My 'New' 1973 412 with Engine Pics

[ClassicCamper]

I finally decided to get a 412! The first thing I want to do is get the motor running sound before I remove it for paint, detailing, and hopefully a Gilmore A/C compressor.

Here is what I've done so far:

Checked compression: 120-122 PSI in all cylinders
Points
Cap/Rotor
Adj. Valves
Replaced most hoses
Set timing

After all of this, the car starts right up, and is really quick upon acceleration for about 1 second. After that it bogs down. If you let it warm up for 10 minutes, it runs marginally better. If I let up on the accelerator from full throttle at around 40 MPH, the car will gain momentum/power.

So, I need to get a few obvious items out of the way prior to diving into that.

Hopefully, some of you can assist with 2 questions I have right off the bat:

The cold start valve had two wires connected to it:

Wire 1: is a brown splice that goes through the firewall with the A/C lines (under the MAP sensor). Not sure where it leads, assuming starter.

Wire 2: is a small white wire coming through a harness that is shared with the dizzy trigger points MPC.

Issue: The thermo-time switch isn't hooked up to anything and there is an additional white wire coming out of the same harness mentioned above which is dangling and hooked up to nothing. According to the Bosch wiring diagram, the thermo-time switch looks like it simply connects to the cold start valve, so I'm at a loss with that additional dangling white wire out of the same area.

Can anyone assist with some pics or description as to where/how those wires go?


One other question for now.

When I remove this hose:

There is so much vacuum coming from the plenum, I feel like it could suck a golf ball through the hose! If I put my thumb over it, the car stalls.

Is that a correct behavior? (Note: the smaller hose pictured plugs into the hole seen on the plenum where the aux air regulator is. The other end of that hose in this car leads to a vacuum throttle positioner of some type, I'll address fixing that later)

Here are some more pics:

The body of the car is straight with zero rust:

(distributor removed for cleaning or rebuilding)


Looking forward to this project. It's definitely going to be a challenging undertaking!

Ok, one other question: Can a type 2 Bus w/2.0 liter Cold start valve be interchanged with the T 412? The part number is the same except the 412 ends with an "A" and T2 ends with "B".

Thanks in advance.

[raygreenwood]

OK....I wont be able to address all of this right now an I am about to be on the road. I'll do what I can.

Its all little stuff...but actually its all huge stuff as far as D-jet goes. DO NOT DRIVE THIS CAR...until all the injection details are fixed...or you can destroy it.

Some details:

There are only 23 wires in the EFI system. They re all numbered at each end. Get a Haynes manual and take a look at the wiring diagram if you have not already. Wires you cannot figure out...check them by pulling the plug from the ECU and using a volt meter end to end.

OK....

1. The thermotime switch (TTS) is the ground for the cold start valve. A single white or brown wire goes from the TTS to either side of the CSV plug. The other terminal is a switched +...meaning when the ignition is on....its hot.
I am not close to my books but on some cars...I thought that the switched + that supplied the AAR also supplies the CSV. Either way it "can" if necessary

2. The large 12mm vacuum hose is supposed to have massive vacuum on it. That beige nylon nipple it is attached to on the oil breather is a PCV valve.
It is usually defective due to wear....and it was defective in design as it dumps into the manifold right next to the intake port for the MPS. As the engine ages and blow by increases it causes idle issues.

Many of us knock the plastic disc valve out of the PCV making it a straight through hole. Then install a piece of 13mm aluminum, brass or plastic rod into the 12mm hose. Drill a constant bleed orifice through the center of it....start with 3mm and that usually is fine.
So with a constant bleed PCV hole....its not enough of a vacuum leak that you cant adjust around it with the MPS and still maintain very good idle control with the screw on the TB. You get much smoother running and PLENTY of PCV.

3. The hose to the throttle kicker goes to a nipple on the right side of the plenum between the #1 and #2 runners. It also connects to a special plastic "Y" that connects to a spot on the TB underneath and to the hose that goes to the vacuum modulator on the transmission. Wait....let me check on this. I am going off of memory

4. You need to get a T-1 connector cover for that black to white wire in the picture near the fuel pressure regulator and the MPS. That is your cylinder head temp wire and its resistance sensitive.

More later. Ray

[ClassicCamper]

Thanks for the tips Ray.

No, I don't plan to be driving this until the FI is all buttoned up. My goal is to get it running sound and remove the motor for paint, etc.

[Lars S]

Welcome ClassicCamper!
Looks like a car with some potential!
About the compression 120psi sounds to be on the lower side to me (Im used to get 130-150psi) but compression tests are hard to compare since they wary due to battery condition, starter condition, engine temp etc and also your car might be of the California low compression type so everything might just be OK.

Longing to see more pics of the exterior and interior!


/Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold

[raygreenwood]

I would work on the suspension before worrying about paint. Ray

[ClassicCamper]

I agree. I mean painting the engine, not the car. The suspension and brakes will be next.

My strategy is to get the motor running very smooth by tuning the ignition and injection system. Then pull engine to paint/detail/fix minor things. Kinda like I did for my bug:

This will avoid banging about the engine compartment replacing, unplugging and troubleshooting FI system after I painted it. That will have been done already.

[ClassicCamper]

[Lars S]

[raygreenwood]

When you say paint the engine.....I would only paint the tin. Painting the engine block makes a mess of it eventually. Painting the air shroud can be done...but look around hard at technique and materials. There is a thread on thr shoptalk forums that is about this...meither in the type 4rum or 411/412 forums. Ray

By the way....glad you bought that car....nice ride!

[ClassicCamper]

Well now that I looked in the hole for the timing, it appears that the PO was using some type of large screwdriver to move fan around and a fin is broken. There was a cracked piece hanging there; I broke it all of the way off to avoid flying metal:

Does anyone have any leads on a replacement fan? I'm assuming that I can't use a 72+ T2 fan as the red timing mark would not be present. However, that's just a guess.

[Lars S]

Dont know how bad one single broken blade is but if you change the fan be sure you make your own marks for correct timing on it since there are a lot of variations.

There are quite a few fans for sale in the Classified-Parts section on TheSamba:

http://www.thesamba.com/vw/classifieds/search.php?...ywords=fan
http://www.thesamba.com/vw/classifieds/search.php?...ywords=fan


Lars s
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold