Timing confusion !

Discussion in 'Mech Tech' started by redgaz, Aug 7, 2019.

  1. Pic borrowed from the Samba but I don’t know where it originated.
  2. While we're on timing.. is there an easy way to mark up a type 4 timing scale?
    My numbers washed off the metal with the grime!..
    Is it just mark degrees onto pulley and transfer across.?

    Sent from my SM-T580 using Tapatalk
  3. A great day of fettling on the bus today with help from fellow bus owner mcswiggs. Thanks buddy.

    Following the auggestions above, we checked out my distributer to find it has had an aftermarket electronic points added by a PO. Unfortunately, this did not fit correctly and it was stopping any vacuum advance at all by binding. A bit of filing the base to an appropriate shape ended with a distributor that now moves when a vacuum is applied - yours truly sucking!

    Unfortunately, we couldn't get the bus to start on refitting the distributor back together. So a bit more fettling to do...hey ho a great day overall.
    snotty, paradox, Deefer66 and 3 others like this.
  4. Don't forget to stop sucking if your ears start bleeding :eek:
    Deefer66, 77 Westy and Chrisd like this.
  5. I have seen this with two Accuspark units - the unit engages perfectly on the base plate but jams on a screw holding the vacuum advance capsule on.
  6. Update on situation......

    Engine still does not want to start. It cranks over and sometimes spits/ backfires/farts.. you choose the adjective!

    I have checked fuel and new pump, all OK
    I have checked spark to each lead, all ok
    I have checked coil (Intermotor) OK. Primary 3.5ohms secondary 8.5k ohms, voltage 12.5 (so not ballasted)
    Battery is also OK and although the timing is now it not right it is set to about what it was when it worked.

    So next plan is to try an old set of points to see if the ignition module has failed (IAP ac905545) but sparks are going through... So simply put I'm stumped.

    Any ideas as to what I am missing except the obligatory brain cells to rub together.
  7. Have you set the ignition timing?
  8. Here's my aide-memoire on the engine lid

    Chrisd likes this.
  9. Ignition was checked and found to be way out. So fixed that and engine started backfiring. We then found the issue with the ignition module sticking. Fixed that and engine won't now fire. So to answer, timing is about right but not accurate any more.
  10. You'll have to do it again ;)
    Chrisd likes this.
  11. Go back and check those timing marks, I don’t have my glasses on and I can’t see the V-groove on the backside of the pulley but if you’re sure your marks are correct check that TDC on #1 firing stroke actually is TDC on the scale.

    My money is on the timing being quite a few degrees out – you could try cranking the engine and swinging the distributor back and forth until it fires.
    snotty likes this.
  12. Thanks.

    I and one other have checked the mark and the notch is there BUT when timed to that notch the engine started to backfire. I have tried your 'swing' method and no joy yet. This weekend is check TDC with a pencil to see if pulley is showing correctly plus other fettling to get it going again.
  13. Okay, are you absolutely certain that the firing order is correct? It’s easy to get it wrong. And if you’re replaced the plugs try putting the old one’s back in. Have you adjusted the valves?

    It’s not easy to accurately check TDC with a pencil, or anything else stuck down the plug ‘ole, on a Type 4 – the plug is almost horizontal to the cylinder.
    Chrisd likes this.
  14. Will check everything again and then again. Thanks about the pencil pointer ;-)
    77 Westy likes this.
  15. Hi Geoff - I’m the ‘plus one’ in this endeavour. I’m a bit stumped too - the engine was running until we started to fiddle with it :thumbsup:.

    We didn’t touch the plugs or plug leads, just the dizzy. After putting the dizzy back in we set it for 7.5 degrees-ish while cranking and gave it a twizzle, but it didn’t even sound like it wanted to fire, but did backfire spectacularly through the carbs and exhaust after too much cranking.
    We’ll try popping in a spare dizzy tomorrow to rule out a duff module. And then take a look at the quality of the spark.
    Last edited: Jan 10, 2020
  16. I'd say that's typical of ignition timing being well out of whack. Static time the dissy if you can with your module, or even take the module out and stick a set of breakers in temporarily to set the initial timing.
  17. If it spits and backfires it certainly sounds like a timing issue, or maybe the ignition module is breaking down.

    You need to be confident that TDC is marked correctly on the pulley before the timing can be adjusted and with hindsight ‘someone’ should have been suspicious that the timing was 15 degrees out although the engine was running reasonably well. Make sure there are not two V grooves in the pulley and the timing is being set to the wrong one.
    Last edited: Jan 11, 2020
    mcswiggs likes this.
  18. Happiness is an engine that works :)

    Two men, one engine and lots of fettling later....

    After changing the dissy for an old one Dom had we managed to get her started. Put my dissy back but with Dom's ignition module, the engine wouldn't start again...blast and double blast.

    Checked the timing by hand cranking engine round and confirmed timing mark was correct.

    Changed and re-gapped plugs and put a new spare plug in (as we only had one to hand) and hello happiness ...bingo engine fired first time.

    Oh I do love this lark and huge thanks to Dom for his help.

    Shops now closed so will order new plugs and stuff.
  19. One of the wonders of doing this is sometimes by the time you get the timing right, the engine is so flooded it wont run unless the timing is seriously over- advanced..
    Valveandy likes this.

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