83' 500SL no start

[Marc]

Hi Everyone,

I have an 83' 500 SL, drive it a few times a month during nice weather months. It usually starts right up and runs fine. Last fall I had a project and needed some room in my garage for a day so I moved the car in front of my house. It started and ran fine, no problem. The next morning I went to move the car back into the garage and it would not start. It cranked but wouldn't start. Spent all morning trying to get it to run but it didn't start. I thought certain it was a no spark issue because it never even tried to run. However, I pulled a plug to verify and found I had plenty of spark. I killed the battery so I put a charger on it. Came back 8 or 10 hours later and the car started right up. No idea what this issue was. It started and ran fine ever since.

About a week ago, I hadn't driven it for a few weeks but I needed to move it to another garage I have for some cosmetic work. It started and ran absolutely fine for a 30 mile trip. Parked it in the garage. Started my repairs. A couple of days later I wanted to move it out of the garage and it wouldn't start. Same issue just cranks and cranks but won't start. Gave up for the day. Came back a couple of days later cranks but won't run. After trying for a while I did actually get it to start. But it wasn't like normal. It cranked forever, when it finally did start the rpms never went up as usual it just chugged at about 200rpm, doing anything, touching the throttle, moving the air intake plate, caused it to stall. Got this to happen a couple of times then back to just cranking. In between when it just cranked and the day that it just chugged. I had ordered an ICU since they are inexpensive now, I figured this couldn't hurt. So today I come back and again it just cranks. I swapped the ICU though at this point I didn't think it would make a difference. It didn't. I poured some fuel down the air intake. Still did nothing. I pulled a spark plug just to make sure and I do in fact have spark. The plug though didn't look wet. I took a squeeze bottle and squirted fuel into the cylinder. replaced the plug and still absolutely nothing. So, I'm stumped. I have fuel. I have spark. But it didn't even try to run. I can hear the fuel pump running. I don't know what to chase an ignition or a fuel problem? If anyone's got any experience with a problem like this. I love to hear your thoughts.

I appreciate the help.

thank you

[Marc]

Anybody??

Today I jumpered the fuel pump relay just to make sure the pump was running. It had now effect. I swapped out another WUR that I had lying around. That did nothing but I did have fuel when I removed the lines so that would lead me to believe that I am getting fuel up to the engine. I poured some more gas down the intake. It doesn't even try to run. I pulled another plug and checked for spark and I do have spark. Used a squirt bottle and put fuel into the cylinder. Still nothing.

I don't understand how I can have fuel and spark and nothing happening. Unless there is no air???

[Marc]

today I pulled the plugs on cylinder one and five. I have spark on both I have 149 and 150 psi of compression. The plugs are black but they are definitely not soaked. I plulled the line from the fuel dist. that goes to the WUR have fuel there. I cracked open 3 lines on the distributor I did not get a fuel leak until I cranked the engine. I'm guessing because I relieved the pressure when I removed the line to the WUR. If I push down on the air intake plate while these are cracked open I get a stream from fuel from each. Like pushing down on the plate works like a pump. I'm assuming this is normal operation.
What is left, timing? But there was no incident. I drove the car 30 miles it ran perfectly parked it in the garage and it never start again. If it jumped out of time it would have had to have done it while turning the car off, NO??

[Marc]

Ok, let me ask this way. What could be wrong if I have spark (checked three plugs, grounded against valve cover and can see spark
when sitting in drivers seat turning the ignition), I have good compression (cylinder 1 = 150, cylinder 5 = 149) but when I pour fuel down the
intake, or squirt fuel in a spark plug hole it doesn't even try to run?

[Diseasel300]

You have compression. You have fuel. What you don't have is spark, or your timing is WAY off. Check the cap and rotor. Don't overlook the EZL - when they fail they go flaky before failing completely. Just because the spark plug is sparking doesn't mean the spark is strong enough to ignite the fuel/air mixture.

[Marc]

Not that weak spark didn't cross my mind. But when watching the plug fire I can't say that the spark looks any different than any I've seen before. But given that.
1.) I don't have any other options
2.) When cranking it doesn't even try, just like you would expect with no spark.
3.) I poured fuel in the intake and in the cylinder and it did nothing!
It has to burn when ignited.
I have already swapped out the ICU which I believe is what you are calling the EZL. I did clean the cap and rotor with a wire brush. But I will replace Cap, Rotor and coil. We'll see what happens.

