Thread: More Ignition questions.

If it coughs and splutters etc when applying throttle - the first thing I would check is the accelerator pump on the carb is working correctly.

Earth wire on distributor plate broken?..the plate that moves that is attached to the vac unit

Just to check, when opening throttle,
1. you're saying that it runs ok, and does NOT splutter and die with vacuum advance disconnected and plugged?
2. It is spluttering and dying with vacuum advance connected?

If correct, It could be a leak in the advance unit, do a suck test, suck on hose to unit and it should hold with tongue over tube, but you did say it was new.

I would assume it's getting too much advance maybe, possibly broken springs on the mechanical advance. Allowing it to advance too much, too early with both vacuum and mechanical working.

Easy to check, Unplug the vacuum, then hold timing light at the static 10deg mark, get someone to open the throttle, see if the timing moves, it should not until, say 2,000rpm. depending on variant of distributor.

If it moves instantly, then suspect worn or broken springs on the mechanical. Or they have come off the plates, easy to happen when messing with points, lifting distributor button etc.

Just an idea.

The OE strombergs have ported advance taken from just above'the throttle butterfly so it is active on only part throttle.
The Holley may have the advance tap just in the manifold and give far too much advance.
Does the Holley have two advance tap offs. If so try the one nearest the throttle butterfly.
regards PhilipA

Thanks for the response, I have double checked accelerator pump and the earth wire in the distributor, and the vacuum advance holds suction. The vacuum tapping on the Holley is pre butterfly, I have also tried connecting to a vac port on the manifold ( for the diff lock) and that was worse. I will investigate the other suggestions today, but as always, I appreciate the help freely given on this site, it makes owning characterful British vehicles much more enjoyable.
Cheers,
Woolly.

Originally Posted by Woolly

Thanks for the response, I have double checked accelerator pump and the earth wire in the distributor, and the vacuum advance holds suction. The vacuum tapping on the Holley is pre butterfly, I have also tried connecting to a vac port on the manifold ( for the diff lock) and that was worse. I will investigate the other suggestions today, but as always, I appreciate the help freely given on this site, it makes owning characterful British vehicles much more enjoyable.
Cheers,
Woolly.

Start the motor and let it idle. check the vacuum advance hose, if there is vacuum there, you have it plugged itno a port on the wrong side of the throttle butterfly. There should be no suction on the hose until you open the throttle. Just keep trying any hose connections on the carby until you find one with no vacuum at idle, but vacuum with the accellerator open. Another possibility is you have the mixtures wrong on the carby (mabye big vacuum leaks) and have the throttle open far enough that it isn't using the idle circuit to idle.

Spin it round to top dead centre then pop cap off and check rotor button is pointing squarely or just before where no. 1 on the dizzy cap would be (mark dizzy body where no. 1 spout is on the cap) or preferably the little mark on the lip of the body (if these have one).

It is easy to drop dizzy in and have drive gear mesh with rotor button a bit too far from the post in the cap and as it advances away from the post the spark can't jump the gap .

Also set final points gap with a dwell angle meter. Initial setup with feeler gauge to get started.

More checking out of suggestions……..the springs for the weights seemed ok, but as I had the remains of another distributor with slightly heavier springs, I replaced them. No difference. Then I tried relocating the distributor with the shaft one tooth to move the rotor arm in front of the no1 spark plug lead contact. It fired reluctantly but would not run. There is no noticeable vacuum in the tube from the carby at idle, but given the effect when connected, there must be plenty when revved.
Decided to get a bit more scientific and marked the crankshaft pulley in approximately 10 degree intervals. With vacuum tube off, static timing 10 btdc, timing would increase slowly to and hold about 20 btdc at quite high revs ( no tachometer on these oldies) , with vacuum connected, timing would rapidly climb past 40 degrees and then start misfiring badly.
I am now wondering whether the distributor has been fiddled with in the past, as when I bought points for it (I took the old ones to match) I was told they were not the correct ones for 1980, or whether there are other vacuum advance fittings. This distributor doesn’t have a dwell angle adjustment either.
Not sure what road performance should be, but my high kilometre 300tdi Disco is better up my local test hill, so I feel I’m missing out a bit.
Looks a bit like a replacement distributor may be the way to go, any recommendations, please?
Thanks for all the help, it is appreciated.
Cheers,
Woolly.