Hi, My 71 Lemans (Pontiac 400) is running rough and backfiring out the exhaust. I recently installed a Pertronix Ignitor kit and Flamethrower coil but did not help. I believe the cap, plugs and wires are okay. I also changed the fuel filter. According to the plugs, the engine is running rich since the plugs have a black dry soot on them. The timing before the Pertronix change was 13 BTDC. Now when I adjust the timing, I have to adjust it so that the line is far below the timing marks in order to get 16 in hg of vacuum. If I set it at the 12 BTDC as required, the engine runs very poorly and lo vacuum.I didn't remove the distributor to install the conversion kit. The gas may be bad as it has been in the car for awhile. I added octane booster, gas line antifreeze and some new gas but no change. What am I missing? Vacuum leaks?
Can anyone help me out as my son wants to drive it as he just got his license and I don't want him to think that I am a loser at fixing old cars!I am willing to buy beer in exchange for labour!
The engine ran poorly before I added the Pertronix kit. I checked the wires and they are in the correct firing order. The Ignitor kit is a Lobe sensor model so there is no gap adjustment. Thanks for help.
This is an external coil not HEI -am I right? If so check the polarity. Coil hooked up with wrong polarity will cause a very simular condition. It's possible she ran badly before if the points were bad. Worth a check anyhow.
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'68 Parisienne 2+2 Convertible Matador Red (Resale Red but not for sale).
You don't provide much history, is this a recent barn find, etc? I'd check for:
1. Vacuum Leaks (if still has the original rubber vacuum lines, change them).
2. Fuel - you indicate the car has old fuel in it. Is there a way to drain the tank and put in new fuel. While you're at it, take a look at the fuel pump.
3. Change your spark plugs, wires, cap, rotor, etc.
4. Verify you have the full 12 volts to the coil & pertronix Your car originally had a breaker point ignition, which required a resistive wire limiting the voltage to the coil. You need to have an ignition switched 12 volts to the coil & pertronix.
5. You may have a stuck float or something in the carb.
Likely offenders are the ignition components, and vacuum leaks.
I have had my car for 25 years and only driven it occassionally. The plugs,wires,cap and rotor are newer.The gas is from last summer and I don't remember if I added stabilizer to it in the fall. I wired the pertronix to a 12v ignition source on the fuse box. How do I check the fuel pump? I have a vacuum/pressure gauge that I could use. How much pressure should a factory pump produce?
Another weird thing is when I check the timing, my timing light would flash intermittently. i checked my timing light on my 72 GTO and it flashed like it should. To me, it means that the #1 spark plug is not getting the proper spark or not getting it at the right time.
Thanks, Pete
-- Edited by 71judge on Sunday 2nd of October 2011 07:15:16 PM
The engine was rebuilt a number of years ago but has not been driven much since. It was not running well before I put in the Pertronix either. Thanks, Pete
It still sounds to me like weak spark. You need to put it on a scope and check the secondary voltage and pattern. Or at least get one of those Princess Auto spark testers to see how strong the spark is. Weak spark will seem like fuel problem.
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'68 Parisienne 2+2 Convertible Matador Red (Resale Red but not for sale).
I'd be warming up the engine & then do a Compression test with throttle wide open & coil unplugged, this will give you a starting point to engine condition, if OK then move onto the ign. system then fuel system. Would def. get the old gas out of car as it's junk in a matter of 3 wks. run high test in it as the eythanol in reg. will "ROT" your neoprene hoses & carb. & fuel pump "innards" Ate the fuels bowls right out of car club members Holley Double pumper on his 28 Ford "Vickey" & no, it doesn't have historic plates on it!!!!!
Are you sure the engine was rebuilt & properly, these US Poncho's are hard on T/ chains, ASK ME!!!!!!! good for around 40 thous. mi then you do it again before youre left at the side of road [been there,done that, used the Tee shirt to clean my hands]
-- Edited by dualquadpete on Wednesday 7th of September 2011 01:09:46 PM
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Some times I wake up GRUMPY, but today I let her sleep in !!!!!!!!BLACKSTOCK Ont.
Did you get anywhere on this? Kind of sounds like bad ignition wires to me, yes, they do go bad. If gas is a year old, how much was in the tank, how much new gas did you add. Hmm, now that I'm thinking about it, popping thru the exhaust sounds like timing. I'd pull clean/replace the plugs and try a different set of wires (off good running engine if possible). Friend once replaced cam, chain plugs, wires, etc. After a day and a half and a no start situation, they put the old cap, rotor and wires back on and got the engine running. Funny stuff, frustrating, but funny later. much later. Good luck.
Did you check the dist. to see if it was installed "right" in the 1st. place??? I'd roll the engine up to TDC on #1 & pull the dist. cap & see if the rotor is pointing to #1 on cap???? It's easy to be out a "tooth" or 2!!!! Still think a comp. test will tell you alot, then go from there,thats how I found out the valves were "TOO TIGHT" in the 52 w/350V8 & that engine was "rebuilt" by well known shop, mistakes can happen in the best of machine shops.
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Some times I wake up GRUMPY, but today I let her sleep in !!!!!!!!BLACKSTOCK Ont.
The engine was rebuilt about 20 years ago but has been rarely driven in that time. The distributor has not been removed for many years and ran fine in the past. I bought a spark tester and each plug is getting a spark. The exhaust is leaving black soot on garage floor indicating a rich mixture. I removed old gas and put in new gas but no change. I got it started and went down the block,ran poorly,quit and would not restart.I now believe that the carb is the problem. I have ordered a carb kit on ebay and will rebuild it next. If that does not help, then i will look at the fuel pump and ignition again. Thanks for all your help. Pete
-- Edited by 71judge on Sunday 2nd of October 2011 07:24:39 PM
hi i see there hasnt been any updates for a while on this thread, did you get the car running right? if not send me a pm i have a very good friend in kitchener who does a lot of work on old cars and bikes(mechanic by trade) i know he could figure out whats wrong with your car! he does work at home in his off time. let me know if you are interested, fred.
I am willing to buy beer in exchange for labour!