71 Fast Back Recommissioning

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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 29th April 2019 - 10:00pm

Back on topic, did you have a chance to do any more work on this over the weekend ?
David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon

JackReddick
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Re: 71 Fast Back Recommissioning

Post by JackReddick » 10th May 2019 - 5:57pm

Been a few weeks due to my grandfather passing and i’ve been helping out alot down in Bognor with my nan and the rest of the family etc

Anyway, update time! I had an aircooled speciailst over today that i know, he’s found it’s only running on cylinders 1 and 3. He removed the ht leads individually with the engine running, when 1 or 2 were removed the engine note changed dramatically. When 3 and 4 were removed there was zero change.
I’m going to borrow a compression tester over the weekend hopefully and see if that shows anything. Oh the joys 😂

On a more positive note he said i’d gapped the valves correctly and i’ve relocated the fuel filter down next to the gearbox as some of you recommended
Last edited by JackReddick on 11th May 2019 - 11:22am, edited 1 time in total.

JackReddick
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Re: 71 Fast Back Recommissioning

Post by JackReddick » 11th May 2019 - 11:03am

So this morning i’ve done a compression check across all four cylinders and got the below
Cyl 1 130 psi
Cyl 2 85 psi
Cyl 3 130 psi
Cyl 4 135 psi

Cylinder 2 has low compression. I also did a continuity test on the leads to 3 and 4 and ot appeared they were damaged/broken so swapped them for new leads but still no life in cylinders 3 and 4.

Any suggestions?

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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 11th May 2019 - 11:13am

JackReddick wrote:
11th May 2019 - 11:03am

Cylinder 2 has low compression. I also did a continuity test on the leads to 3 and 4 and ot appeared they were damaged/broken so swapped them for new leads but still no life in cylinders 3 and 4.
Do you mean 3 and 4, or 2 and 4.....different to what you said before and quite important
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 - 11:21am

937carrera wrote:
11th May 2019 - 11:13am
JackReddick wrote:
11th May 2019 - 11:03am

Cylinder 2 has low compression. I also did a continuity test on the leads to 3 and 4 and ot appeared they were damaged/broken so swapped them for new leads but still no life in cylinders 3 and 4.
Do you mean 3 and 4, or 2 and 4.....different to what you said before and quite important
Sorry it’s 3 and 4, i’ll amend my original post. Both the chlinders on the left hand side of the engine bay

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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 11th May 2019 - 11:24am

First of all, condolences. Never easy to loose a relative. But its nice to hear your are returning focus to the car.

The below post would point us towards the two faulty cylinders.
broady_6 wrote:
22nd April 2019 - 1:38pm
Have you checked the exhaust at each head port. Ideal from cold start him up and then touch each branch, before they get too hot. Obviously be very careful. If one is cold/colder than the rest then it'll pin point the problem. But as David said, a carb off again won't hurt. I've just done a two year resto on mine. Including ultra sonic carb cleaning. It drive pretty well, but hesitates, I've just pin pointed that the right hand carb is under fueling. So either a float issue, or something's found its way in.
Just to clarify the cylinder numbers, stood at the back of the car. Right hand side the cylinder furthest from you is number 1. Nearest is number 2.
Left hand furthest is number 3, nearest is number 4. I suspecting you've got the HT leads in the wrong order. Ive done it before and it resulted in an engine which ran like the one in your video.

The firing order is 1432.
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JackReddick
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Re: 71 Fast Back Recommissioning

Post by JackReddick » 11th May 2019 - 11:31am

broady_6 wrote:
11th May 2019 - 11:24am
First of all, condolences. Never easy to loose a relative. But its nice to hear your are returning focus to the car.

The below post would point us towards the two faulty cylinders.
broady_6 wrote:
22nd April 2019 - 1:38pm
Have you checked the exhaust at each head port. Ideal from cold start him up and then touch each branch, before they get too hot. Obviously be very careful. If one is cold/colder than the rest then it'll pin point the problem. But as David said, a carb off again won't hurt. I've just done a two year resto on mine. Including ultra sonic carb cleaning. It drive pretty well, but hesitates, I've just pin pointed that the right hand carb is under fueling. So either a float issue, or something's found its way in.
Just to clarify the cylinder numbers, stood at the back of the car. Right hand side the cylinder furthest from you is number 1. Nearest is number 2.
Left hand furthest is number 3, nearest is number 4. I suspecting you've got the HT leads in the wrong order. Ive done it before and it resulted in an engine which ran like the one in your video.

The firing order is 1432.
Thanks mate, i appreciate that.

Yes that’s correct, cylinders 1 and 2 fire, with 2 having the lower compression.

