Warm hard start and stutter from stop. - PeachParts Mercedes-Benz Forum

patbianchi · #1 07-06-2007, 01:49 PM

My 500sl 91 seems to have a warm not hot start problem. If it sits for 2 to 5 hrs it will crank for a while before it starts and rough idle for a minute or so.

Perhaps related problem, from a stand still and warm engine it will stutter a bit in the initial acceleration. Can't find any vacuum leaks and on cold start runs perfect?

Any suggestions?

Pat

waybomb · #2 07-09-2007, 10:37 PM

Fuel accumulator?
Bad injector(s)?

wallster · #3 07-10-2007, 08:40 AM

my money would be on a fuel accumulator as well. The accumulator is a diaphram more or less that keeps the fuel injection line pressurized. If it's old or worn, it won't hold the fuel pressure and when you go to start it, the fuel has to be pumped back to the injectors thus producing a hard start when warm. My '80 450sl did the same thing and replacing it fixed the problem. It's a normal maintenance item anyway so that's a good place to start.
The small outlet end is connected to your fuel tank so I would crimp that off (i used a hemostat) or the job is messier than normal.
Good luck, let us know if it helps.

wallster
'80 450sl

bbeberness · #4 07-11-2007, 06:51 AM

Hey Pat, was the fuel accmulator the problem. My '85 380sl has the same problem. Easy initial start and then a hard start after running for awhile.

Thanks

Ben
1985 380sl

sublettd · #5 07-12-2007, 09:06 PM

I seem to recall reading one of the smart techies on the forum stated the fuel accumulator only comes into play on cold starts.

I just went through replacing the fuel filter, fuel accumulator, injector seals, insulators and O-rings, and the fuel pressure regulator on the back of the CIS. None of them corrected the problem. It came down to at least two bad injectors. Replaced one on the right side of the engine and it eliminated about sixty percent of the stumbling. Still need to replace one on the left side and I expect that to fix the rest of the stumbling, as well as the hard starts.

Recommend if you decide to replace the injector(s) that you do the seal, insulators w/O-ring and all of the injectors. Should run in the vicinity of $250.00. My mechanic charged $200.00 labor when we did the injector seals and insulators--without doing the injectors. Should have bit the bullet and bought the injectors since I was going to replace everything but them. Also had to replace the idle air distribution hoses, which were about $17.00 each.

While I probably spent more tracking the problem down than I had to, I replaced parts that had 140,000 miles on them. They would probably soon need to be replaced anyway, so I got a leg up.

Let us know what you come up with as the fix.

ScottinSoCal · #6 07-12-2007, 09:24 PM

Quote:

Originally Posted by sublettd

I seem to recall reading one of the smart techies on the forum stated the fuel accumulator only comes into play on cold starts.

If he said that then, no offense intended, he was wrong. Standard item to replace for hard warm/hot start is the fuel accumulator.

Quote:

It came down to at least two bad injectors. Replaced one on the right side of the engine and it eliminated about sixty percent of the stumbling. Still need to replace one on the left side and I expect that to fix the rest of the stumbling, as well as the hard starts.

Leaky injectors will also cause it (because they flood the engine) but that's more rare. My car had both, I replaced the injectors first. That solved part but not all of the problem. Replacing the fuel accumulator finally did it. It also helped the idle - the fuel accumulator smooths out the pressure pulses in the fuel line.

sublettd · #7 07-12-2007, 09:46 PM

Ok, I'll concede he might be wrong about the fuel accumulator. I tossed that out for discussion purposes.

As to smoothing out the pulses, that little $54.00 fuel pressure regulator (K-Jetronic - Primary-pressure regulator with push-up valve) on the back of the CIS probably has more to do with the pulsing than the fuel accumulator does. My old mechanic, who deserted us and went to Orlando, told me the o-ring on the tip of it is what usually causes it to be replaced. He told me to start with that and then move on to the injectors (for the stumbling problem). Turned out he was right on target...as usual.

This car has got more parts and pieces...

bbeberness · #8 07-13-2007, 09:25 AM

Ok guys: I'm new to the MBZ parts game. Where is the best place to purchase my needed parts? I have bought from Ebay but have been scammed a couple of times. I live in a suburb of Portland, OR. Anyone know of a good and honest mechanic around here?? I enjoy getting all of the input from the contributers. Hopefully this will help keep my repair expenses under control. Thanks for the contributions.

Ben

sublettd · #9 07-13-2007, 04:44 PM

I usually check Fastland (Buy Parts link at the top of the page) and ******** AZ for parts prices. I'm partial to doing business with Phil and Roy at Fastlane, but sometimes the price differential between them and ******** AZ is too much to ignore. I don't mind a small price differential when dealing with Phil and Roy because they bend over backwards to identify the right part when I need it for my Euro SL.

Can't help you with the mechanic question. I'm in Florida.

bbeberness · #10 07-20-2007, 09:22 PM

Sounding like a dummy. My cd rom won't ply on my computer. Where is the fuel accumluator and pressure regulator at on the car. '85 380sl

ScottinSoCal · #11 07-20-2007, 10:12 PM

Quote:

Originally Posted by bbeberness

Sounding like a dummy. My cd rom won't ply on my computer. Where is the fuel accumluator and pressure regulator at on the car. '85 380sl

Both are with the fuel pump, down near the rear passenger side tire under the car.

bbeberness · #12 07-21-2007, 08:06 AM

Thanks a million. You've been a great help. Damn thing is so low and I don't have a rack to put it on it would have taken hours to find them with jacking up each end.

YuCrew · #13 07-21-2007, 04:00 PM

I had a similar problem to the one you describe, on my 1984 380SL. Yes, the dealer mechanic said it did not come into play with hot start engine and said injectors are probably leaking. There were so many articles here on fuel accumulator (the dealer also said they were no longer available) that I decided to start there....bought a new accumulator on the internet (identical to OEM except the 3 star logo) and have not had a problem since. That was 3 years ago.

From my experience and exhaustive searches, I predict it's the accumulator. Good luck.

bbeberness · #14 07-23-2007, 10:00 AM

Thanks everyone. You've all been a big help. Now I need to get to work and fix it. I'll try the accumulator first and go on from there. Have a lot on the plate this week so will do in near future and let you all know how it turns out. Thanks again for all your help. Ben

bbeberness · #15 07-30-2007, 04:49 PM

Thanks for all your help. The sl even has more pep. Replaced accumulator and fuel damper regulator. Runs like a top so far.

Ben '84 380SL