flat spot with acceleration

mep67 · Posted: Wed Apr 18, 2012 6:18 pm Post subject: flat spot with acceleration

I'm trying to get my 67 running after sitting in the garage for 3 years. Everything is working well after a new battery and adjustment of the timing and idle. Except, there is a severe flat spot on initial acceleration in 1st and second gears to the point the engine is almost stalling out. At higher RPM's it's running fine.
I'm not sure what the next trouble shooting step is.
Is it possible there might be a blockage in the jets or something? Should I pull and rebuild the carb?

Thanks for the input.

Lucatero · Posted: Wed Apr 18, 2012 6:21 pm Post subject:

What distributor do you have in your vehicle? Did you set the valve lash too?
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64 Beetle Type 1/Totaled after owning 5day!
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mep67 · Posted: Wed Apr 18, 2012 6:37 pm Post subject:

113 905 205K

I did the valves shortly before storing, but haven't redone them.

mep67 · Posted: Wed Apr 18, 2012 6:40 pm Post subject:

Bosch number 0231 137 009

Is that the 009 distributor that seems to suck so much?

66brm · Posted: Wed Apr 18, 2012 6:57 pm Post subject:

Confirm that when you actuate the throttle the accelerator pump in the carb squirts into the throat.
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Lucatero · Posted: Wed Apr 18, 2012 6:58 pm Post subject:

glutamodo · Posted: Wed Apr 18, 2012 8:41 pm Post subject:

NO, the 0 231 137 009 is NOT the bad one.
It is the 0 231 178 009 that is the infamous centrifugal 009.

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

(and actually, German centrifugal 009s in good shape along with single port engines often get along OK)

The 205K/009 is a vacuum-only advance distributor and is a decent one.

Are you still running a 1967 30PICT-1 and is it still a single port engine?

I would do as mentioned, verify spray of the acclerator pump.

Also, an engine that's been sitting, may have bad hoses for the vacuum advance... make sure you're not leaking there.

-Andy

mep67 · Posted: Wed Apr 18, 2012 9:45 pm Post subject:

Thanks so much for the replies. Yes, still single port with 67 with 30pict 1. I think my vacuum hose is prob bad. Just to confirm, should i set advance at 30 btdc at full advance with vacuum hose plugged at distributor and carb? Thanks.
For accel pump, just take off air filter and pull throttle lever looking down barrel?

66brm · Posted: Wed Apr 18, 2012 9:47 pm Post subject:

glutamodo · Posted: Wed Apr 18, 2012 10:05 pm Post subject:

crvc · Samba Member Joined: April 28, 2004 Posts: 1013

I had a 'flat spot' due to plugged heat risers. Once I cleared them the problem was gone.

crvc

tb03830 · Posted: Thu Apr 19, 2012 8:44 am Post subject:

I had this exact probelm. It started when my carb got very dirty inside.

It turned out that the accelorator pump was not pushing enough fuel down the throat due to being clogged. I went through two used Carbs and when I finally spent the money on a good carb it went away. I also noticed that it still existed a little with my .009 but that is normal. I put my SVDA back on and it disappeared compleatly. Yea, I replace a carb that could and later was repaired.

I also noticed at the time I had a very small leak in the Manifold to the #1/2 head. That I am sure contributed.
_________________
"Si vis pacem, para bellum - If you want peace, prepare for war."

1964 Convertible Bug - 1600cc SP engine with a stock H30/31 Carb and SVDA Distributor - Swing Arm Highway Flyer Tranny, Chassey #5 849 630

ejonn · Posted: Thu Apr 19, 2012 10:34 am Post subject:

I just helped with a 67 1500 with same carb and dist. set the timing as recommended and it had a bad flat spot.....reset idle timing with vac line connected ( to 7.5 before with 48 dwell) and it runs like a finely oiled sewing machine.
You might try that....
Im not sure why....but it worked well on that one....

KTPhil · Posted: Thu Apr 19, 2012 11:13 am Post subject:

Make sure the accel pump check ball is free to move (you have to remove the carb and shake it to tell). At least, I THINK I remember the 30 PICT having a check ball... check here first!

Many do not install the accel pump diaphragm right. You have to loosely fit the cover screws, then tighten them with the throttle held FULLY open. If you tighten it with it closed, you may stretch and tear the rubber when you floor it, and you will reduce the pump output.

Also, aim the accel pump spray to go between the just-opened throttle plate and the venturi wall. It should NOT hit either and splatter-- that makes the fuel not atomize well and can cause a flat spot.

Of course, check the easy stuff like vacuum hoses and the integrity of the vacuum diaphragm in the distributor advance unit.

mep67 · Posted: Thu Apr 19, 2012 6:36 pm Post subject:

Well, I pulled the carb and have cleaned and started to put it back together. Replaced vacuum lines; they were definitely dry and leaking.
When putting the carb back together, I found the fuel pump spring was on the wrong side of the diaphragm. The 2 jets (ends up I have an H30/31 carb) were in the wrong spots. Also, there is no spring in for the vacuum diaphragm pump.

Any ideas where to get a replacement diaphragm spring or at least what specs they are

Again thanks for all the help.

tb03830 · Posted: Thu Apr 19, 2012 8:36 pm Post subject:

Get a Carb rebuild kit and all the parts will be in it.
_________________
"Si vis pacem, para bellum - If you want peace, prepare for war."

1964 Convertible Bug - 1600cc SP engine with a stock H30/31 Carb and SVDA Distributor - Swing Arm Highway Flyer Tranny, Chassey #5 849 630

glutamodo · Posted: Thu Apr 19, 2012 8:54 pm Post subject:

Rebuild Kit? Bad name for it, it's more like a gasket set. you'll get a needle/seat that is almost always inferior in quality to the one that's in the carb, some paper gaskets that you may not need as the originals are often still reusable, some O-rings you won't need for a 30PICT-1, and the diaphrams for the choke pull-off and the accelerator pump, about the only things you probably really do need. There won't be any springs in there. Nothing at all about rebushing the throttle shafts, which is part of a REAL rebuild, but that's to be expected because that is specialty work, not bolt-on parts by any means.

mep67 · Posted: Fri Apr 20, 2012 5:51 pm Post subject:

Ok, so I've done the following:

1. got new vacuum line- no leaks now

2. Took carb apart and "rebuilt" it. Switched the two jets on the carb side to 50 in the straight port and 65 in the angled (it's an H30/31)

3. Went to local VW store and got a spring for the vacuum diaphragm pump.

4. Made sure accel pump sprays in the correct area.

5. Looked down throat and can see spray from accelerator pump when the throttle is depressed.

6. Rechecked advance with vacuum hose pluged, it's at 7.5BTDC

I've still got a terrible stumble when I first hit the accelerator to where I'm almost stalling out. Any other ideas before I just take it to a shop?
Also, really basic question here. Do I need to fill the fuel bowl manually?

glutamodo · Posted: Fri Apr 20, 2012 6:31 pm Post subject:

How well does the advance look with the timing light when you have the vacuum line connected? It should jump and advance pretty quickly.

ejonn · Posted: Fri Apr 20, 2012 6:57 pm Post subject:

Just throwing this out for thought...
Does your 30/31 have the 2 vac ports? And if so are you connected to the correct one?

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