I have a 360 FE with the Duraspark setup and the magnetic pickup dizzy. Well I recently replaced my coil and ignition module, as well as the soilenoid for the electrical system, and the battery, and the alternator, and the voltage regulator. I also have new spark plugs and new spark plug wires. Oh and it's also a fresh remanufactured longblock from a local rebuild company.

The engine is running good but doesn't seem as good as it should be, especially on the low end. It doesn't take off from the line like I think it should. I have a motorcraft 2100 carb I think, it could be a 2500. It's got I believe 56F jets in it. I have worked on setting the idle mixture and I think I got the best results with it about 3 turns out, but I am not 100% sure because I had a hard time adjusting it.

Anyway, I hear people talk about how the spark should be blue and not orange, but I am not sure abotu this all. Are we talking about the whole length of the spark, or just part of it? When I hold a spark plug wire next to the block I can get the spark to jump about 1/2 inch max, and the spark is more orange looking except for the point where it touches the block, that part seems kind of blue.

Does anyone have any example pics of what it should look like? Or, are there any more scientific and precise measurements, other than just describing the color of the spark?

If my spark is weak what can I do about it, considering I already replaced everythign but the dizzy? Can the dizzy cause this? I thought it wouldn't matter since all it does is tell when to spark, the dizzy itself doesn't have a part in MAKING the spark does it?

By the way, I fixed my friend's 1994 Ford Thunderbird last night, it has a V8 engine with some kid of distributorless ignition system. He was having problems with the engine running rough. My God that ignition was amazing, when I disconnected wires from the distribution block, I could hold them over an inch away and the spark would jump all the way to them, and very blue! My friend tried the same thing and got careless, and a spark jumped to his hand over an inch, and knocked him backwards! The spark looked like the demonstration the guy at the parts store did for the MSD ignition. Also, when I disconnected the spark plug from the distribution block, if I got the plug far enough away, the spark would dance all over like lightning around the inside of the plugin socket! It's like it was so powerful that if it had nowhere to go, it would just shoot out into the air! I wish my spark was that good, I am having spark envy now

By the way, his problem was that he washed his engine with a hose, and the next day his car was running but it was sounding rough, like it was missing, but only at higher RPM's and under a hard load, it would idle fine and cruise OK once the RPM's got up. Well, when we pulled the plug wires off the spark plugs, the spark plug holes were FULL of water, and so were the plug booties! I made fun of him a lot! But I was impressed how well the engine still ran with water all in there.

 

With electronic dist. ignition you should have a blue spark that will jump a 7/16" gap at least. Yellow means it is very weak, more like you would find with a point system. I would suspect you got a wrong coil that belongs with a point system.

 

Hey guys, I was looking around on this web page, and I found someone's suggestion that you can hold a dollar bill up to the tailpipe, and if you have bad valves, the dollar bill will sometimes get sucked back onto the tailpipe.

So, even though I have a freshly rebuilt engine, it doesn't seem to be running quite right... so I quickly went outside and tried this test. I have dual exhaust, and on BOTH sides, it would randomly suck the dollar bill onto the tailpie for a split second! It would be blowing the bill away from the tailpipe, then suddenly with a POP noise the bill would suck onto the tailpipe for a fraction of a second, then get blown off again. Uh oh.. I feel a sinking feeling... this is not good! But I don't see how my valves could be bad... I didn't do the rebuild myself, it was a company that does rebuilds all the time, how could they have screwed up valves on BOTH sides of the engine?

However, I searched around the internet and found someone posted this:

"<!--StartFragment --> When I first started working on cars, in the last days of points and condensers, we often tested for misfire by holding a dollar bill in the exhaust stream. If the bill was periodically sucked back toward the tailpipe, you had a misfire. If the bill was sucked out of your hand and into the tailpipe, you had a burned exhaust valve. "

OK, so is it possible I might be having a misfire, but not bad valves? Maybe a misfire caused by an ignition problem instead of bad valves? I hope so... I already suspect my ignition isn't working quite right.

 

make sure your coil is getting a full 12 volts...

 

Randon just means a cylinder randomly miss fired (a fairly normal occurance). A regular consistant suck in means a dead cylinder.

 

I will check again but I think the sucking in was random.

But I don't understand how it could ever SUCK from the exhaust, can anyone explain? See, I understand if an exhaust valve isn't closing all the way, when the cylinder goes down to fill with gas and air, it would suck some air back in through the exhaust manifold thus the suction... but how could there ever be sucking in caused by just a misfire, but not a bad valve?

I really hope you are right though, if I have bad valves that would be a nightmare for me.... I am in college and my schedule is so tight I have almost no time ever to work on the truck. I spent 100% of my very short 2-week summer vacation installing the rebuilt longblock in the truck and getting it running, and now I am up to my neck in school and it is hard enough to keep my head above water. The place I bought the longblock from has a warranty but the way it works, you have to remove the engine and bring it back to them in order to get things straightened out. What a nightmare.

Any easy to fix things that might cause a misfire, and sucking at the tailpipe? I have a little bit of time on the weekends for small jobs.

Just out of curiousity, could the EGR valve have anthing to do with this? I disconnected vacuum from it but I did not block it off entirely. I didn't check to make sure it isn't leaking. Is it possible for the EGR valve to open by itself or something, or somehow interfere and cause misfires?

 

If I disconnect the + terminal of the coil and measure from the wire, with engine not running and ignition to ON, I get 12 volts.

However, when I connect the wire to the coil then measure with it connected, it is only about 6.5 volts.

