[T3] Loses Power After Running

Jim Adney jadney at vwtype3.org
Thu Sep 9 08:16:55 PDT 2021


Sorry for not replying to this sooner. I was hoping that someone with more 
Type 4 experience would have an answer for you.

I'm absolutely NOT sure about this, but your symptoms make me wonder if 
you're overheating. Here are some things you might check.

Is this Type 4 engine getting proper cooling air from the Type 3 body? It 
needs to be sucking air from the cooling air ducts in the body. If it is just 
sucking air from the open space to the rear of the engine, it will be getting 
hot air to cool itself. That would be bad. Effective ducting can be done, but 
it's quite difficult.

Timing to 7.5 BTDC sounds rather advanced to me. Check to see how far 
advanced it gets at high RPM. If it gets much above 30 BTDC then you 
should drop back to less advance at idle. It may be useful to verify, with a 
long screwdriver down a spark plug hole, that TDC is where you think it is.

Remove the spark plug wires from the plugs and inspect down each hole for 
mouse nests. If you find the tin filled with nest material, you won't be getting 
sufficient cooling to the cylinders. Fixing this may require pulling off the tin or 
maybe even pulling the engine first.

Could there be a clogged fuel filter, or a clogged filter screen in the bottom 
of the tank? It's possible that enough fuel is getting thru to sustain idle, but 
once you start asking for more power the carbs are starving. If you pull the 
hose off the bottom of the tank, you should get a pencil sized stream that 
puts out a scary amount of gas (DO THIS OUTSIDE!) If it dribbles, there's 


On 9 Sep 2021 at 3:23, Tony Rongey wrote:

> I'm working on a T4 1700 in a manual '68 Square (it came with the car).  It's got dual Brazilian Solex 32s on short manifolds.  It's got an electric fuel pump that's factory set for 3.5psi (haven't tested that).
> It starts and runs well, idles fine. #2 plug shows a little oil burning. Dwell is 44deg and timing is just before the 7.5 mark, carbs are balanced at idle and at speed on the snail gauge.  I can start it and drive it around for about 5 minutes regardless of how long it's been idling.  After that it suddenly is just barely running.  It's not rough like a miss.  It starts with kind of a surging feel then becomes more of a smooth non-existence of power.  It will die at a stop if I don't give it some pedal.I've noticed that after that if I park it and leave it idling after that it will speed up a few hundred rpms then slow back down over about a 1 minute cycle.  If I try to drive again it starts out OK, but within about a minute the power is gone.
> Does anybody have a clue what I should be looking for?

Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA

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