Guac's Bucking Issue - Distributor

NOTE: This issue has NOT been resolved. What appeared to work in this article didn`t... The intermittent symptoms just became intermittent again...

The Guac`s Distributor Failure

Resolved 12/29/2006

Symptoms

• Bucking at high rpms that feels like fuel starvation
  
• Bucking immediately after upshifting that also feels like fuel starvation
  
• All symptoms intermittent
  

Description

Shortly after buying the Guacamole Bus last April, these symptoms appeared. At high (over 4k) rpms, and immediately after upshifting into 3rd only, the bus would buck like there was either no fuel, or the ignition just shut off. This was intermittent, and didn`t seem to affect highway driving at all. In fact I drove to CA in May with no problems until I got there. But once there it was even worse.

Troubleshooting and further misery

As mentioned, once in CA, the problems were worse. Happening nearly every time I drove. This was bad because I didn`t want to try driving back to CO with this problem. In fact, I stayed in CA an extra day to try to resolve it.

I went to VeeDub Parts in Huntington Beach (http://www.vwparts.net) and bought new points, condensor, cap and rotor. I talked to the counter guy there about a coil, and he insisted that a bad coil would be an all-or-nothing problem. Nothing intermittent like I described. The guys there tend to be more knowledgeable than most counter monkeys I`ve run into, so I took his word for it. (This will haunt me later.)

So new points and condensor, same problem. Sigh.

I got back to my in-law`s house (where we were staying during our visit to CA) and started going through the fuel injection system testing everything and looking for vacuum leaks. Everything tested good. I couldn`t test fuel pressure because I couldn`t find a fuel injection pressure gauge without all the bizarre fittings that every other car seemed to have. But the double relay tested fine, the injectors tested fine, etc.

I was going batty. I posted on both The Samba (http://www.thesamba.com) and the Type 2 List (http://www.type2.com) and everybody suggested what I`d tried. I also went ahead and bought a coil at Autozone which had no effect. (See my writeup about that piece of crap here: http://www.donimages.com/guac/coilautopsy.html.) Until someone suggested fuel pressure. Since I had no way to test it, I was told try just replacing the fuel filter. I happened to have a spare with me so swapped it out, replacing some of the rubber lines in the process since they were pretty deteriorated.

The problem went away! YAY!

Drove home and had no more problems.... For a while. It would appear every so often, and a quick fuel filter swap would always resolve it.

Next trip to CA, in late July, it started happening again in earnest. Fuel filter swaps were lasting shorter and shorter periods of time. But there was an additional issue mixed in. I noticed vacuum leak symptoms as well... Misfires, gentle bucking when maintaining speed, etc. "Ah ha!" I think. It MUST be vacuum related!

After much fiddling I found the elbow to the aux air regulator was cracked. The PO had repaired the elbow with silicone. I knew about this, since he did it while I was present, but had forgotten. It lasted pretty well IMHO. A new elbow was available at Vee Dub for a few bucks so I bought it. I still had a vacuum leak, and the main bucking problem was also still present.

I went ahead and bought a Bosch Blue coil at Vee Dub during this period, with no difference in any effects.

Just before I was scheduled to head back to CO, I swung by my in-law`s (I`d been staying with my mom this trip) and started looking for the vacuum leak with my father-in-law. Finally found it. The fuel pressure regulator uses vacuum to help reduce the rail pressure during decel and at idle. The diaphragm was leaking in the FPR. I pulled the vacuum line off and plugged it. No more vacuum leak! Yay! Still have that @#$^ bucking though...

A little while after getting back to CO (with zero bucking on the way home, thankfully) I started looking for the problem again. I posted over on the IAC board (http://www.itinerant-air-cooled.com) about the problem, got the same kinds of answers I`d been getting. Note: I stopped posting over at The Samba because of some personal issues with other members.

I cut open a fuel filter to see just what was blocking it. If it was rust I`d need to pull the fuel tank. Here`s the results:

http://www.donimages.com/guac/images/fuelfilter/

As you can see, NOTHING was blocking the filter!!! Aside from a slight darkening in the bottom half of the filter element (where the filter is constantly soaked in fuel) there was nothing at all in there.

