engine backfire and popping in the headers

[Lumpy Grits]

Day in and day out NAPA is much better that Autozone will/could ever be.
There is a reason why so many pro-wrenchers buy from NAPA, instead of Autozone and their like.
Respectfully,
LG

[neilbyrd]

Well I installed the pertronics ignition and my jeep ran like crap. Real rough would barely idle. I looked at the instructions and they stated that if it ran rough than I should run a 12 volt jumper from the battery and that it is a normal problem. I tried that and it did not help. I double and triple checked the gap and it was right. I also installed a stock coil from napa because I heard that sometimes the accel coil causes problems. I put the points back in and it ran good so I am going to make a run up the mountain this weekend with the stock coil and see if it acts any different. I am curious, the coil is being blown on by the fan and of coarse it is hot air does anyone think that it could be overheating the coil when I am making those long uphill runs?

[Jeeperator]

A typical coil can and does withstand normal underhood temps. Quik question did you replace the condenser also with the points when you put in the ballast resistor. Weird that the pertronix dont work right you sure you installed it right?

[Lumpy Grits]

DANG, it runs then it does not.......That is the worst type of ele. issue to fix.
Does the eng misfire after or shortly after the ele. fan starts?
How does it run when you turn on EVERY ele. item you have? AKA load down that alt.
Starting to SWAG that you may have a internal broken wire somedangplace in your loom.
Have you had any ing. switch issues lately?
LG

[Russ Chung]

Let's review:
1. Initially, we determined that the problem of engine misfiring had to do with the carburetor. Neil re-jetted and adjusted the float levels and apparently solved the problem.
2. A few weeks later, he again encountered engine misfiring. It seemed to be OK when the weather was cool, but misfired when the weather warmed up. He tried multi-electrode spark plugs, but it made no difference. He replaced the points and the ballast resistor and his engine ran OK--for awhile.
3. There seems to be a correlation between engine temp and the misfiring problem. On cool days, the engine temp is cool, and there is no problem. On warm days, the engine temp is warm (but it does not overheat), and the engine misfires.
4. Neil has installed a high performance Pertronix ignition system, but the engine still runs rough.

My thoughts:
The high engine temp could be a SYMPTOM or a CAUSE of the problem. If the high engine temp is the cause of the problem, then we should be looking for cooling system problems such as the cooling fan, the water pump, the thermostat, etc. If it is a symptom of the problem, then we should be looking at other systems such as the ignition system, the carburetor, and/or the timing. Personally, I think that the high engine temp is a symptom, and not the cause of the problem.

Troubleshooting thoughts:
1. Make sure that the carb settings are still OK. Look at the plugs and see if they are still clean
2. To eliminate the possibility that the underhood temps are affecting the coil, test drive your Jeep with the hood removed
3. I recall that you could not find the timing marks on the harmonic balancer. Did you set the timing by just turning the distributor until it ran smoothly or did you set up a timing mark? Hopefully, you have a timing mark and can set the timing to specs.
4. Hook up a voltmeter to the primary side of the coil to see what voltage is getting to the coil while you are test driving it. I understand that the Pertronix ignition has no breaker points, so you don't need a ballast resistor. You should have close to 12 volts at the coil.
5. Hook up a voltmeter to the electric fan to see what voltage is getting to the fan while you are test driving it. It should be close to 12 volts.
6. Is there a heat riser that heats the intake manifold so that the fuel vaporizes properly? If so, check the heat riser valve to make sure that it is not stuck "on".

[Lumpy Grits]

I still feel that there could be a carb. lean issue at play here. Due to warm day over heats cold day its ok......HMMMmmmmm
Check the intake manifold bolts, gasket might be leaking air under high draw/load conditions.
Volts are fine on the fan. But I feel amps used would be more interesting to know.
We still don't know about the alt. output with the high amp drain ele. fan is now in use.
Coils need a steady ele. supply and don't like volt/amp drop offs/spikes.
To the OP...Do you have a volt meter in you Jeep? IF, yes. What does it show for voltage when the engine starts to get hot.
Strange,
LG

[aw12345]

I'll reiterate my previous post, problem happens at 210 degrees engine temp, so the obvious starting point is to run it at 210 degrees and diagnose from there. You use an electric fan so it would be fairly easy to keep it around that engine temp, then see if it acts up just revving the engine with the Jeep not moving, etc. You narrow down exactly what you do to make it act up, you will be well on the way to solving it.
Unless you narrow it down it's a crap shoot with a lot of time, money and frustration waisted with questionable results

[curtis]

Has the thermostat been changed?

[Jeeperator]

I went back and reread the first post and the engine NEVER ran good right after he changed the jets. The only time it ran good was after the ballast resistor was installed , a week later it doesnt run good again. Who knows whats going on now. NEIL Did you reset the timing after the pertronics install?. Its does not work the same as the points setup therefore the timing needs to be readjusted. Did you do that? If so what did you set the timing at? That pertronics is not plug and play.

