Dune Buggy Won't Stay Running
Will Sheppard
pict 3 carb. It starts right up and idles for a few minutes then dies and
is very difficult to restart. When it does restart it won't run properly -
if I hold it at a steady rpm, let's say 2000 it will rev for about 10
seconds then the rpms dive and it dies. A lot of fethering of the pedal
and fooling around is required to get the thing back in the garage but for
the first several minutes it seems to run normally. This seemed like a
carb problem but I just got a working-when-pulled carb and the problem
persists!
Any ideas?
Speedy Jim
Since you've pretty much ruled out a bad carb, I would be looking
for a vacuum leak. The choke masks the leak by enriching the
mixture at first.
The obvious places to look are the rubber booties on the manifold and
the carb flange-to-manifold.
If you could get it to run a bit more consitently, you might try the
old spray-solvent trick around suspected areas, but that's hard to
do with an engine that won't stay running.
In extreme cases, I have resorted to applying compressed air (low
press) to the manifold. Create some kind of adapter (duct tape!)
to feed the air into the top of the manifold. Take the rocker
shafts off so all the valves are closed. Use soapy water to look
for leaks.
Might be a good idea to do a compression test beforehand.
Speedy Jim
http://www.nls.net/mp/volks/
Will Sheppard
> Since you've pretty much ruled out a bad carb, I would be looking
> for a vacuum leak. The choke masks the leak by enriching the
> mixture at first.
>
Thanks for the suggestions Jim, I think you've solved it! Of course it makes
sense now but for so long I had it in my head that I had a carb problem... I
started the car and sprayed carb cleaner here and there with no effect (choke
fully on.) The car stopped running when I stepped open the choke a bit. I
tightened the screws on the boots and could now get the car to run on the 3rd
or 4th step on the choke assembly. Now when I sprayed carb cleaner at the
manifold-to-head junctions there was a noticeable difference in the idle as
it sucked the cleaner in there. I'll get new rubber boots, clamps, manifold
gaskets on Monday and check that the ends of the manifolds are nice and flat.
Hopefully it will be as simple as that!
Will Sheppard
> They worked fine for the factory in production, but in real
> life you need to seal them.
I'll do the same. Thanks again!
Speedy Jim
They worked fine for the factory in production, but in real
life you need to seal them.
Speedy Jim
http://www.nls.net/mp/volks/
Will Sheppard
manifold in the process because I basically screwed up positioning it
before I started tightening the bolts. I replaced the rubber boots, got
everything snugged in and tight and it all looked good. I started the car
with some difficulty and struggled to run it for maybe 30 seconds. It was
really loud like TAK-TAK-TAK-TAK as the engine ran and it started popping
and snorting. Clearly I had the firing order mixed up but that noise! Now
I've got the firing order right and it will run but still with the loud
noise. I get no noise when the starter is turning the engine without it
being fired up. I can't really tell where the noise is coming from, from
the back it sounds like it's right in the middle of the engine. In the
manifold removal process I also removed the carb, coil and fuel pump. This
noise was not present before I started this job. What have I done??
Speedy Jim
With engine idling, block off the muffler tips. That will help
test for exh leaks (might be the source of the noise).
If there are no leaks, you should be able to stall the engine.
If there *are* leaks, you will be able to hear them more precisely.
Might even have a helper block the exh while you get underneath.
Maybe the noise is something else, but I'd start there.
Speedy Jim
http://www.nls.net/mp/volks/
jjs
news:Xns960DA5A82...@24.64.223.211...
> [...] What have I done??
Don't freak out yet. An exhaust manifold leak by the head can make a very
hard metallic sound. Get a length of tube and put one end to your ear and
poke around underneath around the header and see if you can locate it. Maybe
you will be lucky.
Will Sheppard
>
> With engine idling, block off the muffler tips. That will help
> test for exh leaks (might be the source of the noise).
> If there are no leaks, you should be able to stall the engine.
> If there *are* leaks, you will be able to hear them more precisely.
> Might even have a helper block the exh while you get underneath.
Well after some messing around the noise is all gone, or at least almost
all gone. I was having trouble getting one side of the manifold to seal
and when I pulled it off I found a piece of the old manifold (The one that
I broke) that was still stuck to the gasket sealer. I removed this,
resealed the gasket and put it back together the engine now sounds pretty
much like I'm used to VW engines sounding. There is still a mild tak-tak-
tak-tak that may be normal, It doesn't sound like anything to worry about
anyway. The car runs much better now but after doing a valve adjustment and
setting the points and timing it is still lacking power under load and
doesn't rev as smoothly as it should. I'll check it out today with the
dwell meter and try timing it with a strobe instead of static timing and
see how that goes. I'd like to check the manifold vacuum to ensure that
I've got all the leaks taken care of. Where should I take a reading and
what should it be? This is an AE series bus engine with a 34 pict 3.
And thanks for the continued help!
Will