603 cracked fuel line........then injector knock - PeachParts Mercedes-Benz Forum

Brian Carlton · #1 12-15-2006, 06:48 PM

Took the '86 on a 560 mile jaunt down to Raleigh, NC.

About 75 miles from destination, I notice it running on five cylinders and find a decent fuel leak on the #6 line, right at the pump.

Continued to destination on 5 and had to drive it another two days until the line came in. Total mileage on 5 was about 150. Very easy on the engine......no turbo utilized at any time.

Put the new line in place and find that the injector presents some light knock at idle and up to about 1000 rpm.

Drove it 200 miles today with decent loading at times.........no real change.

So, what's damaged? Any thoughts on how the injector or prechamber could sustain damage due to operation without fuel?

dieseldiehard · #2 12-15-2006, 07:19 PM

Brian, you had turbo utilized or you wouldn't get out of the driveway! I tried running a 603 without the crossover pipe, that is basically the same as no turbo. The 603 is a dead duck without boost! Worse than a sick 240D even!

I bet you need an O-ring seal in one of the delivery nozzles. Its about the cheapest part on the entire engine but there's a bit of work to install it, and the plastic clips that secure the lines usually always need to be replaced when removing them they crack (why am I telling you that? Oh, its for the education of novices who haven't had the experience of cracking the clips off to get the lines loose!)

It could also be an injector nozzle I suppose - with no fuel maybe the orifices in the injector plugged up? Try swapping nozzles or better yet run some MolyLube stuff thru them

Hit Man X · #3 12-15-2006, 08:22 PM

Same deal happened to me, two fuel lines were cracked at the base. I just ordered up all six lines and the DV seals. Will report back...

I had a very large fuel leak at the No 1 and No 4.

Brian Carlton · #4 12-15-2006, 10:58 PM

Quote:

Originally Posted by dieseldiehard

I bet you need an O-ring seal in one of the delivery nozzles. Its about the cheapest part on the entire engine but there's a bit of work to install it, and the plastic clips that secure the lines usually always need to be replaced when removing them they crack (why am I telling you that? Oh, its for the education of novices who haven't had the experience of cracking the clips off to get the lines loose!)

It could also be an injector nozzle I suppose - with no fuel maybe the orifices in the injector plugged up? Try swapping nozzles or better yet run some MolyLube stuff thru them

Reid, I can't fathom how the #6 o-ring would fail due to the loss of pressure in the hard line? Any ideas on this?

I'm leaning more toward the #6 injector, but, would operation of the engine without fuel to the injector cause damage to it?

Any thoughts appreciated.

I actually did run the engine with minimal boost at all times. It never got above 2400 rpm (about 55 mph).

dieseldiehard · #5 12-16-2006, 12:03 AM

Quote:

Originally Posted by Brian Carlton

Reid, I can't fathom how the #6 o-ring would fail due to the loss of pressure in the hard line? Any ideas on this?

I'm leaning more toward the #6 injector, but, would operation of the engine without fuel to the injector cause damage to it?

Any thoughts appreciated.

I actually did run the engine with minimal boost at all times. It never got above 2400 rpm (about 55 mph).

Minimal boost is still boost! I'll bet you had at least 6+ psi at take off, it comes up quick on the 603's
Anyhow maybe I'm half cocked about the O ring being involved. I always blame them when you have nailing on the 603.
Swap injectors, its easy to do, see if it moves to the next cylinder. I have used that technique and didn't bother to use a new heat shield with no problems as a result.

Brian Carlton · #6 12-16-2006, 11:08 AM

Quote:

Originally Posted by dieseldiehard

Minimal boost is still boost! I'll bet you had at least 6+ psi at take off, it comes up quick on the 603's
Anyhow maybe I'm half cocked about the O ring being involved. I always blame them when you have nailing on the 603.
Swap injectors, its easy to do, see if it moves to the next cylinder. I have used that technique and didn't bother to use a new heat shield with no problems as a result.

It's been awhile since I had the gauge on the 603's. Maybe they'll give some boost below 2400 rpm, but, it's probably minimal.

I'll do that injector swap and see if the knock moves with the injector.

It's very minimal, and, if you didn't know the engine, you'd probably ignore it. You cannot hear it from inside the cabin and you need to pay attention to notice it above the lifter noise that seems to have returned with a vengeance.

