Firing Order on 2.0L Aircooled CU

[speedracer]

Hi all,

I'm having a few problems getting my engine running right, it will turn over and fire but it wont tick over. It a 2.0L CU Aircooled Engine.

At TDC cylinder 3 is firing. It this correct? ...or should it be cylinder 1 firing?

I know the firing order is 1-4-3-2 but I'm not sure how this is orientated from TDC.

Thanks,

Neil

[bigherb]

No 1 is front right,
2 rear right.
3 front left,
4 rear left,
the front of the engine is the flywheel end.

[ghost123uk]

Hi Neil, first we must, in the customary and polite fashion, introduce ourselves.

We are Club 80-90 and we live all over the place. We have been into T25 vans of all types for a long time. We do a lot of camping and similar activities and hope perhaps to meet you at a campsite or maybe a VW show some time in the future.

We do have a couple of questions of course as all T25 owners do, like, where in the world are you ? and, do you plan doing a lot of camping, or is yours a work van ?

Then we can of course answer some of your questions =

It sounds like your engine is timed 180 degrees out. It is normally number 1 that should be firing when the timing marks line up.

Remember that the TDC mark only indicates TDC for one cylinder (supposed to be number 1) Also remember that it does not "fire" at TDC, it fires at a set amount before TDC (known as BTDC) this timing figure will be in the wiki, top left of every page on this site, or in your Haynes, or of course on hundreds of website. So, with that in mind, is your timing set correctly ? That could cause your symptoms.

[speedracer]

Ok. I'm starting to think that my dizzy is 180 degree's out and that the rotor should be pointing to cylinder 1 when the engines at TDC.

[ghost123uk]

Yes but that is not a big issue, it can be set like that and run just fine, as long as the timing is correct, (though whilst "in there" you might as well swing the dizzy round, swap the leads round and have it right )

[ghost123uk]

A quick search on here found a thread all about CU ignition timing = https://club8090.co.uk/forum/viewtopic.php?f=37&t=86548" onclick="window.open(this.href);return false;

[speedracer]

Hi,

Thanks for your help! I've been a member for a while but these are my first posts. I haven't had much trouble with my T25's up until now. My campers are are just for weekend fun, I'm not sure why I have two, I guess I got the bug. Ones a westy pop top and the others a high top. I'm down in Dorset, near Bournemouth.

I'll swap the leads round tonight, check the static timing and fire her up again. Fingers crossed! I was getting a bit worried that it might be a sticking/sealing valve problem, but maybe not.

[RedGus]

Ok. I'm starting to think that my dizzy is 180 degree's out and that the rotor should be pointing to cylinder 1 when the engines at TDC.

We've been talking about this kind of problem quite a bit recently, for example here:

https://club8090.co.uk/forum/viewtopic.php?f=37&t=121260" onclick="window.open(this.href);return false;

I tried to explain in that post that it's important to do everything from first principles when setting your timing, so that you don't "assume" anything. Just to be absolutely clear, the timing mark on the pulley will (should) line up with the correct static timing position for number 1 cylinder. This is the case for just about every petrol engine. As Ghost says, it won't usually be TDC, for a few technical reasons. On most engines, it's usually a few degrees before TDC, but on the Aircooled CU, for example, it's actually 5 degrees AFTER TDC, for reasons to do with minimising emissions. So, it's not that the "engine's at TDC", but that cylinder number 1 is at its correct firing point relative to TDC. Each of the other pistons will arrive at TDC in turn, too.

In my contribution in the link above, I explained a procedure for getting the firing order correct, and the leads in the right place. As Ghost says again, it actually doesn't really matter which way your distributor body is pointing (like 180 degrees out, for example), as long as the rotor arm points to no. 1 at the timing point, and the remaining leads are in the correct order. Sometimes, though, you might find that the leads would not reach if you had the dizzy in a non-standard orientation, not to mention the vacuum hoses.

You don't mention if you had fiddled with anything else before your engine wouldn't start, but it really ought to, once your timing is correct, given a healthy spark and fresh fuel.

James

[ghost123uk]

Good input James

[ajsimmo]

Ok. I'm starting to think that my dizzy is 180 degree's out and that the rotor should be pointing to cylinder 1 when the engines at TDC.

