i have a low mileage 87 xj6 that has sat for a long time, my mechanic has drained the tanks changed the fuel filters and has replaced 3 fuel pumps, the car will start good run for a while then the fuel pump starts to scream then a few minutes later it will die, as long as your giving it throttle it will continue to run, my mechanic says the fuel return is not working properly>>>>>anyone have any advice??

 

Welcome to the forums John,

I've copied your question from New Member Area - Intro a MUST to XJ6 & XJ12 Series I, II & III forum for advice from members with the same model.

Graham

 

Hi John,

Graham is in the U.K., where a 1987 XJ6 is an XJ40. But in the U.S., a 1987 XJ6 is a Series III, so I have moved your post once again. I believe that your mention of fuel "tanks" confirms my interpretation that you have a Series III XJ6, since the XJ40 has only one fuel tank.

Here in the Series III forum you will find members who are very knowledgeable and will hopefully be able to offer some helpful suggestions.

You can download the Fuel System section of the Series III Workshop Manual from this forum at the link below:

Jaguar Series III XJ6 Workshop Manual - Fuel System

For the other sections of the manual, see this link:

XJ6 & XJ12 'HOW TO' quick links

Cheers,

Don

 

thank you

 

Hi John.- I have an 86 XJ6 and just fixed all my return valves on mine. If you have not studied how the fuel system works, a real quick summary

In the trunk both tanks are connected to a three way valve that is switched by the dash tank switch. The output of this valve goes to fuel pump which pumps fuel to engine

When your dash switch is IN the driver tank is used, OUT the pass tank. The dash switch also changes which fuel sender is being read so your fuel gauge shows the level of the selected tank

This valve can be broken or fail or not work especially after sitting. For $100 I suggest replacing. So that is how fuel is pulled from the tanks and pushed to the motor. But the fuel injection circuit is a closed loop so what about the return to the tank?

There are two more valves, 2 way, one by each rear wheel under a cover plate in the wheel well. These valves open an shut based on the selected tank. The fuel line returning from the motor to the tank splits at a T with a line going to each valve and then from the valve to the tank

When you select the pass tank the pass side return valve opens and the driver side valve closes. The forces the returning fuel to go back to the tank it was drawn from. And vice- versa when you switch to driver tank

The returning fuel to the tank can easily be seen by opening the gas cap and using a wooden (no metal... sparks!!) bit of dowel or skewer to push the metal flap down. With car running you can see fuel pouring out of a small pipe end back into the tank. This is the easiest way to check if the return system is sending fuel back to correct tank

I just replaced all 3 of my valves I described because I was seeing some very odd and intermittent behavior

Order the valves and have your mechanic replace. Cheap fix. Dont try to use old valves of unknown age that have been crusting over internally for years

Best of luck -Randy

 

There isn't much to the return system that would cause a running/stalling problem. If clogged, you'll end up with too much fuel pressure...which is a problem.

With the engine running open the gas caps and use a screwdriver to open the spring loaded flap in the filler necks. You should be able to actually see a stream of gasoline flowing into the tank. If you do, that's as good as it gets. Whether the gas is returning correctly to the tank is was drawn from is a different matter with fixes already mentioned. But, one of tanks should have that visible stream of returned fuel.

I suspect you still have rust/contamination in the fuel system and that's why it isn't running right and that's why 3 fuel pumps have failed. This is a common problem on these cars when they've been sitting in storage. Remove the filter and empty the contents into a clean jar. If it looks like anything except fresh gasoline, you still have a problem with the fuel....which means you still have crud/rust/dirt in the tanks.

Installing additional "pre-filters" before the fuel pump is a common practice to protect the pump. How quickly these filters clog depends on how bad the tanks are. At one extreme there's installing new fuel tanks. Expensive and labor intensive.

At the other end is simply replacing the "pre-filters" a few times until all the loose crud in the tanks works its way through.

Cheers
DD

 

thank you this has been very helpful, where is the best place to purchase said valves?

 

Many suppliers but I have had good luck with Welsh. If you Google Welsh Jaguar you will find it. Let me find my receipts for exact part numbers and I will update again

Randy

 

If you plan to replace all three, Welsh has a kit with all three. Not really cheaper than the individuals, but one thing to order. Part num CAC-3938-K for about $226

If bought individually, I bought these parts:

CBC-4269 Three way valve in trunk $80
CAC-3938 Right hand return valve $80
CAC-3939 Left hand return valve $60 (Oddly it is not marked as LH like the RH one is... but correct part)

There is another 3 way valve listed as part number C44918, but not sure what that is. Possibly a Jaguar brand part, versus one from a supplier??

Good luck. Consider replacing fuel hoses too if they look ancient

Randy

 

Thank you so much worzella for taking the time to provide this information

 

Let me know how it goes with solving this issue.

 

I'm waiting on my mechanic to get around the changing the return valves out to see if this helps