CovenStine
Junior Member
- Joined
- Dec 9, 2015
- Posts
- 20
- Reaction score
- 6
- Ram Year
- 1999
- Engine
- Cummins
Hello, all
I have a rather unique problem, and was hoping I could get some insight from you.
I bought a ’99 Cummins about 18 months ago, and started having issues, and after a ton of time & parts, she’s still not running right.
The short version? I have a new head, a new injection pump, removed the tuner, and tried a computer swap, and the truck still sounds –and smokes –like injection is happening in the #6 cylinder after the valve opens. I believe this to be electronic in nature, and I’m trying to figure out what electrical or computer issue could be causing it.
The long version?
The lift pump died on me in September, but was caught quickly thanks to the pressure gauge the previous owner added after he killed an injection pump. Might be related, might not.
Over thanksgiving break, I noticed some throttle lag & surging, and sort of figured that it was an APPS, but once I wasn’t hauling anything anymore, the issue went away, and I thought nothing more about it.
Come mid-December, the truck started running rough and smoking badly- no catastrophic sounds or anything, as far as I heard/can tell.
I took it to the shop, where they found an “Injector Pump” code in the primitive computer, so- since she passed a compression test- they replaced the injector Pump.
Upon startup, she still was running just as rough, and smoked just as badly. Upon further testing, the truck failed a Leak-Down test, apparently leaking out the exhaust valve of the #4 cylinder. The head was found to be leaking & damaged from an old overheating problem & an over-rev, resulting in some old valve contact- again, in #4. The bent pushrods were replaced, the head was replaced (and rebuilt by the local Cummins specialist machine shop, as the ‘new’ head was assembled poorly) and everything was buttoned back up.
This time, upon startup, she was still running just as rough, and smoking just as badly- subsequently they found a VERY minor leak in the Leak Down Test in the #6 cylinder, but nothing else is obvious mechanically. Upon further trial and error, they found that if the #6 cylinder is starved for fuel, the smoke problem goes away (but obviously, it’s still running very rough).
The mechanic seems to think it’s a problem in the bottom end of the motor, and is of the opinion that it’s time to just rebuild the motor and be done with it.
I disagree for 3 reasons:
So now I have a truck that isn’t running right, with a brand new radiator, injection pump, and head, sitting in my driveway for me to ATTEMPT to fix.
AAAAAnd I'm wishing I'd just bought a 12-valve and been done with it...
Any thoughts, suggestions or even judgements would be most appreciated. Thanks!!
I have a rather unique problem, and was hoping I could get some insight from you.
I bought a ’99 Cummins about 18 months ago, and started having issues, and after a ton of time & parts, she’s still not running right.
The short version? I have a new head, a new injection pump, removed the tuner, and tried a computer swap, and the truck still sounds –and smokes –like injection is happening in the #6 cylinder after the valve opens. I believe this to be electronic in nature, and I’m trying to figure out what electrical or computer issue could be causing it.
The long version?
The lift pump died on me in September, but was caught quickly thanks to the pressure gauge the previous owner added after he killed an injection pump. Might be related, might not.
Over thanksgiving break, I noticed some throttle lag & surging, and sort of figured that it was an APPS, but once I wasn’t hauling anything anymore, the issue went away, and I thought nothing more about it.
Come mid-December, the truck started running rough and smoking badly- no catastrophic sounds or anything, as far as I heard/can tell.
I took it to the shop, where they found an “Injector Pump” code in the primitive computer, so- since she passed a compression test- they replaced the injector Pump.
Upon startup, she still was running just as rough, and smoked just as badly. Upon further testing, the truck failed a Leak-Down test, apparently leaking out the exhaust valve of the #4 cylinder. The head was found to be leaking & damaged from an old overheating problem & an over-rev, resulting in some old valve contact- again, in #4. The bent pushrods were replaced, the head was replaced (and rebuilt by the local Cummins specialist machine shop, as the ‘new’ head was assembled poorly) and everything was buttoned back up.
This time, upon startup, she was still running just as rough, and smoking just as badly- subsequently they found a VERY minor leak in the Leak Down Test in the #6 cylinder, but nothing else is obvious mechanically. Upon further trial and error, they found that if the #6 cylinder is starved for fuel, the smoke problem goes away (but obviously, it’s still running very rough).
The mechanic seems to think it’s a problem in the bottom end of the motor, and is of the opinion that it’s time to just rebuild the motor and be done with it.
I disagree for 3 reasons:
- For about the first half-second of running after startup, the truck sounds FINE; I think that there is no way anything is heating up fast enough that the problem is coming from thermal expansion
- The “bad” cylinder (according to the Leak Down Test) has moved from #4, with known valve contact, bent pushrods, and a bent valve, to #6. All 6 cylinders have throw/travel within spec, all 12 rods have throw/travel within spec, and the only way a valve could open earlier than it’s supposed to, would be if the lobe MOVED on the cam, but all 11 other lobes stayed put- which I think is impossible.
- I’m SURE I have not over-revved or overheated this motor, and I’m 99% sure that the previous owner didn’t either. That means it’s been running with a cracked head, bent valve, and a bent pushrod for 100k miles+, so this teensy leak in #6 shouldn’t even be noticeable.
So now I have a truck that isn’t running right, with a brand new radiator, injection pump, and head, sitting in my driveway for me to ATTEMPT to fix.
AAAAAnd I'm wishing I'd just bought a 12-valve and been done with it...
Any thoughts, suggestions or even judgements would be most appreciated. Thanks!!