1989 xj40 fuel tank question

Okay .y tank is out and I have a couple holes to braze shut. My question is as I was rinsing the tank I noticed the supply to the pump (external fuel pump) was not giving a steady flow when full of water? Is there a restrictor in there or have I got a blockage? If I give a blast with the hose I get a solid stream for a few seconds and I can see the return line in the tank which I assume has a check valve, but the supply to the pump has me perplexed.

I don’t have an answer to your query but do have some questions about these tanks. Does your fuel return line enter the tank in close proximity to the output line to the external pump? I ask because I am working on solving a very hot weather fueling issue with my 1990 XJ6 which can stall when I believe the overheated fuel vaporizes before reaching the pump which causes the pump to cavitate. I have been led to believe the two lines are located in a swirl chamber inside the tank. I don’t know why there would be a check valve in the return line as I see no need for it but Jaguar did some strange things from time to time.

The check valve in the return line is to hold line pressure in the fuel rail. If that fails then it takes quite a while to build it up again unless you do the ignition on off on off on trick at least three times, and if your car has the intank fuel pump the return does enter the swirl tank.

My fuel lines, supply and return are side by side. I have the fuel sender off and can see the fuel return inside the tank. For some reason there is a rubber hose that goes toward the front of the tank and just ends into the tank. There is a hose clamp on the end but nothing attached to it? Makes me wonder what should be there. I did find a bunch of melted plastic in there which I have removed. Leak check and back in I hope.

Perhaps we are confusing the fuel pressure regulator with check valve. It is my understanding that the vacuum controlled fuel pressure regulator (which on my 1990 4.0 liter XJ6 is mounted on the front end of the fuel rail in the engine compartment) controls the line pressure in the fuel rail. There may, however, be a check valve in the supply line so fuel pressure does not flow back to the tank when the fuel pump is not running. This valve may be part of the internals of the pump itself. Anyone know for sure?

1989 xj40 pics of the tank

The black plastick is something melted then rehardend in the tank, fished it out? Fuel drain on the left return then supply to external fuel pump.

fuel return inside tank.

cleaned and raedy to go!

I think you may be right about the pressure regulator, see my pic of the return inside the tank.

No the check valve has to be on the return line, I had to insert one on my ‘92 when the original gave up. I placed it after the FPR in the engine by

Used to have someting in there, maybe that is wat all th melted plastic was.

Robin,

There are in effect two check valves - one in the feed line from the fuel pump and the other in the fuel pressure regulator (FPR) in the return line to ensure that the fuel rail maintains a ‘hold pressure’ of around 21 psi and to avoid ‘vapour lock’ after engine shut-down to facilitate the next start.

On the cars with the external fuel pump, the check (non-return) valve in the feed line is attached to the output side of the external fuel pump.and is easily replaced. not so for the cars with the in-tank pump - that check valve is part of the immersed pump. If that fails, some have fitted a check valve in the feed line outside of the tank.

i guess your fitment of a check valve in the return line was to compensate for a failure of the FPR to provide that function?

Took a while but I managed to get these little rattlers out of the tank! No way I was putting the tank back with something loose in there!

There were 3 of them and they look like bbs flattenned on one side.

Hmm, not sure, haven’t got the car now, moved up to a XJR, I just know that I was having to crank and stop for a long time until I did the key cycling. Check valve in the return line solved the problem so maybe it was the FPR that was failing :man_shrugging:

Where we can buy a new fuel tank? Mine is full of dirty and the last owner put a filter in outside from this to fuel pump. But I think with the time this pump will die like the last changed

New fuel tanks are no longer available. Unfortunately, we’re stuck with what we’ve got or forced to find a good used one.

I found a nice one at garden street upull it in Ft Myers Fl. Its still there, external fuel pump I think!

Can you give me the contact (better mail)…today we check mine but i want search something before so i’m ready