Fuel issue

[Blackrat1638]

Hi,
I have recently aquired a 1970 roadster which has a fuel delivery issue in that after 20 mins or so on tickover it will cut out due to lack of fuel. After about a half hour it will restart until it again stops due to lack of fuel. It has not been in use for around 6 months, but was fine when last used and when it is running it is running fine. When it stops the fuel pump is still ticking away but nothing gets to the carbs. The fuel tank is only around 1000 miles old, the fuel pump a moprod unit. I have tried with the fuel cap off but no joy. Not surprising as it was running fine a few months back. The fuel pump does make some odd noises so I am of a mind to change it and the flexihose attached to it. Am I missing something? Thanks.

Gary

[Ian F]

A difficult one, but it seems most likely a pump problem. Not sure about a Moprod unit? I would fit an SU unit as original.

Ian F

[Blackrat1638]

Thanks Ian,

That's what I thought I would do. Just wondering if there's something I missed!!

Gary

[Ian F]

Nothing obvious to me, I would have suggested the fillet cap, but you have covered that.

Ian F

[Bumpa]

On my recently finished rebuild I experienced the exact same thing. The first time I took the car out, with newly refurbished carbs and a new fuel pump, it ran fine at town speed, but when I got onto the by-pass and got it up to 60 mph fuel starvation kicked in and we slowly ground to a halt. While sitting wondering what to do next I noticed that the fuel pump was hammering away nineteen to the dozen, so after 5 minutes or so I turned the key and it started right away. It took a couple more episodes to get it home again.

I took the feed pipe off the rear carb and measured the flow rate and it was poor. It turned out to be all the rubber pipes were significantly blocked, particularly the one from rear to front carb, so the fuel couldn't get through fast enough when the engine needed it. Replacing them with ethanol resistant pipe effected a complete cure.

[Ian F]

That sounds like a solution Mike, but what is slightly puzzling is that if the fuel pipes were blocked, why would the pump keep pumping?
I would have thought that it would "sense" the pressure in the pipework and stop pumping (as it does when the float chambers are full)?
Perhaps I am missing something here (wouldn't surprise me.........)

Ian F

[Bumpa]

I agree Ian, and it puzzled me too as I sat on the edge of the dual carriageway listening to it. I can only assume that the small amount of flow that did get through was enough to prevent the pump from stalling. I reckon that filling the car with E5 fuel, when it had never had ethanol containing fuel before, was enough to destroy the inside of the pipes.

[Blackrat1638]

Thanks for the further replies. I have replaced some of the fuel hoses and will do the other couple at the weekend. My concern, as mentioned, is the pump seems to run with no fuel flow at the carbs. If the hoses on the outlet onwards were blocked I would expect the pump to stop. I'll blow the metal pipes through and if all else fails replace the pump.

Gary