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CJ8 weber conversion timing/backfire problem

1982 CJ8 6-cyl.

Did the Weber conversion.

Problems with timing/advance.

If I understand correctly, the only vacuum line that should now be
involved is that the line that comes out of the distributor should now
go directly to the carburetor. Everything else should be plugged. Is
that correct?

If I do this, and set the initial advance at idle as per the info
sticker on the vehicle to +-5 degrees it runs well. But, under harder
acceleration it will backfire HARD at higher revolutions. Under easy
acceleration without revving it up it seems to do great. Timing light
doing this without load shows that it goes full advance almost
immediately.

If I go back and run the vacuum as it was originally plumbed, through
the CTO valve (with all the other now extra vacuum hoses plugged) --
it has a huge flat spot on acceleration and still backfires (though
maybe slightly less hard) like above. The timing light shows a MAJOR
retarding immediately upon acceleration; then goes to full advance.

If I set the initial advance to about 10 degrees or more it doesn't
have the above symptoms with the vacuum hoses either way, but also
doesn't have much power at take-off.

Air pump is still connected and, I assume functioning.

And, fwiw, correct new plugs, wires, rotor, and cap.

What am I missing; what should I be doing now?

Thanks .....

Mike

-----
Michael Pomeroy
pomerom@yahoo.com

Re: CJ8 weber conversion timing/backfire problem

Which carb did you have?

Was it the electric one or no computer?

If the computer is still in the system, it can act strange, so can a big
vacuum leak somewhere or EGR messing up...

And No, you can't plug off all the vacuum lines....

The Charcoal canister still needs to be working as does the EGR valve
and if you live anywhere near freezing, the air filter hot air flaps.
The EGR actually uses a thermostat in the air filter along with the CTO.

Check this site for info on the computer and on the vacuum lines needed
for a 'basic' good runner.

http://home.sprynet.com/~dale02/ignmods.htm

Check his index at the bottom too!

I run my 86, well, 78 engine at 9 deg with the ported vacuum, (vacuum
when the throttle gets punched), no computer, running 91 octane 'gas'
and it just rocks!

I have 3:31 gears and pulling out onto a 40 mph road, if I give it too
fast it will light up my 33x9.5 BFG muds and squawk off and will wrap
the spedo in 4th, forget 5th...

I tried the stock manifold vacuum and found a dead spot. I tried no EGR
and found a dead spot.

No backfires, that is something else.

Loose plug wire?

Major leak at the intake or exhaust manifold?

The carb came loose? (They like to do that at the base plate once they
get warmed up the first couple times, <grin>, seen that a lot over the
years)

One port on the carb still open?

A line to the CTO that opens to nothing?

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

Michael Pomeroy wrote:
>
> 1982 CJ8 6-cyl.
>
> Did the Weber conversion.
>
> Problems with timing/advance.
>
> If I understand correctly, the only vacuum line that should now be
> involved is that the line that comes out of the distributor should now
> go directly to the carburetor. Everything else should be plugged. Is
> that correct?
>
> If I do this, and set the initial advance at idle as per the info
> sticker on the vehicle to +-5 degrees it runs well. But, under harder
> acceleration it will backfire HARD at higher revolutions. Under easy
> acceleration without revving it up it seems to do great. Timing light
> doing this without load shows that it goes full advance almost
> immediately.
>
> If I go back and run the vacuum as it was originally plumbed, through
> the CTO valve (with all the other now extra vacuum hoses plugged) --
> it has a huge flat spot on acceleration and still backfires (though
> maybe slightly less hard) like above. The timing light shows a MAJOR
> retarding immediately upon acceleration; then goes to full advance.
>
> If I set the initial advance to about 10 degrees or more it doesn't
> have the above symptoms with the vacuum hoses either way, but also
> doesn't have much power at take-off.
>
> Air pump is still connected and, I assume functioning.
>
> And, fwiw, correct new plugs, wires, rotor, and cap.
>
> What am I missing; what should I be doing now?
>
> Thanks .....
>
> Mike
>
> -----
> Michael Pomeroy
> pomerom@yahoo.com

Re: CJ8 weber conversion timing/backfire problem

And I left out one very important detail -- it BACKFIRES THROUGH THE
CARBURATOR!

Not the exhaust.

Help please ......

