Return of bucking. A jinx and a curse? Solved!

[Lanval]

I wish I could get to it right now, but I have to meet a deadline.

Yeah. Real life. Getting in the way of my priorities since 1968.

You're doing what you can with the time you have. No one here can ask more than that.

So. If it's virtually un-reproducible when stationary, I'd be very interested to hear what you were doing exactly when you did manage to reproduce the bucking... I also think you're description points to fuel flow, but there are a few other things to consider even so.* When you do get it to buck, is throttle maxed?

Additionally; when you're driving on the road and it bucks, does the engine smooth out when you go off the throttle? Does it stop bucking when: throttle off (coasting) but in gear? throttle off (coasting) and out of gear (neutral)? Does it buck regardless of either throttle or in/out gear?

I'm also still wondering about the camping trip... was it unusually dry when you drove to the camp? Since you mentioned it being humid, I still wonder about the ECU. I jumped through a lot of hoops before I finally replaced the ECU in my vanagon (no start issue). My vanagon still bucks for the first 5 minutes of driving when it rains here. Doesn't matter if it rained overnight and it's dry now, or it's raining at the moment of driving. In either case, bucking 'til it starts to warm up. This would suggest a dicey connection somewhere. However, since I live in the SW desert, it's not much of an issue. If I moved to somewhere rainy (Oregon, my old home) or humid (Midwest/East Coast) I've wondered if the problem would be more constant, like yours.

Best,

Michael L

[aopisa]

Just a quick update.

I found time to install the new fuel pump last night. Figured it would be a 20 minute job or so. Due to my very thorough ineptness as a mechanic, I had it installed 2 hours later in 90 degree heat after a series of mishaps, a lot of very loud cursing and yet another unexpected gas bath. So, no problem with flow from the tank and the fuel filter when cracked open looked clean as a whistle as it always does.

The test drive around the neighborhood did not produce any bucking. That proves nothing as the bus has now been sitting for a few days so I expected it to be on its best behavior.

Today is forecasted to be in the mid-90's so we will see what happens after I get it really warmed up. I must admit I am a bit hesitant to take it out too far after getting myself stuck the other day. This bus has gone from being a strong runner I had a lot of faith in to something I lack any confidence in at all.

Lanval- If bucking returns, I will answer all of your questions in as much detail to the best of my ability.

Thanks and stand by for further updates.

[Lanval]

Sits back with a frosty cold soda, and awaits, patiently, a reply of which he is, in all manner, unworthy.

[luftvagon]

There is only so many things it could be. I listed almost all of them. If checked and ruled out, it is time to move onto FCU/ECU.
Did you re-check your Temp Sensor II? If it is loosing ground, it is instant stop.

There is an old video card trick you could try. You could always bake your ECU/FCU (opened and exposed) for 8 minutes at 385°F.
Guys bake their video cards when solders start loosing contact. It may work on the FCU, or it may completely destroy it.
If not, you could always try to buy one. Either way sucks.

Huh, I should make a bench tester for the stock FCU.

[luftvagon]

Here is some more reading material:

http://x19.xwebforums.org/wiki/images/e ... Manual.pdf

and

http://www.thesamba.com/vw/archives/man ... r_1974.pdf
(You will have to print it)

The AFC manual is the bible of L-Jetronic, and it is what helped me troubleshoot my issue.

Now.. if you scroll to "Engine Misfiring", you will also notice they talk about alternator and regulator. There is voltage compensation that occurs.... something to ponder. ...

[luftvagon]

Here you go:

[aopisa]

So it was not the fuel pump as I thought that would have been too easy.

Drove into town with no problems. Ran an errand at the hardware store. Upon leaving the hardware store (heat soak?), real problems developed. This issue has gone from mildly annoying bucking to basically can't drive condition. Barely made it to a parking lot to do some checking. Swapped in the new coil since that was next on the list. No dice.

It seems to idle fine, but now the problem can be reproduced standing still while the throttle is advanced when before is was only under load. This results in an almost total loss of power when on the road. After sitting in the parking lot for a few minutes, I started it up and was able to drive nearly trouble free to the ex-wife's house. Let it sit for over an hour, tried to drive home, but had to turn around and pretty much gun it back to her house.

Here is a video that I took, which will probably not help too much:



I hope to let it sit a while longer just to see if I can get it home and in the garage later today.

