Ok so I have a dilemma! When the fuel pump stops the fuel pressure drops to 0 almost straight away - now other than a leak (I'm certain it's not this) this could only be fuel pump or pressure regulator. The pressure regulator is a standard ford item on the end of the fuel rail and the fuel pump is a cheap eBay Bosch knock off one, ordinarily I'd suspect the pressure regulator but with my experience of cheap eBay bits I'm not so sure - I've never looked inside a fuel pump so I don't know what goes on in there.

I'm hoping the collective on here will have some experience to help me guess which one to change first. I've tried clamping the hose either side of the pressure regulator to see if it makes any difference to pressure drop speed but can't seem to get it to make any difference. It seems to hold a steady 4bar when the pump is running (seems a bit high for a std ford pressure regulator but I don’t trust the accuracy of the gauge!)

Thoughts welcome

Pump should hold the pressure when it stops, 4 bar is way too high for a standard fpr!

If you clamp the hose after the fpr and it drops I would suspect fuel delivery. Any leaks would be detected by your nose..

With the pump running engine off clamp off one hose and obsereve the presure drop when you switch off the pump then repeat for the other hose.

Usually with injection systems it is usually a leaking valve in the pump. Leaky pressure regulators usually show as leak diaphragms with fuel leaking to the vacum side which is fairly obvious as it causes an over rich mixture. Likewise a leaky injector.

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Originally posted by coozer
Pump should hold the pressure when it stops, 4 bar is way too high for a standard fpr!

If you clamp the hose after the fpr and it drops I would suspect fuel delivery. Any leaks would be detected by your nose..

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am I missing something here
but wouldn't you expect the pressure to drop if the pump stops? so ask why is the pump stopping?

I have tried the clamping hoses without much luck - I think it must be getting past my hose clamp but don't want to make it any tighter as it's already putting unpleasant dents in the pipes! I think it's dropping slower when the pump side is clamped off indicating a pump problem.

Can anyone recomend a good inline external fuel pump? The one I have is something like this:

External In-Line Injection Fuel Petrol Diesel Pump Bosch Replacement 0580464070

so anything that be a direct ish replacment would be ideal!

If the check valve in the pump has failed, the easy/cheap solution is just to fit an external valve. Sytec do one that will work at 4 bar.

The check valve is usually in the output connector of the pump body. Not sure it makes any difference. I've run without one for about five years and my pressure drops in a second when the pump stops.