If you've an old rotor arm, temporarily put it in place on the shaft while the distributor is still fitted in place on the engine. Rotate the rotor arm in the direction of normal rotation, and you should feel the shaft move, and the weights beginning to move out being held by the springs.
(I say use a spare, because if you're a bit heavy handed, you'll break it)
If the shaft doesn't rotate, it's seized up, and you'll need to take it apart to free it up.
If the shaft rotates, but without any resistance, your springs have broken, and you'll need to get some new ones before you take the distributor apart.
If you do take it apart, be warned that the wires for the Hall sensor are quite fragile, and unless the distributor is recent are already quite weak (they're a common failure).
However, a much better way to check the advance is to use a strobe light.
Why do you think there's a problem with the advance mechanism?
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Have a feeling that the dizzy on this car is just there to fire the sparks to the plugs. All timing is done by the ECU. Certainly earlier 1.8 PB engine (Golf GTi) in a Mk2 did away with bob weights and diaphragms. Initial timing is done by moving the dizzy, but running is all done by the ECU, including retarding the timing when it starts to pink by a knock sensor.
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Hi Woodspeed,
Surely it can't; if the dizzy is static then the electrical connection between the coil and the plugs is also at a fixed time.
For ECU timed ignition (rather than just trigged as in this case) you'd need cam sensor and a DIS type system.
James
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>>For ECU timed ignition, ...., you'd need cam sensor and a DIS type system.
No, Woodspeed raises a valid question - which was at the back of my mind as I typed - I took the view that as you were asking a very specific question that you *knew* there were bob-weights and an advance mechanism in there.
It's perfectly possible for the distributor to be a solid, fixed device, and any delay to vary the timing being done by the controller, based on engine speed, load, and temperature. There may be non bob-weights at all, the shaft may be solid.
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Hiya
The timing cannot be changed if the dizzy is fixed.
From Wiki - "The distributor also houses the centrifugal advance unit: a set of hinged weights attached to the distributor shaft, that cause the breaker points mounting plate to slightly rotate and advance the spark timing with higher engine rpm. In addition, the distributor has a vacuum advance unit that advances the timing even further as a function of the vacuum in the inlet manifold."
The golf mk3 is electrically trigged (aka hall effect sensor) but still relies on the dizzy for the advance.
No vacum hoses on mine - hence the original question.
James
Edited by Javalin on 20/02/2009 at 12:50
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>>The timing cannot be changed if the dizzy is fixed.
That's not true, and the wikipedia, while being a good guide, isn't a reliable source to quote from.
It's quite possible, and has been done on many vehicles, to have a distributor with a solid shaft, and timing being advanced by a controller elsewhere.
>>but still relies on the dizzy for the advance.
Possibly, but also, possibly not.
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Hi Number_Cruncher,
Can you give details? Not wanting to argue, but to understand how it would be done otherwise....
Admittildy wiki can be misleading, but I have the same info in several reputable car books.
Thanks,
James
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OK, for a moment, forget about advance weights and vacuum capsules. The switching unit in the distributor (whether its points, optical, variable reluctance, or Hall effect, is just a camshaft angle sensor.
Once you have an electronic trigger unit which drives the coil, you can decide to send a spark exactly when you obtain the switching signal from the distributor, or, you can choose to delay the spark.
If you choose to send a spark exactly when the distributor switches (like points based conventional systems), you need to do something to advance the spark as the engine speeds up, and to retard the ignition as the engine is placed under more load - hence you end up with mechanical advance weights and vacuum capsules.
If, however, you choose to implement a delay of your choosing, you don't need the crude mechanical devices, and the distributor shaft may be solid. The distributor is set so that it switches very early in the cycle, say 60 degrees before top dead centre. The control unit knows the speed of the engine, and so, by waiting a calculated period of time can send the spark at the right time for the particular engine operating conditions, say 10 degrees BTDC. The controller knows the engine speed, because it can calculate it based upon the time between the pulses from the distributor, and it may know the engine load from a manifold absolute pressure sensor.
