CJ8 weber conversion timing/backfire problem

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M

Michael Pomeroy

Guest
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
[email protected]
 
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
> [email protected]
 
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 <[email protected]>
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
>[email protected]


-----
Michael Pomeroy
[email protected]
 
On Sun, 14 Sep 2003 18:12:28 -0400, Mike Romain <[email protected]>
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
>> [email protected]


-----
Michael Pomeroy
[email protected]
 
Carb came loose...

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

Michael Pomeroy wrote:
>
> 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 <[email protected]>
> 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
> >[email protected]
>
> -----
> Michael Pomeroy
> [email protected]
 

"Michael Pomeroy" <[email protected]> wrote in message
news:[email protected]...
> 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
..



 
On Sun, 14 Sep 2003 23:33:49 GMT in rec.autos.makers.jeep+willys, Michael
Pomeroy <[email protected]> was alleged to have written:
>And I left out one very important detail -- it BACKFIRES THROUGH THE
>CARBURATOR!

Re-check that all your spark plug wires are connected right.

 
Just a note to let those who have offered suggestions know that I have
read and considered them all.

I think the problem is probably directly related to a greater lack of
knowledge and understanding than I thought.

So today I bought enough vacuum tubing to replace all the old stuff
(it is an '82, so this can't but help), but the earliest I can get
back to working on the Jeep is this coming weekend.

In the meantime I will be studying and thinking and working through
all the suggestions in my mind. Then I plan to thorougly document
where each hose currently runs (in case all else fails I can put them
back like they are now) and then try to make it right.

When I do I'll let everybody know how it goes -- or have more
questions to ask.

Thanks .....

Mike

On Sun, 14 Sep 2003 21:16:16 GMT, Michael Pomeroy <[email protected]>
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
>[email protected]


-----
Michael Pomeroy
[email protected]
 
If I can be of assistance, feel free to ask.

I see more of those 80's engines with vacuum lines running incorrectly
than I see set up properly.

Lots of 'mechanics' out there even get lost in that maze, so don't feel
too bad....
;-)

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

Michael Pomeroy wrote:
>
> Just a note to let those who have offered suggestions know that I have
> read and considered them all.
>
> I think the problem is probably directly related to a greater lack of
> knowledge and understanding than I thought.
>
> So today I bought enough vacuum tubing to replace all the old stuff
> (it is an '82, so this can't but help), but the earliest I can get
> back to working on the Jeep is this coming weekend.
>
> In the meantime I will be studying and thinking and working through
> all the suggestions in my mind. Then I plan to thorougly document
> where each hose currently runs (in case all else fails I can put them
> back like they are now) and then try to make it right.
>
> When I do I'll let everybody know how it goes -- or have more
> questions to ask.
>
> Thanks .....
>
> Mike
>
> On Sun, 14 Sep 2003 21:16:16 GMT, Michael Pomeroy <[email protected]>
> 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
> >[email protected]
>
> -----
> Michael Pomeroy
> [email protected]
 
Other than being loud and startling, does backfiring hurt anything?
Mine backfires occasionally, esp. when the engine is hot and has been
running all day, but it is infrequent enough that I haven't worried
about it.
 
Just my 2 cents worth on this. My '76 CJ had the original Carter POS carb,
and the even worse Prestolite breakerless ign. I really wanted to keep the
thing stock but after too many months of the cold running stumbles, farts &
backfires from the carb, and endless stalling episodes caused by the
ignition & its bundle-of-snakes wiring, I tossed the entire setup. I
replaced the carb with a Weber 551 kit (installed on a 2 barrel manifold
from a 258) and installed a DUI ignition kit. PRESTO, now the thing runs
like a top, no stalling, better performance & mileage.

"Joshua Nelson" <[email protected]> wrote in message
news:[email protected]...
> Other than being loud and startling, does backfiring hurt anything?
> Mine backfires occasionally, esp. when the engine is hot and has been
> running all day, but it is infrequent enough that I haven't worried
> about it.


 
Joshua Nelson wrote:

> Other than being loud and startling, does backfiring hurt anything?
> Mine backfires occasionally, esp. when the engine is hot and has been
> running all day, but it is infrequent enough that I haven't worried
> about it.

What kind of "sabbatical" do you call that? Why are you still trolling here?

 
Cal Wheeler <[email protected]> wrote in message news:<[email protected]>...
>
> What kind of "sabbatical" do you call that?


I thought several days off, including a weekend, would be long enough
to get you to calm down and act like an adult. Alas, apparently not.
Back to the killfile you go!
 
Joshua Nelson wrote:

> Cal Wheeler <[email protected]> wrote in message news:<[email protected]>...
>
>>What kind of "sabbatical" do you call that?
>
>
>
> I thought several days off, including a weekend, would be long enough


for people to forget how much of a troll and liar you are?

 
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