Vacuum Advance not holding pressure - broken?

[sjmtlewy]

It looses vacuum, even when covering the end. I've ordered a new unit, will also get a new arm, HT leads and plugs while I'm at it.

Could this cause the lack of power, or is that likely to be soemthing else?

Will let you know how it goes

[dugwiththevwbug]

it would be a great start to change all that you have described.
especially if the vacumn diaphragm has gone this would efect your dynamic timing advance at the top end of your rev range ie poor running at top speed

whilst your at it check the small fuel filter in the fuel inlet pipe on the carb.
it is located inside the spigot and is very small and is cone shaped I remove them gently with a wood screw this could be restricting the fuel flow just enough to slow things down.

worst case you will need to find someone with a strobe light and check the timing as if out the van will run poorly. Pity your not closer or i could take a look for you.
regards doug

[sarran1955]

Hello,

When you say it looses power, perhaps it would be worth doing a compression test. 'Home tune' diagnostics test the compression by measuring the cranking voltage, that is to say the load on the starter motor as it turns the engine under compression, or you can buy a compression tester. The important thing is that the compressions should all be about the same, say 120psi..

But rule Nr 1 is to change and fix one thing at a time, so look at your ignition first. It is possible that the centrifugal weights in the distributor are stiff, behaving correctly at low speeds but not under full power. a little oil can work wonders in a tired distributor.

Let me know how you get on.

Cordialement,

[sjmtlewy]

Right, I have:

- new plugs
- new HT leads
- new rotor arm
- new vacuum advance
- distributor stripped and weights oiled
- adjusted accelerator cable to acheive full throttle
- pumped up tyres to 52psi rear, 38psi front
- replaced a couple of dodgy old fuel pipes
- cleaned, greased and tested fuel pump
- cleaned carb with hand over intake trick

and its like a completely different van. Feels genuinely powerful and responsive.. stunning.

Also, vac advance was definitely knackered comparing it to the new one.

[dugwiththevwbug]

well done dude
happy dayz

regards doug

[sarran1955]

Hello,

Felicitations


Cordialement,