Fuel Injection Buses EEC Valve Repair

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Amskeptic
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Fuel Injection Buses EEC Valve Repair

Post by Amskeptic » Sun Aug 14, 2011 10:57 am

This is a commonly overlooked failure in the late fuel injection buses that happens to steal all of your vacuum advance as well as increase the smell of fuel vapors in the engine compartment.

The EEC valve was an evolution of the technology required to trap fuel vapors from the fuel tank. Since 1970 or so, Volkswagen merely plumbed the fuel tank vapors to a charcoal canister that was force-fed fresh air from the fan and dumped its vapors into the air filter any time the engine was running. Unfortunately, the need to reduce hydrocarbons rendered this simple system inadequate, particularly after a heat soak where gas vapors just spiked those HC emissions through the roof and made the car run too rich when first started.

VW decided to meter the fuel vapors into the engine through a valve, the EEC valve, so that these extra HCs would only be added during high airflow periods, and what better time than at full vacuum advance? A tee off the vacuum advance hose pulls the EEC valve diaphragm from its spring-loaded seat, thus allowing fuel vapors from the canister to enter the air filter body.

Problem is that fuel vapors and rubber diaphragms don't get along too well, and the diaphragm gets dried out and brittle. When it leaks, the vacuum advance vacuum signal disappears. To test, remove the vacuum hose to the EEC from the vacuum advance tee and apply vacuum to the hose. This looks odd and unsettling to the passer-by. It should hold, and you can sometimes hear the diaphragm clunk. If it just passes air, well, try this procedure:

1) Remove air filter cover by releasing the clips and pulling out of the engine compartment. You can leave the AFM side of the air filter in. Place on a counter, VW thoughtfully provides one just above the engine. With several small flat-bladed screwdrivers, gently pry the outside ring of the plastic housing out from the inner circle of the EEC valve, You will see six or so plastic tabs cast into the plastic housing that snap the circle in place. Be nice here. Work it. Pry and pry, just get things loosened up a bit. Do not turn the screwdrivers as this will make it look like beavers have been chewing in there. After you have gotten irritated, focus on one side of the circle and get the screwdrivers all lined up and go for the final snap-out free push. I found three screwdrivers all pried simultaneously on one side finally released the inner circle.

2) Repair the diaphragm:
Image
Like a speaker, it has an outer suspension "gutter" where you will find cracks and maybe a split. Clean off the glycerine that VW hoped would protect the rubber. I used carb cleaner and a paper towel. Dry thoroughly. Smear a thin layer of Permatex Ultra-Black RTV into the gutter all the way around the circle. Work quickly so the RTV doesn't start to set and pull up with your finger. Keep it thin but contiguous. Clean any excess RTV off the outer perimeter where it sets in the housing, this is important for a vacuum-tight seal. Allow to set for a full 24 hours. Clean the housing making sure the diaphragm seat is perfectly smooth both where it contacts the openings and at the perimeter.

3) Set in the opening flat center facing down. You can see the repaired area:
Image


4) Place the plastic disk on the diaphram with the spring seat facing up.
Image

Here it is just sitting there, waiting for a spring:
Image


Look, there is the spring, now:
Image

5) Now carefully clean the perimeter of the valve housing where it is going to snap in the air filter housing. Use a patented IAC razor blade technique to make a perfectly square edge that is smooth all the way around the perimeter. Use a light coating of grease on the valve where it will contact the diaphram and along the edge so it will snap under the moulded clips of the air filter housing:
Image

Press the valve housing over the diaphragm/plastic disk/spring (with the word "Knecht" facing directly towards the canister nipple, if you care about such things):
Image

Test for vacuum. It should now hold. Reinstall air filter housing making sure you have a perfect seal between the filter media and the cover as you snap down the four clips. Reinstall the charcoal canister hose and the vacuum hose from the vacuum advance tee. Now you can test with a feathered throttle at 3,000 rpm to see that you get 36-40* vacuum advance.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 93,996 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

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airkooledchris
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Re: Fuel Injection Buses EEC Valve Repair

Post by airkooledchris » Thu Dec 27, 2012 2:37 pm

thank you for this excellent write up!

was this unit put into use after this repair? If so, did it hold up?

was the black RTV only applied to the top/outside of the valve, or also applied to the inside/inner layer?


this is the state of the unit im working on currently:
Image
1979 California Transporter

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Amskeptic
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Re: Fuel Injection Buses EEC Valve Repair

Post by Amskeptic » Thu Dec 27, 2012 4:22 pm

airkooledchris wrote:thank you for this excellent write up!

was this unit put into use after this repair? If so, did it hold up?

was the black RTV only applied to the top/outside of the valve, or also applied to the inside/inner layer?
Looky here, Mildred, somebody done come to our store finally . . .