#7 12-16-2006, 11:18 AM

My guess is that running with reduced fuel pressure to that injector may have clogged or damaged that injector. My thought is that the engine compression will result in reversed pressure on the injector, maybe pushing some soot into the nozzle. Have you tried running some purge to clean it out?

Brian Carlton · #8 12-16-2006, 04:02 PM

Quote:

Originally Posted by Craig

My guess is that running with reduced fuel pressure to that injector may have clogged or damaged that injector. My thought is that the engine compression will result in reversed pressure on the injector, maybe pushing some soot into the nozzle. Have you tried running some purge to clean it out?

I run my usual Power Service conditioner on each tank.

Over the last 250 miles, slowly, the injector knock has reduced slightly. So, with Power Service and some additional fuel through that cylinder, I might just dodge the bullet.

dkveuro · #9 12-16-2006, 04:28 PM

It is not unusual for an injector to knock/nail for 1 to 2 thousand miles after rebuild or other changes. If compressions are above 350 on each hole then run your purge and add some miles...I'm betting it will quieten down soon.

Does slightly loosening the line nut at the injector make it quieter ?

.

Brian Carlton · #10 12-16-2006, 04:45 PM

Quote:

Originally Posted by dkveuro

It is not unusual for an injector to knock/nail for 1 to 2 thousand miles after rebuild or other changes. If compressions are above 350 on each hole then run your purge and add some miles...I'm betting it will quieten down soon.

Does slightly loosening the line nut at the injector make it quieter ?

.

Thanks DK.

It's outside right now. I previously loosened it to the point where I lost the cylinder and then tightened it again.........no change in results.

I'll give it a try with less torque on the hard line. BTW, how does this affect the combustion characteristics?

Brian Carlton · #11 12-16-2006, 05:10 PM

Quote:

Originally Posted by dkveuro

Does slightly loosening the line nut at the injector make it quieter ?

.

There is no change in sound as the nut is loosened until the pressure drops and the cylinder doesn't fire.

Hatterasguy · #12 12-16-2006, 05:49 PM

I don't see how a lean mixture in one cylinder could affect the injector or PC much. Well if it wasn't firing at all and was still getting some fuel it might have a bit more carbon maybe? Swap that injector around and see if the sound follows it.

Give it a few WOT runs she will probably clear up.

dkveuro · #13 12-16-2006, 08:17 PM

Quote:

Originally Posted by Brian Carlton

There is no change in sound as the nut is loosened until the pressure drops and the cylinder doesn't fire.

Hate to be bearer of bad tidings but that sound like the piston to wall clearence is at top limit.
Had a 603.9 here recently that did the same on #2. It was a semi siezed piston and had galled the thrust face lands of the piston skirt. Compression was okay but needed honed out and new piston installed....noise was gone....however it's worth chasing the noise to other holes to verify.

.

#14 12-16-2006, 08:26 PM

Quote:

Originally Posted by dkveuro

Hate to be bearer of bad tidings but that sound like the piston to wall clearence is at top limit.
Had a 603.9 here recently that did the same on #2. It was a semi siezed piston and had galled the thrust face lands of the piston skirt. Compression was okay but needed honed out and new piston installed....noise was gone....however it's worth chasing the noise to other holes to verify.

If you read the first post, this started with a leaky fuel injection line. What you are suggesting would be quite a coincidence.

dkveuro · #15 12-16-2006, 08:29 PM

Quote:

Originally Posted by Hatterasguy

I don't see how a lean mixture in one cylinder could affect the injector or PC much. Well if it wasn't firing at all and was still getting some fuel it might have a bit more carbon maybe? Swap that injector around and see if the sound follows it.

Give it a few WOT runs she will probably clear up.

Reducing the injected fuel will change the TDC piston loading, but not change the noise much until cylinder no longer fires if the piston is damaged.

If the injector or pump is faulty, the noise reduces as fueling is taken away. Most diesel engine noise is due to fuel burn characteristics and at the beginning of the burn there is a very high pressure wave that is heard as a knock or the typical idle clatter of a diesel engine. This is why injection systems are now designed to inject a small amount of fuel just prior to the main fuel load. This stabilizes the piston and the chamber temperature to allow a smoother quieter burn for that stroke fuel quantity.

.