An engine miss! argh!

[Denee007]

I got the truck all cleaned up in our air conditioned garage, so that when we would leave for the Nifty50ee's, the cab would be cool therefore the AC would have a chance to keep the cab cool. However, we were just going to drive it a few miles down I-10 to check it out and get gas.

As soon as I cranked it, I could feel it! Like someone pulled a spark plug wire off feeling. I was hoping that a plug wire came off; something simple. But that's not the case. My exhaust doesn't have a crossover pipe, so I could put my hand at the exhaust and feel/hear a miss on the left side of the engine. When up to 45-50, I don't feel it as much, but at idle, it shakes the truck a little.

However, right now it's really too hot to mess with! So I guess when the engine cools down completely I'll pull the spark plugs on the left bank to see what's up. How does a person check to see which plug it actually is? Could I pull a wire at the cap vs at the plug? Would that hurt the distributor?

Just a little sad, the truck looks so nice and was running so well!
dne'

[solidaxel]

I use a spray bottle with water at the exhaust port or a Inferred gun to check the temp, try that

[Dan in Pasadena]

The old fashioned way (I DONT suggest you do it) was to grab each plug wire bare handed and you could instantly tell which wasn't firing right!

Without an engine analyzer you can pull one wire at a time and if you don't notice the engine sound change - its the cylinder you pulled the wire from that's misfiring, OR put a large paper clip or something else metal in the plug boot and hold it near a good ground. While its running you'll SEE the lack of a consistent spark.

Another old timers trick is to run the engine at idle at night, pop the hood and peek and sometimes you'll see an errant spark coming from a bad wire, the coil, etc.

Hope this helps some. Let us know what you find.
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[Russell Ashley]

If you are running an HEI ignition you shouldn't pull plug wires off while the engine is running. That was OK back in the points-and-condenser days but not a good idea now. I'd try the infra-red thermometer or either run it in the dark as Dan mentioned and look for sparks. If you have an old timing light that has the electronic pickup you can just clamp it on wires until you notice one that is not lighting it regularly, I've done that before.
I hope you find a bad wire or plug, not a cylinder with low compression.

[Denee007]

Thanks y'all! Harbor freight has one of those thermometers on sale, but I may try my timing light like Russell suggested. I need to recheck my timing anyway while I have it out. It's just that it was running so well!

[1project2many]

The old fashioned way (I DONT suggest you do it) was to grab each plug wire bare handed and you could instantly tell which wasn't firing right!

You can do this safely without damaging anything if you are careful. One method is to connect a test light to ground, then place the tip near the bottom of the plug wire boot at the distributor cap as you carefully remove the wire.As the wire begins to move away from the cap, the spark will jump to the test light as it's an easier path to ground. You still run a risk of being shocked if you move the test light or if the lead to ground becomes disconnected. If you get no spark out of a particular cylinder then you've identified the problem as being in the cap and / or rotor.

Another method is to get a spark tester such as a KD2756 and connect it in series with the plug wire. This tester makes a nice, loud "snap" each time spark travels across it which is helpful if you're working by yourself. You'll have to shut off the truck and move the tester to a different wire in order to check all of them.

The timing light trick works if spark energy isn't getting through the wire but if you have a shorted plug the light may flash anyway. So if the light indicates all plugs are firing I wouldn't call the test a done deal. I'd find a better test.

Also, a good old fashioned visual inspection can work well. Once the engine's cooled off, fire up the truck, idle for a very short time, then shut off. Pull each plug until you find a wet one. Then check wire, cap, rotor, plug, etc.

[mknittle]

Geezz Just wear gloves and pull the plug wires off one at a time like we did before there were complicated gadgets. Why does a person need an infrared sensor to fix a spark plug?

[mr48chev]

The main thing about pulling plug wires while it's running with an HEI is don't do it bare handed or you will end up sitting on your tailfeathers a few feet from the truck. The old points and condenser rigs usually just give you a good tingle but the HEI has around 40K volts to the plug. They make special insulated pliers to pull them off.

If you have been doing anything with the plug wires since you drove it last check the wires to make sure you have the firing order right and haven't crossed 5 and 7 as along with being right beside each other on the left side they are right beside each other in the firing order and it is very common to get them mixed up. Everyone who works on their own sbc or has worked on one has done that ditty at one time or another. Even when you think you are being careful you can get them crossed.

Also back track to think of anything you did in the engine compartment since you drove it before it started missing. You may have knocked a vacuum hose off or something like that. I don't think there are any vacuum connections on SBC manifolds that directly affect the left (meaning driver's side to me) of the engine but if you are calling it the "left" side as you look at it from the front the vacuum line for the modulator on the trans usually hooks into the fitting on the runner to number 8 and it is easy to knock the hose off the modulator if you are poking around that area cleaning. Sometimes the modulator line just comes loose and you get a vacuum leak and miss too so if the miss is on the passenger side check that.

[1project2many]

The main thing about pulling plug wires while it's running with an HEI is don't do it bare handed or you will end up sitting on your tailfeathers a few feet from the truck. The old points and condenser rigs usually just give you a good tingle but the HEI has around 40K volts to the plug. They make special insulated pliers to pull them off.

