Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Reaching out for some sucking advice :-)

I'm after some plus 8 owners experienced advice re Rover engine ignition vacuum advance.

Could somebody confirm or deny that if they took off the little vacuum pipe from the inlet manifold and sucked hard on it whether they can see the distributor plates in the distributor rotate?

I have a Triumph Stag which uses the same Rover distributor (I think its Lucas) and I'm getting mixed responses to this question. My car starts and ticks over lovely but is unhappy at higher revs. I suspect the vacuum advance diaphragm has gone hard after sitting idle for many years.
I cant move it by sucking on the little tube but it works fine when using a minivac brake bleeder pump, so am confused?

I feel sure somebody on here will know if a mere human (other than Bonnie Blue ) can move the advance mechanism just by sucking on the pipe

Thank you in advance lol

Yes in my experience the base plate should move when suction is applied.check to see if you can manually move it by rotation and also that the fly weights are free to move.

Hi Sewin,
Thank you.
It does move with suction but I'm trying to understand how much suction is required.
I can't physically apply enough suction by mouth but with a mini vac it moves.
I'm just trying to determine if this is normal or if the diaphragm has gone hard and the engine cant move it properly :-)

You should be able to move it with mouth suction - may be something binding (a long screw?)

A vacuum pump is useful. The gauge lets you know how much vacuum you have created, and by pulling a vacuum, leaving it, and watching the gauge, you can see if there are any leaks. https://www.machinemart.co.uk/p/gunson-77003-vacuum-pump/ you can get them at various prices via ebay, atc.

Its not that useful if you don't know what pressure its supposed to work at :-)

That's why I was asking lol

My mini vac has a gauge but tells me nothing really lol

have you also checked the vacuum hose to the inlet manifold from the distributer. These can crack and leak effecting the vacuum advance and also causing an air leak into the inlet manifold which effects fuel intake too.

According to my notes the base plate should start moving around 5 inches Hg and reach the full movement at 15 to 17 inches Hg. May be a coding on the diaphragm to denote the start finish and advance

Now that is a great help, thank you so much :-) I'll be out checking first thing on the morning.
Thanks again :-)

Again from my notes, the vacuum advance measured at the distributor is around 8 degrees. There's a guy at Rimmers who knowledgeable on distributors, but only those with points. He did write a book about refurbishing distributors, but since we moved house there is a whole lot of things I can't find and that book is currently gone awol