XJ6 Series 3 Cycling on acceleration when cold (amende

(Con Saris) #41

Yep that is now the plan. Started pumping fuel from the tanks today.

I agree Frank but as the car gradually died over some minutes is it not possible that the filters somehow gradually blocked up. In any case I know the car will run if fuel is present. I had fuel pressure while it was running, now I have no pressure and the car does not run. I don’t have fuel flow at the rail or the main filter. Neither do I have much flow at the tank outlet. It points to a blockage in the tank and the only way I can be sure is to doing the tanks again. I do have more experience with this car now and am sure I will do a more thorough job this time. I have fashioned a pump set up and am draining the tank that way through the sender hole. I intend to leave about a gallon of fuel in the bottom and will use that to flush out the tank initially with another after removing the filter. I’m trying to be methodical about this so if you can think of anything there thing I can do please let me know.

(David Jauch) #42

Draining the tank with the onboard pump is safer, but you’ll be fine. The in tank filters can clog up gradually, but I’m somewhat stuck in the injection department.

Is the topic title still correct? Why would only cold acceleration cause stutter and dying? It’s now no start but the other issue still applies right?

(Frank Andersen) #43

You keep talking about ‘the tank’, Con - what about the other…? :slight_smile:

The only blockage ‘in’ the tank is the in-tank filter - which can be inspected and replaced without any further work on the tank. While refurbishing the tank has its own merits; if you find no debris or filter problem when opening the tank drain - refurbishing will not rectify the problem. And that’s a lot of work with little gain if the problem is elsewhere…

Have you actually tried blowing back through the changeover valve hose to the tank? A clog may be in the hose/inline filters - and tank refurbishing will then not solve the problem. Though a clogged hose presents its own problems…:slight_smile:

My thinking is always concentrated on getting a car back on the road with minimum fuss and time loss. And getting the engine running tends to identify the real cause of the problem - then, and only then, to take actions as required…

xj6 85 Sov Europe (UK/NZ)

(Con Saris) #44

Hi Frank, I don’t mean to be a pain I am just a little confused with what is going on but you do raise an interesting point. The hoses. These have been clamped using G clamps when I installed the extra filters. Both tanks are not flowing correctly and now I am wondering if maybe the hoses have internal blockages due to the clamping. I do not know how old these hoses are and I guess it is possible for them to be cracked on the inside especially if they are are of the multiple layer type. In any case I am going to have to complete the tank draining to replace these hoses. So I will continue with my plan and add hose replacement to the rest of things to do.
I feel I am close to the solution of the intermittent no fuel problem that has dogged me for a long time now, and if this fixes it it in only because of the knowledge and patience of yourself, David and others who have given their time to help me out.
Thank you

(Frank Andersen) #45

Clamping is a necessity from time to time, Con, the trick is not to tighten more than strictly necessary. It should then be harmless to the hoses - but you can’t know what POs have done over time…

You have of course checked fuel flow by disconnected the filters you installed?? And you did test the flow with the filler lid open? That both tanks and their lines should suffer equally at the same time is just suspicious…

When the tank drains are opened ‘something’ may come to light…

And you are certainly not a pain - it’s all very interesting…

xj6 85 Sov Europe (UK/NZ)

(Con Saris) #46

Well I think I’ve had a bit of a break through. I emptied the RH tank today and pulled the filter from the inlet pipe. I then blew air into the outlet. There was a definite resitance to the pressurised air then it cleared. I poured about 4 liters of fuel into the tank and let it wash out. I found what looks like one of the screens from another filter in the fuel that sloshed out. Hmm :face_with_raised_eyebrow: Now I don,t know for sure where this came from but it was not there before I pulled the filter off. Maybe it was in the pipe? In any case I then did the same for the LH tank and pulled the filter. That one looks like it hasn’t been changed from new. :smirk: Blew air through until it went through easily. Put everything back together primed the motor and cranked the motor. Fired straight away and ran ok for about 10mins before I turned it off. Hoping that with be the end to that problem! Once I am over the fumes I’ve inhaled I will spend a little time checking the pressure again and maybe set the timing. But for now I’ll just run the motor and maybe risk a run around the block. The pics show the two filters, The RH one is the cleaner of the two and the screen that came from the tank is next to it. The other is the rust that came from the LH tank. Will be expecting more of this in the inline filters that I recently installed.
Thanks to Frank and David for your input in solving this mess,

(Frank Andersen) #47

You did the work, Con - and well done it was…:slight_smile:

What was puzzling was that the engine did not run on either tank - it’s almost unheard of - it throws the pursuers off the scent. The rust particles shown is negligible - as would be expected with the rinsing done…

xj6 85 Sov Europe (UK/NZ)

(Con Saris) #48

Yes the state of the filter on the LH tank looks like it wasn’t going to let much through without either a thorough cleaning or replacing. I think that maybe the car has been run only from the RH tank, perhaps because it wasn’t performing that well from the LH tank. Here’s hoping Ive solved the problem for good. The capacitor mod seems to have solved the cycling problem especially now that I have replaced the broken micro switch.

(David Jauch) #49

Happy you made it. Some crud will always come out, but usually no filter screens. Hopefully it’ll run well for some time now, to enjoy the summer…


(Carl Hutchins, Jr. ) #50

Great news:

Kudos to each of you. Two providing expert guidance and the other in the execution of it. Team work at it’s best. Add in good writing. that resolves loss in words…Often a major hindrance.


  1. Get a compressor or even a hand pump. Lungs and petrol are not a good match… recalled from my early days of siphoning fuel, ugh…

  2. I think a PO was in the tank and lost a screen there. or perhaps even at the factory!!!

  3. You may have to swap in a fresh pre pump filter in from time to time til the tanks run clean.

Again, good work…


(Frank Andersen) #51

The ‘capmod’ was likely OK all the time, Con - and cannot cause the described cycling. The cycling was caused by the failed microswitch - now rectified…

You are out of the woods - thanks to your endeavours…:slight_smile:

xj6 85 Sov Europe 9UK/NZ)

(Con Saris) #52

The labour would have been much longer if I had been left to my own endeavours. It’s great to have a forum like Jag-lovers to point me in the right direction. While I have been a classic car lover for ever I have never owned or tried to restore a vehicle as complex as this Jag. The fact that there is always someone here that has had similar problems helps keep my interest from waning.
Thanks again to everyone who has posted here, I am sure this post won’t be the last on this car, I still want to do quite a few things to the motor (restore the fuel injectors etc) but they can wait for a bit now that I think I have a running car.

(Aristides Balanos) #53

I found the exact same square filter thingie layng on the bottom of one of my fuel tanks…
Still to this day I haven’t figured out were it came from.


(Con Saris) #54

Weird huh? Starting to think your car may have been assembled by the same guy as mine :grinning:

(phillip keeter) #55

Could it have been introduced to your tank when you filled it?

(David Jauch) #56

I very much doubt that especially given BL Jaguar‘s weird production byproducts of the day.
Depending on the size of the screen the filter might have been changed before but one of its screens came off before or while changing. Or it was doubled up because the production was sloppy. No easy recovery once lost in the tank.

(Aristides Balanos) #57

Mysterius mystery…

(Carl Hutchins, Jr. ) #58

Oh, yeah, an old tale that seems to fit everywhere…

A “Monday morning” car or a “Friday afternoon car”.

I recall a tale of a task of seeking a mystery noise in the rear of a USA coupe. Vintage not recalled, but not recent. Resolved. A Coca Cola bottle, behind the upholstery card. Was it cola or more potent???