Is there an LPG expert in the house?
Discussion
Here we have a P reg Corsa 1.4 with a non working LPG set up (Although a full tank of gas!)
The idea was to get a cheap commuter between son and self because my Pajero and his Subaru are breaking the bank at the pumps. Bought of ebay with the fault declared by the seller it is already earning its keep on petrol only but we have now started 'tinkering' to get the best bit to work.
Switch inside the car has 3 positions, on petrol its fine. On mid position you can hear the gas start up and looking down the SPI throat the petrol cuts off and the car runs but only for exactly 5 seconds then cuts out. The third position of the switch produces no effect at all.
There are 2 solenoids, one before the evaporator and one after. These give an audible click when the switch is operated and again at the end of the 5 seconds. A meter shows that power to these is cut, so it's not that the solenoids are faulty.
When the switch is operated there is a relay amongst the aftermarket bits which cuts the injector and powers the solenoids via the system's own little ecu.
Now, for test purposes only I connected a temporary switched supply to the solenoids and found that if this switch is operated at the same time as the selector on the dash then the change to LPG takes place seemlessly and the car runs perfectly on LPG.
Therefore my idea is to bypass the system's ecu box by taking a feed from the selector relay (live when the injector feed is OFF) and using this to power the solenoids. however, thinking that I need some sort of safety cut off switch I would run the feed via a second relay in which the switching side is triggered by something related to the engine running. First thought is the alternator light but you may have some better suggestions.
The result should be - I think - that switching over whilst the engine is on petrol will cut the injector and open the gas solenoid but if either the engine stops turning or if the ignition cuts then the gas solenoids would close.
Final thought..... It is suggested that these systems should be triggered by the Lambda sensor and indeed there is a wire going from the sensor to the LPG ECU. Surely though, if the Lambda was faulty then the car wouldn't run so well on petrol?
What we want is a cheap to run car, what we don't want is a big expolsion!
How do you rate this as a solution to the problem, especially safety!
The idea was to get a cheap commuter between son and self because my Pajero and his Subaru are breaking the bank at the pumps. Bought of ebay with the fault declared by the seller it is already earning its keep on petrol only but we have now started 'tinkering' to get the best bit to work.
Switch inside the car has 3 positions, on petrol its fine. On mid position you can hear the gas start up and looking down the SPI throat the petrol cuts off and the car runs but only for exactly 5 seconds then cuts out. The third position of the switch produces no effect at all.
There are 2 solenoids, one before the evaporator and one after. These give an audible click when the switch is operated and again at the end of the 5 seconds. A meter shows that power to these is cut, so it's not that the solenoids are faulty.
When the switch is operated there is a relay amongst the aftermarket bits which cuts the injector and powers the solenoids via the system's own little ecu.
Now, for test purposes only I connected a temporary switched supply to the solenoids and found that if this switch is operated at the same time as the selector on the dash then the change to LPG takes place seemlessly and the car runs perfectly on LPG.
Therefore my idea is to bypass the system's ecu box by taking a feed from the selector relay (live when the injector feed is OFF) and using this to power the solenoids. however, thinking that I need some sort of safety cut off switch I would run the feed via a second relay in which the switching side is triggered by something related to the engine running. First thought is the alternator light but you may have some better suggestions.
The result should be - I think - that switching over whilst the engine is on petrol will cut the injector and open the gas solenoid but if either the engine stops turning or if the ignition cuts then the gas solenoids would close.
Final thought..... It is suggested that these systems should be triggered by the Lambda sensor and indeed there is a wire going from the sensor to the LPG ECU. Surely though, if the Lambda was faulty then the car wouldn't run so well on petrol?
What we want is a cheap to run car, what we don't want is a big expolsion!
How do you rate this as a solution to the problem, especially safety!
I have no knowledge of how the system works but would suggest something is wrong in the system and the ecu is safely shutting down. Bypassing this would be, IMHO, foolhardy.
If you persist with your bypass then the oil pressure switch would serve to shut down the system when the engine is stopped. The alternator light feed will not work.
Steve
If you persist with your bypass then the oil pressure switch would serve to shut down the system when the engine is stopped. The alternator light feed will not work.
Steve
Thanks lads and I particularly like the idea of using the oil pressure switch.
Problem is that a proffessional diagnostic could well cost as much as the car is worth. As for safety I think I'll rig it then take to an LPG intaller and just ask if he thinks it is safe.
I'll post again when we have tackled the job.
Problem is that a proffessional diagnostic could well cost as much as the car is worth. As for safety I think I'll rig it then take to an LPG intaller and just ask if he thinks it is safe.
I'll post again when we have tackled the job.
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