That's what the test light is for. Let the spark go through that to ground instead of your self.

When DIS was new GM sent their techs to special classes. We learned things like always pull wires with your right hand and make sure your left leg isn't touching the body. That way spark energy won't cross through your heart and cause a heart attack. Well, I don't know of any DIS heart attacks but I can say it hurts pretty good when you get zapped through your hand and the voltage exits through your leg back into the vehicle.

[OrrieG]

Originally Posted by 1project2many

That's what the test light is for. Let the spark go through that to ground instead of your self.

When DIS was new GM sent their techs to special classes. We learned things like always pull wires with your right hand and make sure your left leg isn't touching the body. That way spark energy won't cross through your heart and cause a heart attack. Well, I don't know of any DIS heart attacks but I can say it hurts pretty good when you get zapped through your hand and the voltage exits through your leg back into the vehicle.

Same reason electricians are taught to put their left hand against their leg when working in panels or around high voltage, if you get zapped the path of least resistance is down your arm thru the leg bypassing the heart.

[Russell Ashley]

When I suggested that you not pull a plug wire off while an HEI equipped engine is running was not so much to prevent getting shocked, but rather to protect the distributor. Under normal conditions the voltage to the plugs only builds to a point where the spark will jump to ground through the smallest opening, the plug gap. If you pull the wire there is no place for the spark to jump to and the voltage will build to the point that it can arc within the distributor. If you are lucky it will only ruin the rotor, but can cause worse problems.

[Denee007]

What I've done so far;
I bought one of those infrared thermometers and I've been walking around with it seeing the temp of everything!

I cranked the truck, then aimed the thermometer at each exhaust, it varied greatly from on the left bank(drivers side) front was 119 middles were 140, and the rear was 119 also, but I only ran it for a short time so I wouldn't get it too hot to be able to pull the plugs.
I don't think it worked, or maybe it did. I would have thought the temp of the ceramic coated header would have gotten extremely hot QUICKLY!

So, I pull all the plugs and they all look about the same, nothing indicating a "foul" plug, at least to my eyes. No oily, gas soaked plugs.

So, like I have nothing better to do, I went ahead and performed a compression test;
All cylinders showed 150 psi with 4 revolutions. One scared me as it "sounded" too easy as the starter motor turned the engine over, but it was OK.

Next, I've never checked a spark plug with an ohm meter, but I did it for the heck of it! I set my vom to ohms, placed one lead to the electrode on the plug and the other to where the spark plug wire attaches. VOM set on 200k, ranged from 5.0 - 8.5 ohms, which btw tells me nothing!

The plugs are AC delco R45TSX.

History of my distributor: Dave Chapman was here the day I went to crank up my sbc for the first time. It wouldn't start! We tried and tried, suspected something in the distributor. I finally found a wire that wasn't making connection, and it fired up~! The truck ran very good for a short amount of time, but then it would run for about a minute and die! This went on for a while until I put a new module in. Since then it's been running great, until now. The Distributor is no high end dist., I'm sure it's chinese origin. The same thing happened to the distributor in my 67 289 Mustang engine, the module died. Perhaps the chinese modules can't stand the Texas heat! lol

Warning Will Robinson!
UPDATE! I took my ohm meter and checked all the wires, #'s 2 and 4 wires measured 40-50 ohms! I had a couple wires left from my other HEI system, put them on and it runs smooth again! As much as I would like another ignition system, I guess I'll buy a set of plug wires

I proud to have troubleshooted with y'alls help! Any ideas on igntion systems that aren't so pricey like MSD?
dne'

[vht]

Denee, I've seen a lot of those cheap HEI dist give all kinds of problems. The best 1 is the MSD HEI that you can get from Jeg's or Summit for around $135. I had a set of new wires go bad on my Chevelle, won't say the brand name on here, but they had less than a 1000 miles on them. Relaced them with MSD wires. Some of this new performance stuff you buy now is junk. I went through 3 manual fuel pumps in less than 100 miles before I ended up buying a aeromotive billet pump that works great, but the other brand name pumps should have been fine. Quaulity has gone down hill fast in the last few yrs. Hope everything works out for you.

[1project2many]

The original HEI systems were capable of throwing a spark across a 1/8" plug gap. I've run HEI on 12:1 engines running to 7500 in roundy-round stuff for multiple seasons with no problems. If you must buy an MSD I always recommend the race products. Personally, I've had too much trouble with their street ignitions.

[Denee007]

On my 67 Mustang, the mechanic installed the same HEI in it. The module did the same thing about about 50 miles. I replaced the module and it was fine from there on, but I decided to bite the bullet and get an MSD setup.

I was excited to have a neat looking, good named something under its hood. I bought the coil blaster(not sure of the name), but hooked it all up, timed it, and ran it. 10 miles later, I parked the mustang, came back a little later, it wouldn't start!

