engine misfire

[HawaiianGauer]

Aloha & Happy Thanksgiving! Before I dive in, I’d like to thank all those that have (and will) contribute to this forum. I’ve learned a ton & would be lost without it – thanks for helping people like me.

My current problem is cylinders 1 & 2 are not firing. I believe this is true because when you pull the ignition cables (1 at a time) off the distrib, there is no change in RPM. Also, I see no spark no matter how close I position the ignition cable as I reconnect it.

Before I replaced the ignition wires with a brand new set today, cylinders 3 & 4 were not firing. Yes, I swapped out all the ignition cables and the cylinders not firing moved from 3 & 4 to 1 & 2.

Now here’s the rest of the story: I bought the Gauer thru one of our trusty sponsors in March. Among other things, he carbs were rebuilt & tested before the dealer shipped the vehicle. Upon receipt, the vehicle ran great, no issues. To include up a gradual incline on a highway I frequently drive – always a test for low HP vehicles. A hill where your typical 4 cylinder Jeep cannot maintain the 55-60MPH without downshifting at some point. Shortly after purchase, I almost turned the vehicle into a submarine driving thru a deep mud puddle. That’s when this journey started, approx. 6 months ago. Meaning, the vehicle has not run as well as when I first got it since that puddle dive. Runs, but not quite right (can’t maintain speed up the highway hill I mentioned, among other things). For most of the past 6 months, I’d say the vehicle’s been running at approx. 90% power (always based on that highway hill – how the engine responds). Here’s a brief rundown of what I have done since then: replaced distrib cap (Bosch); replaced coil (Flamethrower Epoxy); replaced radio noise suppressor; took apart & cleaned Molex connector; replaced spark plugs; adjusted valves (3 times); replaced ignition cables (today). I’ve also played with timing quite a bit & have made minor adjustments to the carb mixture screws (they are currently set at 1.5 turns out). I have frequently removed, inspected and cleaned out the inside of the distrib (although never noticed anything significant). I have frequently removed & cleaned the spark plugs (like today). The few times the engine was running really bad (like recently with no spark to 2 cylinders), the spark plugs to those cylinders would be fouled with fuel when I’d pull them out & inspect them. I did a compression test a few weekends ago - all 4 cylinders had the same result (~150).

Some of the actions taken above, I think, did help the situation at times, meaning I think I've had different problems at different times (ex: valves were way out of tolerance the first time I checked them & setting them made a big impact). For most of the time period that I have owned this vehicle, the engine was running at about 90% strength. Outside of the parts I replaced, most of the time I fiddled with timing and carb mixture screw combinations. There were times cylinders 3 & 4 had a weak spark (meaning, after pulling the ignition cable off the carb, I would notice a slight decrease in RPM & when I placed the cable close to its connection on the distrib, I would see a weak spark). Always back to 90% - can't maintain speed on that highway hill, occasional backfiring as I'd floor the gas in an attempt to maintain speed.

Today, I also swapped out the new distrib I bought about 4 months ago with the one that came with the vehicle (I could never confirm or deny that distrib was bad). No change – cylinders 1 & 2 not firing. I also re-ran the old ignition cables I just replaced today – no change. I re-installed the new ignition wires & called it a day since it was time to have Thanksgiving dinner.

I think I’m out of parts to replace. Suggestions?

Also, ref the diagram I’ve attached – I gotta ask the dumb question. Given the picture, where the mark on the fly wheel is in relation to the stagnant pointer – would that be an example of ATDC or BTDC?

FYSA - I have a Petronix ignitor.

[Jimm391730]

Hey Hawaiian,

First, the timing pointer question: since the engine rotates clockwise as viewed from the front, the top of the pulley rotates from the passenger side towards the drivers side; so in your view the mark has not reached the pointer yet which makes the timing advanced, Before top dead center. I also think of it as that the mark needs be on the "easy to see" side of the pointer (the top of the pulley).

Now to your ignition problems: Despite your detailed description (which is a huge help in understanding your problem) you did not say if you have the stock shielded ignition wires, plugs, and cap, or have changed to civilian components. Since the problem moves as you exchange wires (are you moving plugs, too? If so, it could be plugs - what is the gap sent to?) the problem must be in the wires.

