90 300 E Fuel Injectors
 

I have a 90 300E and my local shop says that the reason my car starts rough is that the injectors are not holding the fuel while the car is off. He says there is a pump that keeps a small pressure on the fuel to keep it ready to fire upon startup. And that when they leak some fuel into the cylinders, its like a mini flooding. And that's why it starts rough. It runs fine once its running.

Ok after all that....

My question is...I see the fuel injectors on line to purchase and they are not that expensive. The injectors seem pretty easy to get to on this straight 6....

Is changing the injectors something I could do myself or are there many tricks that could cause alot of problems if not done right.

I would like to try if it's feasable.
Maybe a good shop manual could help?

Thanks
Steve

It is a DIY project.
 

However, use all the precautions while working with fuel i.e. Disconnect the battery. Also change the all the seals associated with the injectors. :D

Looking for Help....
 

I have decided that I relly need ot change the injectors.

If anyone has any diagrams on how to do this I would really appreciate the help.

Thanks
Steve
90 300E

There is no ''little pump'' keeping the pressure on.
That' the fuel accumulator job's to do that.
My opinion, your troubles are not caused by leaky injectors
JackD

Diagnosis..??
 

Thanks for the opinion...
If the injectors are thought to be ok, what then could cause the car to cough and sputter so much when it is started until it is running?

Thanks
Steve
:confused:

Hmm... Same here
 

I have the same symptom on my 92 300e (2.6).. On most attempts to start the car, the car hesitantly shakes/runs rough for that first initial second-or-so of startup, then it runs great.. I replaced plugs and ran Techron Fuel cleaner in the tank, which hasnt helped.. I too am considering replacing the injectors, because of their low price.. (and, they *appear* at least, to be easy to replace)... What other areas of the M103/M104 engine could cause this odd initial rough running of the engine during startup? Could one suspect the fuel pump(s) perhaps?? (don't these cars have like... 2 pumps?) I'm stumped!

-Miles

92 300e 2.6
120k

Long shot but, try this...
 

Turn the key until you have all the dash lights on but DO NOT start the car. You should here the fuel pump activating. Wait a few seconds (the longer the better) then try to start the car. If it starts with no problems you have a fuel pressure leak somewhere, most likely the fuel accumulator, check valve at the fuel pump, leaky fuel injector/seal among other things. If you want more specific help, have your mechanic do a fuel pressure test...Good luck!:cool:

Like the previous post said , a fuel pressure (leak down) test would most likely identify the problem. But there could be so many other reasons for your problem:
*Ignition system (cap, rotor, wires, spark plugs (only use OE, not any other make/type.)
*weak coil
*Cold start valve
* temperature sensor,
*vacuum leak
*Fuel pump, (2)
*Fuel accumulator
*Fuel filter
* Others less likely:
* Stretched timing chain
*low compression
You really have two options:
1) Throw parts at it until you are lucky enough to replace the right one.
2) Have a good/solid diagnostic made by a knowledgable/competent pro.
In most cases, solution no.2 is less expensive.
Good luck
JackD

Hey buddy How long long does your car have to sit before it starts rough? If it sits all night and then starts rough, and then clears up after a few seconds it's probably a leaky injector(s) or leaky fuel distributor. If it starts rough after only a short time of being off, it's probably a REALLY leaky injector(s) or fuel distributor! Have your mechanic connect a fuel pressure guage and verify correct pressure when running, and then shut it down. If there is a large pressure loss that will eliminate an ignition problem. You may need to keep the pressure guage connected overnight. If you find a pressure loss it's easy to determine if it's a bad injector. You can remove the injectors and re-connect them to the fuel lines, and then turn on the key to pressurize the system( don't worry, they won't spray unless the air flow sensor plate is pushed down ). If any nozzles are leaking you'll see droplets on the tips. If no droplets form, the leak is someplace else ( most likely the fuel distributor). If you lose fuel pressure rapidly, the check valve in the pump is probably bad. Don't forget to check the distributor cap and rotor! You'd be surprised how often this is overlooked! Good luck and let me know how you do.