I think someone told me that is normal?

 

Disconnect tells you nothing. Connected and not running also tells you nothing, Engine running tells you what's happening while the engine is running and that is all that matters. With 6.5 volts running tells me you have a resistance wire in the coil wire curcuit which is for a point system

 

Are you sure?

http://www.autozone.com/images/cds/g...3d800a5070.gif

It shows there being a resistor inline on the "run" circuit. Wouldn't that make the voltage lower?

 

By the way I forgot to mention I get a small puff of black smoke when I rev it!

 

Idle mixture is probably a little over rich, has nothing to do with the ignition. 6.5 volts sounds low, should be closer to 8 volts but you are working on it and will have to decide what is or isn't acceptable.

 

I tried running a wire directly from the battery positive to the positive coil terminal to see if the engine ran better or had a fatter spark but it didn't seem to help. I would like to get that resistor out of the system because I think the coil I bought doesn't need one, but I can't seem to find where it is, can you help me find it?

Right now the spark will jump about 1/2 inch and it's pretty fat, but orange in color. I thought it was supposed to be blue.

Anyway, I have a bunch of new information, Bear and others, please tell me what you think about this:

As I said earlier, I did the dollar bill test and it was popping onto the tailpipe like it was trying to suck it in. I did it again and paid closer attention, and it is not happening randomly, it is happening very regularly. So, I tried the same test on my 4 cylinder Kia Sportage just out of curiosity, and it did the same thing... but my Kia is running really smooth and runs great, so this is weird. I tried it on the two cars my parents have and theirs didn't suck in at all, they were just a steady blowing out of air... however, those engines were both V6 and they had a single tailpipe that combined all the exhaust. When you are doing this test, does it matter whether you have dual exhaust? My exhaust comes straight from the exhaust manifolds, back to under the bed, each side has a 36 inch glasspack, then the tips come out the back under the bumper. There is no crossover tube or anything.

It seems wierd to me that the dollar bill is popping in and out equally bad on both tailpipes, so whatever is wrong, it is apparently equally wrong on both sides of the engine.

But now that I think about it, isn't there an exhaust cross-over passage in the intake manifold, leading from one side to the other? Oh man... So if I have 1 bad exhaust valve, when it sucks in exhaust, the suction could get transferred to both sides of the exhaust manifold, right? Dang...

So, thinking, wow I am screwed I must have bad valves, I decided to pull the plugs and check compression. First of all, my plugs are this nice tan color, I think they look good compared to what the manual shows. So I do my compression test, and every cylinder is reading 120 PSI. I did 5 cranks each cylinder for the test. Is that normal pressure for a 360? I know it sounds low but this engine has a pretty low compression ratio...like 7.8 I think? So is 120 low or normal or what? My repair manual doesn't say.

So, I thought maybe the intake was pulling in exhaust gasses from the EGR valve leaking. My vacuum is low too so that seemed like a good thing to check. So I took off the carb and EGR valve and nope, the EGR valve works perfectly, assuming I am testing it correctly. If I suck on the part leading to the intake barrels, there is no airflow, unless I apply vacuum to the pot on the back. I also can not blow on the exhaust hole, it is sealed until I apply vacuum to the pot. So, I would have liked to blame my EGR valve but it doesn't seem to be leaking.

So, I am pretty stumped. This dollar bill test really confuses me why I am getting the result that supposed to mean my exhaust valves are burned. I hope they aren't really burned or sticking or whatever.

My engine is running hot too, which I think might be related, but it hasn't gotten hot enough yet for the radiator to boil over, and I always was told that if you were hot enough for engine damage, you would have a boiling over radiator.

I had a couple other ideas, couldn't a leaking intake gasket wreak havoc like this, allowing some cylinders to suck exhaust gasses in?

Another idea I had, my cast iron intake is from the old engine and it was very rusty and corroded on the inside, i had it hot-tanked, but didn't have the functionality checked, is it possible that there could be a leak somewhere between the exhaust passages inside of the intake, and the intake passages? Any cool tricks I could use to test for this possibility?

Anyway, I am stumped to the max, please help if you can.

 

first off, take the dollar bill and give it to your buddy. now that thats outta the way, forget about it. i think you're worrying too much about it, and it isn't the problem. the spark needs to be blue or you're not gonna make any power. got another coil laying around? know someone that does? how was the spark before you made all your electrical modifications? the resistor is just a wire, a big, fat wire they call a resistor wire because it offers, well resistance.. LOL did you buy one of those cool chrome coils from your local parts store? if so, they're junk. i learned that one the old fashioned way....

 

Ford never used an internal resistance coil. If they sold you the wrong one (it will be labeled one way or the other) if it is and that is part of the problem. The resistance in the primary wire is in the wire itself not a seperate resister.

Ignore the dollar bill test BS. Your compression test shows that you have no bad valves. A leaking intake does not suck exhaust in, it sucks air in which causes a lean condition and a misfire. To find pull plug wires off one at a time while running. The one(s) that cause not change in rpm are bad, could be a bad plug or wire too.

Running hot can cause the engine to have several different problems. Do you have a thermostat in the engine? Quite worrying about exhaust to intake leaks, it's more likely the EGR. I always block mine. I think you are looking for a problem that doesn't exsist.

 

Cam overlap will suck exhaust back in at the tips. If you have a H or X crossover you will get a mixed misfire from both tips. Without starting a ignition brand war I only run one type by Crane, their XR 3000 trigger with LX91 coil which doesn't need a ballast resistor.

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