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Hiya - thanks for that - just what I was after.
I'll check.
>Why do you think there's a problem with the advance mechanism?
The car has a history of bad/inconsistent performance/low mpg. Recently put a new belt on the car and corrected the timing which has helped. It still has a lumpy idle but is fine when under load. MPG has suffered a bit to - but waiting to see what a correctly fitted cam belt does to it. Also as the engine winds up you can feel lumps as the power appears - I guess might be the advance changing and sticking?
Also got to do a compression test to see what the new belt has changed - might show other issues now...?
Am i correct in saying that the dizzy should have the spark near TDC for idle and earlier for higher RPM/load?
Cheers,
James
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I very strongly suspect that on this engine the distributor has no advance system of either kind, timing being adjusted by the ECU.
The car on which I changed the cambelt (see other thread) will be here this weekend - I'll have a look for you if the question is not resolved by then.
659.
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The timing is nearer TDC at idle, but earlier BTDC (before) as revs rise. From memory the TDC mark is a diamond on the flywheel, which can be seen through the hole between gearbox and block when the green plug is removed. Moving the crank clockwise the next circle mark is the static timing (about 6 degrees). From memory (please look at a decent manual) the revs have to be increased to around 2000 - 2500 where the timing should be about 22 degrees, although I think (again from memory) this engine is set at idle to 6 degrees BTDC and the ECU corrects as the revs rise. If knock/pinking is detected, it auto retards.
The Wilki item you were looking at is an old system (points base!).
VW with K jetronic up to about 89 used bob weights and diaphragms - and worked quite well.
There are no bobweights or diaphragm within the dizzy on a Mk2 GTi of about 89 - 90. Engine PB.
Later engines Mk3 are similar 1.8 but can be fitted with multi injectors (90BHP) or a single injector (75BHP). All Mk3s had a cat too which will not take kindly to running at the wrong igniton timing.
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Hello again all,
Well I stand corrected - so thanks for not getting (too) feed up with me!
The dizzy is indeed solid. Also solidly rusted into the block... There is a little bit of play in it - but not more than a degree or two i'd say.
OK - I still don't get it - so... The dizzy is driven by the the intermediate shaft and has four points. Therefore as the cam & dizzy are at the same speed - both are 1/2 crank. So each point on the dizzy get hit once at (near) TDC before the ignition stroke. If there is only one electrical connection at that point - how is the ignition timing change-able?
Also checked the flywheel marks - they are indeed there. Cool.
I've ordered a timing light.
Thanks all,
James
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>>how is the ignition timing change-able?
read my post timed at 14:37 all is explained there.
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As indeed it is. Possibly one point of confusion results from the HT switching.
The spark is generated by the sudden interruption of current in the LT side of the coil. This is done by the ECU as previously outlined. As the spark will occur at differing crank angles according to the advance required, it follows that the HT switch (rotor arm and segments) need to have sufficient tolerance to accept these variations. This is why a rotor arm has a broad "tip" which is considerably wider than the segment in the cap.
In this respect, the "solid" distributor is no different from its mechanically and vacuum advanced predecessor.
659.
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>>This is why a rotor arm has a broad "tip" which is considerably wider than the segment in the cap.
Quite so.
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"The dizzy is driven by the the intermediate shaft and has four points. Therefore as the cam & dizzy are at the same speed - both are 1/2 crank. So each point on the dizzy get hit once at (near) TDC before the ignition stroke. If there is only one electrical connection at that point - how is the ignition timing change-able?"
The contact at the end of your rotor arm is (or should be!) in the form of a broad blade which thereby allows the spark to jump for some degrees either side of the centre timing point.
The timing is so clever on these it'll even send several sparks to each cylinder on start-up, which probably accounts for why they start so well.
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Hello PDP,
Ahhhhhh!
