stevecora46

My 1992 300SL has 87K miles on it. Every once in a while it doesn't seem to want to run smoothly. It starts fine, but then when you give it some thottle, it cuts out and acts like it's not going to run. You can nurse it along and it will finally get going and run OK, but when you give it too much throttle, it cuts out. Once it gets up to speed, it seems fine, unless you apply too much throttle. After a while, the problem goes away and car runs like it's supposed to. Today, I took it out on some errands and it started cutting out in city traffic. I haven't had it out in about 2 weeks. This is a very sporadic problem. It probably happens about once every 20 times I take the car out.

It seems like it's fuel related. I've had the car since August, 2003. I had a new E.H.A. valve put in it about a year ago. It actually had the same symtoms as it does now. I was taking it to the local Mercedes dealership to have the oil changed and a new battery installed (I've since learned to avoid the dealership), and on my way it started cutting out and I didn't think I was going to make it to the shop. They diagnosed the E.H.A valve. I've put new plugs in the car, but I've not changed the fuel filter nor have I replaced the plug wires or anything else ignition-related. Any suggestions would be helpful.

Thanks, Steve

swany

Definately change the fuel filter, it could be something as small as a blocked fuel filter giving you problems. Who diagnosed the EHA valve, the dealer or another wrencher?

Start with the fuel filter and work your way down.

stevecora46

Thanks. The dealer diagnosed the E.H.A. valve. Said it was leakig fuel where it connects. I took their word for it. Are there any special tricks to changing the fuel filter? I subscrip to Alldata, so I'll pull down the instructions. Sometimes Alldata is not real detailed, so any advice is appreciated.
Thanks, Steve

c4791p

There are actually two fuel filters, and Alldata DIY has great instructions. You need to get your car up on a lift because this is not something you want to do on a creeper with the car on jack stands.

Main caution, release pressure on the fuel tank by opening the gas cap, but even then you need to be pay particular attention to alldata's instructions or you'll have fuel spraying all over the place at fairly high pressure.

You might also want to check the condition of your rotor and distributor cap. I bought my 92 used and it appears that nobody had ever changed mine. I even took my car to a local mechanic I trusted when needed the 135K major service and complained about hard starting, and they started talking about rebuild of the FI system.

Was up on this board about a year ago and read a comment from one of the member technicians (wish I remembered his name so I could thank him) who essentially said he'd seen more MBZ with hard running problems caused by bad rotor/cap/wires/plugs than with FI problems, and to fix those things first.

I bit the bullet even though my trusted garage didn't even mention I might need rotor/cap/wires, and changed them all. Every hesitation, hard starting, etc., problem went away. I've 144K miles on mine now and it runs smooth as a clock at 600RPM Idle with not a hint of oil usage, smoke, etc., passes annual smog with levels near perfect.

Chuck

NPI-FUEL

Chuck,

I totally agree with your comments about distributor cap on these cars. My 90-300SL had misfiring issues when I didn't drive the car for a couple of days. Invariably after 5-6 miles the car would stall. Waiting 15 minutes would clear the problem. Dealership replaced fuel pumps, didn't change a thing. When it happened second time I got a $2700 list of things to change and there was never mention of sparkplugs or distributor caps. I didn't go for it as I figure out by then they didn't have a clue. OTOH, since this is my daily driver I didn't bother replacing this immediately. I found an independent Mercedez Benz trained tech that diagnosed the problem immediately over the phone as soon as I described the symptons. He replaced distributor caps and the sparkplugs. (Someone had installed platinum which is a big no-no for this car.) Since then I never had any issues again ... purring like a *****

Regards

rwmatthews

So...what was the final solution. My 1992 starts great, runs great until operating temp is hit and then if just sputters and misfires until it dies. I leave it sit for 30-60 minutes and start it up and all is good.
I've tried new plugs, new rotor, new wires, new fuel filter, (only one) where is the second one?
Other wise I am about to give up, leave the keys in it and let it get jacked.
Help please.

nevilledoreen

I have the exact same problem with my 1993 300sl it has the 24 valve 104 engine .
Have you fixed the problem?
If so how?
I am located in Australia my EMAIL address is
nevilledoreen@yahoo.com.au
I would appreciate your advice as I am desaparate the car is so unreliable

Kind regards
Neville

SLCL

I don't know if all MY are the same but my 1999 SL500 fuel filter is located on the RR wheel. Jack the car up, remove the wheel, you should see a black cover. Remove the cover and there will be the fuel filter.

I've just replaced mine last weekend. There was nothing wrong but I just thought I replaced it (since I was changing my spark plugs and valve cover gaskets). I've never done it before and it took me about an hour (would have been much faster if the fuel didn't spray all over me lol). If you have the claims and claim down the hoses leading to the front end of the filter then you should be fine. 3 ton jack and jack stand and creeper worked just fine for me. The filter cost less than $50 here in the US so it would not hurt to try which could cure your issue.

If the car dies when it's hot and won't start until it cools down then you might need to replace the CPS (crankshaft position sensor) as well.

Greg Townsley

I have experienced the same issues, but have only experienced it after having washed the vehicle (92 500SL). So far,runs fine the following day and continues to run smoothly until the next time we wash the car (by hand)

At a loss as to why myself??

MercedesTheBest

some water into the fuel tank? possibly.

MBs Only Now

I know these posts are from years ago, but anyone having this issue might want to look to the ignition system rather than fuel system right off the bat (as is the case with many other MB issues). Although the fuel filter is exactly what my mechanic went to first, I insisted he look at the cap and rotor. This was after almost two years of headaches, with another owner and I on a forum putting our heads together to find the culprit. It turned out that once the car had been running long enough, the sparks and resulting heat from the worn parts couldn't maintain a connection. Symptoms include shorter and short periods after starting until the car begins to stutter, stalling, overall power loss, and the car often starting fine when it's cold.

MBs Only Now

You don't mention replacing the distributor cap. I know this is an ancient post, but for those out there having these symptoms, go directly to the cap and check it out. Replacing the rotor and not the cap is a little out of order (unless the cap is already new).