Yes, please repair both sides of the damaged area. RTV needs as much surface area as you are willing to provide. Thin and broad will help maintain the necessary pliability and will help keep the RTV bonded to the diaphragm.

My August 2011 repair is holding up well in the BobD.
ColinCan'tWaitForSummer
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 93,996 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

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airkooledchris
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Re: Fuel Injection Buses EEC Valve Repair

Post by airkooledchris » Wed Jan 02, 2013 4:07 pm

Thanks Colin! The repair is holding up fine in it's initial test. Ill put some miles on it and report back if it ever fails.
1979 California Transporter

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Re: Fuel Injection Buses EEC Valve Repair

Post by Jivermo » Fri Jan 25, 2013 1:32 pm

After unsettling several passersby, I determined to repair my EEC diaphragm, of which I was certain was faulty. Sure enough, when I pried the cover off, I found the rubber cracked and holed in several places. It's repaired now, thanks to this informative and instructive "how to". This got me wondering about what the demand would be for a new, reproduction rubber diaphragm. I'm sure some of you are familiar with this "parts printer": http://www.jaylenosgarage.com/extras/ar ... d-parts-1/ I think that the time is not too far off when we can get some of these NLA bus parts recreated at reasonable prices. It can't come too soon!

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Re: Fuel Injection Buses EEC Valve Repair

Post by airkooledchris » Fri Jan 25, 2013 3:34 pm

don't forget to check your work after some miles. I repaired mine and it seemed to be holding up OK, but after a few hours on the road it developed a very small leak again.
I haven't cracked it open yet to see how bad it looks on the inside, just want to remind people to double check it after a while, and once in a while, to be sure it holds up well.
1979 California Transporter

Reid
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Re: Fuel Injection Buses EEC Valve Repair

Post by Reid » Fri Jan 25, 2013 5:39 pm

Someone is making them. I ordered a new S tube from someone selling them on ebay, and it came with the new diaphragm stuffed inside. I've had it in the pocket of my jacket for weeks. If I ever get around to installing it, I'll report back.

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Re: Fuel Injection Buses EEC Valve Repair

Post by Amskeptic » Sat Jan 26, 2013 4:46 pm

Jivermo wrote:After unsettling several passersby, I determined to repair my EEC diaphragm, of which I was certain was faulty. Sure enough, when I pried the cover off, I found the rubber cracked and holed in several places. It's repaired now, thanks to this informative and instructive "how to". This got me wondering about what the demand would be for a new, reproduction rubber diaphragm. I'm sure some of you are familiar with this "parts printer": http://www.jaylenosgarage.com/extras/ar ... d-parts-1/ I think that the time is not too far off when we can get some of these NLA bus parts recreated at reasonable prices. It can't come too soon!
That is remarkable. Let's scan some heads, pistons, cylinders, hell the whole thing, let's go let's go let's go . . .
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 93,996 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

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Amskeptic
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Re: Fuel Injection Buses EEC Valve Repair

Post by Amskeptic » Sat Jan 26, 2013 4:50 pm

airkooledchris wrote:don't forget to check your work after some miles. I repaired mine and it seemed to be holding up OK, but after a few hours on the road it developed a very small leak again.
I haven't cracked it open yet to see how bad it looks on the inside, just want to remind people to double check it after a while, and once in a while, to be sure it holds up well.
Chris, as the author who doesn't want to write procedures that end in dead-ends, I have to ask:

what was your cleaner?
what was your cleaning procedure?
what was the dry time?
what was your rtv?
how thick, both sides?
what was the cure time?
did you use the razor mill technique at the flanges?
grease on perimeter?
were the plastic "snaps" damaged?

