Not switching over to petrol

[Sir Brixalot]

Running perfectly on LPG but just dies when I try to switch over even at 70mph. Pump and rod have done about 5000 miles so shouldn't be that. What would you advise I try first?

[Mocki]

The petrol switchover solenoid ....

If you manually switch it onto petrol will it run .
If not, check petrol is actually getting to it .
Then
Check the wiring onto it isn’t green and furry , and that it’s is actually connected .
If the wiring seems all in order with a visual check , check you are getting 12v at the two spade connectors when unplugged from the solenoid .

It’s common on some of the older ones for the plunger to seize , so the electro magnet doesn’t make it move . Undo the nut on the top of it and clean the plunger rod .

[Sir Brixalot]

Thanks. I'll have another look at it, had a brief look and switched it on and off a few times. Changed it about 2 years ago. I had noticed that the petrol drains back to the tank inside a couple of days and can be a pain to get back to the carb but normally not a problem at speed

[Mocki]

Argh, the rest of the story ...
if petrol is draining back , and it’s not usual for it to actually happen , it’s the pump failing , for it by design is a non return valve , being a diaphragm pump

[Sir Brixalot]

They don't seem to last. Toying up on whether to go for an electric instead.

I was baffled because I could get petrol to the carb sucking on the hose but couldn't get it through the pump sucking on te out hose but when I blocked the inlet I could get a vacuum sucking on the outlet.

[Mocki]

Electric is a no brainier , it’s does away with the switchover solenoid, it does away with cranking the engine over and o er if having to start on petrol when stationary and it’s cheaper to buy .

I did to years ago .

All you need is a 20amp 4 pin auto relay , which you use the trigger wires from your petrol switchover solenoid on, to run the electric pump which you mount down next to the filter near the tank outlet .

https://www.ebay.co.uk/itm/380369295080" onclick="window.open(this.href);return false;

[Sir Brixalot]

Cheers. One more thing. Looking at the relays on Ebay there is a choice of normally open and normally closed. Do you know which one i need? OOI where did you site the realy in your van?

[Mocki]

Normally open , ideally with built in fuse , minimum of 10 amps
I fitted mine in the right hand far corner of the engine bay behind the air filter housing , out of the way and to keep the wiring tidy as it was going down that side of the van to the pump . You may have to extend the wires that go to the petrol switch over solenoid , which will be your trigger , you can take a feed live from the stud in the black electric box to take to the relay and obviously you need to run a feed down to the pump and connect the pump neg to chassis as close to the pump as possible

The pump will only come live when you switch to petrol on the lpg control switch , and will prime the system without the engine running you will hear it clicking until the system is full then you can start .
Switching back to lpg is the same as it always was, nothing changed .

[Sir Brixalot]

THat's a comprehensive and easy to understand reply. Save me doing a wiring f-up. Never knew I could get a feed from the black box

[Mocki]

You can of course also get a feed off the big connection on your alternator also, but the post in the black box would be the right thing to do