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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / July 2006VW Dune Buggy issues...
Please follow this one for a bit: I'm working on a newly acquired chopped down VW Beetle Dune Buggy. Not a pro job... obviously some guys in a backyard did it. It's a 70 chassis with a 69 Solex 30 PICT 2 carb on a 1600 74 motor. It runs a little sluggish and then the throttle picks up unexpectedly and idles up and down with no pattern. We might see it speed up twice a lap or we may go 10 laps without it, but suddenly it's like a governor kicks in or the throttle was punched for an instant. I replaced the vacuum line, disconnected the throttle positioner completely while plugging it's line and securing it's linkage. Pinned the choke open. I tried running it with the advance disconnected and plugged... and saw the same throttle phenomenon. Now the head scratcher: Decided to pull and change plugs and commented to the son about how carbon built the Left ones were (assuming the Driver side is still Left when the motor is in backarsewards ;-). I then pulled the Right (passenger) ones and saw they looked nearly new and were soaking wet with gas even though we didn't run it for a couple of days. I put a screwdriver in each wire and could see spark, but I don't know how viscous it should be. We fired it up and I smelled each pipe and the Right side smelled gassy... then ran it a bit and noticed the right was barely hot and the left was very hot. We then beat the tar out of it around and around the field for a good half hour and I could touch the Right manifold with the back of my hand (it was barely warm) while the left was too hot to risk getting skin near it. One time that thing kicked in and ran so hard just as I made a bend up hill downshifting to first that it tried to spin the rear end clean around and then didn't have enough uuuumph the next moment to sustain second. I'm guessing that something is making the Right side start running for an instant here and there and at most other times it seems to be no more than a weak air compressor over there. I could see if a valve stayed open or something how this could happen with one cylinder, but what could possibly make both cylinders on one side behave in this off/on manner at once????? > Please follow this one for a bit: > [quoted text clipped - 35 lines] > something how this could happen with one cylinder, but what could possibly > make both cylinders on one side behave in this off/on manner at once????? The first thing I would do is a complete tune-up. Plugs, points, wires, cap, rotor and etc. Then adjust the valves and check compression. If everything checks out ok but fails to correct the problem, it is time to pull the heads and do a valve job or rings. Pulling the engine and replacing the pistons and jugs on a VW is easy. Good Luck, Hank > Please follow this one for a bit: > [quoted text clipped - 35 lines] > something how this could happen with one cylinder, but what could possibly > make both cylinders on one side behave in this off/on manner at once????? Sticking valves is the first thing that comes to mind, but I guess there are other possible causes. Perhaps a cylinder leak down test is in order.  SignatureKevin Mouton Automotive Technology Instructor "If women don't find you handsome, they should at least find you handy" Red Green I would be thinking loose head maybe. They do come loose often and need to be retorqued back on. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) > Please follow this one for a bit: > [quoted text clipped - 35 lines] > something how this could happen with one cylinder, but what could possibly > make both cylinders on one side behave in this off/on manner at once????? > I would be thinking loose head maybe. They do come loose often and need > to be retorqued back on. I've had a lot of air cooled VWs and never had a head come loose but ... I'd pull the valve cover & check your rocker assembly on the cold side. Each side shares a single pushrod rocker assembly for each half of the engine. If that's coming loose, you'd actually have both cylinders on that side with the valves held closed by the valve springs. That would likely beat the Hell out of all your pushrods on that side, and possibly the camshaft too. I've also heard of stock rocker assemblies used in competition breaking with similar results. You didn't say if this motor has any mods done on it, so I'll assume you still have the stock hollow-tube rocker shafts on it. The racing guys all use solid shaft rocker assemblies and hydraulic lifters. That requires some machining (not much really), but it makes the engine a lot more reliable without changing any valve geometry or displacement. Of course, once you get one of those apart and realise that a 1776cc upgrade is a great balance of power and reliability, you might not have a stocker for long. ;) Cheers, - JJ >> I would be thinking loose head maybe. They do come loose often and need >> to be retorqued back on. [quoted text clipped - 16 lines] > great balance of power and reliability, you might not have a stocker for > long. ;) Thanks to all for the replies. I doubt very much this has any modifications to it other than typical hillbilly trying to make do with something already on hand. I'm also looking at whether the manifold might be leaking on that side. Interesting note on the pushrod that I'll have to take a look at if it ever stops raining again. Can't get the tarp off of it when it's like this :-( I'm also looking at whether the manifold might be leaking on that side and some of the other things mentioned when I get a chance. This is not for racing, as such, it's just a billy-past-time for the kid who just turned teens to have some fun on a track we're breaking in for him on the farm, here... so I'm hoping to find reasonable solutions to just keep it going around and around. > This is not for racing, as such, it's just a billy-past-time for the kid who > just turned teens to have some fun on a track we're breaking in for him on > the farm, here... so I'm hoping to find reasonable solutions to just keep it > going around and around. Have you ever looked inside the distributor? There are parts in there that need regular maintenance. -jim >> This is not for racing, as such, it's just a billy-past-time for the kid >> who [quoted text clipped - 6 lines] > Have you ever looked inside the distributor? There are parts in there > that need regular maintenance. I thought the original was too long and felt (by mentioning that I had disabled the advance at one point, and looked at the spark) that I said enough to suggest I had looked at ignition issues. I guess I was not clear enough but... the overall ignition looks good. Thanks for the input. > >> This is not for racing, as such, it's just a billy-past-time for the kid > >> who [quoted text clipped - 11 lines] > enough to suggest I had looked at ignition issues. I guess I was not clear > enough but... the overall ignition looks good. Nope sounds like just exactly the opposite. Sounds like you need to put a new set of points in this baby. By definition, anybody who continues to operate an engine like this when it's firing on only 2 