View Full Version : Dual Fuel Troubles

11-04-2007, 09:19 PM
Today my Propane Gas 460 ford pickup just wouldnt (for the first time ever) Run well on gasoline. Usually i try to run gas through it every month but its been sitting a bit more than usual due to working in a machine shop again. (temporary contract job till xmas then oh youre layed off forever merry xmas) anyhows the engine wouldnt go much over 80 kms an hour on gasoline yet propane still runs well?? It seemed to be starving for fuel. Any ideas engine machinist gurus?????

11-04-2007, 09:36 PM
Fuel starvation would be my first guess.

As I understand it, propane requires no fuel pump to flow fuel the motor, gas does. Maybe the diaphragm in the fuel pump is about shot.

The first thing to check would be the gas fuel filter. The tank might me rusting causing blockage in the filter.

I've never seen a gas/propane fueled motor, just one or the other. How is it setup? A carb and a propane "carb"?

11-05-2007, 06:55 AM
to avoid confusion

gas is petrol

and propane is LPG

in LPG cars with a petrol carburetter.
it is possible for the carb seals and diaphragms to dry out and crack ...
you need a new petrol carburettor seal and diaphragm kit including new petrol accelerator pump diaphragms ....or a new petrol carburettor complete ..

you should then in future run on petrol for a few hundred yards ..every couple of days ...to stop[ them drying out .

if you have petrol injection ...this does not apply

i had exactly the same thing happen to me ...on a previous car .......

i bought a brand spanking new carb off ebay (30)...very cheap ...as i had a car with not so common sought-after carb

all the best.mark

11-05-2007, 07:27 PM
Hi Madman

Assume that is a carbureted engine with an Impco mixer on top. If so, it could be running too rich. On "petrol" , there is a diaphragm on the mixer that needs to be raised in order to allow enough air in to run properly. It is usually raised with a (Boden) manual cable or if the installer is imaginative, he'll drill and tap that top chambre (1/8" NPT) so that a solenoid valve can supply a vacuum to pull it up, making the switchover automatic AND complete with the throw of a switch. See the first picture in this link:


So, you might check to see if that is in working order.

On my dual fuel carbureted engines, I always switch to "petrol" at the end of the day. This keeps the carburetor "lubricated" and ensures an instant start the next time.

I have another truck that depends on the Boden cable at swich over and it runs ok up to about 80 KM/HR without pulling the diaph out of the way. Over 80 it chugs along like it is running on both gas and propane.

11-05-2007, 09:34 PM
It could just be crappy gas. When did you fill up the gas tank ? I had that happen with my motorcycle. I did not have one for a few years and let the gas sit in the tank over the winter without putting stabilizer in it. :mad: