View single post by subwoofer
 Posted: 06-13-2015 10:03 am
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Joined: 04-01-2008
Location: Sandefjord, Norway
Posts: 599
I'll have to ring Mike on Monday and find out more, thanks for the heads up Gordon! I need a crank angle sensor assembly anyway, crank fire ignition is a lot easier to hide than EFI. I am thinking to mount a VW coil pack on top of a gutted distributor, would not stand out since the distibutor is obscured from view. VW part numbers 032 905 106B (wasted spark) or 06A 905 097 (individual coils).

But back to the matter at hand, a bit of differential diagnosis:

1. It is not running hot, dial is mid-gauge and stays there even when idling for a long time. No indication that the oil is overheating either, oil pressure ~2 bar at idle with 5W-40 oil when it is in trouble.

2. Intermittent contact in tachometer or fuse for switched circuit. Seems unlikely since it never misfires when revs > 2000 RPM. I have had intermittent contact at the fuse box before, that behaved rather differently. TODO: verify that I actually have spark when cranking after it dies.

3. Stale fuel. Fuel is from last year, but it did the same thing last year when the fuel was fresh. Also, expected outcome of stale fuel is hard starting and poor idle, especially when cold. Neither seems to be true.

4. Overheating Pertronix: Not probable, since enough revs will restart it. Electronics generally cool down rather quickly, so does not explain trouble restarting an hour after it stalled.

5. Fuel frothing: Not probable. Idle is nice and smoothish, carbs mounted with rubber insulator washers and plastic spacer plates as supplied by Mike when I bought the engine and carbs. No noticable extra shaking before stall.
Carbs are Spec 5, btw.

6. Heat soak problem in carbs: so far the most probable cause. It explains the time constant, inlet manifold is hot to touch for a long time after driving.

I need to install a WBO2 to see if mixture is moving quickly or slowly before it stalls.