Check valves on fuel system?

[p-Bar]

My brother has a 12 valve and has replumbed both fuel and return lines along with adding a Stewart Warner float in tank to match up to the SW fuel gauge. It's hard starting , I suggested that he needs check valves . What say you? Return line too? Thanks

 

[BigPapa]

I’m assuming you’re talking about a 1st Gen VE 12-Valve since that’s where you posted. It’s much different from the 2nd Gen 12-Valve P-Pump fuel system.

 

[p-Bar]

Yes its a 93 ,12 valve .

 

[Jim W]

I would be concerned about the DELTA P through the check valve and flow restriction that can occur. I did use check valves in the hydraulic systems and pilot operated checks valves that I designed when working. But I always considered the Delta P and flow constraints that will occur in a check valve since there are flow restriction that do occur.

Just saying

 

[p-Bar]

Thanks Jim something to ponder. Guess try to buy oversize so it doesnt hinder flow.

 

[petersonj]

My brother has a 12 valve and has replumbed both fuel and return lines along with adding a Stewart Warner float in tank to match up to the SW fuel gauge. It's hard starting , I suggested that he needs check valves .

I am not sure why you would want to add check valves. If I understand correctly, the OEM fuel system includes a engine block-mounted mechanical lift pump. That lift pump already has check valves.

If the hard starting issue is from air getting into fuel lines while the engine is shut off, then I would start looking for the source of the leak (usually between the fuel tank and the lift pump suction. Or, the lift pump could be failing - as in worn / dirty leaking check valves

Was the hard starting occurring before or after the "replumbed both fuel and return lines" event?

- John

 

[p-Bar]

Thanks John for the reply. Hard start after replumb. He did have the old sending unit that the fuel line hooked up to so I had him blow and suck on it and there was definitely a check valve in it. Your thoughts?

 

[petersonj]

More questions. Is the hard starting happening every time on a cold engine? A warm engine? All of the time. Has the truck been driven after the work was completed? A bit more detail here would help.

If it was just one hard start after the re-plumb, I would consider that normal. There would be a lot of air that would have to be purged. Some of that air probably made it to the high pressure fuel injector lines.

There is a fixed displacement vane pump inside the VE injection pump. Any air in the fuel lines should purge quickly from the operation of the lift pump and internal vane pump once the engine is running.

- John

 

[p-Bar]

Thanks John let me confer with him and get back to you.

 

[Jim W]

Doesn't the 12V have a P-pump installed for that model year? I know my son's 1996 24V has a P-pump installed on his engine.

 

[petersonj]

I believe the '89-'93 used the VE pump and the '94-'98 used the P-pump.

- John

 

[BigPapa]

I believe the '89-'93 used the VE pump and the '94-'98 used the P-pump.

- John

Correct-a-mundo.

 

[bighammer]

I'm guessing the earlier rotary pumps would operate similar to the P pumps, with a set of delivery valves at the pump exit to maintain line pressures and another valve at each of the nozzles.