Help! 93 300D engine issue - PeachParts Mercedes-Benz Forum

axm1955 · #1 01-04-2007, 11:47 AM

Hello all,

Need some solid answers to a relly nasty issue. My wifes DIESEL 300D (W124) when started this morning only operated on 3 possibly 4 cylinders out of 5. Very rough shaking and some loud clonking, could not ascertain if bottom end or top end for sure. With my experience of gas car engines it sounded like mains or rod bearings, but not having anything to loose I gently raised the trottle allowing more fuel mixture to enter and to my surprise the noise begin to subdue and the 1/2 missing cylinders begin to fire. I could hear some somewhat intermittent tapet tapping louder then normal but nothing major. After shutting it off to do some looking and hair scratching to logically think this through, restarted it and it ran fine as alway's.
This is the first time it has ever doen this.

Additional data: Around injectors 1 and 2 (closer to front of engine) have been leaking (or at least it appears to be coming from that area) diesel, I can only observe it on the side of the head and gestimate to be coming from that immeidate area. It also has been idling rougher over th past month, but I was waiting for a little warmer weather to pull the injectors and rebuild them to eliminate the leaks.

Thanks for any mechanical info you can provide to help me better diagnose this before something happens.

Adriano

Parrot of Doom · #2 01-04-2007, 12:22 PM

Check your glow plugs. If it only happens when cold, thats most likely the cause of the problem.

axm1955 · #3 01-06-2007, 02:19 PM

Thanks for the reply.

Anyone knows where I can get an injector rebuild kit including all seals? And a break-down of the injector assembly?

Thanks

Adriano

sixto · #4 01-06-2007, 02:35 PM

Before you tear into the injectors, replace the return lines, the braided hose that goes from injector to injector. If they're wet or damp, they're either at fault or contributing to the fuel leak. A meter's worth of hose from the dealer is $10-12. Cut to size as you remove the old hoses. Some have luck with auto parts store hose (3.5mm?) but original style hose lasts the longest.

Check that all the injector lines are securely clamped. As the clamps loosen and break, they allow the injector lines to vibrate and rub against each other. This constant movement weakens the ball-and-cup seal at either end but more commonly at the injector end. If the line is leaking at a compression fitting, you need a new line. Not terribly expensive.

Inejctors aren't something the typical DIYer rebuilds at home. It's not a complicated process but there is precision involved and you need a device to check and balance the flow and spray pattern among the set. Diesel shops charge $20-40 per injector for this service. There's probably an authorized Bosch service center in your area or try a reputable independent MB shop.

Sixto
93 300SD

sixto · #5 01-06-2007, 02:36 PM

The return line on the far end of the injector next to the firewall has a plug. That's how it comes from the factory.

Sixto
93 300SD

axm1955 · #6 01-13-2007, 11:48 AM

Thanks Sixto for all th input,

The return lines were replaced not too long ago and are not wet. My local MB repair center does NOT rebuild the injectors due to low percentage rate of success (they not I) claimed on the container re-sealing after rebuilding.

Now I'm in the process of locating injectors, they want $95.00 ea for them.

Do I need a special wrench to take them off the head? My 300SD does, I see some 1/8" ears protruding (180 degrees apart) at the bottom of the injector housing right next to the head. My 300Sd has two flat areas onopposite of the injector housing which also appear to need special tooling.

BTW as an aside I have ben a mechanic for almost 20 years, but these are my first 3 german made diesels and I love the tight tollerances used so precision measuraments are a joy to work with, not a challenge

Adriano

TMAllison · #7 01-13-2007, 01:17 PM

ALWAYS fix the leaks first.

Cut 1/2" off the return lines if you have enough length and plug them back on the injector nipples. It may not be the hose weeping but rather the connection to the nipple.

A rebuilt injector is as good as a new one as long as the nozzle hasn't been damaged somehow. Find a local shop that works on big rigs who can pop test, balance and check their spray patterns.

sixto · #8 01-13-2007, 04:34 PM

Bozio brand injectors seem to have a following in this forum.

You can use any 27mm (1-1/16"?) deep thin wall socket. The thinner and cheaper the socket the better. 12 point works better than 6 point unless the return line nipples on all injectors happen to align with the points on the wrench flats. If you use a socket that fits the injector too closely, it will bend the nipples inwards and you'll probably cause a leak bending them back to position.

Torque is 70-80Nm.

Don't forget new injector seals.

The plastic shields around the base of the injectors don't have to be replaced. MB doesn't stock them anymore.

Sixto
93 300SD

fj bertrand · #9 01-13-2007, 04:53 PM

replace the glow plugs, all 5 of them. If the engine runs smooth after warm up, its not the injectors. Why create more trouble for yourself???

axm1955 · #10 01-27-2007, 02:57 PM

Thanks to all who posted.

Acquired remanufactured injectors by the sponsor of these forums and installing them as I am writing this.

What was throwing me were the plastic shrouds at th ebase of the injectors, they have 2 protruding ears (what I refer to as bunny ears) at 180 deg. (oposite each other) and did not know if I needed a special tool to remove them.

Adriano

sixto · #11 01-27-2007, 03:08 PM

The plastic shrouds pull right off. They fit into the splines in the prechamber. I don't know what they're for other than to collect dripping fuel. MB doesn't sell that item anymore.

Did you get new injector seals? Make sure to remove the old seal before dropping in the new seal. Note which side is up.

Sixto
93 300SD 3.0