Yeah, I can't see any good reason to spend $75 and not just spend $125 on a 15 year old part...

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1988 420SEL 170K

opps, I mean $200...

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1988 420SEL 170K

i am interested in this exchange. as i have a 1986 560sel with 247,000 miles.

over the last 5,000 miles it has become hard starting when warm after it has set for over 30m minutes.

runs fine when it is running. and idles ok. but always starts rough.

my mechanic thinks that it is OK but if i want it improved, the injectors need to be replaced.

i had thought that they had been replaced at 200,000 miles, but according to the service records, these are the original injectors. hmmmmmmmm.

any opinions?

all ears.

It does sound like a fuel delivery problem. I would be careful not to leave out the possiblity that it may be a combination of issues rather than just one. That said, if you are on you original injectors, replacing them would be logical at this point. Its a testament to the fact that you only use high-octane fuel that you've lasted this long. All new seals, injectors and breathers should be under $300 and just take an afternoon (I'll be doing the job tomorrow, so I'll let you know). You should also replace your fuel filter ($20) if you haven't already.

In my case I lucked out, the firm I work for had an old ultrasonic cleaner than no one has used for years. It was used for drafting pens and so on. I guess some people clean jewelry in it but thats about all. Anyway, after I pull mine tomorrow I'm going to leave them in there for a couple of hours and then blow them out with carb cleaner. I was mostly worried about my leaky seals but this certainly can't hurt.

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1988 420SEL 170K

Often the CIS injector seats wear unevenly with age and will start to 'leak' on shutdown, even though they had a good spray pattern., This leads to hard hot starts(flooded cylinders), and worse, lots of gas dribbling into the affected cylinder.

Sometimes the leaking is due to trash (gum ) on the seat and can be cleaned with a bench flush with strong solvent. these things open and close many times a second a idle (buzzing), and do eventually wear.

I would recomenf replacing all the injectors and all the rubber, including all the vacuum lines. It gets hard with age and you WILL have vacuum leaks, if not now, for sure when you remove them.

A good smooth slow idle (500RPM) results only with good injectors and no air leaks.

Another source of 'flooding /gas smell' can be the fuel distributor diaphraghm, and replacement is only alternative. If, on shutting down th eengine, removing the air cleaner, and pushing down on the air plate you see liquid fuel in the manifold, the disrtibutor is leaking.

Kebowers,

Thanks for the heads up on the distributor. Hot starts are usually no problem for me but I'll double check to be sure. You wouldn't happen to know which year they switched to the brass injectors would you? Also, which solvent would you recommend?

Tomorrow is the 'big day' for this and several other repairs/updates. I've been looking forward to sunday all week. :p I can't wait to see if this fixes the smell and starting issues.

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1988 420SEL 170K

I own 2 Diesel P/Us, a Diesel tractor and work on Diesel equipment. In all cases whenever I take the injectors in to the local fuel injection service they will 'pop' (check out the spray pattern) them for free. I don't know about MB or gas injectors but I can't think that they would be any different.

$%*$%&!!

Wouldn't you know it! I was almost done, everything going smoothly and I pulled a bonehead move and split one of my breather hoses! The upper hoses all look great but sure enough the one that runs the length of the valve cover and attaches to each injector holder was hard and inflexible.

Is there a more specific name for this piece? I looked on Fastlane and I can't figure out which one it is. Actually none of them seem to fit this discription and there aren't any pictures. Also, can the car be driven without the piece? I'm going to try and seal the crack with a gasket sealer but I don't think it'll hold much pressure...

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1988 420SEL 170K

the part number on the piece is 116 094 25 82, but it doesn't turn up anything on fastlane.

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1988 420SEL 170K

Never mind, I found it in Partshop. Fixed the breather with epoxy, should hold for a day or two until the new breather gets here. Otherwise the job was a huge success, car starts beautifully on the first try, no smell, no hesitation... Love it!

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1988 420SEL 170K

Well, time to pony up the truth for those who might follow. I should have taken the advice to replace the injectors all along but I had to learn the hard way (typical -ask my girlfriend).

After about a week the old injectors started to clog and show the old symptoms again. I bought new injectors and installed them over the weekend along with a new fuel filter and check valve. Huge improvement! It feels like a %15 increase in horsepower along with noticeably lower idling. Now she's sharp and responsive off the line without the slightest choke or stumble and she stays at 700 rpms without the slightest bump or bobble. I'm sure this will mean better milage too.

I replaced all the rubber hoses and all the rubber vacuum line connections while I was in there just for good measure. It was a very rewarding and realitively easy day's work. I'd recommend it to anyone pushing 150K in a heartbeat.

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1988 420SEL 170K

Just got back to this. If you are having a problem on warm start it is usually due to a leak down of fuel pressure. The easy test is turn the ingnition on you will hear the fuel pump run for a couple of sec's do it a couple of times. Then try to start, if it starts up with no problem, then you have a pressure leak some where. It is usually caused by the accumulator, if not then it is a leaky injector.
Good luck.
m

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Martin Ingram
Colorado Springs
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)

Albert,

I agree entirely with what Martin said although I would suggest one thing. If you're going to DIY, first replace your injectors (because you really aught to with that kind of milage), that'll run you about $250 in parts. Along with that replace your fuel filter ($20) and your check valve ($11). See where that gets you, if you running well then you are all set. This is what I did.

Otherwise the accumulator is the most likely suspect as the fuel pumps seem to run forever. Its about $120 or so and you wouldn't want to replace it if you don't need to.

Also, do a few searchs on 'fuel pressure leakdown' and 'vapor lock'. Read a bunch of posts and look at what stevebfl has to say in particular. Although I didn't have a hot starting problem (vapor lock) after reading his discriptions I realized that my case was almost classic fuel pressure loss.

good luck!

Also, take the time to do Kbowers fuel distributor test, pray this isn't your problem, its big bucks.

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1988 420SEL 170K

....but it was done before I had a digital camera, so no pix, I'm afraid.

u da man!

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe