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1972 Beetle Loses Power at Sustained High Speed / RPMs



 
 
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  #1  
Old April 20th 06, 07:39 PM posted to rec.autos.makers.vw.aircooled
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Default 1972 Beetle Loses Power at Sustained High Speed / RPMs

Hi all.

Bear with me, I'm brand new to this.

I have a 1972 Beetle that I recently bought. It has run perfectly
until a few days ago when it stalled on the freeway. I was eventually
able to limp home, and I replaced the fuel filter, which looked like it
might be clogging, and cleaned the screen in the fuel pump. It ran
fine the next day until I was driving home and got on the freeway
again; it died in the exact same spot. This time I could not start it
and had to tow it home.

I replaced the air filter and opened up checked the carburator, which
seemed to be in normal working order (nothing obviously wrong with it,
anyway, but this is the first time I've looked at one, so what do I
know?). At this point it would start, but stall after a couple miles
and need to cool down in order to start again.

Finally, I broke down and took it to a mechanic. He found a bad valve
and fixed it, claiming that was the cause of my problem. He also did a
general tune up, replaced the plugs and points, and replaced the
condenser, which he said was the wrong part. The car was running great
when I left there.

Unfortunately, within a minute or two of getting on the freeway, it
stalled again. It was definitely better than before, and I was able to
get off the freeway and drive normally on surface streets to my
destination.

Basically what happens is I get up to speed (around 65-75 MPH) and ease
off the gas, at which point the engine seems to misfire a bit and lose
power in spurts. I respond by giving it more gas, and it loses power
altogether, and the engine dies as soon as I take it out of gear.
After sitting for a few minutes, it starts again but runs rough and
quickly dies again when the RPMs get high.

It seems like a carburator problem to me, but I am at a loss as to how
to correct it. Any ideas or suggestions would be greatly appreciated.

Thanks,
lukas

Ads
  #2  
Old April 20th 06, 08:08 PM posted to rec.autos.makers.vw.aircooled
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Default 1972 Beetle Loses Power at Sustained High Speed / RPMs

wrote:

> Hi all.
>
> Bear with me, I'm brand new to this.
>
> I have a 1972 Beetle that I recently bought. It has run perfectly
> until a few days ago when it stalled on the freeway. I was eventually
> able to limp home, and I replaced the fuel filter, which looked like it
> might be clogging, and cleaned the screen in the fuel pump. It ran
> fine the next day until I was driving home and got on the freeway
> again; it died in the exact same spot. This time I could not start it
> and had to tow it home.
>
> I replaced the air filter and opened up checked the carburator, which
> seemed to be in normal working order (nothing obviously wrong with it,
> anyway, but this is the first time I've looked at one, so what do I
> know?). At this point it would start, but stall after a couple miles
> and need to cool down in order to start again.
>
> Finally, I broke down and took it to a mechanic. He found a bad valve
> and fixed it, claiming that was the cause of my problem. He also did a
> general tune up, replaced the plugs and points, and replaced the
> condenser, which he said was the wrong part. The car was running great
> when I left there.
>
> Unfortunately, within a minute or two of getting on the freeway, it
> stalled again. It was definitely better than before, and I was able to
> get off the freeway and drive normally on surface streets to my
> destination.
>
> Basically what happens is I get up to speed (around 65-75 MPH) and ease
> off the gas, at which point the engine seems to misfire a bit and lose
> power in spurts. I respond by giving it more gas, and it loses power
> altogether, and the engine dies as soon as I take it out of gear.
> After sitting for a few minutes, it starts again but runs rough and
> quickly dies again when the RPMs get high.
>
> It seems like a carburator problem to me, but I am at a loss as to how
> to correct it. Any ideas or suggestions would be greatly appreciated.
>
> Thanks,
> lukas
>




Could be overheating.
When it happens, does the engine seem hot? Can you pull the dipstick and
hold it in your bare hand while you check the oil level? Is there enough
oil? Are the engine bay tin and seals in good shape / in place? The
engine bay must be sealed, NO air must enter from under the car. Very
often there's tin pieces or seal missing, and the hot air from the
exhaust system rises up into the engine bay and finds it's way into the
fan... and hot air won't cool the engine enough.. the engine then starts
overheating, and thus producing even more hot air, and making itself run
even hotter... and soon this it will die.

Jan
  #3  
Old April 20th 06, 08:09 PM posted to rec.autos.makers.vw.aircooled
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Posts: n/a
Default 1972 Beetle Loses Power at Sustained High Speed / RPMs

wrote:
> Hi all.
>
> Bear with me, I'm brand new to this.
>
> I have a 1972 Beetle that I recently bought. It has run perfectly
> until a few days ago when it stalled on the freeway. I was eventually
> able to limp home, and I replaced the fuel filter, which looked like it
> might be clogging, and cleaned the screen in the fuel pump. It ran
> fine the next day until I was driving home and got on the freeway
> again; it died in the exact same spot. This time I could not start it
> and had to tow it home.
>
> I replaced the air filter and opened up checked the carburator, which
> seemed to be in normal working order (nothing obviously wrong with it,
> anyway, but this is the first time I've looked at one, so what do I
> know?). At this point it would start, but stall after a couple miles
> and need to cool down in order to start again.
>
> Finally, I broke down and took it to a mechanic. He found a bad valve
> and fixed it, claiming that was the cause of my problem. He also did a
> general tune up, replaced the plugs and points, and replaced the
> condenser, which he said was the wrong part. The car was running great
> when I left there.
>
> Unfortunately, within a minute or two of getting on the freeway, it
> stalled again. It was definitely better than before, and I was able to
> get off the freeway and drive normally on surface streets to my
> destination.
>
> Basically what happens is I get up to speed (around 65-75 MPH) and ease
> off the gas, at which point the engine seems to misfire a bit and lose
> power in spurts. I respond by giving it more gas, and it loses power
> altogether, and the engine dies as soon as I take it out of gear.
> After sitting for a few minutes, it starts again but runs rough and
> quickly dies again when the RPMs get high.
>
> It seems like a carburator problem to me, but I am at a loss as to how
> to correct it. Any ideas or suggestions would be greatly appreciated.
>
> Thanks,
> lukas
>


It does indeed sound like a fuel problem (but maybe not carb itself).

Troubleshooting this kind of problem is tough even for the experienced.

If it were mine, I would want to know if there is fuel in the carb bowl
when it dies. This will tell you where to go next and beats by a mile
the "let's change this part and see what happens next" approach.

You could also check to see if there is spark when it dies but this
does not produce as clear cut an answer.
------------------

How deep into this do you want to get?
It's possible to check the carb fuel level but there are dangers
involved with a hot engine.

You can observe the accelerator jet discharge as the throttle
opens and this will *sometimes* tell if the carb has fuel or not.

Some less direct approaches:
If this is a Standard Beetle, there is a mesh screen in the
fuel tank outlet. These get clogged after, say, 34 years. <g>
You can remove the screen but the tank needs to be near empty.
Possible to view the screen by taking the fuel gauge sender out.

Super Beetles don't have the screen but may have an in-line filter
under the tank.

Next, starvation can be caused by a tank that doesn't vent.
Easy test is to go for a drive with the filler cap loosened.

--------------

Well, this may point you in some of the directions I would take.

Speedy Jim
http://www.nls.net/mp/volks/
  #4  
Old April 20th 06, 10:48 PM posted to rec.autos.makers.vw.aircooled
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Default 1972 Beetle Loses Power at Sustained High Speed / RPMs

Wow, thanks for the quick response and the good advice. Sounds like I
might be in over my head, but I'm ready to get my hands dirty.

Jan, you might be onto something with the overheating. There's plenty
of oil in there, but it's probably way overdue for a change (I know, I
know). I have noticed it gets surprisingly hot (have the third-degree
burn on my calf from the exhaust pipe to prove it). I'll change the
oil and see if it helps. I will check the seal on the engine bay, too.

Jim, I did check the screen in the fuel pump and it is clear (wish I'd
talked to you first, I did it with a full tank and damn it was messy).
I'm not confident I can figure out how to check the fuel levels in the
carb, but I'll give it a shot. And I'll try loosening the filler cap
next time this happens.

I ordered the Muir book and the repair manual, so hopefully I'll be
less mystified after I do some reading ;-)

Thanks again. I'll let you know when I sort it out.

lukas

  #5  
Old April 21st 06, 09:10 AM posted to rec.autos.makers.vw.aircooled
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Posts: n/a
Default 1972 Beetle Loses Power at Sustained High Speed / RPMs

Butthead wrote:
> On 20 Apr 2006 14:48:07 -0700, "
> > wrote:
>
>
>>Wow, thanks for the quick response and the good advice. Sounds like I
>>might be in over my head, but I'm ready to get my hands dirty.
>>
>>Jan, you might be onto something with the overheating. There's plenty
>>of oil in there, but it's probably way overdue for a change (I know, I
>>know). I have noticed it gets surprisingly hot (have the third-degree
>>burn on my calf from the exhaust pipe to prove it). I'll change the
>>oil and see if it helps. I will check the seal on the engine bay, too.
>>
>>Jim, I did check the screen in the fuel pump and it is clear (wish I'd
>>talked to you first, I did it with a full tank and damn it was messy).
>>I'm not confident I can figure out how to check the fuel levels in the
>>carb, but I'll give it a shot. And I'll try loosening the filler cap
>>next time this happens.
>>
>>I ordered the Muir book and the repair manual, so hopefully I'll be
>>less mystified after I do some reading ;-)
>>
>>Thanks again. I'll let you know when I sort it out.
>>
>>lukas

>
>
> A quick way to test the free flowing ability of the fuel system is to
> use an electric pump hooked up to your feed line at the carb. Just let
> it pump as fast as it will. If there is any obstruction, fuel flow
> will be shut off or severley slowed within seconds. If not, its in the
> carb or fuel pump.
> Have you checked the coil? It sounds as if it could be a bad coil too.
>

I had a similar problem on my 64 back in 1969. It started to miss and
lose power at speed. It got so bad we had to stop at a VW dealer and had
them check the ignition system. Seemed to run ok for a few miles then
the same thing. Pulled into a gas station at the next off ramp and the
attendant looked at the engine took out his pocket knife and pulled off
the slide on connector on the coil. It had some corrosion on it so he
scraped it clean and said he couldn't help us. Well I started it up and
away we went. It was still running perfect when I sold it four months
later when I left for Viet Nam. Apparently it had built up enough
corrosion resistance that when it needed good spark under load it just
wasn't getting enough juice to do the job. Check all your connections in
the ignition system and make sure they are good and clean. How old are
your plug leads. I had a miss under load with my 95 Isuzu Rodeo and when
I replaced the plug leads it went away and my mileage improved a mile or
two per gallon.

Wes Pearson
  #6  
Old April 21st 06, 01:25 PM posted to rec.autos.makers.vw.aircooled
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Default 1972 Beetle Loses Power at Sustained High Speed / RPMs

The fix for me was an electric fuel pump I installed under the fuel
tank. I never found the exact cause but it never happened in the
winter. The group was a big help for me. I got the fuel pump from Auto
Zone which had one listed for 74 vw from mexico which has worked fine
with 3 lbs rated flow. I also suggest a fuel regulator. The pump cost
about $35.00 and the regulator about 25.00. Dennis

href="http://albums.photo.epson.com/j/AlbumIndex?u=4025706&a=32090944&f="Den's
Dogs</a>

href="http://albums.photo.epson.com/j/AlbumIndex?u=4025706&a=30209382&vt=vp">Den's
1977 Puma</a>

  #7  
Old April 21st 06, 01:57 PM posted to rec.autos.makers.vw.aircooled
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Posts: n/a
Default 1972 Beetle Loses Power at Sustained High Speed / RPMs

In my two cases, it was two different things, so bear with me.
First was on my '66. The coil started going bad, with a mid throttle
miss, which by the next day left me pretty much stranded in the middle
of a 4 lane intersection. I had to rev it to the moon in order to get
it off the side of the road, that's how often the coil was firing.
2nd was in a '67-'69 ******* of a car. The fuel line from front to rear
was clogged just enough to starve the engine on the freeway. I could
drive 2-3 miles, and the engine would lose powerr and die. Wait a few
minutes, and it could suck enough to get me a another couple miles,
then do it all over again. This is where *I'm* leaning as to where your
problem lies.
What I did to fix it was get a roll of mechanics wire from the HELP
section of the auto parts store. Disconnect both ends of the fuel line
(you'll have to remove the tank for this). Straighten the wire out and
wad up the end to about the size of a small pea. Feed that in the line
and make back and forth motions, feeding a little more each time.
You'll probably get almost to the outlet on the other end, but most
likely not, due to the curve it takes on the way out. Just pull it back
out and go from the other end.
Once it's clear, flush all the loose crap out with some gasoline and/or
compressed air, hook it back up and see if that helps. Put a fuel
filter near the outlet next to the tranny so as not to clog the carb
with anything that may still be loose or comes loose later. You can get
a generic $1 filter from the counter at the auto parts store, or a FRAM
G-2 for about $4, which has barbed ends so it's harder to pull off. Use
hose clamps in either case.

  #8  
Old April 21st 06, 07:03 PM posted to rec.autos.makers.vw.aircooled
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Posts: n/a
Default 1972 Beetle Loses Power at Sustained High Speed / RPMs

Update: I'm going to try replacing the fuel pump. I took it back to
the mechanic and we disconnected the fuel line from the carburator to
make sure it was getting fuel from the pump. There was a steady flow
when the engine was running well, but when the problem was happening it
wasn't flowing at all or came out in spurts. I don't think it is
clogged, since it flows fine sometimes. So I guess the pump is broken.
Too bad, because it is a nice chrome pump, and the replacement I could
find on short notice doesn't look as good. Oh well, if this fixes it i
can start looking for a better one and replace it later.

  #10  
Old April 21st 06, 08:58 PM posted to rec.autos.makers.vw.aircooled
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Posts: n/a
Default 1972 Beetle Loses Power at Sustained High Speed / RPMs

Speedy Jim wrote:

> wrote:
>
>> Update: I'm going to try replacing the fuel pump. I took it back to
>> the mechanic and we disconnected the fuel line from the carburator to
>> make sure it was getting fuel from the pump. There was a steady flow
>> when the engine was running well, but when the problem was happening it
>> wasn't flowing at all or came out in spurts. I don't think it is
>> clogged, since it flows fine sometimes. So I guess the pump is broken.
>> Too bad, because it is a nice chrome pump, and the replacement I could
>> find on short notice doesn't look as good. Oh well, if this fixes it i
>> can start looking for a better one and replace it later.
>>

>
> Keep your nice chrome pump (IMHO).
> Pumps don't usually work sometimes and then quit for a while,
> only to have miraculous resurrection later.
>
> I don't think you have exhausted the clogging and/or tank venting
> possibilities yet.


More thoughts:
A fairly easy test you can do-

Take the fuel line hose off the pump *inlet*.
You may have to make some "creative" extension to the hose.
Put the hose end in a suitable fuel container.

You should be able to get flow by gravity.
If necessary, jack the front of the car up slightly.

Run maybe 1 gallon of fuel out this way.
If you get a strong, steady stream that doesn't diminish,
then I'll concede that there is no blockage and/or vent problem.
<bg>

Jim
 




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