Just rebuilt my manually operated AED (oxymoron!) and my HS8's on a '71 2.8 litre. I can run the car by throttling the AED but as soon as I close the AED she dies. Carbs are clean, proper sized needles with new jets, good fuel flow to bowls, no obstructions throughout the carbs and I checked all of the vacuum lines to ensure there's suction. Began with the jets down 1.5 turns and continued to 3+ turns with no result. She actually ran fine when AED was all gummed up but not now. Feel like I'm missing something very simple. Anyone have any thoughts? Thx much.

 

Remove the Bell Chambers and pistons.

Switch ON the Ign, and the pump will/should run and fill the carbies.

Look down at the top of the jet, and you "should" see fuel about 3mm or so below the top, AND this is with the jets set FLUSH with the bridge.

If that is OK, or even near enough move on to the next suggestion.

Some carby TO manifold gaskets have the holes for the vac missing, or only in one place so the orientation of said gaskets is critical. NO vac = NO piston movement = NO running engine. Those pistons must rise inside those Bell Chambers for the engine to even have half a chance.

Damper oil, I use ATF, and I am NOT starting an oil war here., its just what I have used for 40 years, and none of the SU cars gave a hoot.

1 1/2 turns down on each jet from flush with teh bridge has always been my "starting point".

If you have fuel in the jet, then vac to raise the pistons sounds like it is AWOL.

 

Grant, thanks much for the response. You’ve struck a chord with your gasket advice. That’s the first thing I’ll check as I’ve covered all of the other bases. Fingers crossed!

 

Turns out it was something simple although not very obvious. The needles weren’t fully seated and were sitting slightly proud preventing fuel flow from the jets. Thanks Grant for the insight into the gaskets. Always good to learn something new!

 

Good find there.

Simple cars these Jaguars.