Is a Dented Spark Plug Bad?

[campoj2]

The Nightmare Scenario Continues

The "Basket Case" vehicle as it now known is a 94 FZJ 80 with 220K on the clock. The HG went, my oil turned into chocalate milk, and as a result the bearings started to make some funny noises. I was looking at replacing the HG and some lower end work that no one wanted to do.

There were 2 courses of action:
1. Complete engine rebuild
2. Find another motor

I choose to find a replacement motor, and I did. The engine came from TN with 89K. Yes 89K!

The install went with the usual challenges of removing something out of 13 year old car that spent its entire life in the Northeast. But in the end it was in, and running smooth as sewing machine. That is until today, may I remind you that the truck is still at the repair facility with less 1/4 mile on the clock since the install.

So today I go to check up on it to see how things were going and I could tell by the look on the Tech's face that something was not quite right in Toyota Land.

Well I was right, Big Jim, aka Mr Toyota, said we've got problems. I said what problems could we possibly have? He said "YOUR #3 PISTON DENTED THE #3 SPARK PLUG!. I said "say that again" and he did.

Engine Motor theory #1 "PISTONS DON'T HIT SPARK PLUGS"

So the nightmare continues...what to do???? Rebuild the 220K motor, fix the 89K motor...set truck on fire!

The nightmare happened, and it is essentially this, rebuild a fried motor or take your chances on a second motor? And right now I am in the drivers seat of the worst case senario, 2 bad motors.

I contacted the vendor and they told me to find out how much it will cost to fix their motor, and that's what I am doing right now.


ANY IDEAS??

 

[gray]

The Nightmare Scenario Continues

The "Basket Case" vehicle as it now known is a 94 FZJ 80 with 220K on the clock. The HG went, my oil turned into chocalate milk, and as a result the bearings started to make some funny noises. I was looking at replacing the HG and some lower end work that no one wanted to do.

There were 2 courses of action:
1. Complete engine rebuild
2. Find another motor

I choose to find a replacement motor, and I did. The engine came from TN with 89K. Yes 89K!

The install went with the usual challenges of removing something out of 13 year old car that spent its entire life in the Northeast. But in the end it was in, and running smooth as sewing machine. That is until today, may I remind you that the truck is still at the repair facility with less 1/4 mile on the clock since the installed it.

So today I go to check up on it to see how things were going and I could tell by the look on the Tech's face that something was not quite right in Toyota Land.

Well I was right, Big Jim, aka Mr Toyota, said we've got problems. I said what problems could we possibly have? He said "YOUR #3 PISTON DENTED THE #3 SPARK PLUG!. I said "say that again" and he did.

Engine Motor theory #1 "PISTONS DON'T HIT SPARK PLUGS"

So the nightmare continues...what to do???? Rebuild the 220K motor, fix the 89K motor...set truck on fire!

The nightmare happened, and it is essentially this, rebuild a fried motor or take your chances on a second motor? And right now I am in the drivers seat of the worst case senario, 2 bad motors.

I contacted the vendor and they told me to find out how much it will cost to fix their motor, and that's what I am doing right now.


ANY IDEAS??

Only two ways I can see a piston hitting a spark plug;
some idiot (previous owner or mechanic) put in a plug that
was too long, or, someone rebuilt the engine with the wrong
length connecting rod or piston, and then never ran it (not sure
if that is even possible)

Check the dented spark plug to make sure it is the correct type.
The mechanic should have done that; This sounds odd.

I once spent $3000 to have a "low mileage" auto-tranny put in
one of my vehicles; it only lasted 15K. Lesson I learned;
either buy brand new, or rebuild it, yourself.

G

 

[SteveH]

Silly suggestion, but be sure the correct plugs were installed in the engine. Do a compression test, and tell us what you learn. 'Spark plug dented' is fairly imprecise term - was it shattered to bits by a piston hit, or was the gap closed by a tap? If the piston is no longer connected to the crank, there should be other signs beyond a 'dented' plug.

 

[Leroy]

this is bizarre. assuming it is a stock motor with 89k miles and not a rebuild (no chance of wrong length con rods or incorrect pitons) then it must be the wrong plug. was there significant damage done? you said it was running like a sewing machine. if that's the case what changed? i'd pull all the plugs and take a look in there and make sure the piston is ok and there's no damage internally. then get some new plugs. if the plug did shatter and peices are inside the chamber then you have a problem. what could cause the piston to suddenly rise higher and crash into a plug? ....very odd.

 

[campoj2]

The dented part of the spark plug was metal portion where the spark is produced, the metal hook at the bottom of the plug.

