Let's replace a fuel injector on a 84 300SD - Mercedes-Benz Forum
 
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post #1 of 5 (permalink) Old 02-08-2002, 11:23 PM Thread Starter
 
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Let's replace a fuel injector on a 84 300SD

Sorry, no picture this time.<br> <br> After the glow plug saga, I started to smell some diesel fuel once I stopped the car. Lifted the hood and noticed fuel injector #2 had a slight leak. Not so much to interfere with engine start/operation, but if the leak got bad enough - probably cause knocking and other issues.<br> <br> SO... fuel injector replacement time. Called Kragen and there is no injector replacement equivalent. This is strictly a dealer part. Call dealer and there are two options. Purchase brand new injector at $270 (for one) or purchase rebuilt/remanufactured injector for $60 with core exchange (extra $10 without core exchange). I went with rebuilt/remanufactered one. Hopefully the unit I got was remanufactured instead of rebuilt. Anyhow, on to pulling the old injector.<br> <br> Two ways to do this. You can remove the entire fuel line to get to one injector OR remove the single fuel line feeding the leaky injector. The problem is that the fuel lines are held together in place with metal clamps. To remove a single fuel line, you'll need to remove these metal clamps with an 8mm socket.<br> <br> I suggest removing the single fuel line. It's a pain undoing the small metal clamps, but this introduces less air into the system when all is done and makes restarting the car easier.<br> <br> Use a 17mm wrench to remove the fuel line from the injector and from the fuel pump. Some diesel fuel might leak out, so have some paper towels ready at both ends.<br> <br> Once removed, get some paper towels and cover the exposed fuel pump line.<br> <br> Unplug the overflow tubes from the fuel injector.<br> <br> Use a 27mm deep socket (yes, 27mm!) to remove the fuel injector. Depending on how tall of a socket you use, you may need to use an extender arm. I was using a 27mm deep socket with a 3 inch extender with a 1 inch insert to the socket wrench.<br> <br> Don't throw it away. You'll need this injector as your core exchange to bring to the dealership. <br> <br> Installation is just the reverse of the above.<br> <br> Injector needs to be tightened to 55 ft-lbs. Dealer was nice enough to tell me this little piece of information.<br> <br> Once everything is tightened. You'll need to loosen the fuel bleeder nut (with 17mm socket) and operate the fuel pump to get as much of the air out as possible. Surround the fuel bleeder nut with plenty of paper towels to absorb the diesel fuel. Tighten the bleeder nut when done.<br> <br> Wipe up any diesel fuel lurking around.<br> <br> Start up the car. There'll still be some air in the fuel line (or fuel lines if you removed the ENTIRE fuel line). In any case, it may take a few cranks to get the fuel pump to push the fuel through to the cylinders, depending on how much air is in the system (this is why I suggested removing one fuel line instead of all of them).<br> <br> Most of this stuff you can find in your basic Chilton repair manual. They just leave out stuff like what size tools to use or the dilemmas you run into. I hope someone finds this helpful.<br> <br>
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post #2 of 5 (permalink) Old 02-09-2002, 04:38 AM Thread Starter
 
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Re: Let's replace a fuel injector on a 84 300SD

Wow, that's a lot of good info Esteves. Thanks for posting it. Glad to hear the stealership had a lower cost option for you.
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post #3 of 5 (permalink) Old 02-11-2002, 10:11 AM Thread Starter
 
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Re: Let's replace a fuel injector on a 84 300SD

Esteves,<br> Did you replace the 'pre-ignition cup', also? I'm curious as to the condition of this item. It looks like a large spanner, to get the 'cup' out, not sure though.<br> Regards, John F. '81 240D
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post #4 of 5 (permalink) Old 02-11-2002, 02:30 PM Thread Starter
 
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Pre-Ignition Cup. Are you referring to the the Prechamber?

<br> Just so where on the same page, I'm guessing you're referring to the prechamber. This is the area between the injector (sometimes referred to as nozzle holder) and the cylinder head. A ball pin in the prechamber controls the release of fuel into the cylinder. Is this what you mean?<br> <br> If so, I did not replace this. I think it would be very difficult (just from looking at it) to try to remove the prechamber without pulling the valve covers and who knows what else.<br> <br> The prechamber is held by a lug nut. What size is it? I have no idea.<br> <br> Also, there is a seal between the prechamber and the injector (nozzle holder), so I doubt you could even get a look into the prechamber with the injector removed.<br> <br> The only thing I can think of to get a view of the prechamber would be to remove the glow plugs and then use those tiny snake cameras to look inside. Glow plugs do directly into the prechamber. Of course, this is a totally inefficient and costly way to check out the prechamber.<br> <br> For the most part, I don't think it's worth checking out and I wouldn't worry about the prechamber.<br> <br> Then again, maybe there is a way to check it, but it's not apparent to me at the moment.<br> <br> <br> <br>
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post #5 of 5 (permalink) Old 04-14-2005, 09:10 AM
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RE: Let's replace a fuel injector on a 84 300SD

Guys wish me luck, i am going to have remove the prechamber. On my 1989 190d i have compression leaking between the head and the prechamber. So i have no choice other than pulling it out. i have ordered the tool from mercedes and they told me its comming from Germany (i am in canada). once i receive it , i will go ahead and do it. any suggestion would be much apreciated.
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