82 vanagon bucking at 3000 rpms

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Randy in Maine
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Re: 82 vanagon bucking at 3000 rpms

Post by Randy in Maine » Wed Aug 24, 2016 9:26 am

I was thinking the small vacuum line that opens and close the valve.
79 VW Bus

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SlowLane
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Re: 82 vanagon bucking at 3000 rpms

Post by SlowLane » Wed Aug 24, 2016 10:09 am

The air-cooled Vanagons didn't have EEC valves, neither Federal nor Cali. The water-cooled ones did, but it was a separate piece from the air cleaner and was called something else by then, so a search for EEC and Vanagon won't turn it up. I have retro-fitted the later valve on my van. Not sure if it truly has any effect, but it's a feel-good thing.

I'm pretty sure the 1/2" hose MountainHide is referring to is the hose from the charcoal canister to the air cleaner. There is no valve interrupting that connection.

Oh, and apologies if I came across as irascible earlier. Sometimes the inner curmudgeon demands to be let out.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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MountainPrana
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Re: 82 vanagon bucking at 3000 rpms

Post by MountainPrana » Wed Aug 24, 2016 12:09 pm

SlowLane wrote: I'm pretty sure the 1/2" hose MountainHide is referring to is the hose from the charcoal canister to the air cleaner. There is no valve interrupting that connection.
MountainPrana was referring to the hose, trying to learn what I can about all this stuff, but not trying to detract from the conversation! :flower: Thanks for clarifying that the charcoal canister has no valve, I've been wondering about it. Sounds like it wouldn't be affecting MountainHide's bucking at 3,000 rpm.

Tim

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SlowLane
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Re: 82 vanagon bucking at 3000 rpms

Post by SlowLane » Wed Aug 24, 2016 12:58 pm

MountainPrana wrote:
SlowLane wrote: I'm pretty sure the 1/2" hose MountainHide is referring to is the hose from the charcoal canister to the air cleaner. There is no valve interrupting that connection.
MountainPrana was referring to the hose, trying to learn what I can about all this stuff, but not trying to detract from the conversation! :flower: Thanks for clarifying that the charcoal canister has no valve, I've been wondering about it. Sounds like it wouldn't be affecting MountainHide's bucking at 3,000 rpm.
Whoops, my bad. All you Mountain Men look alike from here. :geek:

No, I don't believe it's related. Randy was trying to point out the easily-overlooked vacuum leak that a busted EEC valve will cause on an EEC-equipped bus. I believe the vacuum hose to the bus EEC valve is supposed to have a restricting orifice in it which would hopefully limit the effect of such a leak. The Bentley for Vanagon does show such an orifice for the valve on the water-cooled models.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

cegammel
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Re: 82 vanagon bucking at 3000 rpms

Post by cegammel » Wed Aug 24, 2016 2:12 pm

Dang it! Now mine is bucking! Contagious Vanagon disease....

luftvagon
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Re: 82 vanagon bucking at 3000 rpms

Post by luftvagon » Sat Aug 27, 2016 4:50 pm

I love the bucking bronco issue. Once or twice I logged the bucking behavior, and it was fueling related, or lack there of -- but it could also be no spark. As always, picture of the engine bay to start with, vacuum at idle? vacuum leaks usually wreck more havoc on idle than mid, and wot. fuel pressure good? AFM track good and consistent? cabling good, and resistance free? TSII firmly grounded? AFM tightly plugged?
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

luftvagon
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Re: 82 vanagon bucking at 3000 rpms

Post by luftvagon » Sat Aug 27, 2016 5:08 pm

One thing to note with L-Jetronic, your van will start and idle with no AFM voltage, and it will run at load even with intermittent voltage, but it will usually buck; An example of this is if your AFM potentiometer track has dead spots. This can be bench tested with ignition on, and manually moving the wiper through entire range, and observing the voltage on the pin out.

Another thing that could be causing intermittent bucking are FCU grounds (usually under the intake plenum), or the main ground strap.

The next thing to be on the look out would be the double relay. I personally suggest getting rid of it, and making your own using newer parts. An easy item to replace -- or buy a new one for $70 -- or build your own for under $10 - two relays, two pig tails, and some red and black 16 gauge wire, and a diode or two... hell, throw in a few LEDs (and resistors) for easier diagnostics. It wont hurt to check and clean fuel switch inside AFM either.

