ProteuS Posted January 14, 2009 Share Posted January 14, 2009 Hi Chaps, I have a 1988 RRC 3.5 v8 efi (flapper) that i used to use as my general run around / toy but it's now been removed from road use and is just for off roading. My problem is, the vehicle will start on petrol, then after a while the idle starts to bounce then the engine kills itself, - i had thought this was possibly due to the flapper or anti blowback valve. whilst driving i would normally have to put on the throttle whilst holding the brakes to keep it running. Now it comes to lpg, the vehicle switches to lpg very smoothly and easily when the revs are up, however when the switch is done to lpg, it will not idle on gas untill the revs have been kept above 2k or so for at least 10-30 minutes, after that it will idle perfectly and is fantastic. My problem is, now i intend to use it infrequently for little jobs here and there and some off roading / loading trailers / pulling trees down / shifting boats I would like it to be able to start and run on gas, or at least start on petrol and switch to gas pretty quickly. It's not worth much and I dont really have the money to spend on it at the moment, so is there anything i could look at to try to get it to start / run on gas sooner? Any help is much appreciated Quote Link to comment Share on other sites More sharing options...
woodytz Posted January 14, 2009 Share Posted January 14, 2009 Hi Chaps, I have a 1988 RRC 3.5 v8 efi (flapper) that i used to use as my general run around / toy but it's now been removed from road use and is just for off roading. My problem is, the vehicle will start on petrol, then after a while the idle starts to bounce then the engine kills itself, - i had thought this was possibly due to the flapper or anti blowback valve. whilst driving i would normally have to put on the throttle whilst holding the brakes to keep it running. Now it comes to lpg, the vehicle switches to lpg very smoothly and easily when the revs are up, however when the switch is done to lpg, it will not idle on gas untill the revs have been kept above 2k or so for at least 10-30 minutes, after that it will idle perfectly and is fantastic. My problem is, now i intend to use it infrequently for little jobs here and there and some off roading / loading trailers / pulling trees down / shifting boats I would like it to be able to start and run on gas, or at least start on petrol and switch to gas pretty quickly. It's not worth much and I dont really have the money to spend on it at the moment, so is there anything i could look at to try to get it to start / run on gas sooner? Any help is much appreciated Hi , you should be able to start from cold, depending on the switch.Its probably got a temp sensor somewhereand this tells the switch when to cahnge fuel. One important thing,you stand a much greater chance of backfire starting from cold. Post some pics up of the switch and the system,i,ll see if i can guide tou through a diy tune up. cheers Woody Quote Link to comment Share on other sites More sharing options...
stumpy2268 Posted January 14, 2009 Share Posted January 14, 2009 In my experience, there should be an adjustment on the gas changeover switch which varies the point at which the switch from petrol to gas occurs. This is generally a small screw which is recessed into the switch housing, and which should be turned fully anticlockwise to allow you to run on gas from start-up rather than have an automatic switch over at a certain engine speed. Whilst there are those who will try to convince you that you must run on petrol before switching to gas, think how a forklift truck operates ! Adrian. Quote Link to comment Share on other sites More sharing options...
ProteuS Posted January 14, 2009 Author Share Posted January 14, 2009 Thanks for the help everyone, I'll try to get some pictures up when i get back to the truck. I can best describe the switch as a three position rocker switch, with left being petrol, and centre / right being lpg. this is as best i can tell. I have always manually had to start the vehicle on petrol, then switch it over to the right. The box has about 4 amber lights on it, and a red / orange one that goes to green when on lpg. If i recally correctly there is also a wire running out from the box with some sort of button on, but i have never known what that does. I'm not sure if that is of any help. Quote Link to comment Share on other sites More sharing options...
