extended period. Currently it's been running with just filling the bowls manually.

My fuel pump ticks away but I'm not getting any fuel delivery from the outlet side. Full disclosure I am using a two gallon can at the rear of the car For now.

I am seeing a minute leak at the Brass junction where the long fuel line from the rear meets the short line that goes up to the pump, Not sure if a very minor leak here with cause some type of air injection problem preventing the pump from moving the fuel forward....

I'm off to the hardware store to pick up a 5/16ths new compression fitting to take care of that But the question remains how would the pump be running been know fuel delivered....

Thanks

[Steve Simmons]

A leak before the pump can suck air and cause the pump to run rapidly yet deliver nothing. If the pump is clicking rapidly then that's likely your issue. I assume you've tried it with the hose disconnected from the carbs?

[Mark McCombs]

Hi Steve

Yes, I have the line from the pump to the first carb disconnected and in a jar. Its spitting a very small amount. I can feel the hoses pulsing too, but no flow. I will replace that compression fitting junction and see.

Thanks

[John Cockrem]

Mark are you sure you have the correct pump assuming you have an SU. I think a TF pump for example is designed to "push" the fuel as its located at the rear whereas a TC/TD pump is designed to suck the fuel. Not sure what the physical differences are between the pumps.
Just a thought presuming you have checked for blockages in the line et all.

[Mark McCombs]

Hi John

I ran a test copper line with a short rubber line with hose clamps to mate it with the copper line from the pump and it pumps fine. So I had a minor a minor air leak at that joint.

So I suspect I need to source the correct copper line olive fittings for for original line fitting for the joint under the passenger floor. I am guessing that the taper of the compression olive is different than what is typical compression fitting here in the US.

Can anyone confirm?

[Duncan M]

Mark-
I think the TD may have started using olives. For the TC, the original copper lines had special end bits soldered on. You can make them out in the Moss catalog pic under the "tank to union" pipe. https://mossmotors.com/fuel-pipe-tank-t ... ssoc=46778

Then for perspective you can look at the "union to pump" pic. Same end bits, you just cannot see them in the pic.
https://mossmotors.com/fuel-pipe-union- ... ssoc=46780

Should be able to de-solder them from old lines and re-use. No idea who might sell just the end bit or what they are called.
Duncan-

[Mark McCombs]

Thanks Duncan

That makes sense as I once owned a 1945 bsa motorcycle that had the same solder on fittings for the oil pipes. Unfortunately, and I don't know why he did, the previous owner clipped those off When he disassembled the car. So ill need to source each of those solder on ends from somewhere.

Anyone have any thoughts?

Ps, please see my new subject post.....

[cdrolshagen]

Hi
here you get all the parts you need,


https://www.vintagecarparts.co.uk/categ ... s-fittings

cheers Carl

[Duncan M]

Well done, Carl. Thank you-

[joel hutchins]

Mark;
Assuming you are using the original type S U pump, is the diaphragm still good or did you replace the pump with rebuilt or new. When I started this in 1973 I bought a rebuild kit from Moss and rebuilt mine and it worked for awhile. I am not sure they are available any more. If the thing clicks it should work unless the diaphragm is not functioning.

Regards, Joel.....

[Rob Reilly]

Yes, diaphragms can get old and stiff after many years. They are available from su-rebuilders.com and Moss and Burlens and others. These pumps are not difficult to rebuild.
There are electronic conversions available which either reduce the arcing at the points, or eliminate the points altogether.
Also there is a filter inside the pump. Clean that out.

[Duncan M]

When the pump gets a new diaphragm, the adjustment of the points throw-over can be a bit tricky. If not adjusted right the pump will pump fast and not get enough pressure. Can also be not adjusted right and it will tend to stop pumping when it should be pumping. Second half of article from this site goes the adjustment. http://www.mg-tabc.org/library/fuel_pump/supump2.html

The TC pump had no diode or resistor or anything electronic to moderate the spark intensity in the points. I fitted a "transil" along the lines of the John James article. Works just fine. Should make the points last forever. I observed the transil cuts down on visible spark intensity by around 80%. Interesting thing about a transil is it will not make the pump polarity sensitive or alter the pumping intensity. Neg or positive ground, either way. The pumps that came later with a diode would only work with whatever polarity the diode was.

Littlefuse brand transil 1.5KE24CA

[Ray White]

I have also added a transil to the pump. It not only protects the points but also prevents damage to sensitive electronics, like the CIS distributor.

When I added relays to protect vulnerable dashboard switches, I chose ones which have a diode in them as ordinary relays also emit harmful voltage spikes.