Aircooled VW South Africa

Hi all,

Haven't posted for a while since I've been away working and haven't had much time to work on let alone drive my bus! But got her running again recently after redoing my heads, pistons and rings, and a thorough service of my shitty carb, a Brosol h30/31 PICT. So it starts well, drives fine on flat roads but as soon as I try go up a hill and shift out of first it stalls. If I stay in first she'll rev right to the red line but as soon as I try grab the next gear she just wants to die. After a lot of reading I figured it's under jetted for my 1600 DP, so I swapped the 120 to a 127. Still can't go up hills.

My fuel is clean, I've cleaned the inside of the tank too, and it's got a new fuel filter. I also tried a new fuel pump. Anyone have any ideas? I read recently it could be a worn fuel pump pushrod...?

Thanks all!

Mike

Had the same issue but different symtoms

Idle is fine and rev clean, the moment I hit 1st gear it dies

Changed my points and all was sorted

If she revs in 1st but stalls in 2nd, it can not be fuel, have a look at your valve settings and your compression.

If you have a fuel problem up a hill it is normalcy your float, and fuel level in your float chamber.

But this sounds like lack of compression.

Herman

sounds like ignition to me too. As soon as you need some power, the flame cuts out (spark isnt enough) = thats my guess.

As always with mysterious symptoms, swap the consdensor before checking anything else.

Thanks for the help ouens.

When you say spark isn’t enough Tony you mean my coil might be buggered? Got good voltage at the coil. Surely if there’s spark enough to cause ignition while driving then it should be enough all the time? I’ve never heard of ignition dying off as you need more power. Can you explain?

Btw it’ll happily accelerate all the way into fourth on flat roads...


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retrovan wrote:If she revs in 1st but stalls in 2nd, it can not be fuel, have a look at your valve settings and your compression.

If you have a fuel problem up a hill it is normalcy your float, and fuel level in your float chamber.

But this sounds like lack of compression.

Herman

Thanks Herman. I don’t think it’s a float problem because if I stay in first it seems I could drive up hills all day.

Positions, rings and heads are all recently overhauled so I’d be surprised if it’s compression but will test.


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Check the choke

Poppy62 wrote:
"Surely if there’s spark enough to cause ignition while driving then it should be enough all the time?"

No.
The distance a spark can jump is related to pressure of the mixture as seen by plug's electrodes. (Light throttle= partial vacuum compressed by 7.5= lower actual pressure than: full throttle atmospheric compressed by 7.5:1

If a spark can jump 4mm under atmospheric, it may only jump 0.5mm when compressed 8x.

Some old plug testers had a compressed chamber and a window.

Remember the old vacuum tubes/"valves" from pre-transistor era? Vacuumed so that electricity flows even at low voltages. Temperature also plays a role, the cathode, (negative in that application), is heated.

Poppy62 wrote: "I’ve never heard of ignition dying off as you need more power."
I did experience that, during early days of LRP fuel. Caused by plugs being fouled by LRP rubbish additive.

Exactly what Dawie said, the higher the load, the more energy the spark needs to light the fuel. If your spark is reaching its energy limit before it can jump the gap and light the fuel, then it wont jump the gap.
Poor spark can be caused from a faulty coil, it can also be caused by a bad earth, cracked distributor cap, faulty condenser (as others have said you should change), corroded or incorrectly gapped points, old spark plug leads, wrong charging voltage from the generator or alternator, fowled or worn spark plugs, worn rotor.... a whole host of things.
Start by changing your condenser.

I don't know if you're still running points, but it may be that your point gap is not set correctly.

If the gap is too big, the points do not stay closed long enough (too little dwell angle) to fully charge the coil, which causes weak spark. Dwell angle is the amount of time (measured in degrees of distributor cam rotation) that the points remain closed. Initial point gap determines dwell angle. If the points are set too wide, dwell angle (the time they remain closed) is small.

Setting point gap to spec with a feeler gauge does not always result in proper dwell angle. As points age, one contact starts burning away in the centre, effectively increasing point gap, and reducing the time to charge the coil. What seems like a correct feeler gauge setting, is actually too big. I normally set the dwell angle, using my timing light to avoid this problem. Dwell angle should be between 44 and 50 degrees.

Not aircooled related, but I had an issue on my mercedes 220S ponton when I changed from points to an electronic pertronix conversion. The car struggled to go uphill and after some reading I discovered that the coil resistor had to be removed. Everything is now sorted.

Thanks guys, will follow advice and report back...


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Right, so...

First checked points while was waiting for shops to open. Adjusted, bus ran worse!
Got new coil (just in case, old one was Bosch Blue was from my old Landy and 15+ years old) plus condensor and points.
Fitted all except points because new points won’t fit in the dizzie despite me modifying them on a bench grinder. Old points are in good nick though so doubt that’s the problem. Anyway, after all of that: no change. In fact now it even sounds rough when revving up in neutral, lots of hesitation.

What the hell am I missing???


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Do not want to sound negative, but do a compression test 1st, if its the problem you got it in one,

If not, you have eliminated the main possible cause, and can then move on to the ignition system.

It will tell you where to look, inside or out side the engine.

After that I would look into timing of the valves and the ignition timing.

If too much advanced, it will also lack power. (fire after compression stroke)

Herman