Now the van will absolutely not run with infinite resistance on the TSII, or simply said, if the TSII is wiggling and losing contact with the engine ground, it will cause the engine to not deliver any fuel. Just disconnect the TSII and try starting your van. It may start for a brief second due to residual fuel or cold-start valve.. but that's about it. It is the Achilles heel.

Timing wise? Ignition coils do go bad, and so do points, and Pertronix... but usually those things would become evident at all RPM, sooner or later.

Fuel delivery vise? See Colin's threads.. could be deliver problem at higher RPM.. but that also becomes evident at lower RPMs, sooner or later.

Wiring? Resistance goes up with heat, so, in that case, if everything checks out, and you still cant find it.. and it only happens on hot engine, this would be another place to look at....

And then there is the ECU. When you go through the entire FCU troubleshooting guide (which is very easy to follow, and 100% complete -- it will point you to the fault), it is the last thing in the document. Check and replace FCU with a known good item.

Good luck, please dont forget to tell us how it went.

Luftvagon,
The Bucking Vanagon Self Proclaimed Expert
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

cegammel
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Re: 82 vanagon bucking at 3000 rpms

Post by cegammel » Sat Aug 27, 2016 7:02 pm

Oooooo...Luftwagen says smart stuff. I want to know more about this home-made fuel pump relay. I spent $110 on a new one, btw...

luftvagon
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Re: 82 vanagon bucking at 3000 rpms

Post by luftvagon » Sat Aug 27, 2016 7:10 pm

1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

Mountainhide
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Re: 82 vanagon bucking at 3000 rpms

Post by Mountainhide » Wed Aug 31, 2016 10:26 am

Yes it does. I hooked up a vacuum guage today and I'm running 9". I got some carb cleaner and sprayed it down everywhere needed and the vacuum never changed. Going to the shop tomorrow.

luftvagon
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Re: 82 vanagon bucking at 3000 rpms

Post by luftvagon » Wed Aug 31, 2016 8:40 pm

Save your pennies, fix the problem yourself.

https://www.thesamba.com/vw/archives/ma ... Manual.pdf
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

luftvagon
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Re: 82 vanagon bucking at 3000 rpms

Post by luftvagon » Wed Aug 31, 2016 8:43 pm

Track "Engine Misfiring", and you will find your fault:

https://www.thesamba.com/vw/archives/ma ... r_1974.pdf

You do need to print this double sided to make it easier to read. Otherwise, you will struggle to go through the PDF.
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

luftvagon
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Re: 82 vanagon bucking at 3000 rpms

Post by luftvagon » Wed Aug 31, 2016 9:07 pm

Sometimes, we just want Internet to tell us whats wrong, and that magically replacing that one part will resolve the issue. I am totally guilty of this. The best advice I can give you, is to use the troubleshooting guide (yellow book) to systematically approach the issue - ENGINE MISFIRING (which is evident through a feel of bucking or lurching), and then use the AFCU manual to examine components in greater detail. I have no doubt that you will isolate your issue within one day. You will need a few simple tools, and a good analog (and digital) multi-meter.

I have been in your shoes, and I feel you... but the worst thing you can do now is take it to a shop, and rob yourself of the know-how, and credit of getting it fixed. These primitive fuel "computers" are primitive to say the least, and unfortunately they wont give you an answer unless You look for it. It's there, waiting for you to discover it.

I only gave up on my L-Jetronic , after going through this guide many times, and refusing to believe my "FCU" could be bad. At first I thought I fried my unit during troubleshooting, only to find out my unit still had water condensation, and water corrosion. I purchased another working ECU, but decided it would not be worth investing more time. Looking back, I could have easily rebuilt entire system, whilst eliminating double relay, injector resistor pack, and AFM to MAF conversion... but fun is that.

Looking forward to reading about your progress.. Please post some pictures so that we get a better sense of "state of maintenance".
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

luftvagon
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Re: 82 vanagon bucking at 3000 rpms

Post by luftvagon » Mon Sep 05, 2016 4:49 pm

:bounce:
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

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Amskeptic
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Re: 82 vanagon bucking at 3000 rpms

Post by Amskeptic » Tue Sep 06, 2016 9:45 pm

luftvagon wrote::bounce:
Where'd he go?
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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