Stag running issues, revs rise then cut out

[Jonny-Jimbo]

So, a friend of mine was driving her Stag up to Scotland at the weekend. She got a long way, from near Coventry to Penrith, when she encountered a few issues.

Without wavering on the throttle pedal, the revs would rise up, then just drop off until the car cut out, and then it wouldn't restart.

They got recovered to a car parts shop and changed the coil. The car then restarted straight away and ran well... only to do the same thing again about 50 miles later... and then again once more before making it home.

The car is pretty much standard, and is well looked after. Only major change from stock is electronic ignition.

Having suffered hard to diagnose faults of my own on my 2500TC engined Mk1 which turned out to be electronic ignition failure, I've suggested that could be the cause. However, I'm not that well versed on Stags, so just wondered if anyone had any ideas?

[RobPearce]

Depends on the type of electronic ignition. When I owned a Stag, it developed a tendency to conk out completely at light load. This turned out to be down to a (slightly) worn bearing on the vacuum advance plate. Most distributors are designed to cope with that, because the vacuum advance acts on the opposite side from the points, so the plate tends not to move in the direction of the all-important gap setting. The Stag distributor has two sets of points, set roughly 90° apart. One of them always opens up or closes the points gap as you go on and off load, if the bearing is worn. When I discovered that, I fitted Lumenition and fixed the problem entirely.

That said, if the problem occurs after driving for a bit, then "self-cures" once it cools down, it sounds possible that it's a failing EI box, but it could also be a fuel blockage (the dreaded rubber slivers) or pump failure (it's electric on a Stag) or coil ballast resistor.

[Martins Stag]

Was the under bonnet fuel filter full when she was having the issues? Fuel pumps can cause issues and the easy check is to see you have fuel in the filter and then work from there?

Martin

[Roger Keys]

The revs rising on there own suggests an air leak. To the point its so lean it stops. Whislt changing the timing could do the same, ir rise in revs, i dont see why that would stop it unless it changed so much. I dont really see that as a credible failure mode.

 

[Pete Lewis]

think i would have a look for  a perforated carb diaphragm

Pete