Debugging the van

Hello!
Yeah I'm still alive.

I recently bought a shiny new battery for my Van so I could continue diagnosis of its condition.

After I dropped the battery in I had the prime opportunity to turn it around in the carport by going around a culdesac near the house.
On doing this I made it most of the way with it chugging weakly. Had to restart lots of times to get it back up the driveway. Later discovered very shagged fuel line; Replaced now with new 1/4" line (was 3/16" for some reason before).

It'll sometimes start from cold with autochoke engaged. Otherwise I have to pumpity pump while cranking until it starts.
After it startts it may or may not idle.
It _looks_ like the accelerator pump is working, and there is no shortage of fuel pressure. This still leaves my big X factor. Vacuum?

Does anyone have a vacuum gauge they can lend me for testing? I bid on eBay but they go for too much to justify a one-off test.
I may be wrong about vacuum but it sure does feel like it.

Incidentally I pulled off the carby to air filter thingy (1800 dualcarb) from the master carb. As always when the idle circuit is removed from the pipe it tries to die. But it kept chugging until it died with a small backfire in the manifold.
Would an inlet valve be the problem? It gets 110PSI all round on all 4 cylinders IIRC.

Anyway, any help would be appreciated.

Thanks.

sounds like you may need to do the full carb tune thing as described in the haynes workshop manuel. good luck

try another carb it really sounds like a buggered carb orthe galleries are full of vw crap

I picked up a cheap vacuum / fuel pressure gauge on eBay. It arrived today so I took the opportunity.

First, I nailed a massive vacuum leak. The air preheat valve thing was no good. I must have reconnected a bad unit or something. My memory vaguely recalls it just being plugged in the past.

Anyhow, it worked.

Pickup on acceleration is much better, but not perfect. Still sounds rough as anything. The carbies still probably need a good cleanout again.
It probably also need new sparkplugs too.

Doesn't idle right now but I'm pretty sure a tweak of the idle screw will fix that. After all it was sucking a whole stack of air before.

Sorry about the self reply.

I was doing a little more probing and gave the carbies a bit of a degreaser and toothbrush clean.

I found another problem.

On the slave carbie the accelerator pump diaphragm had slipped inward on one side causing a mighty fountain of fuel when the accelerator is used.
It seems as though it happened because the jet is blocked.

This leaves me with two problems:

* Unblocking the narrow jet tube.

* Getting a replacement diaphragm.

The diaphragm looks like it can be salvaged but not for the long term. around where it was wrinkled there are beginning signs of cracking.


I would say this explains the hesitation and rough running pretty much.

So, can anyone enlighten me on either issue?

Thanks.

I would order a set of gasket kits for your carbies that come in a boxed set and are available through Repco and also 5 litres of kerosene and carefully disassemble each carby ONE AT A TIME MIND YOU and completely clean each one and then refit to the the manifolds , but DO NOT fit the throttle crossbar linkages and then carefuly balance the idles and mixture screws on both carbies till it runs smoothly , then and only then now reconnecect the crossbar linkages and push with your thumb on where the throttle cable pulls from just slightly and check that both carbies butterflys start to move at exactly the same time.
If this fails to fix your rough running i would now also check the rocker clearances that should be set at .006" and can be set as follows 1 ~ Set the motor to TDC on number 1 cylinder ( the rotor button should now also be pointing to number ones lead on the dizzy cap ) and adjust said cylinder clearances then wind motor BACKWARDS 180 deg and set number 2 then wind backwards another 180 deg and set number 3 and finally wind backwards another 180 deg and set number 4 job done.
And finally i would also replace the points , dizzy cap , rotor , condenser ,leads , and plugs .
So with this all done and you already having a good compresion accross the cylinders you should have a smooth running 1800 type 4 that will save you in fuel what you have spent on your tune up.
Hope this helps your problem .

Andrew

Ah, nice.
For some reason I was scratching my head when you mentioned removing the crossbar. Mentally I removed the balance tubes etc too.

I did a quick scrub and rebuild on the slave carby earlier this afternoon before I saw your post.
I successfully unblocked the accelerator pump jet using a desoldering bulb of all things. I used it to force air back through the jet gallery to unclog it without using anything solid
. Don't worry, diaphragm assembly etc wasn't attached at the time.

I also managed to reseat the diaphragm properly to my surprise. It now squirts happily without any sign of leaking. It'll do for testing / tuning purposes anyway.

I'm hoping to attack the master carb tomorrow. Ie give it another clean and diagnosis.

I can tell you that the valve clearances are spot on. I think I checked them three times after the last topend rebuild to just make absolutely sure, if you know what I mean,.

Yep, compression is spot on. At factory spec and pretty even.

Vacuum gauge didn't show any hint of wobble when I connected it to the intake preheat control vacuum line, so I think none of the valves are sticking.

Points, coil, and possibly condensor (it's been a while. Memory is a bit hazy) haven't had much operating time at all. I replaced them before I drove to QLD. The van only had maybe 1000km on it after that, before it dropped the valve seat. I've been trying to get it working properly since.
So far it has been a fine tapestry of minor things that added up to a vexing issue.

The winding the motor backwards for doing the rockers is a new one to me. I think I'll do it again while doing that just to be safe.

The sparkplug leads all show about the same resistence according to my multimeter. Although for all I know they mightn't be carrying current as well as they could.

Sparkplugs are a definite replace. I don't know whether it has the new set or a mixture of new and old from when I did the second rebuild.

The carby kit is definitely on the cards though. Jets and all seem to be pretty good, but the diaphragm and gaskets need attention.

I'm going to take the scope out to check out the -ve on the coil to make sure everything looks sweet too.

Once i do the quick and dirty on the master carb I'll check their balance like you suggest for sure. If it runs like less of a pig I'll know I'm on the right track.

Since I plugged the vacuum leak I've been hearing a healthy howl from the carb throats. Especially the idle throat.
On that subject something odd did occur. Now the vacuum leak is plugged the air screw has less effect. A bit weird considering the idle circuit would have barely been active before. That's why I'm going to check out the master anyway.

My van has been a costly legacy. I hope to one day actually get it roadworthy again.

What do you mean by Master Carb ???, i am assuming you mean the passengers side carb that also has the poulution guff, but from what you've just said it is more than likely you have a seriosly blocked idle jet and or circuit on the carby that the airscrew has little if any effect , but as we all know it is pretty hard to tune someone elses car down a phone line via the good old net.
Best of luck .

Andrew

Yeah, the passenger side one with the idle circuit etc. The "proper" carb.
Do some of them have pollution gear? I'll have to have another look at my manual.

Mine's just a bog standard unadorned twin carb set for an auto van. My van used to be auto once upon a time, but a stuffed transmission and cost difference between repair / retrofitment meant it became a manual.