How to check out a bi-fuel F-150

[OhMyGas]

Am about to look at a F-150 (2002) bi-fuel and have no idea what to look for in regards to ensure that all CNG components are working correct.
- should it start up on CNG or always on gas first?
- how to check the compuvalve?

any tips appreciated.

[OhMyGas]

Re: How to check out a bi-fuel F-150

Just checked out an used bi-fuel Ford truck, it has a switch with a light to the left of the steering wheel, but the light never comes on and the tank gauge does not change and the motor does not make any sound differences when switching over.
Any ideas what to inspect next?
Could the switch be disconnected? and it would then run of gasoline by default?

[CNGfamily]

Re: How to check out a bi-fuel F-150

...and the motor does not make any sound differences when switching over...

The switch needs to be moved when the key is off; switching with the engine running does not change the fuel used. If you start with the switch in CNG and the light does not come on and stay on, there is an issue with the CNG system and it is only running on regular gas.

[maxman]

Re: How to check out a bi-fuel F-150

If the switch isn't lit in the alt position, it glows green, it's not working. When I got my truck, the alt switch wasn't working. I thought it was out of CNG, but it actually wasn't working. I had to replace the compuvalve. They say the fuel selector switch it supposed to flash with the other warning lights when first starting, but mine doesn't flash, but it is running okay on CNG.
If your light isn't on, it's probably out of CNG and runing on gas. I think they do run on gas by default.
Before you buy it, if the light's not on, the CNG isn't working (or it's out of CNG) and that could be an expensive fix. It cost me $2100 to have mine replaced, but it runs great now.
Max

[OhMyGas]

Re: How to check out a bi-fuel F-150

thanks. After turning the engine off and back on in the Alt position, the truck starts up in CNG mode and the fuel gauge shows almost full (vs. almost on empty on gas).
But if I rev it up and let go the accelerator the engine stalls. The same when I drive and have to stop.
Is this just an adjustment or does this point to same more serious problem?

[OhMyGas]

Re: How to check out a bi-fuel F-150

Had it checked by a mechanic and it was the vacuum hose to the compuvalve.
$153 later it was fixed.

[Airliner]

Re: How to check out a bi-fuel F-150

Good for you. $153 is WAY better than it could have been . . .

[darress]

Re: How to check out a bi-fuel F-150

$153 dollars for a couple feet of vacuum hose. What a deal! I hope it was something else too.