1980 Vanagon - Troubleshooting a well running engine

[vwlover77]

The main timing advance comes from the mechanical advance weights inside the body of the distributor, and they can get gummed up. A quick check: Remove the distributor cap, grasp the rotor, and turn it clockwise. It should twist easily until it hits its stop and then smoothly and quickly spring back to its original position when you let go.

On all the VWs I've ever had with shift points on the speedometer (including water-cooled) the markings were always max speeds. My old '4-speed 77 Rabbit had shift points on the speedo at 30, 50, and 75mph and they were definitely the redline!

[Saylrman64]

Thus the problem.
If I ait red lining her she don't got enough guts to go to the next gear if i'm aimin for a mere 60mph.
First to second no problem.

[vwlover77]

I'm betting on a gummed-up distributor advance......

Remove the distributor.

There should be a small access plate on the side of the distributor body. Pry it off and rotate the rotor. You will see the advance weight mechanism pass by the window. Spray everything you can get at through the window with WD-40 to get the gunk off of it and let it drain out. Place a few drops of oil on the wick in the center of the distributor shaft (under the rotor).

Reassemble and feel your Bus fly! (I hope!)

[Bleyseng]

I agree that you should attack the faulty advance on the dizzy. But take it all apart as I bet the advance plate is gummed up. It rotates and the original grease slowly becomes like thick glue. Take the advance plate apart and clean it spotless. Then re assemble the dizzy with a touch of lite grease here and there to lube fiction spots in the dizzy.

You should have smooth advance now and check it with a timing light. The mark should advance smoothly and to full advance at 3500rpms.

Idle vacuum should be 15hg so if you have less its a few small problems.

did you check the condition of the cam?? a worn out cam can cause low vacuum as do worn out lifters. This is because of crappy valve timing due to worn out parts.
12-13hg is barely ok but the engine should still make power.

[dingo]

You should have smooth advance now and check it with a timing light. The mark should advance smoothly and to full advance at 3500rpms.

Idle vacuum should be 15hg so if you have less its a few small problems.

I just checked my vacuum and it reads 20hg at idle (about 1000rpm)....the timing looks to be about 9 deg (frankly it could be anywhere between 7-10..given the inaccuracy of markings on scale and pulley)

so does this mean im too far advanced at idle ? It feels fine when i pull away from idle..but ive noticed that when i take the rpms up, it goes well past 36 deg maybe even 40deg...this is with vacuum attached

sorry to hijack thread..but it seemed a good time to check things out

also: from dead cold, it takes like ten cranks to start. From even slkightly warm, like 30 secs running, it will start right away. I have checked the cold start valve..it gets 12 V and i can it clicking on. T2 sensor reads 2700 Ohms at about 50deg..what else should i be looking at ?

[Bleyseng]

To check the timing at full advance you pull and plug the vac adv line.
You should then time it to 28 degrees at 3500rpms.

Look at the timing mark and how it moves...it should advance (move) smoothly and the mark should be nice and steady. It should not be jumping around not a 1" blur.

[Saylrman64]

Valve adjustment does not require splitting the case. Remove the valve covers and you are right there.

The statement was "Valve Timing" not Valve Adjustmet".
To change valve timing you do need to split the case.
It would also mean whoever put this thing together screwed it up big time.
The guy I got it from ran the wheels off it. There is no way this thing has been running for xx,000 miles with late vale timing.
I do believe valve "Timing" is out.

[Amskeptic]

I do believe valve "Timing" is out.

Are you familiar with overlap? Turn the engine over by hand, with a Vanagon it is sometimes easier to put in 4th gear and just roll the car by shoving against the left rear tire. Why left rear tire? Because you will be looking carefully at the #3 rockers. When the exhaust valve is closing and the intake just begins to open, find the point where both are the exact same distance from closed. Then check your scale hidden under all the crap through the the license plate. If the timing mark on the pulley is at or near 4* ATDC, your valve TIMING is OK.
Colin

[Saylrman64]

Idle vacuum should be 15hg so if you have less its a few small problems.

did you check the condition of the cam?? a worn out cam can cause low vacuum as do worn out lifters. This is because of crappy valve timing due to worn out parts.
12-13hg is barely ok but the engine should still make power.