I started considering the possibility of something in the tank blocking the outlet. This is bad on a fuel injected bus because the outlets don`t unscrew like on a carb`d bus. That means a definite tank pull, with an engine drop. Crap.

While all this is happening, I`m exploring any other possibility to avoid the tank pull. Also, during this time the fuel pump died. The death of the fuel pump was a perfect fit with the theory that something was blocking fuel delivery since the pump requires a constant flow of fuel to keep from overheating. I bought a rebuilt pump from Bus Boys (http://www.bus-boys.com) - a great deal at $120 for a rebuilt pump done by Fuel Injection Corp. Pics here if you`re curious:

http://www.donimages.com/guac/images/fuelpump/

Through all this I`m still trying to understand why replacing the fuel filter is resolving, even temporarily, the bucking problem. Vapor lock and tank not venting were both eliminated when I tried popping the gas cap, popping a vent line, and just pulling a fuel line at the filter and putting it back on. None made any difference.

I also checked the Air Flow Meter (AFM). Took it out and popped the cover. Everything looked perfect, or nearly so. Some odd burn marks that look like they were designed in. Nobody could tell me much about those, but it tests out ok so I left it. Pics here if you`re curious:

Burn marks

Guts 1

Guts 2

The bucking after upshift wasn`t much of an issue until just recently. Since I`ve pretty much decided swapping fuel filters was a waste of money, I started trying to drive through the bucking. The high RPM bucking would go away, but the upshift bucking would happen EVERY shift now. But if I let the RPMs drop to 1k between shifts, the bus wouldn`t buck at all.

AH HA!!!

These two issues point firmly at the distributor. But I had replaced all the stuff on the distributor, and even checked the internal ground strap, which is well attached and not rusted through.

But the symptoms say distributor. So I grabbed the one out of a 79 engine I have in my garage. The condition of the points and condensor are unknown, but I gave it a shot.

IT WORKED PERFECTLY!!!!!!!!!

Here`s what happened:

(I`ll get better pics of the cap up when I get a new cap to replace it.)

The cap has a scorch mark right above where the ground strap is. Somehow the ignition spark from the rotor was grounding to the strap or nearby instead of going to the cap terminals. Note that the same cap and rotor are being used on the 79 distributor and working flawlessly.

In the second pic you can see the dust from the cap that got burned off / blown off by the spark being misdirected. It`s a nasty muddy mess.

I want to thank everybody at IAC, the Type 2 List, and The Samba that suffered with me through finding the cause of the Guac`s bucking. I suspect I would have given up and taken it to a shop if it hadn`t been for everybody`s support.

Thanks!!!!!!!!!!

Doing the Front Brakes Part 2

Part 2 of Doing The Front Brakes:

Remove the pads: When you pull the pads out of the calipers, pay attention to the backing plates. They have tabs that stick out and the orientation to the caliper piston is important. You need to duplicate the orientation when installing the new ones.

Remove the brake line clip: Use your screwdriver to pry this out. Make sure you`re not prying against the lines themselves, only using suspension components to pry against.

Loosen the caliper: There are two 19mm bolts on the back of the caliper that hold it to the hub. They`re almost certainly siezed. This is where the mallet comes in handy. I tried using a pry bar initially, but it started bending! But a rubber mallet tapping on the ratchet got them loose. At this point you only want to loosen the bolts, not remove them.

Remove the caliper: Get your coathanger or other wire and tie it to the upper shock mount. Holding the caliper with one hand, remove the 19mm bolts. Slide the brake line out of the holder it`s in and lift the caliper off the rotor. Tie the coathanger through one of the bolt holes, making sure the caliper hangs high enough to prevent stressing the brake line.

Remove the rotor: The old rotor should just slide off at this point. If it doesn`t, rap it with the rubber mallet.

Install the new rotor: Soak the new rotors in brake cleaner to remove the waxy oil applied to protect them during storage and shipping. Slide the rotor onto the studs, making sure to align the screw holes. Install the screws. Bentley has a torque spec (12ft lbs, IIRC).

Re-install the caliper: Lining up the bolt holes is kinda tricky for some reason. There`s just really no natural position for the caliper to rest when it`s not bolted in. So be careful not to scratch your shiny new rotor!

Prep the new pads: Put your anti-squeal stuff on the backs of the pads, making sure you don`t get any on the pad braking material. Let them set the recommended time per the anti-squeal manufacturer. (Mine was 10 minutes.)