The stock wires have a relatively small amount of insulation around the high voltage conductor, then have the shield and insulation over the shield. If you put in a flamethrower coil it is possible that the stock wires have been overstressed and now have an electrical puncture through the HV insulation. It is also possible that the conductor is open and won't carry any current at all. Try using a multimeter and measure the resistance from end to end and compare with the "good" wires; the longer ones will have proportionally more resistance with the increase in length. If you have civi wires, inspect them carefully along their length for cuts and worn spots. The Beru wires are great at carrying the HV to the plugs but I've found them to be easily worn if they rub.

Measure the voltage at the + side of the coil while the engine is running; expect to see around 17V. if it is much less than this I would suspect the 4500 RPM module. You can test this by pulling the plug from the module and make a jumper to connect the middle of the three pins in one row to the middle of the three pins in the other row in the wiring harness connector (you don't need to plug back into the RPM module). If the voltage on the coil goes back up then you now have enough voltage to properly run the coil and should get strong spark if the pertronix and other parts are working properly.

On other vehicles I have seen where the spark energy bypasses the plug by jumping to the block around the plug; this was due to bad boots on the plug wire. Mud and dirt may cause the same problem even with good boots if it is left in there.

Because you notice a decrease in power, I'd suspect the RPM module since they seem to fail gradually and slowly snuff the energy out of the spark.

Let us know what more you find out.

[pinzinator]

Could the fuel solenoids not be opening?

[HawaiianGauer]

Jim-
-all elec ignition pieces/parts are civy, no military. That's also how I got the vehicle & the items I replaced have been the same as those that came with the vehicle.
-ignition cables are brand-new. Got them from Kingsborne wires at www.kingsbornewires.com
-plugs are gapped to .76mm. I have not moved plugs between cylinders at any time.

Update: was talking to my son about points, so we re-watched IE's video on Pertronix ignitor installation http://www.youtube.com/watch?v=wivi6tux690 I had forgotten the part about the 1mm space between the module and the ring & I had messed with the module about 3-4 weeks ago for another reason. Sure enough, when I checked today that gap was off. I reset it to 1mm & ensured the mag ring was seated all the way down properly. Fired up the engine for the first time since yesterday & you could tell a huge difference immediately. I shut the engine off & cleaned out the dstrib cap as best I could. I rechecked all the new ignition cables & checked all the spark plugs. Only #1 was wet (rest looked very normal) so I cleaned it and put it back in. Next I reset the carb mixture screws to 1.5 turns out & got my timing light all set up.

Fired the engine up & RPMs were high even after the engine warmed up. Checked ign cables first at the distrib first & all but #4 responded correctly when I pulled the cable off the distrib (RPMs dropped, good spark). While #4 has a good spark, there is no change in RPM when you pull the cable off.

As for timing, it is advanced 3 degrees. RPMs fluctuate unnormally between 1600-2200 RPM. Both carbs spit & sputter consistently (with RPM fluctuation). The air intake is off & so I can see fuel spitting out of both as a carb sputters. A couple of shooting flames too. I tried turning the carb screws out 1/4 turn to reduce RPMs but when I do, the violent RPM swings and sputtering results in either the engine dying or sputtering/running very badly at about ~400 RPMs/putt-putt-putting. I have never had the RPMs fluctuate that violently and have not had the carb's spit and cough like that to date.

So I think that's progress but certainly undrivable.

Thoughts???

[Stekay]

I'd get hold of a vacuum gauge and see what it says.

some ideas:
dirt in a jet
loose wire on fuel solenoid
vacuum leak
wire shorting to ground under compression load

[audiocontr]

As I raise the advance on my craftsman timing light, the mark moves towards the driver side. I then rotate the distributor to bring the line back to the pointer @ 8 on the timing light. Have I been doing it wrong?

[HawaiianGauer]

Jim-
Tested coil - fluctuates between 15-17v. I assume that's acceptable?

Vac test gotta wait. Will check fuel solenoids next?

Any other ideas?

