I have changed them... but your logic is good! I also suspected about them... however I could see the jets of fuel when I pump the throttle after rebuilding the carbs. Maybe I could check them again.edzz wrote:when you rebuilt the carbs did you replace the accelerator pump seals?
http://www.aa1car.com/library/carburetor.htm
http://www.thecarburetorshop.com/Troubleshooting.htm
Can't find vaccum leak. Backfiring, missing on acceleration.
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Re: Can't find vaccum leak. Backfiring, missing on accelerat
Jerome
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Re: Can't find vaccum leak. Backfiring, missing on accelerat
Engine still a mess.
After finding the hose for vacuum balance between the intake manifolds, I expected all problems to be solved.. but unfortunately i am still dealing with backfiring and low power on acceleration. I need to pump the throttle to get the engine to carry load to start the truck.
Idles ok, actually idles very smoothly.
Running pertronix - nkg bp6es plugs changed yesterday - blue Bosch coil
Carburetor rebuilt to the best of my skills and knowledge. New gaskets. Float level checked with the correct tool/technique with engine pump running.
New fuel pump.
New fuel lines. and transparent clean fuel filter.
Got a timing light gun and set it to my best guess of about 5 to 10 degrees advance (about 10 mm from block mark to pulley mark.)
Tested auto advance with RPM and it looks like it is working fairly well. Back and forth.
Idle screws are to 3 turns out now.
Adjusted all valves and found all exhaust valves to be tight. Now all back to 0.2mm.
I bought starter fluid. Sprayed the base of the carbs and the shaft ends. No noticeable increase in rpm.
UPDATE: took the tunnel out, ran the engine without the tunnel and sprayed ether all over the carbs, manifolds, all gaskets.. no RPM increase, and no explosions ( ).
SO: I am back to 0.
I am now going to start with ignition again, and check timing again. Next, all the voltages again.
After finding the hose for vacuum balance between the intake manifolds, I expected all problems to be solved.. but unfortunately i am still dealing with backfiring and low power on acceleration. I need to pump the throttle to get the engine to carry load to start the truck.
Idles ok, actually idles very smoothly.
Running pertronix - nkg bp6es plugs changed yesterday - blue Bosch coil
Carburetor rebuilt to the best of my skills and knowledge. New gaskets. Float level checked with the correct tool/technique with engine pump running.
New fuel pump.
New fuel lines. and transparent clean fuel filter.
Got a timing light gun and set it to my best guess of about 5 to 10 degrees advance (about 10 mm from block mark to pulley mark.)
Tested auto advance with RPM and it looks like it is working fairly well. Back and forth.
Idle screws are to 3 turns out now.
Adjusted all valves and found all exhaust valves to be tight. Now all back to 0.2mm.
I bought starter fluid. Sprayed the base of the carbs and the shaft ends. No noticeable increase in rpm.
UPDATE: took the tunnel out, ran the engine without the tunnel and sprayed ether all over the carbs, manifolds, all gaskets.. no RPM increase, and no explosions ( ).
SO: I am back to 0.
I am now going to start with ignition again, and check timing again. Next, all the voltages again.
Jerome
CRJ Driver
CRJ Driver
Re: Can't find vaccum leak. Backfiring, missing on accelerat
-running pertronix so condenser is not used, it is now just a filler for the hole it fits in.
I cant spot mention if your running civilian distributor cap, rotor and wires. if civilian cap has the rotor been shortened as required?
popping, spitting, backfiring on deceleration is commonly an exhaust leak, I fought with this until I followed Jim L's advice and used high-temp exhaust silicon gasket sealant on my flange gaskets. this didn't get rid of any real performance issues just quit causing people on sidewalks from having their little accidents.
back to the carbs Im assuming you have been using Jim L's excellent write ups on the carbs.
http://www.goatwerks.com/carb.htm and http://www.goatwerks.com/carbarticle.htm
I cant spot mention if your running civilian distributor cap, rotor and wires. if civilian cap has the rotor been shortened as required?
popping, spitting, backfiring on deceleration is commonly an exhaust leak, I fought with this until I followed Jim L's advice and used high-temp exhaust silicon gasket sealant on my flange gaskets. this didn't get rid of any real performance issues just quit causing people on sidewalks from having their little accidents.
back to the carbs Im assuming you have been using Jim L's excellent write ups on the carbs.
http://www.goatwerks.com/carb.htm and http://www.goatwerks.com/carbarticle.htm
Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.
