Anyone have a lead on where I might be able to pick up a thermal vacuum switch for my '89 XJ-S. This is the switch that controls whether there is manifold vacuum applied to the B bank FPR at higher fuel rail temps (above 156F I believe).
I discovered the other day that one of the plastic barbs on my switch is largely snapped off leading to only a poor connection of that 3/16"ID vacuum line.
Seems that this part is not available at the usual suppliers or on ebay etc. I do see a replacement alternate part offered by one supplier $145 plus shipping but am hoping to spend a lot less than that on this–especially since my switch works ok, it’s just the damaged barb giving trouble. Maybe I need to try one of those “plastic welding” things…
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
2
You can just bypass it by connecting the vacuum line directly from the intake manifold to the FPR. Recommended until you find a replacement vacuum switch. If you don’t develop any hot start problems, you might not even bother.
This thing has been discussed recently, including some suggestions for bodges including fitting a solenoid vacuum valve with a switch under the dash that you can push-and-hold while starting a hot engine.
Thanks for the ideas for sources! I will have a look at those options and will look back at other people’s ideas for different solutions
Kirby, I will bypass now and see how it does without. I’m thinking this should make the car run better when cold/cool since it will give the B bank FPR the proper non-leaky vacuum that it ought to have. That alone makes byspassing right now worthwhile.
Incidentally, I discovered all of this while replacing the FPRs which appeared to be original and almost certainly had slightly leaky/soon to be leaky diaphragms. The vacuum hoses of the FPRs were certainly not full of fuel but I think I caught a whiff of gas smell in them so new FPRs to be safe. I think I will keep the A bank FPR for now though after reading a number of old forum posts I now understand better why many people elect to eliminate it.
I am sure that I have one on one of my parts cars if you are interested. Let me know at sjniznik@msn.com. I am going to my storage garage to do some things later today and could pull the part, pack it and ship it by Monday.
Douglas,
Between our two V12 Jaguars, two XJ6s, three XJ6 parts cars, and some spare Jaguar engines I own, I have tested about 10 of these EAC5086 thermal vacuum valves and about half of them tested bad. I tested them on our stove with my Mityvac vacuum tester and a digital infrared thermometer (while my wife was not home). Per my readings in the archives the valve is supposed to be open below 156F and closed above that. Some valves never closed, some valves closed well above 156F, and some valves clicked about 157F but did not hold vacuum. I tried cleaning them in an ultrasonic bath but that didn’t make a difference. If you source one I recommend that you test it yourself to be certain that it works.
Mine did not work, so I removed it a year ago. I have never had hot start problems.
That being said, I’ve been running a 190LPH fuel pump, and am currently switching to a 155LPH pump, both higher than stock pump. So maybe that’s enough to flush out warm gas in the fuel rail all the time?
That’s reassuring to hear! Though I guess you do have a cooler climate than I do.
I’m following your fuel pump progress with great interest as I still have my original pump and it’s definitely in need of replacement. I will probably go for the 155LPH if you give it high marks!
Thanks Paul–happily Mityvac and digital infrared thermometer are both in my toolbox already so that will be easy to test on any replacement I may be able to source. Stephen ^above may have one for me!
And good call on the wife not home–when my girlfriend is over at my place I’m definitely restricted on what car parts can come in the house. Little does she know about the nearly fully assembled exhaust in the kitchen that one day last winter–it was 30F outside and I wanted to test fit some stuff in the warmth ha!
You can heat them until they click, blow through; one side has a little foam vent hidden under the cap? Slide that off and change the foam…
Try a little bit of silicone to glue on the hose. Invisible or close. Mine broke off flush and I tried everything including a nice brass tube jb-welded in… broke off instantly. Silicone holds to this day and quite secure also. Almost invisible. If that doesn’t work you might simply bypass it or try everydayxj.
Oh, I already give my first Walbro pump high marks, I’m sure I will this one too. But I’m going thru the issue of getting such a tall pump to fit well. Will update other thread once I’m done.
It’s just not a plug and play.
It’s all because their pump is a bit tall, and on top of that the output with adapter by electrical connection is like 1.5" long!
Annoying issues but yeah definitely solvable! What about changing the angle of the pump bracket? Could you install it almost vertically (using that hose clamp to stop an even more vertical mounting from sliding down) to allow more clearance so the top end doesn’t foul the metal plate that hides the sump/pump assembly.