On Sun, 14 Sep 2003 21:16:16 GMT, Michael Pomeroy <pomerom@yahoo.com>
wrote:

>1982 CJ8 6-cyl.
>
>Did the Weber conversion.
>
>Problems with timing/advance.
>
>If I understand correctly, the only vacuum line that should now be
>involved is that the line that comes out of the distributor should now
>go directly to the carburetor. Everything else should be plugged. Is
>that correct?
>
>If I do this, and set the initial advance at idle as per the info
>sticker on the vehicle to +-5 degrees it runs well. But, under harder
>acceleration it will backfire HARD at higher revolutions. Under easy
>acceleration without revving it up it seems to do great. Timing light
>doing this without load shows that it goes full advance almost
>immediately.
>
>If I go back and run the vacuum as it was originally plumbed, through
>the CTO valve (with all the other now extra vacuum hoses plugged) --
>it has a huge flat spot on acceleration and still backfires (though
>maybe slightly less hard) like above. The timing light shows a MAJOR
>retarding immediately upon acceleration; then goes to full advance.
>
>If I set the initial advance to about 10 degrees or more it doesn't
>have the above symptoms with the vacuum hoses either way, but also
>doesn't have much power at take-off.
>
>Air pump is still connected and, I assume functioning.
>
>And, fwiw, correct new plugs, wires, rotor, and cap.
>
>What am I missing; what should I be doing now?
>
>Thanks .....
>
>Mike
>
>-----
>Michael Pomeroy
>pomerom@yahoo.com

-----
Michael Pomeroy
pomerom@yahoo.com

Re: CJ8 weber conversion timing/backfire problem

Too lean, jet it.
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Michael Pomeroy wrote:
>
> And I left out one very important detail -- it BACKFIRES THROUGH THE
> CARBURATOR!
>
> Not the exhaust.
>
> Help please ......

Re: CJ8 weber conversion timing/backfire problem

"Michael Pomeroy" <pomerom@yahoo.com> wrote in message
news:q5m9mv8bhd66mhvq15b4c0tcvc0il9nsne@4ax.com...
> 1982 CJ8 6-cyl.
>
> Did the Weber conversion.
>
> Problems with timing/advance.
>
> If I understand correctly, the only vacuum line that should now be
> involved is that the line that comes out of the distributor should now
> go directly to the carburetor. Everything else should be plugged. Is
> that correct?
>
> If I do this, and set the initial advance at idle as per the info
> sticker on the vehicle to +-5 degrees it runs well. But, under harder
> acceleration it will backfire HARD at higher revolutions. Under easy
> acceleration without revving it up it seems to do great. Timing light
> doing this without load shows that it goes full advance almost
> immediately.

Are you disconnecting the vacuum advance when you time it?
__
Steve
..

Re: CJ8 weber conversion timing/backfire problem

For starters, check to make sure the carb isn't leaking at the base.
You can spray some carb cleaner around the base while it is running to
see if the idle changes. While there, give the intake manifold a spray
along where it bolts to the head. If the idle changes even slightly,
you have found a leak.

Vacuum....

Ok, you have two types of vacuum. One is 'ported', the other is
'manifold'.

A 'ported' vacuum only sucks when the throttle is open. Manifold vacuum
sucks the most when the throttle is closed.

I do not know which nipple on your carb is which.... You think the carb
only has one nipple plus the manifold vacuum for the PCV valve? That
could be, but I suspect there is another you are missing hidden under
there somewhere, if so, that can be the backfiring.

How were you firing up the CTO 'timing' advance in your first post
below? It sure sounded like you had a manifold vacuum on it if the
timing was full advanced at idle, then dipped right away under throttle
and slowly advanced after that.

To fire up the EGR and charcoal canister, you need a ported vacuum.
This can be 'T' fitted with the timing advance line if you are using the
ported timing.

One side of the CTO valve will be a switch that only allows air flow
when the engine is hot and shuts off the flow when the engine is cold.

The other side or other nipple on the CTO can, if you have the multi CTO
with 3 or more nipples, only allow air flow when the engine is cold.

You can find this by blowing through a hose attached to one of the
nipples. Once you locate the two nipples that only flow hot, you run a
ported vacuum to one of them. From the other side of it, you run a line
and T it to the EGR and charcoal canister purge valve so they only turn
on when the engine is hot and you are at speed via the ported vacuum.

Any unused nipples on the CTO should be blocked. An inch of hose with a
bolt in it works as a plug for them.

This 'could' give you a little bit of hesitation on a medium warmed up
engine because you are missing the air filter thermostat, but once fully
warmed up it will go away.

Oh and just in case... when you set the timing, the vacuum line needs
to be off the distributor and the line plugged with a bolt or pencil or
something.

Hope this gets you somewhere...

