I recently changed out the three fuel valves, tank selection valve and the two fuel return valves on my '86 XJ6. On my first fuel fill after the job I noticed that the tank levels seemed to be dropping in unison although I was running only on the left tank (power off position). I confirmed that the fuel return valves are doing their job with no bleed past on the opposite tank as verified by looking down the fill pipes with engine running. When the tanks were both down to a quarter full I refilled the left tank only and returned to my garage. Sure enough, the next day the level in both tanks was the same with the guage reading just over half on each side. So my question is; is my new tank selector valve defective or is there any other mode of fuel movement that could accound for the syphoning between tanks?

Barcho
'86 XJ6

 

If the return valves are diverting fuel back to the proper tanks, the tank selector valve is suspect. If the engine continues to run when either left or right tanks are selected, I would trouble shoot the new tank selector valve. It would have to be stuck in a partially open position allowing fuel to flow from and between both tanks.

Here is my plumbing showing the two shut-off valves directly out of the tanks. Makes filter changes and anything else down stream much less messy to work on. Until I installed the shut-off valves I pinched the flex hoses coming out of the tanks if I needed to fiddle with something.

Dave

 

LT1
I am interested in what sort of shutoff valves you used.
My S3XJ6 is running with a T piece in place of the changeover valve.
The original selector valves fail regularly.
Otherwise, I have filters the same as you in each tank outlet primarily to protect the pump.
The slightest bit of rust coming out of the tank will be attracted into the pump and retained by the extremely strong permanent field magnets used in these pumps.
Cheers

 

Bill Mac,

I believe this is the one I used. I needed one that was very short and still had the PTFE ball seat. That's important. The PEX nipples are a little smaller than 1/2" hose, but a hose clamp will tighten it up nicely.PFX462 Series 1/2 in. Brass Full Port F1807 400# Ball Valve made by PROFLO.

Dave

 

Dave
Thankyou for that information.
Bill