[neilbyrd]

Ok lots of questions I will try to answer them all here it goes.

I changed the points and the condenser as a set each time, and as far as I know I installed the pertronics correctly (as per instructions).

It does not act up until the temp gets up to 210 the fan is set to come on at 180 it runs fine until then. It will cycle on and off and run fine until 210.

I dont think I have a broken wire in my loom because it runs fine until 210 and when it comes back down it runs fine again.

I have not had any ignition switch problems lately.

I have been timing it with a vacuum gauge up to highest reading and retard back down 1/2 inch of vac.

The primary side of the coil has 12.5 volts after the resistor and I put the points back in because they run better that the pertronics.

I dont believe there is a lean issue because when this whole thing started it was way to rich (wet black plugs) rejetted to good plug read.

Intake manifold gaskets are new all bolts are tight.

I have a volt meter it usually reads about 14 volts I have not looked at it when it is running bad. It lowers to 13 volts when the fan comes on.

I have a adjustable fan controller so I can set it to 210 I just dont know what to do once I get it there.

Yes the thermostat is new and it is a 160 degree unit.

I tried to set the timing when I put the pertronics in I moved the dizzy all over the place and it just kept running real rough almost like it was not firing on all the cylinders.

Just to clear things up it does not run rough all the time it only runs rough at 210 on a long hill going back down it cools down and smooths out. Dont know for sure that the 2 are connected but I think they are. Before I put the pertronics in it was running smooth after I took the pertronics out it is running smooth. I have a stock coil brand new from napa in the jeep right now to try and eleminate the acccel being he problem, I have not tried it on the hill yet but plan in tring it in the morning before work so I will lit you all know. I dont expect it to help any.


If any one wants to come fix it for me I will cook them a steak dinner. hahaha

[aw12345]

Start with running it around 210 degrees then start with isolating the problem kinda like this does it run rough at that temp when standing still?
If it does not run bad that way immediately then keep running it around that temperature for roughly the same amount of time that it takes you to go up that hill to the point where it runs bad. If it does not misbehave that way, then move on to driving it still keeping it around 210 degrees, start with the barely moving in first gear then immediately shift it to third gear and floor the beast, does it backfire then? if not you can pretty much rule out an ignition problem. So when the ignition problem is ruled out it's time to move on to a fuel supply problem especially if it either needs to get hot or it does take a certain amount of driving to get it to act up. Once you get your problem narrowed down and you can create it at will, you can start ruling things out. Among other things you could try and see how much fuel pressure you get at the carb when all of this is going on should ne somewhere between 3-5 psi and not fall off when you run the beast under full load and wide open throttle. If all that is as it should be I would start looking at the way the carb bowl vents as well as how the fuel tank vents.
Some pics of the carb and how your vacuum lines are run, how the tank vents and how you got various things hooked up and so forth would make this web diagnosing bit a lot easier also.

[Russ Chung]

Neil,

As Art said in his post, we need to rule out (or confirm) the ignition system as the source of the problem. Once we eliminate any ignition problems, we can "move on to the fuel system" as Art said in his post.
1. Change to a hotter thermostat
2. Set the electric fan controller to 210 degrees
3. Run the tests that Art suggests in post #116

I would like to suggest one additional test scenario. Run the tests with and without the hood installed. That way, the engine coolant temp would be 210 degrees, but the underhood temp should be cooler. It might give us an idea whether high engine coolant temp is causing the problem, or is a symptom of the problem and the problem is due to high underhood temp.

[neilbyrd]

I will have to see if I can set up that test tomarrow I have to work today. So I am going to make a test run right now see if ditching the accel coil make a difference.

[6spdYJ]

Okay, now we go to dumb questions... Have you checked to make sure that your fan is in fact pulling air through the radiator? I have seen one installed as a pusher, but wired as a puller, so it sat in front of the radiator and tried to push air out in front of a running vehicle. Great for reducing under hood temps at a crawl, but fatal on the road. Also, have you replaced the radiator cap? This question is a bit premature, does it actually blow off into the puke tank? I have had a weak cap cause overheating before. It would only happen after a freeway run over 30 miles, followed by sitting in traffic. The only fix as to let it cool off - until I replaced the cap. Be aware - I've also had it happen with a brand new cap I got with a brand new radiator. As for the Accel coil, I tried two of them in Chevy HEI's. Long story short, stock worked, Accel didn't. Hope it helps.

[Jeeperator]

I believe changing the coil is a good call. A bad coil can cause these intermittent problems. If the coil is bad and gets too hot its possible for it to cause misfire. Which will cause excessive fuel to enter the exaust and it will ignite and backfire. So I am pretty sure the fuel system is fine because obviously its getting too much fuel if it backfiring. A lean condition will cause detonation or ping. Points style ignitions only need ~9 volts to work properly 12+ volts is to high for points. I assume when you checked the voltage when it was when the ignition was cold or not running. The ballast resistor should provide more and more resistance as it heats up.