fuel system woes, non-return valve in my CVR(T) Sturgeon

[teletech]

Next time you are having issues with your Cummins CVR(T) fuel system not bleeding after fuel system work and before you replace the fuel pump, you might check your non-return valve.

 

Ever wonder what's inside one of these? Me neither, I just assumed it was a plate or ball and a spring which was about right.

 

The problem was, I couldn't get the system to prime and cracking the high side it appeared the fuel pump wasn't working. Some fully charged batteries and a replacement fuel pump later it still wouldn't work. Suction applied to the output resulted in fuel but it slowly drained back down. I finally decided it had to be a bad non-return valve (the one by the tank) and on removal (yep, a smelly, oily job in a cramped space... you have to love armor) and disassembly there was a bit of what looks like straw or grass in there allowing fuel to return from the outlet of the pump to the input. This valve is located before any filters.

 

Really I rather wonder why there is even a fuel pump bypass in these vehicles? The pump is run all the time anyway which actually is a bad idea since it makes fuel system damage more likely to result in a fire and wears the pump for no good reason, mine is on a switch so I can just run it when priming the system.

You can draw fuel through the pump with minimal restriction even if it's not running and if it's valves get a little punky running the pump will tend to clear it so part of me is tempted to remove this valve and cap the ports but I do worry the perhaps the stock Bendix pump might not have the volume at the very top end?

 

I haven't put it all back together but I'm sure when I do my symptoms will be gone.

 

So, next time you are chasing fuel gremlins, remember that even a part with just a couple moving pieces can cause you trouble and it's good to clean out this valve when doing fuel tank cleaning.

 

good luck out there,

[sirhc]

The electric fuel pump on the diesel vehicles is just there to prime the system. As soon as the engine starts the mechanical pump on the engine kicks in and the electric pump just circulates fuel round the bypass.