Dirty rotor arm

[Steve T]

Hi all
Had an odd problem this morning when leaving a campsite, van started first turn of the key on choke fast idle, blipped the throttle revs died down engine running sweet, got out of the site, onto the dual carriageway and before up to running temperature the van started to lose power, missing and back firing, although the backfire was slight and rare. The van would run sweet when in lower gear high rev but in fourth and running between 40 & 50 it felt sluggish no power, knocked out of gear and it would idle without stalling. Got off dual carriageway on A road found a lay-by and thought it may be worth checking distributor cap for condensation due the rain last. As now up to temp I was sure it was not fuel related as it idled ok and ran fast, auto choke was not sticking.

Distributor cap bone dry, checked rotor arm and found it dirty on the brass part that passes current to the 4 segments in the cap when turning, gave it a good clean and gave a general check around making sure no vacuum leads off anywhere, did a suck test on advance on dist, all ok. Got back on the road and this has sorted the problem, it is running sweet, plenty of power. Thankfully it was a simple fix. Thought I would post as it is a simple job to tick off the list if any one has similar problems.

[California Dreamin]

Coincidence me thinks....for every 1 thou rubbed off the rotor end you ADD an extra 1,000volts REQUIRED to jump the LARGER gap.
The spark erodes and leaves a black deposit...but this IS conductive and SHOULD NOT be removed.
An old trick was to squash the end of the rotor arm in a vice to make that gap smaller...just buy a new one I say.
Cleaning the distributor cap and rotor arm in thinners is a good idea to minimize deposits that promote tracking, scraping segments and rotor arm ends with screwdrivers and abrasive material such as emery cloth is NOT.


Martin

[BOXY]

Check your HT leads are pushed home properly on the plugs and cap. Taking the cap off might have partially re-seated a lead and temporarily "fixed" the problem. Did you check the fuel filter by the tank to see if it looked dirty?

[Steve T]

Hi
Good point about the cleaning of the rotor arm, I don't use grit paper or anything too abrasive, I rub it on the tyre to clean it, I was given this tip years ago to avoid getting the gap wider. As for the fuel filter, it looked ok and van got me home without any issues but will over the next few days when time allows change it as a matter if course, a lot of fuel has gone through it recently after a few long trips running quite low at times. Plan to do a good service and exhaust gas test with my trusty CO analyser before any major stuff to carb to see if it is just mixture or any issues with diaphragms or wear Thanks for the replies.

[CovKid]

Agree with California Dreamin on it being a coincidence. The symptoms actually suggest the problem is more likely to be either a clogged fuel filter or the small (and hidden) cone-shaped filter just tucked inside brass fuel inlet pipe on carb. What happens is you end up with insufficient fuel at larger throttle openings (typically 40mph+ and often intermittent). Some days it'll do it, some days it won't, but the cure is to clean cone filter and/or replace main fuel filter. Once you hit 40mph+, the carb needs all the fuel it can use and any clogging will restrict power.

The fact you've run low at times will just encourage the build-up of crud in filters. See bottom of this page: https://club8090.co.uk/wiki/Fu ... -_Pierburg" onclick="window.open(this.href);return false;

[Steve T]

Thanks for that, will check out the little filter on the carb and change the in line filter, after I had cleaned the rotor arm I got out my spare filter and screwdriver ready to do after a test, if rotor arm cleaning didn't do the trick, but as it ran ok I thought I fixed it, I gave it some good testing in the high rev range and under load. I don't like to change too much stuff in one go if there is a problem, or you never know what fixed it. Thanks for the link