I am going to do a compression test shortly and will post the results.

Thanks guys, I am continuing the investigation. More to follow...

 

[CJF]

Post up the brand/model of the spark plug.

 

[campoj2]

I am on my to Toyota to get a spark plug and compare it to the one that was dented. If someone sabotaged my truck I am going POSTAL.

 

[CappyKD]

How about this theory. Someone dropped the plug when installing it. How does "Mr. Toyota" know that the #3 piston is dented? Did he remove the replacement engines head? Did he compare the other spark plugs to the #3 one? If they are the same then all should have hit the pistons..

 

[CodyRx7]

lol...

They must make a fortune at that service dept.

The spark plug would be quite destroyed if the piston was hitting it. It was probably just improperly gapped.....or conveniently bent down by the Big Jim guy on his way to speak to you.

 

[concretejungle]

something just sounds foul here. Sorry to hear about your troubles.

 

[CappyKD]

Yeah somethings rotten and it may just be Big Jim......

 

[PHAEDRUS]

Just for giggles, look at the threads on the #3 piston, has it been helicoiled?? This could be your issue as well, More than likely someone dropped a spark plug.
Get a visual scope and look at the top of the piston through the plug hole prior to getting too excited about anything.
Dave

 

[Grench]

So... Thats the next question.

What is standard clearance between the piston at TDC and the tip of the spark plug?

I think it would pretty much have to be measured indirectly, wouldn't it? Position the cylinder at top dead center, measure from the valve cover to the top of the plug, the length of the plug and from the valve cover to the top of the piston with the plug removed.

I'm not planning to pull any plugs any day soon. Just don't knock/leave anything in the cylinder. Could be bad.

YMMV and all that.

 

[informationjunky]

Just for giggles, look at the threads on the #3 piston, has it been helicoiled?? This could be your issue as well, More than likely someone dropped a spark plug.
Get a visual scope and look at the top of the piston through the plug hole prior to getting too excited about anything.
Dave

Scope sounds like best idea, I don't know how he could have seen the piston top otherwise, seems like a long hole throught that cover.

 

[campoj2]

Big Jim is one of the most competent mechanics out there, he worked for Toyota for 18 years and knows his sH*t. He has fixed issues on this rig that no one else could solve.

After a trip to Toyota we can rule out the incorrect spark plug theory. It was a Denso plug that matched the one I got from Toyota.

They did a compression check on #3, no compression.

They did a bore scope, saw nothing....

Now what? Pull the head?

 

[concretejungle]

as my old physics professor used to say.... somethin' aint according to hoyle.

 

[cary]

It sounds like a dropped valve, but you should have seen that with the bore scope.

 

[campoj2]

Quite honestly, I'm hoping it's a dropped valve.

Through the process of elimination theory, it's either a dropped valve or the piston is not doing what it's supposed to be doing. If it's the piston then it's an official can of worms. It took 20 hours to put in the motor...work with what I got or rebuild the 220k motor.

This would be the week that I didn't get a keg for the kegerator

 

[IBCRUSN]

Something smells really bad.

If they borescoped the the cylinder and actually saw nothing I won't believe the statement "the spark plug dented the piston." It would have left a mark, even a slight mark on the piston. I have a difficult time believing their story especially if the plug is the correct P/N that is supposed to be installed. I would be more inclined to believe a story of the spark plug electrode melted off and started bouncing around the cylinder due a mixture issue but there would be much more noticeable damage.

Get a leak down tester (differential compression tester) and check that cylinder. The test will help point you in the right direction if the leak is noted coming from the crank case, intake or exhaust.

Here is a good read on the compression tester:
http://www.littleflyers.com/engcomp.htm
http://www.chiefaircraft.com/airsec/Aircraft/Tools/CompressionTester.html

It is possible to find a plug gap closed by the piston depending on how far it protruded into the combustion chamber. As mentioned above a grossly incorrect plug P/N would have to be installed for this to happen. You would certainly notice it right away because the cyl would essentially be dead (no spark gap to jump) and yes there is the possibility the piston could be damaged but during the cranking phase of starting the piston and plug would have "self clearanced" by closing the gap or smashing the business end of the plug either way a tech should have caught it prior to firing the engine.

Push back and continue to dig for more info, they are not telling you the whole story.

 

[campoj2]

The statement the spark plug dented the piston is incorrect, the spark plug gap got crushed by the piston is more accurate.

I can take a picture and post it if that would help.

#3 is not producing any compression, I'm thinking it's dead?