Thats how it does it!
Thanks!
I'll get the timing light out and see if its setup correctly - I guess if its off a bit from "center" (where it expects to be) then it could cause a problem at idle?
James
Edited by Javalin on 20/02/2009 at 19:47
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For a more detailed explanation ,take a look here
www.bayareamotorsport.com/alphan.html
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I guess if its off a bit from "center" (where it expects to be) then it could cause a problem at idle?>>
My 2.0 has always had an uneven idle too. I even took it to VAG for a diagnostics checkout when I first got it, and no problems were apparent. I think it may just be down to the way the ECU maintains the 800 rpm idle. Unless the knowledgeable contributers here suggest otherwise; as long as the engine is behaving well and does not cut-out or stall, I would not be concerned about it.
Edited by Dynamic Dave on 21/02/2009 at 14:18
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>>Also as the engine winds up you can feel lumps as the power appears
Going back to the problem itself, I would work through the HT system very carefully, checking for good, corrosion free connections, and checking for tracking, open circuits and breakdown. If possible, get the ignition system connected to a good oscilloscope, and make sure there are consistent KV values and burn times on each cylinder.
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Hello NC
Thats the next step. Its had a new rotor cap, arm and HT leads from VW about 2 years ago.
I've got an inductive pickup for the o'scope but last time I checked the king lead appeared fine (about 9kv or so - correct pattern) but all of the HT's to the plugs (which are fairly new) were odd.
I'll check again and post a picture.
Cheers,
James
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Hey all,
Did some sampling on the HT leads tonight. King lead shows as I'd expect. The others seem to have something odd going on. Also out of interest I also hooked up the hall-effect sensor on the dizzy for timing information.
Finally - VCDS showed Lamda of 3%, idle ~~800 ish and timing 5-8' BTDC (or so the ECU thinks).
Fault codes shown were :-
00515 - Camshaft Position (Hall) Sensor (G40)
03-00 - No Signal
00516 - Closed Throttle (Idle) Position Switch (F60)
29-10 - Short to Ground - Intermittent
Not seen 516 before - but I was poking arround near the throttle body.
PicoScope images are here :-
community.webshots.com/album/570252588IJHPGh?vhost...y
Grateful for any thoughts!
Cheers,
James
PS - Happy pancake day...!
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Unless it's an artifact from the sampling of your scope, the KVs look to be widely different between cylinders - that's not right.
For the burn times, I've seen worse - there does look to be some variation between cylinders, does that vary cycle to cycle?
As you can see, the hall effect switching happens ahead of the spark - the two events aren't synchronized.
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Hi NC,
>As you can see, the hall effect switching happens ahead of the spark - the two events aren't synchronized.
so then a delay and then the spark variation
>does that vary cycle to cycle?
what do you mean? The 1-4 plugs all look the same and stay the same....
Rotor cap / Rotor arm? Odd if so - as before they are only a couple/three years old.
Cheers,
James
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I put a new rotor-arm on this lunchtime. Seems better.
Will check with o'scope again tonight.
J
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Further on your lumpy idle issue: on a VW forum someone was complaining of the car stalling when the clutch was in. A suggested solution was to carefully clean out the throttle body, butterfly valve, idle valve, associated pipes, and the crankcase ventilation system in general. Several others who subsequently did this reported that it improved their previously dodgy idle, so perhaps worth a look in your case?
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Hiya
Yeah i've seen similar posts. Not sure exactly what (I know what the throttle body etc is) they propose cleaning....?
Mine is MUCH improved with new dizzy cap and new dizzy arm.
Pondering the fuel supply system ATM - might be the next thing to check. Also pondering valves / head gasket as cyl 3 & 4 are slightly lower than 1-2. Hmmm.
That said - the throttle body (and injector) is also on the list to check out. Injector cleaning is tempting....
Thanks,
James
Edited by Javalin on 04/03/2009 at 16:28
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