The diagnosis sounds right
 

Thanks for the help...

Your analsys sounds correct. The car must sit for a while before it starts rough. An immediate restart is "fairly" smooth. But when is sits over night...It's a bumpy morning! So I really believe it is one or more injector.

I am going to order the injectors, seals and clips tomorrow from my on-line parts place and I should have them by Friday.

I am one of those visual kind of guys...If I can see the steps on paper and then in my head I can do the job. But if I can't visualize it..It's a rough task. That's why I keep hoping that someone has had experience changing injectors and would be willing to share some steps...written or visual.

I'm going to get a Hanes manual tomorrow and hope that will help some.

I'll report to you guys in the forum after the jos is done and let you know how it goes. Hopefully, I'll be able to do the job this weekend.

Thanks again for all your help.
Steve

I have a 92 300sl with the same symptoms as your 300e. I took it to a mechanic who replaced the fuel filters, checked the fuel pumps and determined the rough starting was caused by the injectors. Instead of replacing them he cleaned them and told me to drive the car. It didnt run much better. ($400 later)

He told me the next step would be to replace the injectors. (another $400) It looks like a easy project. Please let me know how you job turned out.

p.s the prevoius owner of my car took it to another mechanic who replaced the timing chain and then told me the next step was to replace the fuel pumps. Its hard to find good mechanics.

88 300CE
 

I'm experiencing the same rough hot starts,though mine won't pass the idle test of our Aircare program.I failed miserably the first oh so innocent trip through,took it to a local import shop and he said O2 sensor,bring it back next week:( .So I replaced it myself and tried again,failed,but only the idle test this time.Hmmmm,pulled the plugs and noticed they were NGK resistors:eek: :eek: ,in went Bosch Super's and a bottle of snake oil guaranteed to make your exhaust cleaner than clean,failed again.
So I went by the repair shop today,really nice guys btw at Valley Eurotec in Abbotsford,and they figured it was the injectors being worn out,sputtering too much fuel at idle,making it fail the idle test.It's going in on Friday to have injectors installed ($240+ labour)and another Aircare test (@$24ea).It BETTER pass!!

Injector mania !
 

3 local autoparts stores turned up a ZERO for the Haynes manual. Undaunted, I will pursue further tomorrow (phone this time). I have found the injectors online for 23.81 ea. + 1.10 for each seal and about 3.00 for each holder that totals about $167.00 for parts. Including shipping. Not Bad!

Had a weird one today...started smelling a burning (i thought) through the vents so i stopped..and the battery sizzling and was spitting fluid out the side! Yikes! pulled it before it blew. I've never seen that before.

Steve

Hi Steve,I don't know if Haynes makes a 124 manual,if you find one let me know.I have the MB cd but it's a pain to use sometimes.

Hi Buddy Save your money and forget about the Haynes manual. It won't help you with replacing the injectors. Let me give you a few tips that will make the job a piece of cake. Remove the gas cap. Residual pressure will cause fuel to dribble out of the lines long after they're disconnected. Crack the lines loose at the top of the fuel distributor just a bit to bleed off system pressure. Be careful when you loosen the lines at the injectors. Look carefully at the bracket that holds the injector in place. When you turn the 14mm fitting, sometimes it spreads the bracket open before it comes loose. A 16mm open end wrench fits perfectly around the outside of the bracket and keeps it from spreading. Once the lines at the injectors are loose the hardest part is over. Loosen the lines at the top of the fuel distributor a few turns and this will allow you to easily move the lines out of the way when you pull out the injectors. The 5mm allen screws that fasten the brackets to the intake manifold can be a bit stubborn sometimes. Make sure you use a quality tool for this step. There isn't much room next to the fuel distributor to get at the screws. A 1/4 " drive bit and ratchet will make it easier to loosen the allen screws in this confined area. Use a bit of lube ( anything will do ) when sliding the new seals onto the new nozzles and DON'T FORGET TO REPLACE THE FUEL FILTER! It's really a simple job if you take your time. Good luck and let me know how it goes.

