new problem

[Bahamut]

when i jump on the gas pedal (in park or drive)

it backfires out the carb and **** near kills and idles like a paintshaker it is acting gutless

i have
checked the timing
checked the plugs
checked the wires
cap and rotor
fuel filter
everything fine

i am going to rebuild the carb but are there any other things i should do??

going to change oil soon but my dipstick is broken and i have been leary of screewing with it


------------------
The Beast
1975 Jeep Wagoneer
Bald Tires
Old 360 4v
Leaking TH400
BWQT W/Reduction unit MUD MASTER
Delco Alternator(riged mounts)
Slightly Saggin Springs
Good Sound system
Parts Killer

[Shane]

It sounds like a ignition problem. How did you check the wires? If there is very high resistance in one or more it could cause the spark to arc in the distributor cap, jumping to the next closest terminal. How is the ditributor shaft, it could be worn causing timing change under engine load.

Shane

------------------
1982 J10 Model 25 Pioneer
My Daily driver since 1988
D44,258(.030" over),T5,NP208,AMC20

[Veepster]

I would check your choke and make sure it is not stuck....but otherwise I would guess your carb rebuild will solve the problem....my only other guess would be to make sure you vacuum advance is working properly..

dipstick...I got the entire assembly from the dealer for something like $10...it included tube and dipstick...if you do not HAVE to change the tube, I wouldn't! I had to drop the pan to remove and install my tube....

------------------
Peace.............BartG

the Green Flash!
78 Cherokee
360 2v, TH400 QT with low
4" skyjacker Rancho 9000's
33x12.50 BFG KO's 8" American Racing Baja Rims
Thorley headers, 3" exhaust, Dyno Max
Infiniti power leather seats
50%Luxury Car, 50%Tractor
http://www.teamgodspeed.com

[Bahamut]

thanks for the quick replys


How did you check the wires

i poped them off and stuck a old plug in it


How is the ditributor shaft, it could be worn causing timing change under engine load


i have no idea how to check


If there is very high resistance in one or more it could cause the spark to arc in the distributor cap, jumping to the next closest termina

brand new wires




------------------
The Beast
1975 Jeep Wagoneer
Bald Tires
Old 360 4v
Leaking TH400
BWQT W/Reduction unit MUD MASTER
Delco Alternator(riged mounts)
Slightly Saggin Springs
Good Sound system
Parts Killer

[Veepster]

check dist by looking for side play in the shaft...remove cap and wiggle shaft..there should be none(or very little) side play...

also to check the mechanical advance.....with cap removed, grab rotor and twist, it should twist about 1/2" or so in only one direction and then when you release it should return to original position

------------------
Peace.............BartG

the Green Flash!
78 Cherokee
360 2v, TH400 QT with low
4" skyjacker Rancho 9000's
33x12.50 BFG KO's 8" American Racing Baja Rims
Thorley headers, 3" exhaust, Dyno Max
Infiniti power leather seats
50%Luxury Car, 50%Tractor
http://www.teamgodspeed.com

[Bahamut]

no wiggle and the other works just as you have described it

------------------
The Beast
1975 Jeep Wagoneer
Bald Tires
Old 360 4v
Leaking TH400
BWQT W/Reduction unit MUD MASTER
Delco Alternator(riged mounts)
Slightly Saggin Springs
Good Sound system
Parts Killer

[Bahamut]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Bahamut:
when i jump on the gas pedal (in park or drive)

<HR></BLOCKQUOTE>

note it backfires when the secondarys open up and i backfires only out the secondarys



------------------
The Beast
1975 Jeep Wagoneer
Bald Tires
Old 360 4v
Leaking TH400
BWQT W/Reduction unit MUD MASTER
Delco Alternator(riged mounts)
Slightly Saggin Springs
Good Sound system
Parts Killer

[trssho]

you may have a burned exhaust valve.

------------------
1989 GW Tan w/106K miles
1989 GW Blk Cherry 69k miles

[angry joe]

I believe that trssho is correct. I had the same problem and just could'nt figure it out.
I did evey thing that Bahamut did.Till I took the valve covers off, while it was running, and noticed that the #1 piston exhaust valve was stuck. So, of course the exhaust had to go somewhere and it was coming out of the carb. Everytime I revved it up, it would backfire out of the carb.

In order to fix it, I poured mystery oil in the engine and left it running for a few minutes without revving or driving it. In turn, it worked the lifter loose. I know that this may sound like a long shot but it worked for me.

Oh yeah, another thing you might want to look at if this does'nt work, is perhaps the cam could have gone flat. That would cause the lifter to not go up and down, in turn not allowing the exhaust valve to open.

http://www.ifsja.org/ubb/mad.gif angry joe


p.s How do you quote a message?

[Bahamut]

i pray that this mystery oil will work

------------------
The Beast
1975 Jeep Wagoneer
Bald Tires
Old 360 4v
TH400 (doesen't leak anymore kinda makes me worry i didn't fix it)
BWQT W/Reduction unit(busted cable)
MUD MASTER
Delco Alternator(riged mounts)
Slightly Saggin Springs
Good Sound system
Parts Killer

[denaliak02]

<BLOCKQUOTE>quote:</font><HR> you may have a burned exhaust valve. <HR></BLOCKQUOTE>
<BLOCKQUOTE>quote:</font><HR> I believe that trssho is correct. I had the same problem and just could'nt figure it out.
I did evey thing that Bahamut did.Till I took the valve covers off, while it was running, and noticed that the #1 piston exhaust valve was stuck. So, of course the exhaust had to go somewhere and it was coming out of the carb. Everytime I revved it up, it would backfire out of the carb. <HR></BLOCKQUOTE>

I found this old thread and think it may be my problem as well.... This morning, the Chero gave a shotgun report out the exh.!!(probably scared the &^%$ out of the neighbors at 7am) Would a burnt exh valve cause this. I just had exh put on, and the exh guy said it's burnt for sure. I can hear a (leak) sound, but he said no leaks were found, his opinion is a burnt valve. I haven't done a compress. ckeck yet, will this tell me for sure?

thanks

[Brown Bear]

If it's burnt, then it's burnt open if anything. Otherwise exhaust couldn't get past it. Usually, backfire through exhaust is running rich. A vacuume test would tell you something, but a leakdown test could tell you more.

