Sytec fuel pump Bosch

Engine Oily Bits, Ignition, Fuelling, Cooling, Exhaust, etc.
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Sytec fuel pump Bosch

#1 Post by Jake » Fri Jul 30, 2021 8:45 am

Hi All, I have a 2.5P1 Mk2 built Oct 1972. The previous owner had fitted a "Bosch" type fuel pump. (Actually a Sytec one). My issue was that the car was sometimes hard to start. I checked spark etc but all seemed okay. So I fitted an inline fuel pressure gauge.
With this fitted it was easy to see why it didn't always start. Turn the ignition on and the fuel pump starts and sounds like its pumping, but sometimes there is Zero fuel pressure, eventually, maybe 2 minutes later the pressure would just kick in and rise up to the correct pressure over about 2 seconds, and the car then starts straight away. I though the pump might be worn or such like so I bought a new one. The car then started and ran fine for the next 2 or 3 journeys. Then the same issue returned.
I took the fuel pump out again and this time I took the M12 outfeed outfeed stub out of the end of the pump. The problem was then evident.
The stub contains a non-return valve. A simple arrangement of a "rubber" (It's soft not plastic) plug with a spring. Normally it takes very little effort to lift the plug against the spring. But now I can see the plug has been "forced" down the orifice against the direction of flow. Presumably after the engine is turned off by the fuel pressure?????
(I pushed the plug back through the orifice in the direction of flow and refitted it and the car starts and runs fine again)
There must be 100's of Triumphs out there using this arrangement has anyone else seen this before or have any idea how/why this would happen.
There is a Malpassi pressure relief valve fitted and the gauge shows just under 110PSI running.

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