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 Post subject: not switching to gas
PostPosted: Tue Feb 20, 2018 6:10 pm 
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Joined: Wed Jun 08, 2016 8:51 pm
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Hi All

I was out at the weekend in my old Ford Econoline 350 motorhome , all seemed well until the changeover switch started flashing ( all lights ) and the engine started going between petrol & gas eventually the switch went dead and it went on to petrol. Not such an issue as I was not far from home.

I found a broken power connector going to the switch so fixed this , the lights are back on the switch but it will not switch to gas , green lights flashing . I guess its a pretty old system ,singlepoint with omvl90 reducer , the switch is an AEB. It can be started on gas so I doubt it has a temp sensor but could be wrong. I am not exactly sure of rpm switchover but I estimate its pretty low 1000-500 when decelerating.

Any thoughts / help greatly appreciated

Guy


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 Post subject: Re: not switching to gas
PostPosted: Tue Feb 20, 2018 11:19 pm 
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Joined: Mon Jan 23, 2012 12:21 pm
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Location: Milton Keynes
I'd have a check of the two solenoid coils - one on the vapouriser, other on the tank. If you can get a multimeter onto them check their resistance, it may be that one of them has died (you will have one per tank, so maybe multiple coils to check if you have more than 1 tank). Equally the wiring to them may be in need of attention, If its what your description suggests there isn't an ECU as such involved, all the (basic) circuitary is inside the switch itself so you should be able to check wiring from there.

It may also be worth having a look at your RPM pickup. I'd suspect the electronics are somewhat like this > http://tinleytech.co.uk/shop/lpg-parts/aeb722-change-over-switch-for-carburetted-engines/


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 Post subject: Re: not switching to gas
PostPosted: Wed Feb 21, 2018 8:57 pm 
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Thanks for getting back Brian.

All tank solenoids where replaced recently , to cut a long story short have made some progress.

I was having a look at the switch today after you said all the control was in the switch rather than an ECU , anyway on the back of the switch i found a small plastic screw. I turned this about half a turn , started on petrol then switched over heard the solenoids switch it ran on gas for about 10 seconds then blew the 5amp switch fuse.
After three more fuses blew i think i got the screw in the right place as it is running on gas and the fuse is intact. I have only had the thing in the yard not out on the road under load but am hopeful , what does the screw actually do ?
I have ordered a new switch from Tinley ( the one you gave a link too) mine is obsolete !
I figure it would probably be wise to change the solenoid on the vapouriser and the one above the filter bowl , there only seems to be one filter , the liquid one , is it ok not to have the inline gas filter ?

Many thanks for the help

Guy


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 Post subject: Re: not switching to gas
PostPosted: Wed Feb 21, 2018 9:45 pm 
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I've never seen a single point with a vapour filter and none of the installation instructions mention one. Blowing fuses suggests that one of the solenoid coils is marginal so maybe you got a duff one?

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 Post subject: Re: not switching to gas
PostPosted: Wed Feb 21, 2018 10:40 pm 
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Location: Milton Keynes
Gilbertd wrote:
I've never seen a single point with a vapour filter and none of the installation instructions mention one. Blowing fuses suggests that one of the solenoid coils is marginal so maybe you got a duff one?


Thinking possibly a shorted wire to earth also a possibility - I'd be checking resistance of the wiring as a whole before putting the new one in place as well as the individual coils. If you have multiple tanks then it generally seems recommended to switch them via a relay rather than directly with an ECU, though with a basic system like this it may not be so much of a concern? If its worked OK upto now I'd guess its fine (and at least the changeover switch is a lot cheaper than a sequential ECU!)

I would assume yours is that version for a carbed engine rather than the alternative injected one from what detail you've given. If you follow the link on the page to the fitting instructions > http://www.aeb.it/Istruzioni-en-US you might find your original switch there (first bit of the instructions on the one i looked at was Italian, but if you go to the second half its in English). That might give you the answer to what that screw adjusts, it may be something like the switchover threshold, Don't know - Simon/Dai or Gilbertd would be the people I'd expect can provide more detail on that than me.

Vapour filter wise I can't see theres any need for one on a single point like this - theres nothing to get gummed up or protect really unlike an injector system once it gets past the vapouriser, the liquid phase one would catch any bits that shouldn't be in there anyway.


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 Post subject: Re: not switching to gas
PostPosted: Thu Feb 22, 2018 11:33 am 
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Joined: Wed Sep 29, 2010 5:01 pm
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Location: Yorkshire
Problematic solenoids, shorts, etc, are of course possible causes for blowing fuses.

That said, look at how the number of solenoids (and current draw) can easily stack up.... Take a 2 tank setup on a carb vehicle - 2 Tank solenoids, plus a solenoid on the reducer (3), then if the engine runs a carb it will have a petrol shut-off solenoid (4). On a carb setup with 2 tanks when switching from petrol to gas the petrol solenoid switches off before the gas solenoids open, so 3 solenoids on at most. But when switching from gas to petrol the petrol solenoid opens while all the gas solenoids are still open (4). If each solenoid draws one amp that's close to 5 amps, shouldn't cause a 5amp fuse to blow but could if solenoid coil(s) draw just a bit more current that expected (they will draw more current at 14v with the alternator working than at 12v anwyay). Sure you got the right coils for the solenoids (I've seen 3ohm injector coils that are usually few with peak/hold power fitted on solenoids)?

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 Post subject: Re: not switching to gas
PostPosted: Sun Feb 25, 2018 10:25 am 
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Joined: Wed Jun 08, 2016 8:51 pm
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Thanks everybody with all the help.

I was in the van yesterday and found another short on the power wire to the switch. The wiring has been routed a bit stupidly too close to the foot parking brake causing it to chaff, I suppose at some time it would be a good thing to consider a re-wire. I also received the new switch but as it seems to be running ok will keep that as a spare.

Thank you

Guy


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