91 350 SD smoke and miss at start
05-01-2010, 06:28 PM
#1
Newbie
Thread Starter
Join Date: Dec 2009
Location: Hazel Green, AL
Posts: 7
Likes: 0
Received 0 Likes
on
0 Posts
1985 300D, 1992 300D, 1982 300SD
91 350 SD smoke and miss at start
A recently purchased 91 350SD inline 6, 3.4 turbo with 162K.
Car smokes and misses at startup. The car was always warmed up when testing and checking prior to purchase... you know the story. I'm trying to solve the inherited issue with little luck. Otherwise aside from a couple small issues, it's a jewel.
Sometimes it smooths out and runs like silk with no smoke, other times symptoms persist. As it warms up and smokes it makes an occasional sound like a small dog sneezing as it misses, sorry thats the only sound I can relate it to.
The problem seems to be in cyl 6 as loosening inj line affects all but six. 1 and 6 injectors were swapped, symptom remained with 6.
Mechanic has verified IP delivery pressure is fine. He suspects a sticky lifter/follower which would explain the occasional smoothing out, or a bent rod which would not.
Has anyone experienced these symptoms and resolved them?
Want to avoid costly exploratory if possible. Your input will be extremely appreciated!
Car smokes and misses at startup. The car was always warmed up when testing and checking prior to purchase... you know the story. I'm trying to solve the inherited issue with little luck. Otherwise aside from a couple small issues, it's a jewel.
Sometimes it smooths out and runs like silk with no smoke, other times symptoms persist. As it warms up and smokes it makes an occasional sound like a small dog sneezing as it misses, sorry thats the only sound I can relate it to.
The problem seems to be in cyl 6 as loosening inj line affects all but six. 1 and 6 injectors were swapped, symptom remained with 6.
Mechanic has verified IP delivery pressure is fine. He suspects a sticky lifter/follower which would explain the occasional smoothing out, or a bent rod which would not.
Has anyone experienced these symptoms and resolved them?
Want to avoid costly exploratory if possible. Your input will be extremely appreciated!
05-02-2010, 02:59 AM
#2
Junior Member
Join Date: Oct 2009
Posts: 67
Likes: 0
Received 0 Likes
on
0 Posts
1989 300 SE
My first thinking is if you do have a bent rod then you'd better get it replaced soon.
A rod really isn't a difficult repair, don't they simply drop in between the cam and lifter? One guy on this board had a bent rod, and it punched through his engine block without warning, a thrown rod can pretty much total your engine. and I dont think you have to replace them all, just the troubled ones, because each lifter can be adjusted individually, right?
I'm getting ready to replace all my rods soon at 150K, just because I've seen a couple horror stories of thrown rods and the damage it does. Ask your mechanic what the best solution is, also ask him: if the lifter is sticky does that mean that you have alot of float on that valve at higher RPM?
Drive gently, and warm-up that engine in the morning before running and gunning, a cold engine has more space between the parts and will rattle and leak more. As your engine gets hot the metal parts expand to proper tolerances at "operating temp" and will be less likely to smoke and rattle.
Thats all I got- Im tapped. I'm no mechanic, just trying to give good advice.
A rod really isn't a difficult repair, don't they simply drop in between the cam and lifter? One guy on this board had a bent rod, and it punched through his engine block without warning, a thrown rod can pretty much total your engine. and I dont think you have to replace them all, just the troubled ones, because each lifter can be adjusted individually, right?
I'm getting ready to replace all my rods soon at 150K, just because I've seen a couple horror stories of thrown rods and the damage it does. Ask your mechanic what the best solution is, also ask him: if the lifter is sticky does that mean that you have alot of float on that valve at higher RPM?
Drive gently, and warm-up that engine in the morning before running and gunning, a cold engine has more space between the parts and will rattle and leak more. As your engine gets hot the metal parts expand to proper tolerances at "operating temp" and will be less likely to smoke and rattle.
Thats all I got- Im tapped. I'm no mechanic, just trying to give good advice.
05-02-2010, 09:29 AM
#3
Newbie
Thread Starter
Join Date: Dec 2009
Location: Hazel Green, AL
Posts: 7
Likes: 0
Received 0 Likes
on
0 Posts
1985 300D, 1992 300D, 1982 300SD
Shurmann - Thanks for your response. I believe the mechanic is talking about a bent piston rod which does not allow the piston to fully stroke. I don't know if he has done a compression check on #6 and compared to others or not which should indicate an issue there. I will verify with him on Monday.
05-02-2010, 12:09 PM
#4
Member
I would check the compression first. If that looks good, I would buy a set of Monarch injectors. They made a huge difference in my car.
07-06-2010, 01:03 AM
#5
Newbie
Join Date: Jul 2010
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
560SEL
the 350SD and 350SDL had a design flaw in the engine and they will all end with catostrophic engine failure. the problem was even worse when they used this engine on the newer, heavier w140 series. Supposedly when the engines are rebuilt, with the new rods, the problem does not reoccur
07-06-2010, 07:32 AM
#6
Member
I have 3 of these cars, and have had even more. The engine may have a bent rod, but I still think you have a fuel issue. bent rods don't straighten themselves and run better ant then go back to running worse.
You would have excessive oil usage and if bad enough the engine may not run right. I have had an engine with way excessive usage and they still run good. They just burn losts of oil.
If it doesn't run right, it's probably in the fuel delivery. But as mentioned before, I would definitely check out the compression and even the leakdown test to try and determine what you have so that you can decide how much to spend to fix it.
I just bought a new injection pump for one of my cars. You can get brand new for $1000. I have not finished putting it in yet, so I can't tell you how much a difference it makes, but I have 189,000 miles and that is alot to still expect precision device like that to be perfectly functioning and calibrated. A rebuild cost about as much as I paid for the new one.
But a brand new set of Monarch injectors made the car run MUCH better.
Oil can also be getting lost through the turbo. Not all these cars had issues. Everyone will tell you that it is the engine. And it may be, but not necessarily.
You would have excessive oil usage and if bad enough the engine may not run right. I have had an engine with way excessive usage and they still run good. They just burn losts of oil.
If it doesn't run right, it's probably in the fuel delivery. But as mentioned before, I would definitely check out the compression and even the leakdown test to try and determine what you have so that you can decide how much to spend to fix it.
I just bought a new injection pump for one of my cars. You can get brand new for $1000. I have not finished putting it in yet, so I can't tell you how much a difference it makes, but I have 189,000 miles and that is alot to still expect precision device like that to be perfectly functioning and calibrated. A rebuild cost about as much as I paid for the new one.
But a brand new set of Monarch injectors made the car run MUCH better.
Oil can also be getting lost through the turbo. Not all these cars had issues. Everyone will tell you that it is the engine. And it may be, but not necessarily.
07-06-2010, 10:03 AM
#7
MBWorld Fanatic!
From what I read Mercedes used a overstock of old rods when the built these engines.They tend to wear cylinder into a oval.To repair heavy rods are used with new pistons and liners.
If rebuilt these are fast and good engines.
If rebuilt these are fast and good engines.
