XJ6 4.2 series 1 engine

[RichardSEL]

Got an interesting fault that I've not visited as the car is over 50 miles away...

First mech visited and found that all pipework connections loose, re-tightened all and fed fuel feed from jerry can into fuel filter -- not from tank as car had been not started (apart from when I bought) and run for over 10 years.
Car starts but then engine dies. Repeat the start and same occurs over and over again.
First mech did not have air filter box connected. Work stopped as that "mech" could not find the fault...

Second mech attended Friday, found same symptom told me he'd also connected fuel feed from jerry can coz as had not been run for many years dirt would've collected in bottom of fuel tank. And anyway would've had dregs of old fuel there.
Same fault. He checked good fuel pressure (new fuel pump installed from Manners) and now no leaks all the way to the carbs.

He wants to remove carbs for "clean and overhaul" back at his workshop as believes float chambers could be with crud now.

I've been with many cars and usually if a car starts then dies then it's the idle position that's wrong. But I don't know these twin SU HD8 carbs with an AED between them. Is there anything I can suggest that's done or checked without removing carbs (presumably on inlet manifolds)

Some cars I've come across in my past don't run correctly without air filter connected. But these were more modern post '03MY. Nor there being a proper fuel back pressure thru correct tank venting and the tank cap being on and sealing. (VW's 2.0L tFSI was tempermental like that). But on a '72MY series 1 XJ6?

Any other diagnostic tricks gratefully received

[PPV]

Have not got HD8 carbs but it sounds like fuel is not getting through. Not sure why he needs to take carbs off. Can you take the top off the float chamber like the HD6 ones to check if crud in float chamber, I thought you could?
If there is nothing in there then it is unlikely that the carbs are blocked as the SU's can tolerate a bit of muck!
There are usually filters in the fuel inlet banjo connection at the carbs, are these in and are they clear?
Are the vents onthe float chambers clear? Also I presume the fuel filter is ok because it sounds like you have the jerry can connected before the fuel pump. I also presume the fuel pump does not stop working and that you can still hear it clicking when started.
If the car starts then if the throttle is blipped it will usually keep on running. It may be the AED is part of it not continuing to run but I only know about the one on the Mk2 and you can check the solenoid on that by earthing the connection and listening for it working. However, as I said if it fires and runs then as long as it is getting fuel (and a spark of course) then it should continue in a fashion. It may spit and bang though which is not good for it.
Hope this helps.
Regards,

[RichardSEL]

The off side tank had been abandoned as it was so rusted up (from the car's prolonged sitting under a tree in someone's back garden) as to be considered beyond redemption

When I got the car someone had been into the fuel system, removed the nearside tank, I'm told plasticised it, then
replaced. But there was no connection -- so whether it was just outside cleaned and then red lead painted I dunno. There's no changeover wiring there, and there was only one fuel pump that the electrician reported as faulty -- of the original Lucas contactor type. So I sent down the D. Manners electronic replacement. Nevertheless, mechanic reports continuous fuel pressure "at the carbs". I don't know exactly where he means as I wasn't there.

All of which history could show that previous owners had been running it with dirty fuel -- or bypassing the fuel filter. With the history, sensible precautions to run from jerry can -- yes can to fuel filter, filter to pump, pump to system lines then presumably AED to carbs. But it's only got 23,000 miles on it. Not enough you'd think for a fuel tank to rust up internally in those miles? When I bought I just saw it run from jerry can to carbs -- enough to know it did actually fire!

What you describe is symptoms of dirt in fuel line / and or at the banjos you mention -- I didn't even know there were gauze ones there. So I've passed your post down to the mech for him to check the banjo filters plus the rest of your very useful reply too -- here's hoping

[RichardSEL]

Dunno if these pix of HD8 would help you to point to float chamber top?
Vents on the float chamber?

