Stuart,
Sounds like the old pump has either 1) a worn spring or 2) bad check valves.
I had a similar problem many years ago with a Spitfire. It had a mechanical
pump but would not hold highway speed. I traced it to a reversed pair of
check valves in the pump. the leakage allowed some gas to get by , but not
enough to deliver the volume necessary for speed. Must have been done by the
DPO or a un-trained technician.
The internal spring determines the fuel pressure to the carbs.
My bet is that there is some cr** (crud?) stuck in the check valves though.
Chuck
Stuart Keen wrote:
> Problems with a L type fuel pump on my TD. The coil is operating, the
> diaphragm is moving. If I put my thumb over the outlet orifice, the load
> almost stalls the pump, which sounds normal. I cleaned the in line
> filter. However, the pump is not delivering enough fuel to keep the
> engine running at driving speeds. What could be the problem?
>
> This is a Mk II TD with two in line fuel pumps. Since only one is needed
> for driving (two were for competition), I have rewired the pumps so only
> one is in line at a time. This way, with a switch, I have a spare ready
> to put on line. My new fuel pump performs correctly, it's only when I
> switch in the older one that the engine starves.
>
> Any suggestions will be appreciated.
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