Dead cylinder proc. of elimination...stuck

Kevin ACR · May 2, 2006

I was firing intermittently the other day on my rear cylinder, header tubes on 9 cylinders were running at ~300f with the rear Dr. side running at 150f (12K miles, 2000 gts)

Then on Sunday it got to where it was obvious I lost the cylinder completely, that dead thumping sound in the exhaust.

What I've done is:

-Replaced spark plug
-Used HEI spark tester to make sure I ahve a good wire/coil, lot of spark
-took the valve cover off, rockers are in place and are torqued
-cranked engine, valves appear to be moving same amount as the rest so assume cam still has a lobe
-appears to be mechanically sound

Next to Fuel?....
-Doesn't viper fire half of injectors on one of two circuits? So injector should be getting a trigger signal to fire otherwise I would have lost other cyl's?
-Can I use a dvom to check for injector pulse? gotta figure out how connector comes off

-Has anyone had an injector fail at 12,000 miles?
-Any ideas on what next?
-I was going to pull injector and have it replaced under warranty, thoughts?

Kind of stuck here in the garage until I can get a v-10 back, thanks

Mark Red GTS Cooper · May 2, 2006

You can move the injector to prove it is the problem, move it to #1

Mark

Kevin ACR · May 2, 2006

Moving the injector is a good idea, why #1 or is it just convenient.

Also, I'm having trouble figuring out the lock on the injector harness to remove the connector.

and...it says to replace the "O" rings when removing the injector, overkill?

thanks

hemibeep · May 2, 2006

If you have warranty, that would be the best way.

1. If not, try a stethascope to listen to that injector, they are noisey. Check injector electric connector to make sure it is not loose/dirty/corroision.

2. They recommend replacing o-rings when you pull them out, but it may be worth swapping two injectors to see if problem moves.

3. intake has internal fuel rail, so a stuck or bad injector should be easy to find.

Yes, 2000 with low miles can have a bad injector.

Kevin ACR · May 2, 2006

I have warranty and might need it.

I swapped injectors and still looks very cold in my problem cylinder on back of the engine, the header on that one is at 110f and rest at 212 or so.

Word to the wise: If you pull injectors relieve the fuel pressure first or when you remove the first one you'll dump a whole bunch of gas from the pressurized fuel rail into the cylinder ( and you can listen to it run into the bore) then have to blow it out before you go on!

At this point I'm at a loss. Seems like the fundamentals are all in place. I even listened to the injectors with a stethoscope and they all sound identical to me.

I'm going to borrow a DRB III (don't know what I'm looking for) but I hate to drive it across town like this to the dealer . this *****!

Mark Red GTS Cooper · May 2, 2006

Even though you get a good spark, try swapping the wire, see if it follows the wire.

Is the compression ok?

Mark

Joseph Dell · May 3, 2006

2 things to do to check for dead cyl:

1 - start pulling plug wires while the motor is running. if you pull a live one, the motor sound will change. when you hit the dead one, no change in sound will occur.

2 - do same thing, but w/ fuel injectors.

this will diagnose the problem quite quickly and cleanly. if pulling plug wires, make sure not to kill yourself.

good luck!

JD

Kevin ACR · May 3, 2006

this will diagnose the problem quite quickly and cleanly. if pulling plug wires, make sure not to kill yourself.

good luck!

JD

As i was reading "pull the plug wires" I'm thinking how the hell am I going to to do that without getting shocked. Then I see "make sure not to kill yourself" , it really struck me as funny. Seriously, I needed that this morning

I'll go after wires and injectors tonight. A lot better than taking stuff apart and hopefully it is a simple fix. Appreciate the input very much!!

Joseph Dell · May 3, 2006

Kev -

I've either done it w/ insulated gloves _or_ start the car, shut it off, pull the wire, start the car, listen, shut it off, plug that one back on and unplug another, etc... not an exact science that way (better w/ gloves) but workable.

good luck!

JD

EllowViper · May 3, 2006

Rule of thumb is that if you can pull the wire from the coil side (aka distributor) vice the plug side, you will eliminate becoming a spark plug...plus you can connect/disconnect/connect to better troubleshoot. However, I haven't changed my wires yet so I'm not sure how much room there is to get at the rear while the engine is running after the cowl is removed. Have changed plugs, no big deal, but pulling wires with the engine running from the plug side would be interesting to watch on video!

Ulysses · May 3, 2006

Is the compression ok?

Mark

Have you tried what Mark suggested. Simple, quick check since wires, spark plug, injectors and spark seem ok.

Jack B · May 3, 2006

Kevin ACR:

I may have missed it, but, have you run a compression test, that will rule out bad rings and/or valves. If you show poor compression the next step is a leak-down test. Like Hemibeep said, the injectors are easy to hear with a stethoscope, they can be ruled out very quickly.

As far as two sparks per cylinder, it is called waste-gate ignition, there is a second spark on the exhaust cycle, that spark is meaningless in your case and won't create the issue you have.

Last but not least if you can can get a borescope you can get a good idea of the physical state of the cylinder

Kevin ACR · May 3, 2006

I'm very pleased to report it was finally fixed with one plug wire and acceleration wise you can really tell the difference! The car went through a full physical `` to get there, live and learn!

I thought spark was good because the spark plug style AC HEI tester that makes the spark jump a good 1/2 " lit up like a tesla coil. I put it back on the road but once it ran for 15 minutes it started to miss, then it went down hill.

After a leak down test, and I was very concerned, I put a wire on cylinder #9, problem gone. I measured the resistance in the old wire 10.9 (decimal place unknown) and the one that worked (used) was 8.9, don't konw what any of that means.

Somehow it was heat related, but my concern is that I put these Mopar Viper wires on 2,200 miles ago and was EXTREMELY careful never to bend them or pull on them. Why would it fail? Does this problem indicate the quality, or could it happen to any brand wire? don't know.

Thanks to all of you with the very good ideas and to Chuck Tator who could have easily sold me wires on the first pass but was very honest and gave me free advice instead. My favorite dealer and I wished I lived close enough to use him!!

Mark Red GTS Cooper · May 3, 2006

Ok,, I said swap a wire and see. Spark does not mean voltage, E (IR) ohms law,

Do I get a gift card,,

Mark

AZTVR · May 3, 2006

Spark does not mean voltage, E (IR) ohms law

Gee, I thought spark was all about voltage ! However, I did miss a lot of Mr. Science's shows.

Jack B · May 3, 2006

KevinACR:

The issue was probably not the resistance (or more accurately the impedance) of the wire. The voltage breakdown rating of the insulation was more than likely the problem. In other words at some voltage level the dielectric value of the insulation is exceeded and a current path to the block is made, therefore, the spark plug is robbed of its spark.

I am sure that the plug wire manufacturers have a simple approach to measuring this value. If you wanted to measure this value it could be done with a 1000V megohmeter (megger). You would twist a bare wire around the insulation, but, leave the connection open on one end, then, connect the megger and apply the 1000V, it will show a certain amount of current leakage on a bad wire.

99 R/T 10 · May 4, 2006

You should probably get a whole new set of wires. If one went bad, how far behind are the others? AB is getting together a group buy on a custom set, might be worth a look. AB wire group buy.

Dead cylinder proc. of elimination...stuck

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