Thanks for the suggestions.

Also, I am in need of a 1170708732. This is the fuel line from the WUR to the fuel distributor. Local MB dealer says no longer available. Unless someone has one I need to find a tool to make the flaired end if anyone knows what that shape is called or find a fitting that fits on the WUR to use a hose clamp if anyone might know the size and threads of that fitting.

Thanks again everyone for your help.

[Diseasel300]

The EZL is the box that controls the spark. It's mounted down in the driver's side fender area sort of behind the headlight. They use the same Bosch 1012 ignition driver that plagues the vintage Porsche and BMW crowd with spark issues.

It's possible you may be flooding. Try unplugging the idle solenoid and giving it a few whacks with the handle of a screwdriver. If it's stuck shut or if the idle control module has failed and is commanding it fully shut, you could have a potential "no air" situation.

You've poured fuel down the intake manifold and gotten nothing. It isn't a fuel problem.

[Marc]

Yep, Has the infamous green wire goes from the EZL/ICU to the distributor.
My wire is missing the black cover on the connector that plugs into the distributor. There is a short bare wire that is not in the connector on mine. It looks like this was connected to a bracket that is screwed into the side of the distributor. At first I thought this might be some kind of ground. But looking at a replacement wire online doesn't look like this exists. Sound correct?

[rsj6667]

Hey I have a similar situation with a 1992 500sl any body have any hints on that??

[Diseasel300]

Originally Posted by rsj6667

Hey I have a similar situation with a 1992 500sl any body have any hints on that??

Unfortunately nothing in this thread will apply to your '92. Totally different ignition and fuel system on the M119's.

You might start your own help thread both here and in the "Tech Help" section (which gets more views than the SL section).

[Marc]

Did I post this in the wrong area? I didn't realize there was a separate tech section.

[Diseasel300]

You won't get much useful help in the Tech section with a Euro. The fuel system is quite different from the US models due to no emissions. This forum and the "Vintage" forum are your best bets for a Euro car pre-85.

[RobertinMN]

Originally Posted by Marc

I have already swapped out the ICU which I believe is what you are calling the EZL. I did clean the cap and rotor with a wire brush. But I will replace Cap, Rotor and coil. We'll see what happens.

Thanks for the suggestions.

Also, I am in need of a 1170708732. This is the fuel line from the WUR to the fuel distributor. Local MB dealer says no longer available. Unless someone has one I need to find a tool to make the flaired end if anyone knows what that shape is called or find a fitting that fits on the WUR to use a hose clamp if anyone might know the size and threads of that fitting.

Thanks again everyone for your help.

Did you pull the oil dipstick and smell it? If flooded, it will stink like gas. Had a similar problem on a 560SL and turned out to be bad coil which would sometimes work, other times not.

Fuel lines can be made--call around and find a shop that has the kit necessary. This is akin to flaring copper for plumbing in your house. Same principle.

[Marc]

Well, rotor, cap, and coil seems to have solved the starting problem. I have a significant mis but now that it is running I can go about tracking that down.
I have to say. I checked three spark plugs before I replaced the parts. I saw what I thought was good spark, but evidently not the case. So I have learned that sight it not the appropriate test for spark.
But what is? If you can see spark but don't know if it is strong enough, how do you test for that?

Also, I am in need of part# 1170708732. This is the hard line from the fuel distributor to the WUR. MB tells me it is no longer available. If no one on here has one, possibly someone would know where I could have one made?

Thank you to everyone for their time and information. I appreciate the assistance.

Marc

[Diseasel300]

Originally Posted by Marc

I have to say. I checked three spark plugs before I replaced the parts. I saw what I thought was good spark, but evidently not the case. So I have learned that sight it not the appropriate test for spark.
But what is? If you can see spark but don't know if it is strong enough, how do you test for that?

Buy a spark tester. It's a little tool that clips on the engine and has a spot to connect the spark plug lead. The head is typically adjustable with a graduated marking between the electrodes. A GOOD automotive ignition system should be able to generate 25-30KV easily.


The rough running could just be fouled spark plugs from running with weak spark. Was it running rough before you had all these starting problems?