Alternative Fuels

Hi
I have a pick up with tanks in tandem under the truck they each hold 29 usg . I drove 500km
And went to fill and got about 75 l in and it just only trickles after that , it does have auto shut off valves
Does any one have any suggestions as to why this is so
Thx

Not getting many responses are you. Tricky to diagnose. Considering it takes 75 L initially it would indicate the stop fills have shut off early for some reason.
First question. Is it one fill valve routed to both tanks or does each tank have its own fill valve?
If it is a single for both tanks it would indicate one tank is full and shut off while the other valve may be faulty.
Are the tanks new or have you owned the vehicle a long time?

Do this as a test. Let the vehicle sit for about an hour and see if the fill speeds up. (Considering they start to fill ok this scenario is unlikely but it may help to explain why some owners see different filling rates at different stations.) If the tanks fill OK after about an hour the issue is heat related. The tanks may be being heated by an exhaust pipeor other source (ie: engine heat flowing under the vehicle) causing the tank pressure to increase higher then the pump can handle. Filling station pumps have the pressure regulated to 30 to 80 PSI differential. These pumps come in various HP. Anywhere from 3/4 HP up to 3 HP. A 3/4 HP pump can only handle about 30 PSI differential and 10 to 20L/min While a 3 HP pump can handle 80 PSI and pump 35 to 50L/min. Differential is the pressure of the storage tank plus the pump pressure. The storage tank temperature is constant depending on the air temp plus sun. A vehicle tank can frequently be hotter, especially under a vehicle. If the tank temperature is 10 or 15 degrees hotter than a storage tank the pressure is exponentially higher in the tank vehicle causing a 3/4 HP pump to just stall until the vehicle tank cools down.

I had a similar problem at local filling station many years ago as I and others would regularly only get a part fill. Other stations would have no problem filling my trunk-mounted tank. The station attendant told me they would sometimes try spraying water on the underbody tanks to cool them off. The problem was eventually resolved when the propane company did some maintenance on their filling system and they may have had to replace the pump.

Thx for the response
Is the 80% auto shut off valve position sensitive
in rotation .
Thx

Tanks, in Australia at least, are built to be fitted with the guard box at a certain degree of rotation. If your tank is not fitted as per manufacturer instructions the auto shut off will change how far the tank can be filled but in my experience it wont make it fill slowly, unless of course the tank or shutoff is fitted upside down.

If it is the standard Manchester or Ceodeux valve the position is important. The valve will be marked "TOP" on the flange or a triangle with a red mark will indicate up. This must be a close as possible to the up position. A slight rotation either way will have minimal impact and only cause the valve to underfill slightly. This is unlikely to cause a slow fill. Although as storm has stated it will fill slowly if it is severely out of position.

This link will take you to Sleegers instructions on installing the Ceodeux style of valve. It is identical to the one Manchester uses.
http://www.sleegers.ca/pdf/STI_Instruct ... llStop.PDF