Where did you get the "15hg" from.
I cannot find an accurate "from the book" number anywhere.
All of my years and all the gauges I've seen indicate somewhere around 17-22 is normal unless you've installed a cam or are running a race engine with other stuff going on.
Well this wagon aint no race mobile!

OK that's it, Nobody say Vacuum without preceding it with words like "My Bentley manual says..." and followed by a number greater than 15.

My Factory manual only indicates vacuum advance specs and Bleyseng was pretty right on.
I verified my advance starts when the book says it should at about 1000rpm. (Like Dingo's)
And it continues on through 40 degrees (again like Dingo's)
Very smooth too.

Now to tally the clues:
Torn down to the cylinders. Inspected and reassembled.
Did not split block or pull connecting rod lower bearing.
This is a smooth sounding and smooth running engine except;
Vacuum is stuck at a clean steady 12 or 13.
She idles radical and low until real warm. Maybe even dies once or twice.
Note: The last guy to work on her removed the air dampener designed to keep air from circulating across the heads until warm.
Idle fluctuates about 900 to 950. (Maybe that is normal)
No top end power.
Plenty of low end (in town, off the light)
Today I swilled out fuel tank (yes, removed, cleaned, replaced)
New fuel filter
Have swapped out;
ECU
Air Intake Sensor
Wiring harness
Cold start valve (has nothing to do with idle)
Thermo time switch (has nothing to do with idle)
Deceleration valve (has nothing to do with idle)
Series resistor
Coil, cap, rotor, wires, points, condenser.

Still need to swap out Fuel pump, fuel regulator and double relay.

So far all we have is the vacuum guide indicates it may be;
Late timing - It's Not!
Compression - I tested twice and have 140 to 145 on all.
Manifold leak - The most likely suspect for the idle and vacuum but not the top end.

And lastly, Bleyseng added the possibility of a bad or work cam.
So far this is the most logical since I really really think there is no intake leak.
And unfortunately I believe this would actually account for both the idle and the lack of top end.
Valves not opening all the way can't allow a full cycle of "in with the good, out with the bad"

So for those of you not asleep after reading this, tell me why I shouldn’t order a long block tomorrow?

P.S. Dingo, My spare T2 reads 2000 and it's on the back porch in 70 degrees.
Also, from the little you disclosed, if you have a manual trany, you're idle should be 800 to 950 and the timing 7.5 degrees. I be if you give the whole thing a little love it will start quicker. Ya know, gap the points, clean the cap, etc.

Anybody wana buy an engine?

[Saylrman64]

If the timing mark on the pulley is at or near 4* ATDC, your valve TIMING is OK.
Colin

Now there is some useful information!
I gota ask, why no. 3 and not no. 1? And how did you get 4*
And to answer my question (I think). It wouldn't matter which cylendar I watched the result should be the same.
And to be clear, we want both rockers in the most relaxed state.
Thanks!

[Bleyseng]

The 15hg is a average number for a good motor, brand new with stock cam will be higher in the 15-20hg range.
Lower than 15hg means there is a problem ie: vacuum leaks or worn cam/ gear/lifters as you noted the crappy slop of worn parts produces low idle vacuum. Remember a engine is a pump!

Aftermarket cams with their different valve timing will also produce weak idle vacuum. this is one of the drawbacks of these cams and then to adjust the FI to still have good idle.

[Saylrman64]

OK but where did the 15hg come from? A book or years of playing with these things?
I need "the" number. I am wasting my life chasing something I don't know if it exists. A vacuum leak or bad cam or towing cam?
If 15 is true and I have stock cam I have problems.
If I have a towing cam (the last guy mabe put it in) then that would explain the poor idle.
But where did my top end go?

The more I think about it, If 20 it ideal and it is an air leak, where does 7 inches of vacuum get let in?
Again, I'm not new to this. I really believe I have chased down all leaks.
That's a pretty good leak.

I may just drag out the air compressor and go try the pressurizing the intake system.
I still need to verify the valve timing. Tnight!

But! If we keep coming up with worn cam, lifters etc.
Will that keep me from getting any top end power to get onto the freeway?

