VX Hard Cold Starting

[AB095]

1985 VX Coupe, needs to be cranked over many times when cold to start. Otherwise will start immediately, checked usualy suspects, car runs well otherwise. Anything obvious I may have missd?

[Nigel]

Hi,
Sounds like fuel delivery to the carb.
Is fuel fresh?
Replace fuel filter first, then check
for pump running on cranking. Hose off carb, fuel spurting out?

Do this and revert if no findings. It's always hard to diagnose remotely but we try.

Nigel

[lancialulu]

On vx there is a curious logic control ( or should be) of the hi pressure fuel pump which only gets power to the pump while cranking unless there is oil pressure…. So cranking is order of the day to to fill the carb to start. Some folk pull the lead off the oil pressure transducer (not the pressure gauge transducer) to make the pump come on as soon as the ignition is switched on…

[AB095]

Changed filter, the filter reservoir requires a few crakns of the motor to fill. The electric pump seems to operate more like a mechanical one! On my Fulvia, the fuel bowls dry if if left for over a week so I installed a supplementary electric pump with a manual switch to prime the carb, worked really well. Is this an option?

[WestonE]

Why install an additional pump when you can remove the oil pressure pump bypass and the carb will fill with ignition on? If you swap the wire from the oil pressure bypass to an inertia switch (sold by Weber and widely fitted to other cars) you keep the crash safety and have carb priming ignition on. PS replace old relays with decent quality new ones. It is asking a lot for them to stay reliable now they are so old.

[lancialulu]

I am going through this all  myself (as my car starts well then dies as it warms up evidencing a weak mixture) and with the standard arrangement with a fuel return , small plastic one way valve and the solex metal pancake inline "pressure regulator" as per the original design I am getting a flow rate at the carb (open pipe into container) of some 18 litres per hour which as the pump is theoretically rate at 160 l per hour seems most of the flow is going back down the return pipe. According to google this could be expected but before I look to change the pump (horrible job) I will do a flow test of just the pump...

I am using the Weston disconnect the oil pressure switch to keep the pump running while I am testing.

[lancialulu]

More data.

Vx Bosch (original pump) free flow c.35l in 10 seconds = 125 lph

Chinese copy pump (seems with out a non return valve) c double that.

I am choosing to get a replacement Bosch pump with non return valve.