Truck died when switching tanks

[DuallyGuy]

Hey there. I was filling up at the gas station yesterday. I started up my truck and realized that I had to switch over to the tank I just filled. Right as I hit my fuel tank selector button, the truck just died. It fired right back up though. Any suggestions why? Thank you in advance.

 

[crazy4offroad]

Did you have to switch it back or did you keep it switched to the newly filled tank? Might have just had an air pocket in the fuel line, like the fuel line lost prime.

 

[J Knight]

I was thinkig air pocket too.

 

[Jims86]

Yarp...have you tried to switch tanks again while running?

 

[DuallyGuy]

I kept it switched on the newly filled tank. No i didnt try it again because I was afraid I would be left stranded. I will try that now that its parked at home though. Thanks a lot.

 

[towjoe]

The spliter valve may not made good contact on switching for the electric fuel pump. Mine done that once in awhile when switching tanks. May make sure you switched the switch fully. My 89 I have to switch to fast or it dies.

 

[chengny]

"as I hit my fuel tank selector button"

Just to be sure; you are aware that the selector valve wiring - as designed - has no control circuit. The switch cannot be just touched momentarily with the expectation that the rotary valve will automatically fully cycle over to the other tank.

In other words, you need are the control ciruit and to maintain the switch in the depressed position until the valve has completely shifted over.

The manual suggests a full "2 thousand count" to ensure that the valve plug has shuttled sufficiently to cause the on/off-line tank ports to be re-aligned.

 

[towjoe]

I always thought the newer splitter valves were a electric silonoid that kicked them over since it made a clunk sound when switching. Maybe I need to disassemble a old one and find out.

 

[Mattchu60]

I am interested in this as well - My truck does the same thing. When I switch from the left tank to the right tank, the truck dies instantly. The previous owner told me both worked, but the right side was dry when I got it. I put around 2-3 gallons into it but everytime I switch it tanks it dies.

Someone mentioned air pocket above - I wonder if that is my issue. How can I fix this?

 

[crazy4offroad]

Best thing you can do is have the transfer valve mounted as close to the tanks as possible, in the middle between them so there is a shorter distance of fuel line between the tanks and valve. No matter what you do that segment of line will lose prime so having the line short as possible will allow the fuel pump to draw the fuel up more quickly. Switching them while driving may allow it to pick up faster. You might want to try experimenting on a road with little or no traffic, that if the engine is running at an rpm above idle, 1500 rpm or higher, will it pick it up faster and the engine not quit.

 

[Jims86]

Best thing you can do is have the transfer valve mounted as close to the tanks as possible, in the middle between them so there is a shorter distance of fuel line between the tanks and valve. No matter what you do that segment of line will lose prime so having the line short as possible will allow the fuel pump to draw the fuel up more quickly. Switching them while driving may allow it to pick up faster. You might want to try experimenting on a road with little or no traffic, that if the engine is running at an rpm above idle, 1500 rpm or higher, will it pick it up faster and the engine not quit.

Thats correct with a carb. ^^^^Dudes are TBI. I have solved this problem in EFI vehicles, but its a little pricey.

 

[towjoe]

How did you fix your problem with fuel injected trucks? I done replaced both fuel pumps, sending units, splitter valve, and dash switch. All new parts from napa to. Mine still does it once in awhile

 

[chengny]

No solenoid, no stop limits, no feedback to the selector.

The dash switch is the only control component. It is a simple DPDT type and will remain in the position it was last moved to. There is no center "off" position as in a DPCO (double pole center off) switch.

Wiring diagram for dual tank set-up.

You must be registered for see images attach

As far as the "losing prime" theory - under normal circumstances, that should not happen. The inlet to the valve should remain flooded and under a slight static head pressure no matter what position the valve is in. This is provided that the tanks are never allowed to be run down to the point that air is introduced to the pump suction lines and the suction side piping is tight.

Simply because there has been no flow through a tank suction line (even for an extended period) is no reason for any air to enter the piping. Condsider a single tank setup - the fuel pump will immediately start delivering fuel even after months of inactivity. No priming period is neccesary. There may be some loss of fuel and subsequent introduction of air on the discharge side (in the carb for example), but this happens only after an extended period. Not while filling up at the gas station.


Also I was wondering about this:

The spliter valve may not made good contact on switching for the electric fuel pump. Mine done that once in awhile when switching tanks. May make sure you switched the switch fully. My 89 I have to switch to fast or it dies.


Why is the power supply to the fuel pump routed/switched through the tank select/gauge indicator valve? Wouldn't the fuel pump be hot any time the key was in the RUN position regardless of which tank was on-line? Why would it be designed so that it would be shut off during a tank switch over? There is no "center off" position and the switching valve will always be lined up to either the LH or RH tank - or if the switch is not depressed long enough while changing over, somewhere in the middle.

If the switching valve plug is, for whatever reason, left in the middle position it will draw equally and allow returns from/to both tanks. Also, in this case, because the contacts for the gas gauge are at the extreme limits of travel, the dash fuel tank level indication will drop to zero.

 

[Jims86]

No solenoid, no stop limits, no feedback to the selector.

The dash switch is the only control component. It is a simple DPDT type and will remain in the position it was last moved to. There is no center "off" position as in a DPCO (double pole center off) switch.

Wiring diagram for dual tank set-up.

You must be registered for see images attach

As far as the "losing prime" theory - under normal circumstances, that should not happen. The inlet to the valve should remain flooded and under a slight static head pressure no matter what position the valve is in. This is provided that the tanks are never allowed to be run down to the point that air is introduced to the pump suction lines and the suction side piping is tight.

Simply because there has been no flow through a tank suction line (even for an extended period) is no reason for any air to enter the piping. Condsider a single tank setup - the fuel pump will immediately start delivering fuel even after months of inactivity. No priming period is neccesary. There may be some loss of fuel and subsequent introduction of air on the discharge side (in the carb for example), but this happens only after an extended period. Not while filling up at the gas station.


Also I was wondering about this:

The spliter valve may not made good contact on switching for the electric fuel pump. Mine done that once in awhile when switching tanks. May make sure you switched the switch fully. My 89 I have to switch to fast or it dies.


Why is the power supply to the fuel pump routed/switched through the tank select/gauge indicator valve? Wouldn't the fuel pump be hot any time the key was in the RUN position regardless of which tank was on-line? Why would it be designed so that it would be shut off during a tank switch over? There is no "center off" position and the switching valve will always be lined up to either the LH or RH tank - or if the switch is not depressed long enough while changing over, somewhere in the middle.

If the switching valve plug is, for whatever reason, left in the middle position it will draw equally and allow returns from/to both tanks. Also, in this case, because the contacts for the gas gauge are at the extreme limits of travel, the dash fuel tank level indication will drop to zero.

The pumps wouldnt take the abuse of constantly running against a closed valve, unless there was a regulator and fuel return before the selector valve.

 

[towjoe]

Then explain why mine was pumping fuel from right tank to left tank while it was running? I changed splitter valve and fixed that problem, but it still dies on occasion while switching. Yes I've changed dash switch to. Most of the time if the pumps deadhead, they blow out the hose from fuel pump to sending unit in tank on fuel injected models. I've seen this problem more in more than one truck that has fuel injection.