CU Timing marks

[kevtherev]

Has anyone got a picture of the crank pully timing mark for a CU?

[steve8090]

Kev, the CU is sometimes difficult to see, turn the motor over by hand until the rotor arm is pointing at no.1 cylinder you should be able to see what looks like a saw cut at the back of the pulley behind the fan belt, corresponding to no1 tdc, then using a timing light set to spec at 4 degrees, also check that you have no more than 30 degs at 2500-3000 rpm with the vac off. We usually disregard the base setting and set it to 30 degs advance at 3000rpm, these motors tend to like a bit of advance on the timing

[kevtherev]

Thanks Steve
struggling with Daz's Dells after a useless rolling road set up
they moved the dizzy to remove the 30 deg value that was found... that all the info we have

haynes does not mention Vac off for idle. Should it be off? (electronic ign)

Erratic sparks and backfire

[steve8090]

Have you got the DIS unit bypassed? timing is always done vacuum off but just for setting base there will be no vac there, suprised with the rolling road, they usually are spot on, get them as close as I can anyway.

There is an earth behind the distributor which if not perfect can cause that problem, for some unknown reason VW made that earth to the dizzy clamp and is the main earth for the electronic ignition, can cause those problems if not perfect.

[kevtherev]

yes bypassed
Going to adjust now with vac off

[kevtherev]

wasn't far out..
compression is 150 on all four
no spark or intermittent on 1 &4

removal of these leads and engine does not falter
replaced leads plug coil dizzy cap arm

good spark down the king lead

[steve8090]

Kev, have you moved the air correctors on the Dells? if you have 150psi on compression and a good spark, then do the obvious and check the engine earth, it just may be breaking down under load, try a different coil, however this sounds more like the carbs just haven't been set properly, there is a fine balance using the air correctors to get each cylinder working properly and yes there are four of them, one for each pot and there is no default, what works for one will not work for the other, take it to someone who knows how to do the job.

[kevtherev]

No not moved the correctors.
It won't idle well
The mixture screws are 6 1/2 turns out
The timing light shows good energy down 4 & 2 but 3&4 give an erratic light

Bit dissapointed we can't sort this.




I think we might have to pay you a visit Steve

[steve8090]

6 /12 turn out, your joking, is it blowing black smoke out? did the peeps at the rolling road move the correctors?, if you want to learn and still do it yourself there is a book I can recommend available from eurocarb priced at $9.95 called the Dellorto Superperformance Tech Book, it tells you all about setting it from base to air correction and setting emulsion tubes correclty, well worth a read if you have these carbs.

[kevtherev]

We have the book... but was a bit wary of moving off from the rolling road set up...

we are now setting mixtures at 3.5 turns out

[steve8090]

We have the book... we are now setting mixtures at 3.5 turns out

Yes much better

[kevtherev]

OK
still only firing on two
No1 and No 3 refuse to fire
yet a plug check reveals a spark when layed on the case (though not a bright flash)

wet plug when removed
Tried another ecu no change
idle control seems to do nothing either connected or bypassed

[dugcati]

how old are the plugs Kev? might be worth replacing em if the age is unknown or old....

[jason k]

Possible Inlet manifold air leak kev?

[kevtherev]

We gave up jase
I think it needs a more expert eye