My brain started wondering; so I pulled no 1 plug, got it to TDC and it was right on the money, gas was there, it should start. I cranked and cranked on the engine, but nothing, not even a hint.
Out of desperation, I loosened the distributor hold down, and moved the distributor one way or the other, I don't remember which, and it fired up! I put my timing light on it, and it the mark was no where to be found, then I started see the mark as I moved the distributor, but the closer I got it to where I wanted, say 10 btc, it died! Of course the vacuum advance was pulled and plugged. No matter what, it could not be timed.

I called MSD tech. It's like going to a doctor, telling them your symptoms, and get, "never heard of this before!" Exactly what the tech said! I asked how many of these have they sold~ thousands he said! and you've never heard of this phenomenon! "no".
At his request ,and my expense, I sent him my distributor, 4 weeks later I got the same distributor back. It did the same thing! I was HOT! I even talked to the same guy, and he sent me a replacement distributor, got it a few days later~ it's been working fine!
I paid over 800 bucks for that system. I still have a little dis-trust in it, but hasn't failed me yet. (knock on wood)

I'm learning a great deal about troubleshooting, but all at the expense of faulty merchandise!

From this monstrosity:


To a much better looking ignition system with a neat air cleaner!

[OrrieG]

Symptoms of dist being off a tooth or so. You can get the engine to run fine, just cannot time it using the stock marks. You could get it to #1 TDC and make your own zero and use after market timing tape to set where you want to be. Of you can just time it by ear and adjust to best running condition. I don't know squat about modern msd stuff but sounds like the inner working that send spark to the wires is not clocked right with the gear shaft.

[Denee007]

Orrie, what you wrote is about THE best explanation I've heard! Thank you!

Originally Posted by OrrieG

Symptoms of dist being off a tooth or so. You can get the engine to run fine, just cannot time it using the stock marks. You could get it to #1 TDC and make your own zero and use after market timing tape to set where you want to be. Of you can just time it by ear and adjust to best running condition. I don't know squat about modern msd stuff but sounds like the inner working that send spark to the wires is not clocked right with the gear shaft.

[OrrieG]

I have bought more than one rig that had the dist hosed up in relationship to the timing marks and am pretty good at timing by ear. Usually happens when someone swaps out a manifold and does not pay attention to the dist when they pull it and is too lazy to fix the problem. Nice looking Mustang, I am trying to talk Jen into Cobra Valve covers, I will show her the air cleaner. On GM another clue is when the vaccum can is cranked around 45 degrees one way of the other from where it should be. You can also get them in 180 degrees out and the engine will still try and run with most of the cylinders hitting close, the others firing on compression and lots of flames out the carb!

[crossfire84]

You can also get them in 180 degrees out and the engine will still try and run with most of the cylinders hitting close, the others firing on compression and lots of flames out the carb![/QUOTE]

loss of eye brows and stash too.

[1project2many]

You can also get them in 180 degrees out and the engine will still try and run with most of the cylinders hitting close, the others firing on compression and lots of flames out the carb!

I know of an IH "M" that ran for years on the exhaust stroke. It was always a bi-atch to get started and the exhaust was a bit loud but it seemed to have plenty of power once it was up and running. The owner finally decided the engine needed rebuilding and tore it down but the machinist doing the work said it wasn't really all that bad. It wasn't until they were re-installing the distributor that they realized that it had been installed 180 out. Strange but true...

[mr48chev]

It's rather hard to believe that she had the truck together and running great with everything good to go and all the sudden the distributor is 180. Gents read the whole first post she wrote. If you haven't read her other threads you might not know that the truck was running good and all the sudden it developed a miss or has a dead hole.

The most common reason for a miss on a sbc in great shape is that plug wires got crossed. Another thing might be that one of the wires isn't secure on the plug or secure in the cap. I've found a lot of plug wires that looked like they were installed right but the connector wasn't pushed down on the end of the plug tight. On just as many I've found the connector on the end of the wire not pushed down into the contacts in the cap good and allowing a miss. The other contributor is a vacuum leak due to a hose or cap being knocked loose. We have all fiddled around under the hood spiffing things up and knocked something loose that needs to be hooked up correctly for things to work and I imagine in the end that is what she is going to find.

On the spark nailing you, I had always told my students that they didn't want to wear their watches while working on an engine because a spark might jump out and make connection with the watch. Sure enough with 15 students gathered around me I reached across the top of the distributor of a running car with my watch on to grab the vacuum advance on the other side to turn the distributor a bit an ZAP the biggest prettiest blue spark jumped right up to my watch band and my head hit the hood of the car with a big bang.

[OrrieG]

Originally Posted by mr48chev

It's rather hard to believe that she had the truck together and running great with everything good to go and all the sudden the distributor is 180. Gents read the whole first post she wrote.

I take full credit for getting the conversation sidetracked, I used the 180 and an example of how things can go fubar regarding ingnition problems, obvoiusly not Denee's problem because it never left the engine.

[G&R's57GMC]

BTW the stock GM HEI puts out 60,000 volts at 1 amp .

That is enough to kill you if it passes through your hart on the way to ground.

Be very careful working with HEI systems.