Intermittent problem

[taff]

I have an omvl r90e vapourizer on my military land rover 101 forward control. The problem is when changing to gas the blue solenoid just after the filter housing (shutt off) is not activating and not letting gas into the vapourizer.
The black solenoid on the vapourizer is clicking ok, I have check all connections, wiring and have changed filter and solenoids, even the change over switch.
I did get it to work briefly by pulling the 12v supply off the coil and putting it back on it seemed to activate the solenoid as there was a loud click and you hear the gas going to the vapourizer.
I tried it again using the switch but to no avail, this is now driving me mad and any help would be appreciated as my next step is rip the lot out and get a new system in.
When it has run on gas it runs fine so this makes me think the vapourizer is ok, I have also stripped that down and could not see anything wrong with it.
Many thanks.

[Tubbs]

What's the brown wire doing from the switch ? Where is it connected to ? If you take the blue solenoid coil off,check the coil resistance. What's the resistance on the black coil ? Are they the same ? You also may have a stuck plunger. Undo the stem post and remove the plunger and spring. Put it all back together. And see if it runs. If it does. Buy a new one. They are only £15-20.

[taff]

Stem is new, think brown wire goes to negative post on coil

[Gilbertd]

What controller/switch unit have you got? It sounds like it isn't seeing the pulses from the coil (or is but isn't taking any notice) so isn't switching. The fact that disconnecting and reconnecting the power caused it to switch and then switch back, says that it waited to see pulses and didn't.

[Tubbs]

Try wrapping the wire round the king lead, 7-10 tight coils, next to each other and then tape over the top.
I fell out with a carb change over switch only a few months ago. I had taken the brown wire to the coil neg, needless to say it did not work. I had forgotten see. I think the aeb switch with the led's that you set will take a coil neg. The old type vip switches wont.

[taff]

Have got two change over switches, the original and a new one. The only difference between them is the LEDs are slightly different, does not matter which one i use it won't change to gas.
Will try wrapping brown wire around king lead, will let you know what happens.
Many thanks for your help on this, much appreciated.

[Tubbs]

Its not many wires :-
Blue- gas electrovalves
Red- 12v switched (fused)
Yellow- petrol solenoid
Brown- rpm (king lead)
Green / white level sender
Black- earth.

If you got two switches and neither of them do what they are supposed to then odds are its wiring.

[taff]

Ok thanks for that, will have a look in the next week or so, if I get it to work I will reply.
Thanks again for the help!

[taff]

Tried wrapping brown wire around king lead, no difference. One thing I have noticed with the ignition on engine not running if I remove brown wire from negative terminal and then touch the terminal I can here the solenoid (fuel cut off) opening with a solid clunk. If I try it with the engine running it will not open.

[rossko]

Is the solenoid you are having trouble with wired the same as the one on the R90? And that one definitely clonks while the suspect doesn't? If so, your RPM feed is fine, and it sounds like time for a new solenoid coil. It was suggested to meter it.

[taff]

Tried a new solenoid coil when the problem started, made no difference. Wiring has not been altered since installation this is what is bugging me why it won't work, will get a meter and see what that says. Thanks.

[Tubbs]

So the switch has a pre programmed timer shot. Solenoid opens with ignition on for a set time. To give it enough gas to start. Then once it sees an rpm signal it opens again giving it enough gas to run. Sounds like the 'enough gas to run' bits the problem. Empty the float chamber. And put a permenent feed to the blue wire. Listen to the reducer. Is it getting any gas ? You should hear a steady schoosh down the pipe. See if it starts and runs like that. Disconnect the feed to the blue. Does it die ? Back to rpm signal.

[rossko]

My point was it's not likely to be RPM issue if the solenoids are wired together and one works while another doesn't. Those questions are unanswered.