greatho

I can see blue spark loss at the plugs and at the coil of my 5.7 engine runs poorly and misses. First attempt to solve this problem - I replaced coil, distributor, rotor, distrib. cap., spark plugs, and wires with Genuine AC parts from the dealer. Problem went away for 1 day and then problem returned. I can again see blue sparks when viewed in the dark under the hood at each plug and at the coil - runs poorly and misses.

olemiss74

What did the original plugs look like when you pulled them out? have you looked beyond the plugs and did a compression test on each cylinder?

SABL

What is the gap on the new plugs??

mack1

Hi greatho and welcome to TSF,

I've not seen blue spark loss at plugs in the night. Does the spark jump from under the wire's rubber cover to the metal base of the plug? It might be normal to see the blue, but I have never had any reason to try it at night. It'll pick a night when it is not freezing and take a look.

It could be plugs fouling out causing the missing. From their posts, I think olemiss74 and SABL suspect the same. An old test for a fouling plug is to slowly lift the plug wire at the distributer or spark plug, causing the spark to jump an additional gap. This actually causes the coil voltage to reach a higher level to make the jump. ( a fauled plug will let the current go around the plug gap giving no spark.) The higher voltage will make the spark jump the plug gap and cause the cylinder to start hitting.

If you try the spark jump idea to isolate a missing plug, be very careful. A good plan is to wear gloves and use well insolated pliars to lift the wire. Don't lean on the finder while you are lifting the wire, and be very sure to keep the other hand off the car. Electrical current across the chest can cause the heart to fibrilate (fast short pluses, but no pumping). If that occurs, you will need a friend to severly pound on your chest to try to get the heart back into step thus preventing death. As I said, be very careful.

A safer way is to just pull the plugs and see if any of them are wet with fuel or oil.

Hope this helps,
Mack1

SABL

Jeepers, Mack1....you're even scaring me....just kidding.

Very true about the high voltage and cardiac fibrilation. The only way I will pull the wire off of the plug is with a spark plug wire puller or if the engine is not running. Pulling the wire at the distributor is a time honored method of cylinder misfire diagnosis. When finding a wire that (when disconnected) produces little or no change in engine idle, trace the wire to the cylinder and inspect the plug for fouling. I may be wrong but in the case of fouling it would seem that the spark would have an easier path to follow and not produce the arcing you are seeing. I don't know if oil (or gas) has any viable insulating properties.

You mentioned that you replaced the ignition components with OEM equipment... that's good but not the best, but they are up to standards.

The reason I asked about the gap with the plugs is that you CANNOT pull the plugs out of the box and install them without checking/setting the gap. Spark plugs are made for many different engines and the gap is set for the most common application..... that does not mean is it your application.

I suspect that your plugs are gapped too wide and with short-term wear on the plugs you are getting arcing along the spark path.

If the problem is from oil fouling, I will go as far to guess that the problem lies in the rearmost cylinders. A very common problem when the oil galleys become obstructed and causes oil to seep past the valve stem oil seals due to improper drainage of oil from the heads.

Help me Mack1 will oil fouling insulate the plug and cause an incomplete circuit??

@Mack1.....what?? You are seeing above freezing temps?? You lucky dog!!

mack1

Hi SABL,

Current takes the least resistance to ground. In a fouled plug, the current flows from the high voltage node through the crud to ground, not across the higher resistance gap. Voltage drop across crud is like drop across a resister. When the voltage across the resister (crud) reaches the level needed to cause current jump across the gap, then it will. That's why the lifting the plug wire and increasing the voltage output from the coil works.

We are having below normal temperatures this week. I don't really care for it. I'm sure you'll get some low temps up there soon.

Have a nice day,
Mack1

SABL

Hi Mack1,

We're getting norms up here, not above freezing. I was just out (mercy run...had to get anti-freeze......NOT vehicular...hehehe) roads are not nice, and rather slippery.

Are you telling me that the spark is more likely to travel through the oil deposit than the gap in the plug?? Please bear with me.... I am far less educated than you and I greatly respect your opinion and knowledge. I need to rephrase, if there is fouling then there is no gap in the spark plug.... the circuit is complete. I am trying to determine why arcing is present when the downstream circuit has been closed..... it seems to me that the circuit has not been completed and arcing (path of least resistance) is occuring to facilitate closing the circuit.

Mack1, I only ask your opinion for my further education. I hold you in high esteem and feel your input is most valuable to the forums @ TSF

mack1

Hi SABL,

Yes, except I would call it current flow through the oil depost. Think of the oil as a resistive element, not a short. If you flow current through it, voltage will build up across it. Since the oil or carbon deposit form a circuit that is parallel to the gap, current will flow through that path until the voltage across it reaches the jump voltage. At that point, current will flow throught both circuits, the depost and the gap. It probably takes about 9,000 volts to jump the gap. The coil will put out up to 25,000 or more volts if it has to. Lifting the plug wire at the distributor causes the coil to put out the new gap voltage plus the 9000 needed for the sparkplug gap. When the plug gap voltage is reached, current will spill across the gap and the voltage won't build up much above that level. Almost like a short circuit across the gap at the jump voltage.

Explaining things without the aid of pencil and paper is a challange for me.

I make sure I don't run out of anti-freeze also.
I made several trips to Findlay before retirement and was lucky enough to miss all the bad weather. Some friends there told me about getting showed in on occasion.

Have a nice day SABL.
Best regards,
Mack1