JSM crew is stumped, yes it is true.

[JSM]

Got the ty started last night, started right up and sounded good. Idle AFR started around 13, as it ran worked up to 14.7 or so. Perfect right?

Problem came is we noticed cylinder #7, and somewhat #5 will start to glow red after about 2 minutes of running. No other cylinder does it.

• So first check was firing order....checked 3+ times that isn't it.
• Pulled plugs, only 10min of run time look like other plugs nothing unusual still clean.
• Checked valves thinking exhaust might be too tight, all fine, no change.
• Unplug injector to that cylinder it goes away obviously.
• Checked timing both with brown wire plugged in (matched tunerpro) and brown wire unplugged right at zero. Brown wire unplugged it gets red quicker.
• Switched injector plugs, still #7 no change.
• Added 10% more fuel no change, subtracted 10% fuel no change. (AFR obviously changed).

Motor sounds fine, no bad noises sounds good. Blipped throttle and it reacts like it should (and scared the poo out of Dobrick leaving me laughing for a few minutes).


So thoughts?

• Partially clogged injector?
• Bad spark plug wire?
• Bent Valve?

This one had all 3 of us stumped last night, we finally gave up at 11:30.

Find this issue and truck is ready to drive again (well missing 2 fenders but that is easy to fix).

 

[bezerk]

Re: JSM crew is stumped, yes it is true.

check 4 times on fire order? i would replace the cap aqnd rotor just to be sure.

 

[NJ93TY]

Re: JSM crew is stumped, yes it is true.

Valve leaking possibly? Did you do a compression test and compare it to other cylinders? Maybe put air into that cylinder, check exhaust pipe for air leak? Did you swap injector's themselves?

 

[bezerk]

Re: JSM crew is stumped, yes it is true.

i don't think a bent valve will do that. it prolly doesn't get enough compression to create that much of an explosion any way. . and would have had a small miss.
too lean or timing is off.

 

[JSM]

Re: JSM crew is stumped, yes it is true.

Our next step is to swap injectors thinking that injector is partially clogged?
Compression test was talked about after that.

Ran out of time last night.

 

[NJ93TY]

Re: JSM crew is stumped, yes it is true.

Our next step is to swap injectors thinking that injector is partially clogged?
Compression test was talked about after that.

Ran out of time last night.

I would check compression first as that is probably easier then swapping injectors. Im guessing leaking valve=low compression=lean=hot=melted piston. Worst case.

 

[JSM]

Re: JSM crew is stumped, yes it is true.

Motor has probably 10-15minutes on it now. Never been over 3k rpm or even under a load yet. I really think the fuel is burning in the manifold and engine itself is not hurt any or bad compression (I could be wrong). Key is why is it burning in manifold and only on #7 (somewhat on #5).

Didn't sleep very good last night my mind was still thinking about it.

 

[T-Bone]

Re: JSM crew is stumped, yes it is true.

Could it be possible something is partially blocking the exhaust manifold ports for #5 and 7 piston? That would definately create the possibility for your dilemma. If not, I would next side with NJ93TY.....leaking exhaust valve OR slightly bent valve. I know you will figure it out since not too much stumps you for any great length of time :tup:

 

[canadian]

Re: JSM crew is stumped, yes it is true.

switch injectors around and see if the the other cylinder gets hot. swap cap/rotor/wires, maybe try a new distributor.

 

[turbodig]

Re: JSM crew is stumped, yes it is true.

Exhaust lifters on those 2 too tight?

Loosen 'em up 'til they clatter, and see if it still does it.

Get a IR thermometer and see how much of a spread you have.

I doubt your injector swap will fix it... if it were that lean, you'd hear it.


Back your thinking up... why are they hot?

Either:

1) timing is way late, and there's leftovers burning in the exhaust ports
2) The exhaust valve is open slightly when the actual burn is happening.


You'd think you'd hear #2, also. #1 can be caused by things other than ignition timing.

 

[ty166]

Re: JSM crew is stumped, yes it is true.

i know this will sound way off the wall and we are talking two totally diffrent motors but on my 59 had glowing head on 5 & 7 , chased timing and firing order for a week. finally figured out a stuck thermostat , no coolant flow. also had a 67 impala that after a good beating would glow only the nuber 7 plug and exhaust runner , that one turned out to be a freeze plug that someone pushed into the block and left in there.

could be way off but just a thought.

 

[GM TURBO]

Re: JSM crew is stumped, yes it is true.

You shouldn't have a #7 cylinder on a Typhoon.

 

[turbodig]

Re: JSM crew is stumped, yes it is true.

i know this will sound way off the wall and we are talking two totally diffrent motors but on my 59 had glowing head on 5 & 7 , chased timing and firing order for a week. finally figured out a stuck thermostat , no coolant flow. also had a 67 impala that after a good beating would glow only the nuber 7 plug and exhaust runner , that one turned out to be a freeze plug that someone pushed into the block and left in there.

could be way off but just a thought.

Good thought. Variation on this... misaligned intake gasket or RTV crud plugging it up...

 

[JSM]

Re: JSM crew is stumped, yes it is true.

Water temps via sensor in the intake were inline, max was 180 last night.

Exhaust header was just off, nothing blocking it, no gasket to slide just RTV copper and I surely didn't put enough on to the block the 1 5/8" port.

Spark plug wires are getting checked next I think.

 

[turbodig]

Re: JSM crew is stumped, yes it is true.

Water temps via sensor in the intake were inline, max was 180 last night.

Exhaust header was just off, nothing blocking it, no gasket to slide just RTV copper and I surely didn't put enough on to the block the 1 5/8" port.

Spark plug wires are getting checked next I think.

Your water temps would be fine... the coolant isn't getting to the "hot" cylinders....

 

[Big Mike]

Re: JSM crew is stumped, yes it is true.

Are they equal or unequal length headers? Maybe this has something to do with the way the exhaust flows, exhaust gasses backing up in the header building heat. Remember that the 7 and 8 cylinders run hot on allot of small block chevys. Maybe something is blocking the water jacket around that cylinder.

 

[T-Bone]

Re: JSM crew is stumped, yes it is true.

Exhaust header was just off, nothing blocking it

Sorry to have wasted some time suggesting the header ports blocked but aside from that or an exhaust valve not properly functioning, I am stumped too. Something is permitting the combustion to either escape the chamber and heat up the header OR something is preventing the heat from escaping properly (restricted water flow was a great suggestion too). Now I am curiously watching this thread to see the culprit.

 

[dgoodhue]

Re: JSM crew is stumped, yes it is true.

Any chance the wiring is off on those two cylinders or damaged during reinstall?

 

[JSM]

Re: JSM crew is stumped, yes it is true.

Here is a picture of the side in question. The rear most cylinder.

Only wiring specific to that cylinder is the injector harness and spark plug wire (to be changed soon as a test). Cap/rotor determine where spark goes, module inside fires all the other cylinders just the same.

I have another cap/rotor to try also.

 

[sy#2921]

Re: JSM crew is stumped, yes it is true.

I also vote for a coolant problem. I recently had an issue with an ls motor that it took forever to get rid of an air pocket in the back corner of the motor. Temps would read fine but the #8 would glow no matter what we did with the tune. Finally we jacked the front of the car up (35+ degree angle) and filled the motor using the upper radiator hose. Finally the pocket went away and has ran fine since. I also filled my syclone motor through the upper hose and never even had to burp the system