1984 Mercedes 380 SL running issues - PeachParts Mercedes-Benz Forum

R107SL · #1 03-21-2015, 04:51 PM

Hello everyone,

I just recently bought a '84 380 SL with engine problem/s. I've been searchig for possible solutions for it all over the internet, but no luck. While searching I came across this forum many times, found some good information here, so I decided to give it a try.

So here is the story. I bought the car knowing that it had running issues, which I hoped I could fix, because the rest of the car is pretty nice. It's suppose to have only 90 000 miles on it. So when the car is cold, it usually starts right up but dies few seconds after. If I try to start it immediately again, sometimes starts and dies and sometimes just cranks.

First I checked the fuel pump, it makes a buzzing sound when I turn the igniton on, and the fuel does come to fuel distributor. I also checked the fuel pump relay - shorted that on the connector and tried running it but no luck - same as before. Fuel pump did run the whole time.

Then I tried the trick with the air plate (in front of fuel distributor). I was pushing it down a little bit while cranking the car. This time it did start, died few times during trying, but I managed to get it running at the end. It did produce a lot of smoke through the exhaust though...

Compression on the engine is good, fuel distributor looks like it could be rebuilt or replaced... So this is where I am standing now, what do you guys think? I took some photos of the engine for reference, any input appreciated!

ejboyd5 · #2 03-21-2015, 08:05 PM

Change the spark plugs.

R107SL · #3 03-22-2015, 09:04 AM

Thanks, I checked all the sparkplugs, looks like its running too rich.

But I found something new, at first I thought the car just has a big exhaust leak, but no, there is an empty hole with thread in the exhaust pipe, where O2 sensor should be I think. There is also a black wire hanging near it.

So obviously I need to order a O2 sensor. Is this the right one?

meltedpanda · #4 03-22-2015, 08:05 PM

Kjet - I assume - PM your email and I will send you a check list

marinos90209 · #5 04-05-2015, 05:14 PM

Hi, i have the same car and i replaced all the vacuum tubes,the one that sit on each side of the intake manifold,plus all the rubber hose as well,runs a lot better now.
good luck with yours

rowdie · #6 04-05-2015, 07:39 PM

You need to install the O2 sensor but that is not the problem currently. The single wire O2 sensor on your model is heated by the exhaust and does not come into play until the car warms up a bit. The problem could be with the WUR (warmup regulator) or maybe a blocked return line. You need to get a CIS fuel pressure tester. The manual will have specs.

R107SL · #7 09-10-2015, 10:43 AM

Hey guys, I left the car sit for a while, because I couldn't find time for it, but now I got back to it. I bought the correct O2 sensor and installed it, so that's now fixed, but made no difference as rowdie stated.

I also removed the wur, carefully disassembled it and cleaned it. No notable difference.

Then I pulled out the injectors and tested them. All of the injector were pretty much not holding any pressure. Some of them did, but started pissing or dripping when the pressure achieved around 30psi and went slowly back to 0. Interesting thing is that all injectors were replaced 3 years ago, there is a date 25/8/2012 on all of them. I decided to try to clean them properly, so I opened the tips on the ends and put them in ultrasonic bath for couple of sessions with 2 different cleaning solvents and also some carb cleaner. Afterwards I tested them again, they were still not perfect, but somewhat better so I reinstalled them. The car started and ran after couple of trys, but I had to recharge the battery so tomorrow we'll se if its permanent solution. If not I'll just get new injectors, which is very probable.

I also noticed something strange. On both of my cars, this 380SL and the '88 560SL (which has high idle hell problem, but it runs and drives) I found giant holes in the intake manifold, to me this does not look original???

The 560 runs extremely high around 2000rpm on cold start.. I would like to buy all new vacuum hoses for both cars. Do they come as a kit from dealership or you have to have all the part numbers?

meltedpanda · #8 09-10-2015, 11:20 AM

no kits that I know of, just look, measure and replace. Those holes are not original. Fortunately they look as though they do not go into the actual sealed intake area. If they do , even through a hairline crack that may be your idle issue.
Get some new injectors, you are better off doing that trust me on that one, or get them professionally rebuilt and pop tested side by side, they need to be within 10% of each other when it come to fuel delivery

rowdie · #9 09-10-2015, 01:31 PM

Nothing to worry about. Just a hole in the casting. My 560 has a hole about 1/4" in the same place.

R107SL · #10 09-22-2015, 08:18 AM

Okay good, I almost had a heart attack . Looks like the old injectors were not Bosch made, and therefore crap. Got all new injectors and replaced them. I also fixed a couple of vacuum leaks, but I suspect there are more, because the car idles at 950 rpm. I also cleaned the ICV with ultrasound cleaner. No noticable change apart from car now always starts and keeps running for at least 20 seconds, sometimes even more and then just randomly dies. I hooked up my fuel pressure gauge and my control pressure (if I got this right) on cold engine start it rises up to around 7 bar and then slowly drops to 3,8 but it's always fluctating... Could be my return line blocked?

Comparison new vs old injectors

https://8czefg-ch3302.files.1drv.com/y3pOTunoaKYRgixslPlNfDSIvKxLdCcgU68qLLcSlof5wjTgk15FvAoD_vk_ycBtEW7W7OvhhOlqtaMnAa2o2I_y60X7LwTkcCCj JFpEpr1KIa25xGT9r8leKXHtTxjJXlEE36tORgt0Xg08B5yTytJlsxrNmUoIdWfO2hJzv43adE/WP_20150916_12_28_11_Pro.jpg

meltedpanda · #11 09-22-2015, 11:12 AM

have I sent you the Kjet manual?
PM me if I did not. The old noggin aint working like it use to