71 Fast Back Recommissioning

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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 11th May 2019 - 5:15pm

Suggestions of things you can still do:

Swap the plugs from 1/2 to 3/4 to eliminate a possible problem with those spark plugs - unlikely, but possible

Did you check and double check the plug lead order on the dizzy against the diagrams I posted earlier

Put a photo up of the dizzy with rotor arm visible when number 1 is at TDC

That should cover just about everything we can help with on the ignition side
David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon

JackReddick
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Re: 71 Fast Back Recommissioning

Post by JackReddick » 11th May 2019 - 5:37pm

937carrera wrote:
11th May 2019 - 5:15pm
Suggestions of things you can still do:

Swap the plugs from 1/2 to 3/4 to eliminate a possible problem with those spark plugs - unlikely, but possible

Did you check and double check the plug lead order on the dizzy against the diagrams I posted earlier

Put a photo up of the dizzy with rotor arm visible when number 1 is at TDC

That should cover just about everything we can help with on the ignition side
Image
Thats with timing at TDC. It’s pointing to plug 1. In clockwise order they are then 4 3 2

I’ve swapped plugs from 1 and 2 to 3 and 4 but no change.
Exhaust for 3 is luke warm, 4 is still stone cold

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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 11th May 2019 - 5:50pm

Great, I think that confirms it's the carb then. The rotor arm is pointing where it should and you have the HT leads in the correct order. The only think not tested in the HT leads to 3 and 4, but I think you already swapped those ?

Lack of fuel, not lack of spark.

Strip and rebuild the left one again tomorrow and if no luck take up one of Broadys kind offers ?
David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon

JackReddick
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Re: 71 Fast Back Recommissioning

Post by JackReddick » 11th May 2019 - 6:00pm

937carrera wrote:
11th May 2019 - 5:50pm
Great, I think that confirms it's the carb then. The rotor arm is pointing where it should and you have the HT leads in the correct order. The only think not tested in the HT leads to 3 and 4, but I think you already swapped those ?

Lack of fuel, not lack of spark.

Strip and rebuild the left one again tomorrow and if no luck take up one of Broadys kind offers ?
Yep, already swapped the leads with no change. Going to see if i can borrow a known working carb from Broady to try and rule that out.

I find it hard to believe it’s lack of fuel seeing as the bowl fills and it squirts fuel fine if you do it manually, but what do i know 😂

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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 11th May 2019 - 6:15pm

Ah, you are misunderstanding how the carb works. It has three circuits inside. Idle, main and acceleration.

The squirt you are seeing is the acceleration. It's pretty useless on its own. All its there to do is to dump an extra shot of fuel in to increase power as you accelerate. To add to the main jets fuel supply. All you are seeing is the green circuit. Which isnt operation all the time.

Image

What you have likely got is a blocked main or idle jet circuit.

In the float bowl at the bottom is a jet, if you take that out and squirt wd40 with a straw. Where does the wd appear?

When you are cleaning the carb, how are you checking all the galleries are clear? Really you need compressed air as i sugeested earlier.

I dont have known working carbs, ive just got a ncie big box of bits. But I have bodys with known clear galleries which you can build into.
The sultan of swing

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Re: 71 Fast Back Recommissioning

Post by JackReddick » 11th May 2019 - 7:03pm

Ah ok! That makes more sense now. That explains why if i open the throttle it fuels and fires/backfires.

I can’t remember exactly where the number 3 jet squirted out when i cleaned it, but it was either the “tap” looking thingy or where the tip of the volume control screw is

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Re: 71 Fast Back Recommissioning

Post by JackReddick » 12th May 2019 - 2:44pm

After getting the arse with the car yesterday, a case of “curiosity killed the cat” struck today.

I decided i’d strip the carb AGAIN and this time be more thorough. I’m now certain all the galleys and jets are clear as i’ve blown them all through with carb cleaner and it’s blowing out of the jets etc.
What i have found however, and not sure if this will be adding to the issue, is a small hole in the tube where the volume control screw is. It certainly doesn’t look factory, so i can only assume i need to replace the lower section of the carb. I’m not sure how well the photo picks it up, but you can make it out, and see light through it when you look at it

Image

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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 12th May 2019 - 4:02pm

I will let Broady comment on the carb when he sees this, but with your persistence and curiosity I am sure you will solve this.
David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon

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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 12th May 2019 - 7:18pm

The hole in the red circle?

Image

Ive checked again 4 in my spares box and none of them have that feature. I expect that's the problem as its effectively and air leak.

Ive put a few bits in a box for you, a pair working cut off solenoids and the butterfly plate and lower half of the carb body. Its not top stuff but it should be good enough to prove the theory.

Though hopefully if that hole and be very careful brazed without and material entering the needle aperture then you could have it fixed.
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Re: 71 Fast Back Recommissioning

Post by JackReddick » 12th May 2019 - 7:27pm

broady_6 wrote:
12th May 2019 - 7:18pm
The hole in the red circle?

Image

Ive checked again 4 in my spares box and none of them have that feature. I expect that's the problem as its effectively and air leak.

Ive put a few bits in a box for you, a pair working cut off solenoids and the butterfly plate and lower half of the carb body. Its not top stuff but it should be good enough to prove the theory.