I do not have much time for much of anything else at the moment. I am away all day tomorrow and it looks like my week is pretty full.

Randy in Maine was kind enough to let me borrow a spare AFM and his LM-1. If anyone thinks that this is where I should be focused, I will try my best to work on it as I want to get his things back to him soon.

IAC day is not until October 3.

Thanks again,

Tim

P.S. In an effort to see if I could get my glowing alternator light to turn off, I installed a new BERU GERMANY made in China (as stated on the box) voltage regulator. Did not work AT ALL. Alternator light was a steady bright red with it installed.

[luftvagon]

That's exactly what mine was doing. Did you follow the flow chart from above? Did you check TSII to see if it is grounding at the connector? Is it tightly screwed in? Does the fuel flow freely when it does that?

Time to open that FCU and send some pictures to see visually if there are any issues.

[aopisa]

Not exactly. I have done many of the things on the checklist, but want to start at the top and work through it methodically. I have checked the TSll, but again need to get in there to get a closer look. Do you mean to check fuel pressure while it is doing it? I need a better fuel pressure gauge as the one I bought from the local FLAPS does not really fit onto the rail.

I can't do anything with it now as it is not at my house. I just tried again and there is no way it is going to make it the 3-4 miles uphill. I probably will have to wait until Monday to get it towed back to my house.

My points gap seems somewhat closed up. Could that cause it? My timing was Ok the last time I checked. Also, when I mess around with the condenser wire it "seems" to get a little better. I would like to install a new condenser, but need the time (and the bus here!) to pull the distributor.

[Amskeptic]

My points gap seems somewhat closed up. Could that cause it?
when I mess around with the condenser wire it "seems" to get a little better.

Allow me to sternly rebuke . . .

Do NOT fill pages of diagnostic stabs in the dark with this legion of willing assistants all trying to help you if you have not taken care of the BASICS first, really, it is too painful.

Please.
Valve Adjustment
Ignition Dwell/Timing
Vacuum Leak Inspection
Fresh Fuel/Good Filter
Electrical Grounds/Connections

That is a lot of basics, but they are critical. The Bentley stresses that all other aspects of the engine must be squared away before you start accusing the fuel injection or "baking" the ECU . . .

If we are on page eight here, and you are just now asking if closed points and weird condenser can make your life a living hell, not to mention the damage occurring to the rest of the car from this lurching and bucking, I can tell you that closed points and a bad condenser can make your life a living hell of poor starting, and bucking and lurching.

Written in a spirit of frustrated love,
Colin

[Gypsie]

I have been reading and hoping for a resolution for your bronco bus issues.

I love the manuals posted in this thread (they have been secreted away in my file folder of arcane pdf manuals...).

While I'm in no position to rebuke anyone as I am as much an explorer of these machines as most here, I will say that I almost spit coffee all over my screen when I read "My points gap seems somewhat closed up. Could that cause it? when I mess around with the condenser wire it "seems" to get a little better."

This is not necessarily your culprit but it is one of the easiest and fairly cheap variables to resolve when tracking down "electrical type" symptoms. Good healthy spark is the goal and assuring that all the players are doing their part to make it happen.
When you say "seems" do you mean it drags your feeler blade harder than before or your eyeballs see less gap? I call for a full replacement of the points and condenser or at the very least a rejuvenation of the points and thorough inspection/ repair of all connections on the dizzy.

I completely sympathize with the test drive woes. Who wants to be towed home every couple days while you track down a gremlin.

Stepping back once in a while to regroup and rethink can bring fresh perspective.

And the point Colin makes about ensuring the "foundation" items are in order before hunting after problematic symptoms is one that we all "remember" at one time or another (for me it has been several times and hours of tail chasing...).

Keep going. You'll find it.

[aopisa]

Well to say I have been embarrassed into submission by the teacher. Never did handle that well in school either.

I will say that my experience with things mechanical is limited and most experiences are first experiences. I have no past history to draw from. What is happening now is forming the foundation of my experience.

I am new to the points/condenser thing. The Pertronix always functioned well without issue. I did not realize that new points could be a problem in a few thousand miles at most. I read on the forums that people are typically driving on points for 15,000 miles.

