Running rich on one cylinder

[dchildress]

I have a 1997 Suburban with the 6.5 and about 260,000 on the clock. I own an oil change shop and have changed the oil in this truck every 2500 miles and put in a bottle of injector cleaner/pump lube/ cetance booster with every tank over the last 7 years and 80,000 miles I have owned it. Replaced fuel filter every other oil change. Do the same with my LB7 Silverado. Newer PMD with relocation kit & cooler behind bumper. New vacuum pump. Previous owner had receipt for new injector pump a month before I got it. Puts out 15 psi of boost then drops to about 10 constant and back to 15 after gear change. Ran aboslutely perfect unitl I parked it in October for a couple of weeks. Went out to start it and got the normal white smoke after sitting but it didn't clear up. No codes. White smokes like crazy at idle and full throttle. No blow by coming out of oil filler neck. Hardly any blow by coming out of breather. Added another quart of injector cleaner with no improvement. Put in 4 injectors on passenger side with no improvement. Mechanic that was working on the truck said when he broke line loose on #5 cylinder, idle would smooth out but fuel would go every where. Second mechanic could not replicate this but did say on #6 cylinder if he broke it loose and retightned it would smooth out for about 10 seconds and start missing again. Any clues? PMD? Injector pump? Burned exhaust valve? Should I spend money and do other 4 injectors? :mad2: We have 7 kids and this (was) our main family hauler. Summer is coming.

 

[3500GMC]

First thought was not enough compression to fire off the mix. Injured cylinder maybe?

 

[RI Chevy Silveradoman]

Welcome to the forum! :welcome2:

Sounds like a bad injector. Or maybe a bad cylinder head?

Take the time to fill out your signature with all of the info on your truck.

 

[bison]

Headgasket dam failing between 5-6 maybe,...i had that on my 6.2,..same symptoms.
I would do a compression test on these 2 cylinders
Is yours using coolant?
I wonder how you manage to run constant 10 lb boost?,.... unless you got only both ways uphill country there

 

[dchildress]

Headgasket dam failing between 5-6 maybe,...i had that on my 6.2,..same symptoms.
I would do a compression test on these 2 cylinders
Is yours using coolant?
I wonder how you manage to run constant 10 lb boost?,.... unless you got only both ways uphill country there

Runs 10 to 15 under full throttle. 3 to 5 cruising. Uses no coolant. Not using any more than normal oil. No fuel in oil. I will have compression check done. Found an ex GM 6.5 specialist who works for county garage and does work on the side.

 

[3500GMC]

Oooo a specialist.

(kidding around)

 

[dchildress]

Oooo a specialist.

(kidding around)

Kinda what I thought too. He worked at a GMC dealership from like 84 to 03 as the head diesel mechanic. He got sick of flat rate and went to work for the county working their fleet of 3500s with 6.5 in them. I'm a born skeptic so we will see. And finding somebody willin to work on it is kinda hard to find

 

[NVW]

I think both mechanics found the same cylinder misfiring, one of them doesn't know which side is odd or even. It's likely #5 as you've changed all the injectors on the pass side.

 

[WarWagon]

I think both mechanics found the same cylinder misfiring, one of them doesn't know which side is odd or even. It's likely #5 as you've changed all the injectors on the pass side.

:hammer: Just what I was thinking.

Injectors are done at 100K. Injectors can burn the engine up at 174K: see my avator pic after the piston melted from a bad injector. Head gaskets are good for 200K.

You should have replaced all 8 injectors at the same time.

I would change the rest of the injectors and then go from there head gasket being next.

 

[dchildress]

:hammer: Just what I was thinking.



You should have replaced all 8 injectors at the same time.

I would change the rest of the injectors and then go from there head gasket being next.

I am going to plug in my buddy's spare PMD just to check it. If not change, going to go ahead and swap out other 4 injectors myself as soon as I can find the time. If that doesn't clear it up....off to the mechanic we go.

Unless somebody wants to buy it as is. In the last 7500 miles....4 tires on 2006 8lug aluminum wheels, front half shaft, U joints, new shocks, new ball joints, maybe and idle or pitman (cant remember) calipers & pads, shoes & drums, new A/C compressor, vacuum pump, alternator, belt, tensioner.

 

[vstech]

... rocker arm button failure is my #1 guess...

pull the valve cover on the dead cylinder side... I bet you'll find a rocker sitting on the head.
if it's been a long time broken, you could have puked a lifter or push rod too...

 

[dchildress]

... rocker arm button failure is my #1 guess...

pull the valve cover on the dead cylinder side... I bet you'll find a rocker sitting on the head.
if it's been a long time broken, you could have puked a lifter or push rod too...

I didn't have a chance to try my friends spare PMD nor have I even looked under the hood to get started on other injectors. Broken lifter or push rod has always been in the back of my mind.

 

[WarWagon]

I didn't have a chance to try my friends spare PMD nor have I even looked under the hood to get started on other injectors. Broken lifter or push rod has always been in the back of my mind.

These engines do have plastic buttons to hold the rockers in place. They break and you now have a valve that stays closed. You would have a miss that you could feel and hear and it would not 'clear up'. The smoke would but not the constant 'miss'.