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Originally posted by JD_975
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I`m sure someone more knowledgeable will correct me, this is only my limited understanding of how the valve works.
Mechanical Spill valves of old controlled the amount of fuel that was allowed to "spill" into the high pressure side of the pump, the pumps had elongated holes on the mounting points which allowed you to turn the pump to fine tune the "spill timing" similar idea to that of an old distributer on a petrol engine which you could turn to adjust ignition timing.
The electronic type of valve fitted to a surf lives on the high pressure side of the fuel distribution block, it appears that it is capable of altering both spill timing and quantity i.e. how much fuel is allowed through and at what stage (timing) dependant on signals from the engine ecu, the engine ecu signal is an odd one too, it seems to supply the valve with a full 12V to one side and alter the voltage on the other terminal between 12V (0V differential) and 6V (6V differential) thus the valve operates between 0-6V, my best guess for this is that the current available to operate the solenoid is higher by reducing the voltage on one side as opposed to having one side of the solenoid earthed and varying the voltage on the other between 0 and 6V, also found you must check the voltage between the two terminals of the connector to the actual valve and not to earth otherwise the readings make no sense at all, the positive side comes in at +12, the switching side reads as a PWM (pulse width modulation) signal. The valve also takes over the duty of the start/stop solenoid found on earlier diesel engines.
Given what the information I gleaned from my internet searching (which as I say may all be wrong!) coupled with my knowledge of common rail diesels suggests, the actual electrical part of the valve is nothing more than a solenoid, normally a solenoid is either on or off (plunger up or down), however with a PWM signal a solenoid can be anywhere in between on or off, thus controlling fueling and timing. If that is correct then the adjustment screw cant be a lot more than merely a preload on the solenoid return spring, the preload would dictate how fast the valve could shut which would determine injection quantity.
My old valve does click when a voltage is passed across it, which would suggest the electrical solenoid is working and your theory about a blockage in the mechanics is correct, I`ll never get the time so if you want the old one to mess with it`s yours for the price of the postage
Mechanical Spill valves of old controlled the amount of fuel that was allowed to "spill" into the high pressure side of the pump, the pumps had elongated holes on the mounting points which allowed you to turn the pump to fine tune the "spill timing" similar idea to that of an old distributer on a petrol engine which you could turn to adjust ignition timing.
The electronic type of valve fitted to a surf lives on the high pressure side of the fuel distribution block, it appears that it is capable of altering both spill timing and quantity i.e. how much fuel is allowed through and at what stage (timing) dependant on signals from the engine ecu, the engine ecu signal is an odd one too, it seems to supply the valve with a full 12V to one side and alter the voltage on the other terminal between 12V (0V differential) and 6V (6V differential) thus the valve operates between 0-6V, my best guess for this is that the current available to operate the solenoid is higher by reducing the voltage on one side as opposed to having one side of the solenoid earthed and varying the voltage on the other between 0 and 6V, also found you must check the voltage between the two terminals of the connector to the actual valve and not to earth otherwise the readings make no sense at all, the positive side comes in at +12, the switching side reads as a PWM (pulse width modulation) signal. The valve also takes over the duty of the start/stop solenoid found on earlier diesel engines.
Given what the information I gleaned from my internet searching (which as I say may all be wrong!) coupled with my knowledge of common rail diesels suggests, the actual electrical part of the valve is nothing more than a solenoid, normally a solenoid is either on or off (plunger up or down), however with a PWM signal a solenoid can be anywhere in between on or off, thus controlling fueling and timing. If that is correct then the adjustment screw cant be a lot more than merely a preload on the solenoid return spring, the preload would dictate how fast the valve could shut which would determine injection quantity.
My old valve does click when a voltage is passed across it, which would suggest the electrical solenoid is working and your theory about a blockage in the mechanics is correct, I`ll never get the time so if you want the old one to mess with it`s yours for the price of the postage
That would be great as I have a spare pump that I sacificed the spill valve back in the earlier days when trying to figure out how to remove it (it had been locktighted and would not turn)
I will email you with my address just do the same and tell me what I owe you.
Your comment about PWM is slightly off, what it means is that the solenoid's on/off ratio is changed ie: ON longer than OFF or OFF longer than ON, which in theory is continuously variable. The pulses can be quite fast and the inherant weight of the solenoid actuator smooths out the pulses so the on/off ratio is averaged.
This would change the timing and volume of the injected fuel.
You are correct that the solenoid is either on or off.
I am still not sure what that adjusting screw is doing but I will have another look at my sacrificed spill valve that is currently just used to keep the crap out of the spare pump.
I will let you know what I find...
Regards John
Email on its way.......
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