OK, sounding like a big red herring here, so starting from scratch what makes you say "At TDC cylinder 3 is firing".
Also I can't glean any evidence from your posts that your dizzy is 180 degrees out?
Don't forget that 2 turns of the crank = 1 turn of the distributor, so the pulley should read TDC at the top of the firing stroke for cylinders 1 AND 3!
For this reason, using a strobe light, you could check the timing with either plug lead 1 or 3, the results should be the same. (for the same reason, you won't see any pulley mark using your strobe on 2 or 4 as it will be at the bottom, 180 deg away).
So if your dizzy is sat with the dual vac can pointing sort of rear/right, close to the cooling flap actuator rod, and you can rotate the engine by hand to the TDC mark sitting at 0deg on the scale and rotor arm pointing at number 1 (notch in body, at about 4 oclock looking down), then you're OK, all should be correct and the problem is almost certainly elsewhere.

As mentioned previously, timing for a CU is 5deg After TDC with BOTH VACS CONNECTED. If you don't have a dual vac dizzy then you can't time it this way. Nearest approximate way is vac pipe off and blocked, then set to 7deg BEFORE TDC (as vac retard would give about 12deg of retardation if it were there). Due to more advance on idle this will raise your tickover, you then have to bring down the rpm on the airscrew on idle circuit ("3rd carb", back left).

ps If you have a 009 dizzy with no vac advance, throw it away.

[speedracer]

Thanks for the advice guys. I'll have another look at it tonight.

My mistake on the 180degrees out dizzy post its not.. I hadn't realised that 2 turns of the crank = 1 turn on the rotor.

I've got a 009 distributer with no vac advance and I've been setting it to 7 degrees BTDC.

Prior to this I've fitted all new fuel hoses, fuel filter, points (set to 0.4), rotor, dizzy cap, coil and leads. I've also replaced a leaking inlet manifold rubber elbow and checked all other pipe work for leaks (there are none)

At 7 degrees BTDC it'll fire up but a touch of the throttle will kill it. It back fires, and occasionally runs on 2 cylinders but then fires on 4 sometimes.

The engine turns over very freely by hand. The chokes are opening and throttle butterflies working. So as I see the only other things that could be wrong are sticking valves, possibly carb jets, knackered dizzy, old fuel, or maybe the electronic gizmos (I'm not sure about how to test those bits though).

Thanks again for all your help on this!

[ghost123uk]

If you suspect the fuel is old, the very next thing is to sort that out. Remember to empty the fuel out of the float chamber(s) too. Modern fuel with ethanol in it is well known for going off.

I have also read that the 009 dizzy is not good on these engines, though that would not stop it from running.

[ajsimmo]

So a couple more bits of info leaped out at me in your last post:
a) you have a 009 dizzy
b) you have points
c) you have changed the leads
d) you may have low compression

I'll try to give a few thoughts on each:

a) the infamous 009 dizzy. There's been lots written on this subject, most of it bad. {see WIKI ARTICLE}
Some retailers are selling this as a perfect replacement for your stock dizzy - it is just the opposite. The engine will run, but only just, with terrible flat spot on acceleration, and well down on power as it has far too little total centrifugal advance so to get the top end power the idle timing must be way more advanced to start with, causing pinking and missing at low revs, and likely engine damage. This is an all-or-nothing racing dizzy meant for souped up beetles doing standing 1/4s at Santa Pod, definitely not meant for a relaxing, smooth and economical drive in a camper!

And b) just makes it worse. Points? Naah. Get rid of them and put a stock electronic ignition dual vac dizzy in, if you can get one. It will run soooo much better. If you must stick with points, it's more important to set the dwell angle than the gap (although they are related, depending on points wear). It wants to be between 40-50 deg, I use a dwell meter, but can be done statically with a test light. Gap wise, 0.4mm is good. Of course, if dwell and points gap is altered, timing must then be reset.

c) New leads. OK, I know it's obvious, but are you absolutely sure the new ones are on the right way, and have you checked again, because the symptoms described sound remarkably like two leads swapped over. Just saying....easily done. Did it run ok before?

d) "engine turns over very freely by hand" is a bit of a worry. Sounds like it's worn out! A CU is usually hard to turn over by hand, mostly coz there's nowtl to get hold of but a hamster wheel and an alternator pulley to trap your finger! As for your thoughts on valves etc, have you done a compression test? That's always handy.

You also mention "the electronic gizmos". What would they be then, given that you have points igntion? You may need to expand on that a bit to enable us to help you there.

Finally for now, going back to the timing issue, I was wondering how you were timing it to 7BTDC if it won't tick over. You mention static timing it, are you doing that with the old test light method or is it running long enough to check with a strobe? Is your timing scale present around the pulley?