Mike

Michael Pomeroy wrote:
>
> On Sun, 14 Sep 2003 18:12:28 -0400, Mike Romain <romainm@sympatico.ca>
> wrote:
>
> >Which carb did you have?
> >
> It was the Carter.
> >Was it the electric one or no computer?
> >
> Yes -- well, had an electric choke. No computer.
>
> >If the computer is still in the system, it can act strange, so can a big
> >vacuum leak somewhere or EGR messing up...
> >
> >And No, you can't plug off all the vacuum lines....
> >
> The Weber from the conversion kit does NOT have all the vacuum ports
> the Carter had. The kit instructions simply say to "Locate the vacuum
> advance hose and connect it to the vacuum advance port on the
> carburetor." No further vacuum related instructions or suggestions.
>
> >The Charcoal canister still needs to be working as does the EGR valve
> >and if you live anywhere near freezing, the air filter hot air flaps.
> >The EGR actually uses a thermostat in the air filter along with the CTO.
> >
> Well, this is good news and bad news. I live in the deep south of the
> USA so (low)temperature extremes are seldom an issue for me.
>
> The air cleaner that comes with the Weber does not have the "hot air
> flap" and does NOT have the connectivity for the lines you describe
> above. So I plugged them for now -- there must be some way for this
> to work without them in the air cleaner housing?
>
> The only line the replacement air filter housing has is for the vent
> from the rear of the valve cover (just like the original air cleaner
> housing).
>
> So the carburetor has one line for "vacuum" and one line to relieve
> pressure from the valve cover. That is it!
>
> >Check this site for info on the computer and on the vacuum lines needed
> >for a 'basic' good runner.
> >
> >http://home.sprynet.com/~dale02/ignmods.htm
> >
> >Check his index at the bottom too!
> >
> Will do.
>
> >I run my 86, well, 78 engine at 9 deg with the ported vacuum, (vacuum
> >when the throttle gets punched), no computer, running 91 octane 'gas'
> >and it just rocks!
> >
> >I have 3:31 gears and pulling out onto a 40 mph road, if I give it too
> >fast it will light up my 33x9.5 BFG muds and squawk off and will wrap
> >the spedo in 4th, forget 5th...
> >
> >I tried the stock manifold vacuum and found a dead spot. I tried no EGR
> >and found a dead spot.
> >
> So, where did you find to get the ported vacuum that works?
>
> >No backfires, that is something else.
> >
> >Loose plug wire?
> >
> >Major leak at the intake or exhaust manifold?
> >
> >The carb came loose? (They like to do that at the base plate once they
> >get warmed up the first couple times, <grin>, seen that a lot over the
> >years)
> >
> >One port on the carb still open?
> >
> >A line to the CTO that opens to nothing?
> >
> I don't think any of these apply, or don't yet fully understand, but
> will keep looking.
>
> I guess I'm just ignorant about how this all should go together.
>
> Mike
>
> >Mike
> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> >88 Cherokee 235 BFG AT's
> >
> >Michael Pomeroy wrote:
> >>
> >> 1982 CJ8 6-cyl.
> >>
> >> Did the Weber conversion.
> >>
> >> Problems with timing/advance.
> >>
> >> If I understand correctly, the only vacuum line that should now be
> >> involved is that the line that comes out of the distributor should now
> >> go directly to the carburetor. Everything else should be plugged. Is
> >> that correct?
> >>
> >> If I do this, and set the initial advance at idle as per the info
> >> sticker on the vehicle to +-5 degrees it runs well. But, under harder
> >> acceleration it will backfire HARD at higher revolutions. Under easy
> >> acceleration without revving it up it seems to do great. Timing light
> >> doing this without load shows that it goes full advance almost
> >> immediately.
> >>
> >> If I go back and run the vacuum as it was originally plumbed, through
> >> the CTO valve (with all the other now extra vacuum hoses plugged) --
> >> it has a huge flat spot on acceleration and still backfires (though
> >> maybe slightly less hard) like above. The timing light shows a MAJOR
> >> retarding immediately upon acceleration; then goes to full advance.
> >>
> >> If I set the initial advance to about 10 degrees or more it doesn't
> >> have the above symptoms with the vacuum hoses either way, but also
> >> doesn't have much power at take-off.
> >>
> >> Air pump is still connected and, I assume functioning.
> >>
> >> And, fwiw, correct new plugs, wires, rotor, and cap.
> >>
> >> What am I missing; what should I be doing now?
> >>
> >> Thanks .....
> >>
> >> Mike
> >>
> >> -----
> >> Michael Pomeroy
> >> pomerom@yahoo.com
>
> -----
> Michael Pomeroy
> pomerom@yahoo.com