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Re: Can't find vaccum leak. Backfiring, missing on accelerat
Yes I have... and found that the front carb is probably the culprit... the acceleration pump puts about half of the flow the back pump does...edzz wrote:-
back to the carbs Im assuming you have been using Jim L's excellent write ups on the carbs.
http://www.goatwerks.com/carb.htm and http://www.goatwerks.com/carbarticle.htm
I started another thread since I am back to carbs.
Jerome
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- audiocontr
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Re: Can't find vaccum leak. Backfiring, missing on accelerat
Did you check the fuel level in the bowls?
1973 712m
1968 Haflinger
1965 Pathfinder
1978 GMC Palm Beach (Hey, its got 6 wheels!!)
1968 Haflinger
1965 Pathfinder
1978 GMC Palm Beach (Hey, its got 6 wheels!!)
Re: Can't find vaccum leak. Backfiring, missing on accelerat
Also helpful in this kind of whacky timing backfiring situation,. Disassemble the distributor so you can see down into the housing where the centrifugal weights for spark advance are. [The dist does not use vacuum for spark advance] Mine was so rusted in there the weights were intermittent and caused symptoms as described above. ...Just a thought.
Thanks,
MaxF
1973 712m Reno NV USA
"The difference between theory and practice is much greater in practice than it is in theory"
MaxF
1973 712m Reno NV USA
"The difference between theory and practice is much greater in practice than it is in theory"
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Re: Can't find vaccum leak. Backfiring, missing on accelerat
I think it was all a lean mixture. Significant change with new idle jets. Changed the 55s for 60s.
JC
JC
Jerome
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Re: Can't find vaccum leak. Backfiring, missing on accelerat
Still dealing with the problem. Changed the idle fuel jets, now will change the idle air jets and see if this works. It is definitely lack of fuel from the idle circuit.
My air idle jets are 130s, I will go to 110 and probably back to 55s on the idle fuel.
Will report!
JC
My air idle jets are 130s, I will go to 110 and probably back to 55s on the idle fuel.
Will report!
JC
Jerome
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- audiocontr
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Re: Can't find vaccum leak. Backfiring, missing on accelerat
It appears more of a carb issue than anything else. Worn throttle shafts... Butterflies that won't seat, lots of possibilities.
Might consider sending to Jim for a rebuild and tune. I eventually bit the bullet and sent mine after countless hours of fiddling. You can find my video on YouTube
Who knows how a previous owner messed them up?
Might consider sending to Jim for a rebuild and tune. I eventually bit the bullet and sent mine after countless hours of fiddling. You can find my video on YouTube
Who knows how a previous owner messed them up?
1973 712m
1968 Haflinger
1965 Pathfinder
1978 GMC Palm Beach (Hey, its got 6 wheels!!)
1968 Haflinger
1965 Pathfinder
1978 GMC Palm Beach (Hey, its got 6 wheels!!)
- Jimm391730
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Re: Can't find vaccum leak. Backfiring, missing on accelerat
Be sure to check the "balance hose" that is hidden under the air tin and connects the two intake manifolds together; the hose there gets significant heat at engine shutdown and is never seen unless you remove both the front and rear air tins from around the carbs.
Jim M.
712W and 710M
712W and 710M
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Re: Can't find vaccum leak. Backfiring, missing on accelerat
Changed that hose... twice, just to make sure. But I agree with Mr Audiocontr... ol? I am dealing with something in the carbs. What is really bothering me is that some days are better than others.. temp? Humidity? Don't know.
The number of things are finite, and you just mentioned the last things I have not played with: shafts, shaft seals and butterflies.
I just don't want to go there.. $$
The number of things are finite, and you just mentioned the last things I have not played with: shafts, shaft seals and butterflies.
I just don't want to go there.. $$
Jerome
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- Jimm391730
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Re: Can't find vaccum leak. Backfiring, missing on accelerat
Testing is easy: at idle, spray around the butterfly shafts with starting fluid; any leaks and the idle will increase noticeably. No change, they are not your problem.things I have not played with: shafts, shaft seals and butterflies. I just don't want to go there..
Jim M.
712W and 710M
712W and 710M
Re: Can't find vaccum leak. Backfiring, missing on accelerat
So you changed the sparkplugs.....did you get the ignition order right....the pinz engine dous not have the normaal 1.3.4.2 ignition sequence but 1.2.4.3..... just my thoughts
off-road until i die
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Re: Can't find vaccum leak. Backfiring, missing on accelerat
Ignition order ok, engine runs great at all regimes except for that little stumble at lo RPM.
Jerome
CRJ Driver
CRJ Driver