mickeyw Posted January 14, 2009 Share Posted January 14, 2009 I can best describe the switch as a three position rocker switch, with left being petrol, and centre / right being lpg. this is as best i can tell. I have always manually had to start the vehicle on petrol, then switch it over to the right. The box has about 4 amber lights on it, and a red / orange one that goes to green when on lpg. If i recally correctly there is also a wire running out from the box with some sort of button on, but i have never known what that does. A three position switch is normally for a carb engine. The efi should have a two position switch. Although most efi setups start on petrol it is possible to start on gas, the way of doing this varies. Both my systems can start on gas by switching the ignition on with the changeover switch set to gas, flick switch to petrol, then back to gas and it will start on gas. Otherwise if you were out of petrol but had plenty of gas you would be a bit stuck! Maybe the button you mention has something to do with starting on gas... Not all systems have a thermal switch controlling the change over, neither of mine do. Have you checked the vapouriser is not icing up? If there's an air lock or insufficient coolant in the cooling system this could be happening, check the water pipes to the vapouriser are getting warm. You mention the vehicle is not used very often. If the ignition system is a little old and has got damp it might cause poor running, which improves once the engine bay has warmed up. Hope this helps... Quote Link to comment Share on other sites More sharing options...
ProteuS Posted January 14, 2009 Author Share Posted January 14, 2009 i don't think it's due to the vehicle not being used for a while, as it was like this when it was getting regular use. even when the engine was warm it would not start on gas, and if switched over from petrol would not idle on gas, untill it had been run on gas with the engine above 2k rpm for about 20 mins. Quote Link to comment Share on other sites More sharing options...
Quagmire Posted January 14, 2009 Share Posted January 14, 2009 If its a three position switch with the 4 green indicator lights then you *should* be able to get it to open the solenoids for a small period of time when you first click the ignition on. On mine this time period can be anything up to 3 seconds and is adjusted by a variable resistor on the side of the switch. If the car does not start in this time and the switch recives no signal from the coil to indicate a running engine then it will close the valves again. To start on gas i simply turn the key, hear tankvalve click and the tank go hiss, wait a second for the gas to work through and then crank. Usually works first time, and often fires better than it does on petrol with choke when cold- no need to vapourise the fuel i guess so better atomisation from the get-go. Quote Link to comment Share on other sites More sharing options...
steve_d Posted January 14, 2009 Share Posted January 14, 2009 The problem may not be petrol or gas related. Does it still have the extra air valve on the front of the left cylinder head? This valve supplies extra air when the engine is cold and a heating element inside it gradually closes the valve. If the engine is very cold the ECU will not ground the supply and the valve will stay open. As the engine warms the element is powered and the valve gradually closes. As it is bolted to the head it will close as the engine warms up despite the ECU. What may be happening is:- It is Jammed. The element has burned out The coolant sensor has failed or is not connected Your changeover is disconnecting the ECU so it is no longer controlling the valve. Steve Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted January 15, 2009 Share Posted January 15, 2009 Whilst there are those who will try to convince you that you must run on petrol before switching to gas, think how a forklift truck operates ! Adrian - this is why you're supposed to run on petrol first: Have you checked the vapouriser is not icing up? If there's an air lock or insufficient coolant in the cooling system this could be happening, check the water pipes to the vapouriser are getting warm. Until there is a supply of warm coolant going to the vapouriser, it will tend to ice up (feels like you're running out of gas). In the summer, you'll usually get away with it, in the winter you'll usually need to drive anything up to a couple of miles on petrol depending on the temperature and your truck - they seem to vary wildly for no obvious reason. Some seem to be quite happy all year round, others freeze even in the summer. The factory LPG focus I have switches almost instantly unless it's starting from cold and the ambient temperature is well below freezing, but that car warms up very quickly - and I've yet to figure out where the vapouriser is! There's no way to force it to start on LPG, but then it's also the only LPG vehicle I've ever come across that can't switch on the fly (in either direction - you have to switch the ignition off to change fuel mode). I don't think in this case it's going to be the vapouriser, though - it sounds like the car has issues on petrol too, and they probably share a common cause. Does this LPG kit have an electronic controller and a diagnostic hookup? If the problem is a sensor fault you can probably interogate it to find out what (I'd guess it's an easier DIY approach than interogating the the 14CU ECU). Quote Link to comment Share on other sites More sharing options...
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