He checked the dash pots

[PPV]

I cannot see from your picture but as the fuel goes into the float chamber there must be a path for the air from the top to get out. On the HD6 carb this is from the top of the chamber. The carbs you picture are not yours though as they look in very good condition!
If the system has been messed around then it could be that the float levels are set wrong, the jets are set incorrectly and so on. It does sound like a godd going over them including properly setting them up is required anyhow.
Regards,

[RichardSEL]

Burlen are now the SU people of merit. And I found a simple diagram of an HD8 on their site.
But can't seem to find the key

There's much info on their site for earlier carbs.
However, they want £270 +VAT +p&p for their restoration per carb
http://sucarb.co.uk/restoration-and-rebuild

For only having had 23k miles of fuel through them, that's a bit rich for me. But I dunno what's been played about with in the past of course. If I could only get the idle sorted then I could get it out of the spray shop (that's ready for re-fit) and I'd have some time to examine / tweak. Burlen say they've currently got a three month lead in time.

<later> Just spoke with their tech help line and most helpful chap pointed to a better chart at:
http://sucarb.co.uk/carbspec/carburetto ... s/id/1265/
with parts list to the left

He said that if car hasn't been run for a long time then the little needle (5) in the float chamber (55) can get stuck in the up position thus causing my symptoms

[PPV]

These are robust carbs and not a lot goes wrong but there are things to check as mentioned especially if laid up for a while as petrol does tend to gum up a bit.
Any competent mechanic familiar with the SU should be able to check it and its setting up.

[RichardSEL]

Thanks for the re-assurance, Paul. The mech that did visit wants to take off the inlet manifold then "strip down" the carbs etc. All without any quote in advance

So I'm waiting on his reply to the above Gurlen helpful hints and asking him to perform them at the spray shop.
I haven't had a reply as yet...

Will update...

[Mgcjag]

Hi Richard....Steve here...we spoke re the wiper motor....with the age of the carbs they could probabky do with a good clean and overhall...i have just stripped my HD8s....have service kits from burlan but not installed them yet.....if you look at the the jets you will see that they have a rubber skirt on the bottom of them.....these will definaly be at least a bit brittal if not cracked and should be replaced ....the channel to the ADU also gets full of crud....i was advised of this by a carb restorer..guess what..mine was....so if your doing a good refurb of the whole car then go for a service of the carbs....you have my contact number if you need to discuss further....all the best.. Steve

[RichardSEL]

Thanks for your assists, Steve. I'm just currently keen to get the car out of the spray shop.
They're being very helpful in not pressing me to remove -- they haven't yet quite completed refit -- but will have done so in the first week of next month.

With only 23k miles up was hoping that it'd at least stay running on tickover. But having not run for many years, mebe was being too optimistic At least, when I go down again can check it for myself What with the olde petrol mebe turning to syrup after all those years, the mech wants to drain out the fuel tank again before he re-connects. But he goes away on leave for a week the week after next. Just when I want his services...

[RichardSEL]

>>He said that if car hasn't been run for a long time then the little needle (5) in the float chamber (55) can get stuck >>in the up position thus causing my symptoms

That should've read: "the little needle (5) in the float chamber (59) "
Chart at: http://sucarb.co.uk/carbspec/carburetto ... s/id/1265/ refers

[PPV]

If the float needle is stuck open then the carbs will flood and petrol will run out, if stuck shut then it wll not get fuel into the carb and it will not run at all!
There could be an issue there but as the car has not been proprly run it will be more likely that the float chamber will have dried out and the float needle would drop open so at least fuel should get in. It is easy to check this operation by taking the top off the float chamber with the carbs in place. You may need a new gasket but I still have the same ones on mine after taking the tops off many times and they do not leak (touch wood).
Regards,

[RichardSEL]

More good stuff I've passed along to the mech.
"...the channel to the ADU also gets full of crud....i was advised of this by a carb restorer..guess what..mine was..."

"ADU"? Same as AED (Automatic Enrichment Device)?

[Mgcjag]

Hi Richard...yes...sorry should have been AED....Steve

[alec2824]

Some years ago my XJ6 would crank and start with the key in the start position - then die as the key was released. It turned out to be a failed ballast resistor! Could this be your problem?