Gotta get this thing at least back to where it was (drivable) - it's gonna be Santa's sleigh here real soon!

[edzz]

when you replaced the cap did you replace the rotor? you are aware that the rotor must be trimmed.

[HawaiianGauer]

when you replaced the cap did you replace the rotor? you are aware that the rotor must be trimmed.

I did not replace the rotor. I do know that if you buy a new one, it needs to be trimmed.

[HawaiianGauer]

Update: I think it’s all about my inability to get the carb mixture set screw/timing setting combo correct. Remember, before I started this thread engine was running ~90% right.

Current situation: I am essentially right back to where I started this thread: runs maybe 80-90% right (not quite as good as before); removing cylinders 3 &4 ignition cables from the distrib do not impact RPMs but both have good spark.

Background: yesterday & today I went back to messing with carb mixture screws & timing. I reset the carb screws to 1.5 turns out. What I failed to mention earlier is that before I messed with the timing for the first time ever, I marked where the distrib gear was when I first got it – so I have a ref point for where the distrib gear was positioned the last time it ran perfectly. I twisted the distrib back to that point today. From there, I played around a LOT with the carb mixture screws (1/4 turn at a time – but BOTH screws were always turned the same amount) and the timing. It got better, it would get worse, back and forth. Most times after adjusting screws & timing and waiting to see how the engine settled, I’d check the impact of removing an ignition cable from the distrib. I probably did this combined routine maybe 15 times today. Removing #s 1 & 2 cables from the distrib would have a significant impact on RPMs every time. Most of the time there was no impact when I pulled 3 &4 (back to the orig problem noted). At one point, #3 dropped RPMs about 90. Never had a combination where removing ign cables from all 4 cylinders impacted RPM. But got it to the 80-90% range (no massive sputtering, huge RPM fluxuations).
I decided to re-research/confirm how many turns I should start the carbs at & see if I could find any more hints working adjusting the combination of screws & timing as I felt I was back where I started before I replaced the ignition cables 3 days ago. Then I re-read EI’s article on Zenith tuning info (https://www-expedition--imports-com.app ... ning_info/ ).

This caught my eye: “Idle Mixture Adjustment Remove and inspect all four idle mixture screws (part #13). They should have a clean taper on the end and not be bent. Re-install them until they lightly seat (by feel), back each one out 1-1/4 turn. Start and warm the engine. Again, get an idle speed of 750-1,000RPM. Back one mixture screw out, say 1/4 turn, listen. If the idle speed increased, turn it out a bit more. If it decreased, turn it in. The aim is the highest idle speed from each screw; keep at each screw until it is found.”

So I tried that technique. The rear carb reacts quickly turning either way. The front carb does not respond as quickly.
That brings me back to my first sentence - “I think it’s all about my inability to get the carb mixture set screw/timing setting combo correct. “

1. When adjusting carb mixture screws to find the sweat spot, do you adjust them both the same amount? Or do you do them independently as described in the Zenith tuning article quoted above? If tuning them independently is the right way, does the fact that my front carb is slower to respond to turns as compared to the back one indicative of another problem?

2. I don’t think I understand what I’m trying to do by adjusting timing and adjusting mixture screws. Nutshell: when I start with the distrib aligned with the mark I made when I first got the truck & I back mixture screws out 1.5 or 1.25, the engine immediately runs badly. If I adjust the timing to anywhere between 9-12 degrees advanced (some people have recommend 12 if you live at sea level, which I do), the RPMs go up to over ~2000. When I turn the carb screws out to drop the RPMs to ~1000, the timing mark moves & usually ends up anywhere from 6 to 0 degrees advanced. Is this normal? Am I doing this right? Meaning, the goal may be 9-12 degrees advanced, but every engine is a bit different and so if mine runs best at ~6 degrees advanced & turning out the carb screws different amounts – then so be it?

3. What about my assumption that removing an ign cable from the distrib & noting no change in RPMs = something is wrong. Is that correct?

4. If my assumption in #3 is correct, is my problem really about learning how to correctly set timing & mixture screws?

[Jimm391730]

3. What about my assumption that removing an ign cable from the distrib & noting no change in RPMs = something is wrong. Is that correct?