I have stated in previous posts buried in this thread that I have:

-Checked the timing which is on.
-Checked dwell which is around 50 degrees and asked if that was OK. The Bentley said it is within spec for older points.
-Checked cleaned and rechecked grounds
-Filled up with Mobil and replaced the fuel filter. The old fuel filter was absolutely clean
-I have not performed a valve adjustment, but will do that before I do anything else

Thanks again for all the help. There is plenty here to keep me busy for a while.

[SlowLane]

I did not realize that new points could be a problem in a few thousand miles at most. I read on the forums that people are typically driving on points for 15,000 miles.

It can depend greatly on the quality of the points. I once had a set of crappy Canadian TIre points fail on me after only two months. Since I had replaced them so recently, I ended up chasing my tail blaming other things because, well, I had replaced them so recently. (And, oh, yes. If you ever find yourself north of the border and in a Canadian Tire, DON'T buy anything electrical from them. It's all crap. Just my $.02 CDN).

When the mental light bulb went on and I bought a set of good quality points and compared them side-by-side with the crappy ones, the difference was obvious. Obvious, of course, once I had them both in hand. Not so obvious when my only point of reference was the crappy points.

Not saying that's necessarily your issue. If Colin installed the points, then you can probably assume they're up to his minimum standards.

A bad condenser can also cause a good set of points to fail prematurely. In fact that's the main purpose of the condenser: to absorb excess energy reflecting back from the coil primary which would simply arc across the point gap if the condenser weren't there.

I will reiterate here my recommendation that you swap out the distributor for the NOS one that you have. It may or may not cure the bucking problem, but even if it doesn't, I can guarantee that when you do figure out and solve the bucking problem, your bus will run smoother than with the 35-year-old mechanism your present distributor has. If the NOS distributor has points and condenser already installed, then you should replace the condensor with a new one (they do dry out over time), and inspect the plastic bits of the points to make sure they haven't started to disintegrate or gone brittle. Odds are that the points in that distributor are OE quality, so compare them with the ones you are using now and see if there's a difference in "beefiness".

If you're not comfortable swapping out the distributor, there's plenty of helpful advice available here. There are a couple of gotchas (in particular: don't drop the little spring under the distributor down into the oiling hole in the case. For that matter, don't drop anything down that oiling hole). But it can be done with a bit of patience and forethought.

[56ovalbug]

Whenever I get new points I check to see if there is any binding between the two pieces. I take them apart and put them back together like this:



The parts should move freely with absolutely no binding. I then put a dab of distributor grease on the post and put them back together. Also, check the plastic bushing for cracks or thin spots - that will give you grief if it goes undetected.

I also only replace the points and condenser as a pair and never separately.

On a cross country trip (Halifax to Vancouver) I was on in my old '69 Westy back in '89 the bus started bucking/hesitating when I did more than 60 mph. I slowed down to 55mph and it was okay for a while but it started bucking again. I pulled over to investigate - I noticed if I pulled up slightly on the rotor button (not enough to pull it off) I could spin the distributor rotor/shaft. Ended up being the distributor. The fiber shims between the drive dog and the distributor disintegrated causing the dog to jump out of the drive gear every so often. I got towed to a VW shop in Winnipeg and got it fixed and off I went... it's a long shot but who knows?

[aopisa]

If you're not comfortable swapping out the distributor, there's plenty of helpful advice available here. There are a couple of gotchas (in particular: don't drop the little spring under the distributor down into the oiling hole in the case. For that matter, don't drop anything down that oiling hole). But it can be done with a bit of patience and forethought.

The points that Colin installed last year are Bosch from Bus Depot. The new spare set that I have are the same. Seems I have heard some trash talk lately on Bosch points from what I can recall.

Do most people replace points/condenser with the distributor in or out of the engine?

My understanding is that in order to remove the distributor you:

-Get engine to TDC.
-Remove distributor (I don't recall a little spring coming out when Colin removed it last year)
-Re-install distributor or replace with new. If new, make sure the rotor is in the same orientation.
-Retime engine/ check dwell
-Adjust idle

I know to put a drop or two of oil on the felt in the shaft and apply a small amount of grease to the rubbing block.

I do have a Bentley and refer to it often. However, I do not find it to be the Gospel that many others profess it to be. The Bentley assumes you have enough mechanical expertise that you are likely to be employed as a VW technician. Since I often lack some the basic knowledge/experience that many of you have, the Bentley can sometimes provide incomplete instructions for me.

Thanks again.