Propane vehicle only runs on auxiliary tank

[Koharski]

Hey guys. So I just bought a propane van. It's a bit of a project, to say the least.

I've got one problem that i'm really puzzling over. The van has two tanks in it -the regular fuel tank, and an auxillary tank that's located on the bottom left. When it's running on the auxillary tank everything is fine. When I flip the switch to use the main tank, the engine won't start. There is definately fuel in the tank. I can see the gauge slowly go up, so i'm assuming going somewhere, but not where it needs to go.

Any ideas what it could be?

 

[pcgeek11]

Sounds like the switch over isn't completing or you have another manual valve somewhere that is closed.

 

[boomerang]

Not at all familiar with this but I assume the gauge is aft of the tanks? You say the gauge goes slowly up on the one tank, does it go quickly up on the other? If so, sounds like there is a restriction somewhere and there is not adequate pressure to start and run. Any chance of a diagram of the plumbing involved?

 

[HarryLui]

Maybe the fuel pump in the main tank is dead.

 

[herm0016]

Maybe the fuel pump in the main tank is dead.

No pumps in propane. It's like a giant grill tank and there is a pressure regulated that looks like the one on your house before the carb. We used propane fork trucks for years. I would start at the tank and check all your connections, go over the lines for any weirdness. Does each tank have a separate regulator? Maybe the main tank was not evacuated properly and there is air in it instead of propane?

 

[Koharski]

Thanks for the tips guys. I've been doing a lot of reading into it. Propane vehicles don't have fuel pumps. They do have regulators. What i'm not sure about is if there is one seperate regulator for each tank, or a two way switching regulator. I'll have to look into that more.

No matter which tank you choose, the fuel gauge moves quite slowly. It stays on even when the vehicle is off, but switching from one tank to the other requires about 60 seconds before the gauge is accurate.