Install the pads: Remember the backing plates? Put them in the calipers in the same orientation they were removed. Then put the new pads in. You may find you will have to compress the piston again. Use the old pads and your screwdriver covered with fuel line or wrapped in a rag to compress it. They should slide in place. Re-install the pins and the cross shaped spring. When installing the pins, use your flathead screwdriver to drive them in (once you`ve gotten them set into place with the tip showing through the hole.) The flathead will prevent driving the pin too far and shearing off the shoulder. A common hammer will work, but there`s not a lot of room around the caliper to maneuver the hammer. So a screwdriver and hammer is easier.

Close reservoir: Remove the rags, wiping up any spilled brake fluid, and replace the cap. At this point I usually pump the brakes a couple times and check for leaks as well as make sure the level in the reservoir is adequate.

Button up: Put your wheel back on, lower the bus, torque the nuts on the wheel, and put your hubcap back on!

Go for a drive and enjoy your newly redone brakes!

Doing the Front Brakes

Symptoms: Pulsing and vibration during braking. Also, this week they started squealing.

Tools Needed: Ratchet, 19mm socket, 6mm hex bit, rubber mallet or hammer, flat head screwdriver.

Supplies Needed: New rotors, new brake pads, brake cleaner spray, anti-squeal spray or goop. A roll of paper towels, toothpicks and nitrile gloves are nice too.

Since I got the bus, the pedal pulsed severely during braking. The PO said they`d done that since he bought the bus. So I figured it was time to check the rotors:

I used a dial indicator to check to see if the rotors were warped and/or of uneven thickness. As you can see above they definitely are. Both sides were bad, though the driver`s side was worse. So I started pricing rotors.

Darn near every one I found was around $85 EACH. And that`s for crappy Autozone quality. That much plus serious shipping fees to get good German ones from one of the bus vendors. So I resigned myself to saving up for them.

Until the VWs On The Green show here in CO.

$45 for a PAIR of German rotors new in the boxes! Here`s how they specc`d out:

The brand is Sebro. They came in with 12.85mm thickness. The limit as stamped on the rotors is 11mm. They were coated with a waxy oil to protect them from rusting, but where they rubbed on the boxes, they did have some light surface rust. No biggie as that will rub off the first time I apply the brakes, assuming I remove the waxy stuff.

The brake pads are Axxis brand. Made in Australia of all places! Cool! I bought them last year from a small import parts shop in Boulder, CO (sorry, don`t remember the name) and they`ve been bopping around in my parts box since then.

So I jacked up the bus and stuck a stand underneath:

I`ve never seen a "perfect" place to put a jackstand under a bus. But that reinforced point on the frame is what I`ve always used. Also, look at the seepage from my steering damper! Guess what I`ll be buying soon...

And here`s what things looked like without the wheel:

Ugh.

I`ve always been of the "the pads will wear to fit the rotors" school of thought. But these looked like the surface of the ocean during a storm!

Anyway, here is the order I did things:

Unscrew the rotor screws: There are two socket head screws that hold the rotor to the hub. They take a 6mm hex bit. Spray brake cleaner in the heads and follow that with a toothpick to pick out any gunk and prevent stripping it out. If you have a partner helping, have him/ her press on the brake pedal to lock the rotor in place while you`re unscrewing those screws. Otherwise, grab on tight...

Open brake reservoir: Wipe off and remove the cap. You have a choice here: Either carefully remove some fluid, or just stuff rags all around the reservoir. I used the rags, making sure to lay one over the opening as well to keep airborne crap from the brake fluid.

Remove the pins: 2 pins on each caliper allow the pads to slide as they wear. Bentley says to use a punch or something similar to drive them out. Bah. A baby screwdriver worked just fine with a rubber mallet to tap them out. You`ll also get the retaining spring (cross shaped piece) out with them.

Compress the pistons: Since I`ll not be using the rotor or the pads, I just stuck a screwdriver between the pad and the rotor on both sides and pried. Make sure the pistons are as far as the pad will push them. DO NOT pry directly on the pistons. You`ll push them in unevenly or tear the seals. By the way, my seals looked beautiful. These were recent rebuilds judging by the double bleeding screws.