[Bleyseng]

The first thing to look at if there isn't proper power is checking the Dizzy. Improper advance, sticking advance, improper timing is usually the cause.
Breakdown the dizzy and clean and lube it carefully so the advance plate operates smoothly.

Vacuum leaks occur everywhere so testing via a leakdown test is one thing but a careful check of all the usual places is in order. Injector seals is a big one, manifold gaskets, etc all need to be prefect

[Amskeptic]

OK but where did the 15hg come from? A book or years of playing with these things?
I need "the" number. I am wasting my life chasing something I don't know if it exists. A vacuum leak or bad cam or towing cam?

The air-cooled VWs with vacuum retard can expect idle vacuum readings hovering around 10-11 in/hg. These include all VWs since 1971 until FI reached the entire line-up. California buses went back to vacuum retard briefly, and these engines will have low idle vacuum.

If 15 is true and I have stock cam I have problems.
If I have a towing cam (the last guy mabe put it in) then that would explain the poor idle.

I think that is highly unlikely. The most common cause for low power in a Vanagon is camshaft lobe/lifter flattening. Who has tested their lifters for convex contact surfaces recently? If you butt any two lifter bottoms together between your eyeballs and a bright light, you should see an ifinitesimal crack of light at the outer edges of the lifters. The lobes can be tested by a dial indicator reading valve lift at each and every valve on one side of the engine. You are not interested so much in the actual numbers as you are variations between all exhausts or all intakes. Vanagons with low power can also have receding valve seats. This can be measured with a machinist's straight edge across the entire bank of valves on each side of the engine: ex. when 2 is at TDC power stroke, the right side of the engine can be measured, and when 4 is TDC power stroke, the left side of the engine can be checked for all valve stem tips at the same level. Any sticking up? Receded valve seat.

Again, I'm not new to this. I really believe I have chased down all leaks.
If we keep coming up with worn cam, lifters etc.
Will that keep me from getting any top end power to get onto the freeway?

I am not new to this either, and I still get tripped occasionally. Remember that L-Jetronic is sensitive to dipstick leaks, breather box leaks (Vanagons have a nice nasty little piece of round plastic that loves to crack along the seam on top of the breather, check it carefully. . . . valve cover gasket leaks, front seal, rear seal leaks, injector seal leaks, intake manifold/gasket leaks (man, I have seen some winners even on fresh "careful" installations) and my favorite mystery low vacuum cause. . . . Sloppy Valve Guides Even On "Fresh" Heads*. Although the breather system is supposed to keep that all within the "measured air" area, in real life, worn intake valve guides exacerbates all the minor little crankcase air entry points because they will help make the crankcase a negative air pressure environment. . . at the expense of your vacuum readings. Worn exhaust guides can pressurize the rocker box area and join the rings in causing positive pressure in the crankcase. . . assuredly unmetered air. 15in/hg, by the way, is fine for a Vanagon Type 4 at idle. It is far more important that you read a strong 20 in/hg on overrun. That means you rev it to 3,500 rpm, when you release the throttle it should snap the needle up to 20-22 in/hg.
Colin
(*so many machinists are loathe to replace valve guides, that they will either knurl your old ones or lie to your face)
(your brakes are NOT dragging and the tire pressures are extremely correct)

When you finally get pissed, crank the AFM sweeper adjustment under the black box cover one full tooth (that's the static adjustment that affects the entire fuel map) counter-clockwise. Go drive. How did it do?

[Saylrman64]

Thanks AmSkeptic. This is great stuff but I need a little clarification on a couple items.
Read on....

The air-cooled VWs with vacuum retard can expect idle vacuum readings hovering around 10-11 in/hg.

What is vacuum retard?

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The most common cause for low power in a Vanagon is camshaft lobe/lifter flattening.

So are you saying that flattened lobes or dished lifters could be why I am missing my topend?

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Vanagons with low power can also have receding valve seats.

Wouldn't I have noticed this when I had the heads of for inspection?

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When you finally get pissed, crank the AFM sweeper adjustment under the black box cover one full tooth

Which goes one full tooth counter clockwise? The wiper arm or the black disk?
To keep it simple, am I tightening the spring or loosening?

Thanks!