[SpruceMoose]

how about this: a bad accelerator pump. if it isnt working, when you accelerate the engine rapidly it will lean WAY out, causing a backfire, and it will run rough until the fuel/air ratio is back to normal. does it go bang if you slowly increase the rpms to the same level as when you stomp on it? and check the pump output with the engine off. see if you are getting a god squirt of gas when you open the throttle. hth.

sm.

[Yaz]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Bahamut:
i pray that this mystery oil will work

<HR></BLOCKQUOTE>

we use mystery oil when overhauling plane engines or when a part is jammed (like a valve)

i had this prob, with me the advance was advancing too much burning the fuel before the valve closed.

[andy d]

i fog my lawnmowers with mystery oil before i put them away. its a great topcylinder lube. i love the smell of it.im with SM, my vote is the accellerater pump too. good to hear from you Bahamut

[denaliak02]

Hey thanks for the tips

<BLOCKQUOTE>quote:</font><HR> Brown Bear said: Usually, backfire through exhaust is running rich. A vacuume test would tell you something, but a leakdown test could tell you more. <HR></BLOCKQUOTE>

thanks B_B, this weekend I may try the leakdown test. I think this is just where you fill the chamber w/air and wait for pressure to drop? is this correct?

<BLOCKQUOTE>quote:</font><HR> SpruceMoose said: how about this: a bad accelerator pump. if it isnt working, when you accelerate the engine rapidly it will lean WAY out, causing a backfire, and it will run rough until the fuel/air ratio is back to normal. does it go bang if you slowly increase the rpms to the same level as when you stomp on it? and check the pump output with the engine off. see if you are getting a god squirt of gas when you open the throttle. hth.
<HR></BLOCKQUOTE>

it doesn't have much acceleration, i have to ease into it, or it will fall on it's face! i'll check the gas flow and see if it's continous.

i was thinking it was a timing prob, cause i just messed w/that, and i haven't exactly gotten around to putting a light to it, just by sound. it starts ok so i figure the timing's close. but i wonder if the accel pump is bad, or carb needs rblt. this weekend i'll check some stuff. thanks SM.

Thanks Jaz, I'll try to eliminate the timing, then focus on the valve or the carb!! what fun huh?

btw, went wheeling this weekend and had a blast! the Chero performed flawlessly!!

thanks to all,
Justin

[Jeep Craze]

Just out of curiousity, what is mystery oil?

[denaliak02]

HA!

akin to snake oil, i believe... just kidding.

i believe it's a shortened brand name, Marvel's Mystery Oil. (help if i'm wrong) you find it near the stp oil treatment, cd-2, etc...

[Dan G]

Marvel Mystery Oil it is. Comes in a reddish rectangular steel can with a label that looks like it was designed in the 1950's.

[Gladi8r]

I get it at Wal-Mart. Always add a Qt of Marvels when changing oil. Keeps the insides nice and clean :D :D

[SpruceMoose]

hey jaz: what do you use the mystery oil for on the plane engines? i have overhauled dozens of them, and i just use the recommended 50/50 mixture of stp and 100w.

btw, a&p since 81, IA since 85.

sm.

[Rogue]

a LEAKDOWN TEST will tell you several things about the inside of the engine. first bar (turn) the engine until the rotor under the cap points to the cylinder in question, this will place that cylinder at Top Dead Center on the compression stroke( within a few degrees which is close enough ), remove the spark plug from that cylinder and add air, regulate the air to 80 - 90 lbs to keep the air from turning the engine, most newer compression gauges have quick connect fitting that readily adapt to your air hose otherwise you'll have to adapt. so now you got pressurized air in your engine now what? listen for leaks, pull the dipstick out - if excessive air is coming out then your rings are shot, listen at the tailpipe - bad exhaust valve, listen at the carburetor - bad intake valve, open radiatior cap if you see bubbles then your head gasket is blown this is not a perfect science of course once a problem is diagnosed it will have to be torn down for visual inspection, sometimes what is thought to be a bad valve seat can sometimes be a valve stuck open and can be verified by removal of the valve cover and remedied with a few taps from a small hammer-this of course would tend to happen to an engine that has sat for a long period of time, a burnt valve is a direct result of a faulty carburetor (power valve) or misadjusted carburetor good luck hope this helps

[Millerluck]

I'm with SpruceMoose

I'm having the exact same problem with my 4350 carb. The secondarys open and pow!

I know its the accelerator pump on mine. looking down the carb with it off. some times it squirts good some times not so good.

The hole the cross shaft goes through is all sloppy. I plan to bush it as soon as the big weekend gets here.

This same shaft controls the up and down movement of the metering rods. So turning that little blue pice of crap nut also will change your mixture.

In my case I belive this slop is causing my problems because the accelerater pump isn't getting pushed down properly,and it's not letting the metering rods up smoothly.

Just my .02


Later

Larry Miller