Leaky Injector or sticky lifter/valve? - PeachParts Mercedes-Benz Forum

zloca944 · #1 04-11-2019, 06:27 PM

Hello guys I have a om603 and I would like to know is it possible for injector to leak when the engine is off.Because in the last 20/30 days it happens not all the time(doesen't matter hot or cold engine)when I start the car and for 2/3 seconds it runs on 5 cylinders and has a little bit of white smoke(unburnt diesel)and after that little bit clicking from the injector and smoothens right out and works as smooth as silk,no smoke,no shaking on idle,just perfect sound of a good running 603

.So is it possible when I turn off the car that one injector leaks a bit of diesel in the cylinder and then after I restart it,it needs some time to pump diesel through that line again.Or is it possible that there is some sticky lifter or valve and there is no compression at that 2/3 seconds on that cylinder until they got unstuck

so that's the reason for unburnt diesel smoke.Just to tell I have checked and calibrated Injectors 15.000km ago(will do it again just to be sure it is not up to them) and also removed head changed lifters and did complete work on the valves,seats etc.(all work was done last year and this started like I said 20/30 days ago so no related)
I would just like to hear your opinions,and will let you know what was the problem(if i solve it

)

MB140300SD · #2 04-11-2019, 07:28 PM

More likely a dead glow plug combined with a lifter ticking

Father Of Giants · #3 04-11-2019, 07:33 PM

Check your glow plugs.

Take a test light and connect it battery Positive (+), unplug glow plug relay and probe the harness.

If the glow plug is good, the test light will become lit.

An open glow plug will not light.

zloca944 · #4 04-12-2019, 05:01 AM

That's why I written,doesen't matter if the engine is hot or cold it happens with the hot engine too.If it happened only on first(cold)start then i would suspect the glow plugs,but it happens also when engine is hot and on operating temperature and it does not happen everytime i start the car.

Father Of Giants · #5 04-12-2019, 05:30 AM

You essentially had your head rebuilt, so that should be out of the equation.

If you suspect a bad injector, purchase some injector seal rings, swap your suspected injector with a known good and see if the symptoms follow it.

zloca944 · #6 04-12-2019, 05:35 AM

This is exactly what I am going to do in next couple days,just wanted to hear your opinions.Thank you guys.

Diseasel300 · #7 04-12-2019, 09:16 AM

Any wetness on top of the injection pump? The delivery valve seals are a known leak area. If you have wetness, or if you haven't done the job in several years, it's a good chance you have leaks which can definitely cause leakdown problems.

zloca944 · #8 04-14-2019, 06:38 PM

Nope everything bone dry,I have changed seals maybe 3 years ago.
I did not had time to dedicate myself to that problem,maybe i will do it this week and report back.

Maxbumpo · #9 04-15-2019, 09:56 AM

Work from simple / cheap to complex / expensive.

This is a text book description of a bad glow plug, and yes they are needed even when the engine is hot. The fact that the pre-glow light will stay on for a few seconds even when the engine is hot is your clue here. The engineers designed it that way.

Next would be a bad injector. Loosen injector lines while the problem is present to see which injector is the culprit. If your injectors have not been serviced for 100k miles or more, it is time.

3rd would be a delivery valve that isn't sealing up or has some other issue. Same diagnosis method (loosen injectors lines to find which one is the culprit). "Rebuild" the delivery valve with fresh copper washer and o-ring.

If none of those cure the issue, then a compression test / leak-down test would be in order.

zloca944 · #10 04-17-2019, 05:18 AM

Yes but the glow plug either works or does not work(and they are new BEHRU maybe 8.000km old),here I have problem once in a ten/fifteen times starting maybe even more,and I can not crank injector because it last only 2/3 seconds top,as I said I will try with injectors and report back.If they are good then I will go further

.

97 SL320 · #11 04-17-2019, 09:23 AM

Quote:

Originally Posted by zloca944

Yes but the glow plug either works or does not work

It is more subtle than that. If the glow plug tip is burned off, that cylinder will smoke / miss until cylinder head temperature rises where a non conductive plug will result in minimal smoke. The glow plug continues to be a hot spot even when power is disconnected. Remember, it is very cold in a pre chamber at start up even with a " hot " engine.

With a cold engine, have someone start it then gently feel the exhaust manifold ports for heat ( use the back of your hand ). The cold cylinder that heats up once the engine smooths out is the problem one.

Another way to narrow down the problem cylinder. Mark the crank for TDC on all cylinders, look through the oil cap and see if the camshaft lobes are visible. Each time you shut the engine down, note where it has stopped.

Engines tend to stop on the compression stroke and at least 2 valves will be open ( lifter under pressure ). The goal is to find a lifter that is under pressure and is collapsing.

zloca944 · #12 04-19-2019, 11:38 AM

Removed and tested injector's all good,tested glow plugs all good,just the tip heats up,so next thing to check are lifters.Will update on progress.

Maxbumpo · #13 04-20-2019, 12:59 PM

Lifters should not go bad after just one year.

Why not rebuild all the delivery valves? Check the seats for erosion while you have them apart.

zloca944 · #14 04-23-2019, 01:38 PM

Found the problem,leaking a bit of coolant in to the cylinder,and it is not firing on that cyl. until it burns or push out coolant thru exhaust valve.I have noticed the hoses are a bit harder than usual,and that in the morning I have a pressure in the system,not to much but still it is not good sign,and started loosing a bit of coolant but no leak.So on Saturday i will remove this head and put other that is rebuilt completely,and pressure tested,so that was the problem all the time.When i put the tank cap on first click(it is not holding pressure so no pressure can force coolant in to the cyl.)and car starts every time like it should.I do not know(still) is it the head or the gasket failure,but will for sure take the head when I remove it to pressure test it.Car was no overheated,temp does not go past 85C,but most of time is 80C,new radiator,new WP,new Hoses,new fan clutch...But as the Queen said"SHOW MUST GO ON",good thing is that I work on MB vehicles and have a lots of spare parts

Maxbumpo · #15 04-24-2019, 09:58 AM

Yep, that would do it. If the head is original, it should be the upgraded head like a #17 or later, maybe even a #20, so probably not a cracked head but more likely a bad head gasket.

How is the oil consumption? Your engine is the notorious "rod bender" which has a bad reputation here in the USofA, but I think in Europe they did not suffer the same problems? When you have the head off, you may want to measure the piston heights on all the pistons, if a rod is bent, that piston will be lower at top dead center compared to the other pistons.