BobD's last trip, still holding vacuum.
Colin :scratch:
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 93,996 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

Jivermo
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Re: Fuel Injection Buses EEC Valve Repair

Post by Jivermo » Sun Jan 27, 2013 8:21 am

I'll contribute to this: Although I have only about 25 miles on my repair, it is holding vacuum well. I cleaned the diaphragm with dishwasher detergent several times to get the glycerin jell off, and let dry in the sun completely. I used the Permatex Ultra Black you recommended-dried about 28 hours before installation. Spread it about the thickness of a dime in most places...tried to be consistent, but it is difficult to get it evenly. Some places was a bit thicker, or thinner. I "patched" the opposite side in areas that showed cracks or where the actual split was. I did the razor scrape and cleaned that part well-also cleaned the groove on the housing where the edge of the diaphragm rests. Used vaseline as the grease-on both the perimeter and the well surface. Plastic snaps were all intact, and the seal appreaed very good to the eye when it snapped in. I spread a bit of vaseline around the groove after I snapped it in. If anyone can recall where the source is for the rubber diaphragms, I would really like to order a couple as backups.

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Re: Fuel Injection Buses EEC Valve Repair

Post by Amskeptic » Sun Jan 27, 2013 9:51 am

Jivermo wrote:I'll contribute to this: Spread it about the thickness of a dime in most places...
If the diaphragm is available (in high quality), that would be best repair (maybe).
A dime's thickness is a bit heavy, but if it is working, what the hey. I did "paper" thin but spread broadly for traction with the rubber.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 93,996 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

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airkooledchris
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Re: Fuel Injection Buses EEC Valve Repair

Post by airkooledchris » Thu May 02, 2013 9:17 am

Amskeptic wrote:
airkooledchris wrote:don't forget to check your work after some miles. I repaired mine and it seemed to be holding up OK, but after a few hours on the road it developed a very small leak again.
I haven't cracked it open yet to see how bad it looks on the inside, just want to remind people to double check it after a while, and once in a while, to be sure it holds up well.
Chris, as the author who doesn't want to write procedures that end in dead-ends, I have to ask:

what was your cleaner?
what was your cleaning procedure?
what was the dry time?
what was your rtv?
how thick, both sides?
what was the cure time?
did you use the razor mill technique at the flanges?
grease on perimeter?
were the plastic "snaps" damaged?

BobD's last trip, still holding vacuum.
Colin :scratch:

Im sure it was in my process somewhere, but I missed this post until now and can't confirm it any longer. Sorry. I'll have it here for inspection, but it wasn't my primary anyway (which works) and I now have a second working one as well. For the time being I plugged the one I did this repair to. Looking back I think there were just too many (and too big) cracks to be able to patch, or I may have needed to use the black RTV a little more sparingly so it couldn't crack as easily.
1979 California Transporter

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Re: Fuel Injection Buses EEC Valve Repair

Post by Jivermo » Thu May 02, 2013 4:13 pm

Colin was by for my Itinerant Seminar last week, and noted that the repair job on my EEC had failed. He mentioned that someone was making the diaphragms again, but did not recall the supplier. Does anyone know who it is?

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Amskeptic
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Re: Fuel Injection Buses EEC Valve Repair

Post by Amskeptic » Fri May 03, 2013 10:05 am

Jivermo wrote:Colin was by for my Itinerant Seminar last week, and noted that the repair job on my EEC had failed. He mentioned that someone was making the diaphragms again, but did not recall the supplier. Does anyone know who it is?
I have checked only some sources so far and cannot find it. I hope it wasn't my brain recording this thread as "someone is making them." If *you* find a source, let me know and I will put it in this forum's "Parts Known To Be Acceptable."
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 93,996 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

Reid
Getting Hooked!
Location: Birmingham, AL
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Re: Fuel Injection Buses EEC Valve Repair

Post by Reid » Fri May 03, 2013 11:05 am

I have one that I bought from a guy on ebay with the username sell2ship. The guy typically sells lots of Unimog parts, but he had several new S boots with the valve stuffed down inside the boot. The boot looks like the mold was made from a cracked S tube, but the valve looks like a clean copy.

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