Setting the timing.

[Bubble Meister]

I timed my van today and always get a little confused by the Haynes manual.

I disconnected (but didn't block off) the pipe from carb to the dizzy. I then set my timing to 5 deg BTDC (DG engine). I then set the idle to 950rpm (upper spec in Haynes), then checked the mechanical advance (approx. 12deg at 2400rpm). I then reconnected the vacuum pipe - the revs increased slightly.

Can someone confirm that I have set my idle correctly or should it be 950rpm after the vacuum pipe is reconnected?

After, I used a Gunson Colour Tune, the flame was blue. I have suspected that the van is running rich for a while (although the spark plugs were in good condtion). I adjusted the CO screw out slowly(Pierberg 2E3), after almost 2 revs the engine note suddenly lifted, seemed smoother. I left it there and went for a test drive. She seems pretty good although I'll take her to work tomorrow - 15 miles plus the choke will be on.

Leaning the mixture has increased the idle but it was getting late so I haven't re- adjusted it. If I do, should it be with the vacuum pipe disconnected again?

Thanks folks

BM

[bigherb]

Yep reset the idle to 900 RPM after the vac pipe reconnected and the carb adjusted.

[kevtherev]

Personally I would try to get the CO checked on a gas analyser, running the mixture too lean can cause damage over time.

[Bubble Meister]

Thank for the replies. If too lean then will the coolant temp increase as the engine runs hotter? Would that cause pre ignition?

[kevtherev]

Thank for the replies. If too lean then will the coolant temp increase as the engine runs hotter? Would that cause pre ignition?

Your cooling system will deal with a lean engine, up to a point.... pre ignition is mainly a timing issue.

[Bubble Meister]

Just had a thought - I turned the mixture screw anti clockwise thereby (unless I'm mistaken) making the mixture richer. We shall see - I'm off to work in a min.

[kevtherev]

E D I T
mixture screw is out for richer

I posted something for a different carb

[bigherb]

Just had a thought - I turned the mixture screw anti clockwise thereby (unless I'm mistaken) making the mixture richer. We shall see - I'm off to work in a min.

Yes you did, screwing out anticlockwise increases mixture, screwing in clockwise weakens mixture.

[Bubble Meister]

Well there was a marked improvement on the way to work. However that performance seems to have tailed off just slightly on the way home!! If I get chance on Saturday , I'll check the timing again. I think it's time to see if I'm closer to the elusive 24mpg.

[itchyfeet]

Are you timing from TDC mark with an adjustable light or timing mark with fixed light?
If using timing mark and fixed light check pulley, if wrong pulley then mark will be wrong timing.

iirc 5 degrees is 7mm ish around circumference but easy to work out by measuring diameter×pi /72

[Bubble Meister]

Cheers IF. I looked into this a while ago and measured the arc. I think I got 7mm too. I'm using a variable timing light but set to 0 Deg and using the 5 Deg mark on the pulley.
I noticed that the dizzy cap can be rotated ever so slightly, even though it's still located correctly on the dizzy. Maybe the cap has settled. I'm not overly concerned as performance is still good.

[itchyfeet]

rotating the cap slightly won't make any difference imo, its the vane/hall sensor position that triggers the spark generation, the cap just delivers it to the right plug.

[Bubble Meister]

Very true. Checking the ignition system is next on my agenda. I want to check the power supply and earth for the black control unit. I have a copy of the VW Transporter carb / ignition manual. This details checks needed.