If you don't get any change in RPMs then that cylinder is not doing anything productive, at least at idle.

4. If my assumption in #3 is correct, is my problem really about learning how to correctly set timing & mixture screws?

And/or balancing the carbs. With two carbs and two idle stop screws (not the idle mixture, but the mechanical stop to the butterfly shafts) it is easy to get them out of sync at idle (once you are past idle it doesn't matter much any more). Sounds like the rear two cylinders are not firing much at idle (or you'd notice a significant and consistent rpm drop as each plug is disconnected). You can also tell by the temperature of the exhaust manifolds; after it has been idling for a while and everything is pretty hot, do the "spitpoppin" test (lick a finger and swipe it past each exhaust manifold, or better yet use a IR thermometer) and see if they are about the same temp. If the rears are too cold then you need to open up the rear carb throttle and back off of the front carb throttle until you get similar temps. Do this with the throttle linkages disconnected so the carbs are independent. Then check/set the timing. Since the spark advance is purely RPM driven, you cannot set the timing correctly unless you have the correct idle speed. Only then start tweaking the mixture screws. You may need to repeat this process as you gradually get things back in shape. Then finally adjust and reattach the carb linkages so that they don't push/pull on the carb levers at idle.

The above assumes that the carbs are tight, not leaking fuel out or air in, and have the correct fuel level.

I've would not expect the coil voltage to fluctuate; if you haven't already done so, try jumpering out the 4500 rpm box (under the dash, about the size of a pack of cigs) to ensure that it isn't adding to the confusion. You can always plug it back in later.

[Jimm391730]

As I raise the advance on my craftsman timing light, the mark moves towards the driver side. I then rotate the distributor to bring the line back to the pointer @ 8 on the timing light. Have I been doing it wrong?

No, that is correct. Timing lights with the adjustable timing knob are actually changing the time of the flash with respect to the spark, as to have the flash coincide with the zero mark on the pulley (handy when the pulley or pointer does not have a degree scale). If you set your light to "zero" then there is no change to the flash; it happens when the spark happens (like good 'ole timing lights). But if you dial up, say, ten degrees advanced then the light figures out how long to delay the flash so that the engine has had time to rotate ten degrees further; then you adjust the dizzy to make the pointer (usually zero degrees or Top Dead Center) align with the mark on the pulley. Now you know that the spark is happening ten degrees advanced, or before top dead center. How long it takes to rotate ten degrees more depends on the rpm of the engine; the timing light has to calculate its time delay based on the speed of the engine (how quickly it detects repeated sparks). Fancy, eh?

So as you increase the advance on the timing light, the flash is delayed more so the mark on the pulley has time to move further towards the drivers side.

Back in the old days you could time an engine by "power timing" it where you would advance the timing a degree or two, take the vehicle out and mash the throttle. Generally the farther advanced you were the more power you would get from an engine; but too far advanced and you would get pre-ignition ("knock" or "ping"). Then you would back off on the timing until the knock went away. It's not as accurate but it was reasonably effective, assuming it was only the timing that needed to be tweaked.

[edzz]

Any chance that you know an old school Porsche mechanic? The older Porsche that used twin carbs are very similar to tune, you just have to get the mechanic over his prejudice.

[blackstack]

I am watching with great interest as my vehicle is displaying exactly the same symptoms as yours. I have done all that you mention except mess with the carbs. My #2 no change in RPM when i pull it. I just ordered new plug wires at the site you mention.

The onset was sudden...returned from a 200 mile no problem jaunt and parked in my yard..next day drive 3 mile drive to PO and almost didnt make it home. loss if power then sudden full power then nothing..... Weird

One question, you said you disassembled the molex connection. Do you mean you got the wires out of the female side? How?

[HawaiianGauer]

One question, you said you disassembled the molex connection. Do you mean you got the wires out of the female side? How?

If I recall correctly, I was able to push each wire forward out of the plastic connector, clean it (or in most cases, verify no corrosion), then push it back into the connector. Gently of course.

Next time I work on the motor I will verify what I just wrote. If I discover my memory sucks, I'll report back to ya....

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