Hey Steve One more thing. When you're done, leave the air filter housing off when you start the engine. Let it run for a few minutes while you CAREFULLY check for leaks. Seeya

Thank You - Thank You - Thank You
 

Thanks for the tips!!!

I will try and get it done this weekend time permitting, but I know that it will go much smoother now that I have been given these quality tips.

I'll let you know how it goes! And I think I'll try and take pics alog the way throughout the job.

Thanks
Steve

So, is your car running better? Was it the fuel distributor or the fuel injectors?


Thanks

Not done yet....sorry
 

Steve,
Your pictures in the "spewing battery" post were great. Thanks for taking time to post it. I can't wait for the picture instructions on installing fuel injectors. I got a 91 300E and wanted to install injectors. The repair manual was useless in detailing step by step procedure. Thanks.

Grim Defeat!
 

Well Crap!

I tried. I got the breather off and loosed the first line off of fuel distributor. But I couldn't get the line of the top of the front injector and then I checked and my 5mm allen wrench was a mess. I had been warned about being careful here so all things being what they are, I decided to be prudent and have a pro do it. My shop owner is a pretty good guy, so I'm gonna ask him to let me see him do the first one so I'll know better next time.
:(

Steve

I have just finished reading all the posting because I too have a rough start only in the morning. The engine will miss for just a second and then smooth out. It has been doing this for at least 2 years so I havent been too concerned. This morning I tried the advice of waiting until the pressure builds up and to my surprise it started fine without missing. My question is 1. Is this common with this car? and 2. Should I be concerned to have it fixed?

This forum is extremely helpful!
Ed

Same problem..
 

I'm having the same problem too on my M103 300CE. I have replaced the following:

1. Fuel Filter
2. Spark Plugs
3. Distributor Cap
4. Rotor
5. Ignition Coil
6. Ignition Cables

Its not an irritating problem but whenever I start her up after a few hours sitting, it'll do what you guys have described - idle rough for 3-4 secs. :(

I want a healthy start. Any solutions or tips? I've gone to mechanics with differing views. Some even suggested replacing parts I have already done. Oh well...

Hey 850R, any solutions or tips? Read this thread and you'll have all the tips you need!!!

How 'bout a vote for valve seals?
 

Hi Buddy:

Just read your post, and I had this same exact problem on my car. My problems were when I tried to start it after it sat for awhile, it was shake, shimmy and get all crazy for about 5-7 seconds, and then smooth out and everything would be A-OK.

I took it to the dealorship, and the first thing that the tech. though of were VALVE SEALS. I have the M103 (190e 2.6), and they're known for getting old and brittle.

He replaced the seals (about $275), and it's been like a gem ever since -- no hard starts any more.

I seem to ALWAYS suggest valve seals when I post ... I'm bound to be right sooner or later!! :)

Best wishes-
Michael.

Valvr seals
 

Thanks Michael,

I agree that they can be troruble, but I just had the head redone in September and the rought starts continued.

I have planned to have my shop replace the injectors for me but have not had the time ( or taken the time) to do it yet. This one of those problems that won't stop you from driving and enjoying your car, but you know you should take care of.

I keep hoping that I'll find some information or diagaram or something that will clear up how to do this job and allow me to confidently do it myself. But alas!:(

Anyway....thanks for the input. This forum does great things for MB cars and their owners.

Steve

Hi Steve:

Best of luck in getting those injectors taken care of. Do you, by chance, experience any fuel smell? I had a GM car when the injectors went bad, and I couldn't bear the stench in the cabin, even with the vents off!!

Guess I'll have to save my valve seals for later. :cool:

You're so right -- this just the best web site. Even though I'm not a DIYer, it helps to know how much it will cost so that I can have my coronary and get it over with before I take it in for repairs. :eek:

Take care and GOOD LUCK.
Michael.