I’ve had my hand on the exhaust port at the head by cylinder 4 and that was cold. I am yet to do it for culinder 3 but it’s currently chucking it down outside so i’ve run indoors to hide

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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 11th May 2019 - 11:32am

If you follow the HT lead which has the red arrow pointing at it. It goes to the left hand head. Does it go to the cylinder furthest away from you or nearest the back of the car?

Image
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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 11th May 2019 - 11:34am

Beat me to it :thumbsup:

If it isn't that then it's a carb problem, now we know it's one bank.

Here's a naff graphic for the cylinders

............||||||||||||-----------------

3...........................................1

4...........................................2
David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon

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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 11th May 2019 - 11:37am

The rotor arm goes clockwise, this has better graphics

https://www.vanagon.org/distributor-firing-order
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 - 11:41am

That lead goes to 3 (furthest from me)
If you pull the throttle with your head looking down the left carb you can see it squirt fuel in?

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Re: 71 Fast Back Recommissioning

Post by JackReddick » 11th May 2019 - 11:42am

The guy who was looking yesterday swears blind there should be a solenoid on the side of each carb which mine don’t have. Is this correct? Or is he maybe thinking of another year/model?

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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 11th May 2019 - 11:48am

Leads are correct then. Ill stand down!

Did you photograph the plugs when you had them out?

Next test take number 3 lead off the plug. Put a spark plug in the end of the lead, put the body of the plug on the block to earth it, have someone crank the engine of and check the spark.

Are they new plugs?

Yes you should see a squirt of fuel down each carb is you operate the throttle.
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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 11th May 2019 - 11:49am

JackReddick wrote:
11th May 2019 - 11:42am
The guy who was looking yesterday swears blind there should be a solenoid on the side of each carb which mine don’t have. Is this correct? Or is he maybe thinking of another year/model?
We have a winner! The solenoid your missing is the idle cut off. Its a little plunger which blocks the jet to stop fuel getting into the engine when you turn the ignition off. It prevents the engine from running on
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937carrera
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Re: 71 Fast Back Recommissioning

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

I would have expected there to be a cut off solenoid too (it stops fuel flow when the ignition is off)

Broady may just know the answer on that plug lead - if you swap 3 and 4 and it doesn't run, then can you get the engine to TDC for number 1 and let's see where the rotor arm is pointing
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 » 11th May 2019 - 11:53am

The left hand carb has got a massive air leak if you've got nothing in that hole.
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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 11th May 2019 - 11:55am

Lots of pictures of PDSIT32-34 carbs here, including the solenoid / cut off valves for you to compare to (I think that's what you have fitted)

https://www.ratwell.com/technical/DualCarbs.html
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 » 11th May 2019 - 11:56am

Image

Just to the left of the accelerator pump square that hole is where the cut of solenoid goes
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 11th May 2019 - 11:57am

937carrera wrote:
11th May 2019 - 11:55am
Lots of pictures of PDSIT32-34 carbs here, including the solenoid / cut off valves for you to compare to (I think that's what you have fitted)

https://www.ratwell.com/technical/DualCarbs.html
Theyre the type 4 version and has quite a few bits not featured on the type 3 version
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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 11th May 2019 - 12:01pm

Extensive discussion here too

viewtopic.php?t=11415
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 - 12:02pm

This is my left carb

Image

Image

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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 11th May 2019 - 12:06pm

937carrera wrote:
13th April 2019 - 9:40pm
I'm a type 4 owner so less knowledgeable on the type 3's
See, I did say I know nothing :)

The link I posted is referring to type 3 solenoids, with a source for NOS
David
1974 412LS Variant
1973 412LE 4 door Fastback / Saloon

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937carrera
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Re: 71 Fast Back Recommissioning

Post by 937carrera » 11th May 2019 - 12:08pm

What's that new shiny brass bit and the unconnected spade in picture 1 ?
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 - 12:11pm

937carrera wrote:
11th May 2019 - 12:08pm
What's that new shiny brass bit and the unconnected spade in picture 1 ?
The disconnected spade is for the choke. The shiny brass bit i assume has been fitted by the previous owner to block off where the solenoid should be? The right hand carb is exactly the same :paranoid:

If the solenoids you mentioned in that other post for the t25 fit from vwheritage, i’ll pop down there monday as they aren’t far from me

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broady_6
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Re: 71 Fast Back Recommissioning

Post by broady_6 » 11th May 2019 - 12:16pm

When you rebuilt the carbs, did you take that brass bit out?

Wiring wise, extend the wire from the choke around to the cut off solenoid when you fit them.

Yeah these will fit https://www.vwheritage.com/058129413e-i ... c-vw-spare
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