Though hopefully if that hole and be very careful brazed without and material entering the needle aperture then you could have it fixed.
Yeah the one circled. Close up you can see something has penetrated it from outside.

Hopefully swapping that part with the one you’ve sent will prove that’s the problem ☺️

I’m getting hopeful again that she’ll soon be running!!! Haha

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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 12th May 2019 - 7:30pm

You've also got a completely cracked spindle. So that's another air leak. In fact it looks like two cracks has propagated there. id say that's a photo of some scrap unfortunately
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Re: 71 Fast Back Recommissioning

Post by JackReddick » 12th May 2019 - 7:43pm

broady_6 wrote:
12th May 2019 - 7:30pm
You've also got a completely cracked spindle. So that's another air leak. In fact it looks like two cracks has propagated there. id say that's a photo of some scrap unfortunately
Is that the bit the rod connects to? I’m eyeing up a carb on ebay for £30 which is complete with solenoid to use to for parts

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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 12th May 2019 - 7:55pm

Ive put a red line along side the crack. and a short one against what is either a crack or a casting mark. In the original photo.

Have you checked for play in the spindles on both carbs? Its pretty comment of them to be worn out, and more common for the wear to be at the other end of the spindle.
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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 12th May 2019 - 8:02pm

JackReddick wrote:
12th May 2019 - 7:43pm
I’m eyeing up a carb on ebay for £30 which is complete with solenoid to use instead
Corrected that for you. :)

If that's on a BIN, then buy it, worth it for the solenoid alone
David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon

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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 12th May 2019 - 8:11pm

doing better than me, I cant find any at that price on ebay unless you've already bought it!
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JackReddick
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Re: 71 Fast Back Recommissioning

Post by JackReddick » 12th May 2019 - 9:16pm

There’s some of sale on the vw parts emporium website too but they look rough as

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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 13th May 2019 - 9:04am

They do, but if they've got good spindles and bushes they could be worth it. You may end up taking the plunge and going for a professional carb overhaul. I've posted you a box of bits this morning. Should get it wed/thurs all being well
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JackReddick
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Re: 71 Fast Back Recommissioning

Post by JackReddick » 17th May 2019 - 6:34pm

BIGGGGGGGG update time -

WE’RE RUNNING ON ALL 4!!!

Turns out the inlet to head gasket was missing. Fitted that and boom, she’s running sweet!

Thanks to Broady for lending me the solenoids and spare carb bits, i’m going to put the solenoids on to see how that effects things.

New problem is the brake lights are now permanently on 😂 still, now i’m optimistic 😊

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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 17th May 2019 - 7:15pm

Well, I didn't see that coming. Glad you got it sorted out. :thumbsup:

Brake light switch is probably operated by the pedal. Make sure it isn't jammed in the on position or shorted
David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon

JackReddick
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Re: 71 Fast Back Recommissioning

Post by JackReddick » 17th May 2019 - 8:55pm

937carrera wrote:
17th May 2019 - 7:15pm
Well, I didn't see that coming. Glad you got it sorted out. :thumbsup:

Brake light switch is probably operated by the pedal. Make sure it isn't jammed in the on position or shorted
A real face palm moment. I’m still not sure if i’m chuffed that it’s working, or p*ssed that i didn’t notice it sooner!

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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 17th May 2019 - 9:47pm

exacellent news! as simple as an air leak :D

The brake light switch(s) are screwed into the master cylinder and pressure operated. Easy test, check you brake pedal has got 1mm of free play at the top of the pedal. If it hasnt then its likely your already preloading the brake hydralics. If it has free place pull the wires off and the master cylinder switch(s) and do a continuity test, Open circuit is correct for brake light off, close circut is brake lights on.
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JackReddick
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Re: 71 Fast Back Recommissioning

Post by JackReddick » 18th May 2019 - 8:59pm

So today i changed the oil for the third time. Again there was a ridiculous amount of crud built up in the sump plate. I reckon i’ll need to change it another one or two times once i’ve done a few miles in it.

I fixed the brake lights, it turns out i’d knocked and bent the pin on the brake light switch so that was an easy fix for a change.

Tomorrow i’m going to take it for a short spin and see what comes up. The carbs need properly setting up by someone so i expect there to be a few problems there. There is also a noise i need to work out from the n/s/f corner. I’m thinking it’s either the bearings or the disc as it’s heavily pitted

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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 18th May 2019 - 9:08pm

I'm glad the brake light were an easy fix.

I'm curious what happened with the small home in the carb where the volume screw sits.

Wheel bearings you should be able to put the car in the air, spin the wheels to feel for roughness and move about to feel for play.
David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon

JackReddick
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Re: 71 Fast Back Recommissioning

Post by JackReddick » 18th May 2019 - 9:34pm

I’m just guessing at the minute, i’ll look into it tomorrow. It only seems to make the grinding noise when turning left, but i’ve only tried driving it once so it needs fuether investigation

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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 18th May 2019 - 10:02pm

wheel bearings need adjustment. theyre look loose which lets the disc wander about and its hitting the caliper is my guess.
The sultan of swing

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