Potential of engine damage from lean fuel mixture or no fuel

[MOOKHILL]

I've got a circumstance where there is an issue with a hole being burned through a piston on the #5 cylinder (driver front hole) of a 1998 Jaguar XJR supercharged vehicle. Some of the claims are that there is no fuel being delivered, which would set a fault code, some more logical ideas are that there is a lousy spray pattern with the injector and it's a lean spray. Any really smart input would be greatly appreciated.

 

[evelrod]

I don't know about "really smart input", not sure I can handle that much stress---However, I holed a piston on a T-coupe years ago because of a "dirty" injector. If it can happen on a Ford, I guess it could happen on a Jag.

Rod

 

[ivymike]

having no fuel delivered is clearly NOT the problem - no fuel means no burning.

 

[patprimmer]

Lean mixture or increased compression from carbon build up or under spec (low octane) or possibly incorrect spark or valve timing fuel could all be the problem. By far the most likely cause is as Rod says, a dirty injector causing a lean condition. Ivymike is also correct. No fuel means no fire means no damage to the piston.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[Apakrat]

The story gets too lengthy on how I learned about failure to speedily replace non firing spark plugs.

Seems one side of the “smart box brain.” thinks the non burned fuel in my 95 Ford Windstar, 3.8 L, V6, need more air and the other side detecting more air, decides to sends more fuel.

When conditions get to some point, the Catalytic Converter ignites, with flames coming out of the connection joint. Usually, the Catalytic Converter requires replacement. Sometimes the automobile will burn up.

At 74th year working on IR-One PhD from UHK - - -

 

[Rob45]

ivymike, it wouldn't be a case of "no fuel" causing the problem, but reduced fuel certainly could: detonation resulting from a lean-out condition quickly leads to very high heat transfer to the surfaces of the combustion chamber, including the piston top, enough heat the piston top is weakened to the point combustion pressures push a hole through it.

 

[ivymike]

um, isn't that what I said? As I recall, the choices were "no fuel" or "lean spray" and I said "well you can cross off the first one".

then again, it's been a month since anyone posted... maybe my memory is just getting bad. oh wait, no, it really does say that right up there in the january posts.

hey, thanks for clearing things up though.

 

[evelrod]

It doesn't make a rat's ass anyway, the OP has never ck'd back since his original post. It was a redundant post in the first place...AND...why jump into a dead thread with nothing new to add, especially without even reading the previous replies ?

Rod

 

[bluebeast]

I know it's old but it might help someone else in the future. A colortune adapter will tell you what kind of burn you are getting in the bad cylinder. It screws into the spark plug hole and allows you to visualize the burn and then you can compare that to the other cylinders.
It is a nice little tool and if you are into building high hp engines and you use a MS system or a programmer then it should find it's way into the top drawer of you toolbox!
About the lean no fuel issue think about that caddy motor that cuts off 4 cylinders when cruising.

 

[evelrod]

Wow...Colortune...Is that thing still on the market? I class it right up there with the 'oldies but goodies'...older products like Marvel the Mystery Oil, Wynn's Friction Proofing and, some of the newer gadgets, e.g., "Tornado" (search function for a full 'debunking' of the "Tornado" on Eng-Tips forum).

Yes, Mildred. I did try "ColorTune" when I was a kid. It was cute. At the time I thought it great, but by and large, time and experience has proven it pretty much useless in tuning a high output engine. Great for my MG-TD, though! Using EGT probes and gas analyzers is much faster and much more efficient. If you know how to "read" a plug (trust me, most techs DO NOT) gimmicks like ColorTune are redundant, if not superfluous.

Rod

 

[dicer]

Any holes that I have seen in pistons were from detonation. It could have been from overheating and loading it, such as racing or extended hill climb. I would think even with a lean condition such as injector problem that normal driving shouldn't cause a problem, since the load is so small if so you would think the driver would have heard it. Evelrod, did that happen with normal driving or?

 

[evelrod]

I've actually "holed" one piston, dicer...That was in my '49 Merc 8BA flathead's Merryman 3 5/16" pop up piston...Racing, of course !!! The 'holed '83 T-Coupe piston was my wife and it was on the street...However ;o( it was probably my fault. I had the boost jacked up to some ungodly pressure and I was too lazy to ck or clean the injectors when she started complaining that the engine "did not sound" like it usually did. Still, it was on the street.

Keep in mind that my wife drove race cars when we were first married in 1962. She's a red headed Irish lass with a lead foot, even today! I have no idea what she was actually doing (don't tell her I said that). She says she was "just driving along in the fast lane and it started making noise and smoking"! ??? ;-)

Rod