cylinders doesn't know what they are doing (let me give you a hint: you are destroying your engine). So you haven't even popped the cap off the distributor. When you do you are going to find a badly burned and worn down set of points. Back when this engine was on the road it was common practice to change the points with every oil change. The points were only really good for about one oil change interval and a set of points only cost something like a buck so it was well worth replacing before they deteriorated since the fuel economy and long engine life from doing that simple maintenance paid for itself a 100 times over in fuel economy and extended engine life. The symptoms you describe are typical of what you see when you neglect this. Also you better check if that vacuum advance is working. Most of these engines back then ended up in the junkyard soon after the vacuum advance diaphragm started to leak. -jim > Thanks for the input. >> >> This is not for racing, as such, it's just a billy-past-time for the >> >> kid [quoted text clipped - 35 lines] > engines back then ended up in the junkyard soon after the vacuum advance > diaphragm started to leak. No... I said that I checked the advance. I did also check the points, the cap, the rotor and the spark at the plug. I have only just acquired this buggy and have about an hour or maybe an hour and a half or so on it total. I'm not destroying the engine, I'm here and a few other places trying to find out what's wrong with it. I used to drive and maintain a lot of these years ago, but I've since overwritten that area of my hard drive with other information you might say, but... I actually remember back then carrying a point file in my road box because of just what you're saying, which is why I said that I went over the ignition right away. Thanks, though. > No... I said that I checked the advance. No you said you disconnected the advance and tried running it like that. You may have a bad advance. These engines could easily be driven for 300K miles. About 90% died at around 60K when the advance went bad. You haven't said anything that would indicate you would know whether your advance is working or not. > I did also check the points, the > cap, the rotor and the spark at the plug. Well you haven't said anything to convince me it's not ignition related. You have said a ton of things that indicate it could be the ignition. Do you want to find a solution or do you want to argue? -jim > I have only just acquired this > buggy and have about an hour or maybe an hour and a half or so on it total. [quoted text clipped - 6 lines] > > Thanks, though. >> >> This is not for racing, as such, it's just a billy-past-time for the >> >> kid [quoted text clipped - 23 lines] > distributor. When you do you are going to find a badly burned and worn > down set of points. Just curious. How does a bad set of points cause just one bank of cylinders to not fire at all, yet the other bank of cylinders fires ok? Wouldn't bad points affect all cylinders the same ? > Back when this engine was on the road it was common practice to change > the points with every oil change. The points were only really good for [quoted text clipped - 18 lines] > ----= East and West-Coast Server Farms - Total Privacy via Encryption > =---- > Just curious. How does a bad set of points cause just one bank of > cylinders to not fire at all, yet the other bank of cylinders fires ok? > Wouldn't bad points affect > all cylinders the same ? yes. that's how it would work if the disc. shaft ran perfectly true - but it doesn't - it will likely wobble a bit and as the point gap wears down to nothing it doesn't affect all cylinders equally. -jim > > Back when this engine was on the road it was common practice to change > > the points with every oil change. The points were only really good for [quoted text clipped - 18 lines] > > ----= East and West-Coast Server Farms - Total Privacy via Encryption > > =---- > yes. that's how it would work if the disc. shaft ran perfectly true - > but it doesn't - it will likely wobble a bit and as the point gap wears > down to nothing it doesn't affect all cylinders equally. That was supposed to be dist. shaft not disc. shaft - %*%@% spell checker. > >> I would be thinking loose head maybe. They do come loose often and need > >> to be retorqued back on. [quoted text clipped - 32 lines] > the farm, here... so I'm hoping to find reasonable solutions to just keep it > going around and around. VW engines have the heads come loose all the time from my experience. Then you have O compression, but if the cylinder slides up from the block, it can tighten the top and get compression again for a while which sounds like your issue. They even just have a flip bar like a brake master holding the covers on for fast easy access. If I remember right you are supposed to torque the heads down at some foolishly low mileage intervals. 3K comes to mind, but I think that is too low or maybe that is after a rebuild. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) >> >> I would be thinking loose head maybe. They do come loose often and >> >> need [quoted text clipped - 55 lines] > mileage intervals. 3K comes to mind, but I think that is too low or > maybe that is after a rebuild. Thanks, Mike. Actually, it was KeepYourSpam that said he never had one come loose. Back in the 'the day' My first FIL and I used to buy Beetles up for maybe 50 bucks sitting in peoples' yards when they complained they had lost power. We knew about the regular service intervals in the owner's manuals (I was thinking 5,000 but you may be right that it was even lower) and we'd retorque the heads usually to find them warped, take them to a local shop that shaved them for like $8 (*that's* how long ago it was) and tune them up, spotweld a kit over the shock towers that a local body panel shop sold, replace the bellows and sell them for a few hundred. For our deluxe makeover we would go to the junkyards and find those old-time heater blowers that looked like modern hair dryers and wire a switch to the battery through the cardboard under the back seat. We took the channel coming from the heads to the ports under the seat and put foil pipe from air cleaners over it to the blower, put more foil pipe on the outlet of the blower and slit the other end down to the size of the floor channels and duct tape them, giving the new owner a forced air defroster so as to not have to scrape the inside of the windshield all the time. Only problem was that if it weren't shut off it would kill the battery when parked in a matter of an hour. I think someone in another forum might be on to something with the intake manifold leaking over there. Took it off only to find no gasket ring and crud built up in a manner that looks like it might possibly have been under the pipe ball. *But* it is single ported, which means that even though it's a 74 motor, someone changed the heads to match the manifold so they could keep the carb and distributor set. Sounds like an ideal situation to have heads not properly installed or worse. Your suggestion to check this fits right in and I will loosen and retorque it. Thanks again. |
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