Back firing on decelleration

[Hedgehog]

Lumpy - Will be done sir. I'm just working down the easy list right now. Setting the timing is easy, it's seeing the timing mark that is always the fun part.

 

[Lumpy Grits]

Know what you mean about the "T" mark
Good luck.
LG

 

[Posi]

Setting the timing is easy, it's seeing the timing mark that is always the fun part.

I brush on liquid paper to make the timing marks stand out.

 

[Hedgehog]

I've highlighted the heck out of the mark, actually seeing the mark is the hard part. If you have an AC compressor you have only a tiny window to shoot the light through and part of that is occupied by a heater hose. So you are faced with attempting to point the light and look through the same hole that only one eye can see through, all the while your eye is trying to focus on the edge of the hole and not down into the hole. It can be a struggle. My light isn't quite strong enough to see well during a bright Arizona day and is to much in black dark, it works well in the twilight hours. It would be only a few minutes work if not for the struggle getting your eye in exactly the right spot to see.

 

[Posi]

I have both a V8 and AC, and I don't view the timing marks from the top. I found good results pointing the light from just left of the grill and under the passenger side fender using a long handle inspection mirror. There I have a good view. It's all about finding the sweet spot.

Try timing a L134 "Go Devil" off the fly wheel. =)
Or 70 MG midget

 

[Hedgehog]

I've tried crawling my big ol' self under the CJ, but lost my nerve with the running engine, moving belts and that spinning fan right there in my face. Doing this usually by myself there simply doesn't seem o be enough hands and arms.

Don't get me wrong, it's not impossible, I've done it about a dozen times, its just a little tricky until, as you say, you find the sweet spot.

 

[Posi]

The thing I'm watchful of is the mirror making contact with the belt. I don't crawl under the Jeep rather kneel on one knee in front of the passenger side tire. I view from the side.

 

[Lumpy Grits]

Be careful around that dang fan.
There's a reason I only have 9 7/8 fingers-
LG

 

[tarry99]

I'm wondering why your messing with idle mixture screws? That circuit is low speed only and only effects just what it says it's for..........Idle.

You stated the motor was Rich..........that is probably part of the problem as anything with an air pump is normally lean. Air injection pumps and smog related equipment will also cause that via leaks.

Backfires are normally excess un-burned fuel in the exhaust system that gets re-ignited by another hot charge...........a vacuum leak or the possibility of an exhaust leak between the head & exhaust manifold should be looked at..........set the timing to whatever it calls for, but I would be looking at the smog system.

Whats the spark plugs look like?

 

[Hedgehog]

I have always felt that the engine was running rich, but nobody around here (Tucson) seems willing to address the question. As you have stated I thought backfiring was caused by excess fuel in the exhaust system. It has been suggested, but I haven't messed with the idle mixture screws.

Now we've gathered a number of thoughts on the subject and I have a bag full of things to check .... plugs (its been a while) .... timing .... replace old gaskets at the header pipe .... check to make sure both idle jets are set the same .... The manifold bolts should be checked, last summer on her first long trip the manifold gasket took a hit from loosened bolts. Several solutions have been offered to take care of that problem. No question the bolts should be checked.

 

[hdgapeach]

Know what you mean about the "T" mark
Good luck.
LG

Yeah, me too!
Had to get the 25 y/o son to run the timing light while I twisted on the distributor the other day! Gettin' old is really startin' to suk (and I had Lasix done in 2005).

 

[hdgapeach]

I brush on liquid paper to make the timing marks stand out.

Heck, them things could be shinning bright neon green and I still wouldn't be able to see 'em like I used to just a few years ago. Maybe a pen camera transmitting onto a big screen HD TV would get it done good enough! Yeah, that'd work...

Had to back of a degree of shade in my auto darkening welding helmet, too! Friggin' welding beads started curving away from the joints I was stick welding. Glasses don't help like I thought they would, either.

Just a part of falling apart, I guess.

 

[Posi]

Lol, I hear yeah