500SEC Fuel system problem
 

I'm having some problems with my newly aquired 1985 500SEC. It starts right up and will idle about 500-600 RPM, when I press on the accelerator everything seems fine until I get to about 1000-1100 RPM then the engine seems to choke and want to die (lack of fuel?). The car had been sitting for about 2 years so I drained the fuel tank, removed the fuel pump, filter, accumulator? pressure regulator? and tank screen. Cleaned everything and got a new filter, checked the fuel pump while I had it out and put it all back together. Still have the same problem. Also the throttle position unit? (circled in the picture) makes an awful lot of noise (clicking) when the key is turned on or when running. I'm new to the gasser world but I've got 2 MB diesels. Thanks in advance

When you try and accelerate does the engine stumble and struggle to rev up, can you rev the engine while in neutral?
P.S thats the cruise control actuator not the TPS

It is doing this in "park" If I put it in "drive" I can idle out the driveway.

cdplayer
 

Check the condition of your distributor cap. Actually take it off and look for cracks. Could be just that simple.

It sounds like the warm-up regulator to me. It suppies enrichment on warm-up and acceleration. A common casualty of extended sitting. If you put a gauge on it, I predict you will see high control pressure.

My 83 500 sec was only used 300 miles in 4 years.
I have noticed on a restart of a hot engine
Actually hot restart was a bit troublesome
as it didn't start right up
I also noticed a lumpy lobbiness to the engine in park idle after the hot restart...

Could this be related to sitting?


Thanks

PS When cold starts right up
idles 1000 in park
but goes down to 650 in drive.

Engine is otherwise pretty smooth & strong

Thanks Again

It could be from sitting, but also from age and mileage. Your injectors may be getting weak and losing pressure, your accumulator the same.

Your idle speed is where you should be with a cold engine. Could be the idle relay, or the temp sensor at the back of the engine.

Where is it located, and what does it look like?
Thanks,

It's on the front of the intake manifold. It has two lines from the fuel distributor, a couple of vacuum connections at the bottom, and a two prong electrical connection.

Thanks Chuck, I removed the air filter housing and did some cleaning with carb cleaner. The air flow sensor? (large round air intake) was very gummed up. After a good cleaning, I could rev it up to about 2000rpm. Squirted some cleaner in the vacuum lines of the warm up / acceleration regulator. Was able to rev it up to 3000rpm. Is the vacuum fitting on top a vent? Or am I missing a line somewhere?

Is this the warm regulator?

I'd have liked to have seen a pic under the air cleaner assembly

I took my filter out yesterday & cleaned some debris out from under it.

I noticed on the lid over the part with the tubing coming out that the lids was sooty ther so I wiped it.

I'd be curious to see whats under the assembly

Glad that seemed to help your porblem.

hitwtom -

The fitting on top is just a vent.

Just a FYI
 

The item circled is the cruise control actuator. the CC amp is under the steering column.

Update, after some more cleaning, and checking vacuum lines (I thought MB diesels had a lot of vacuum lines) It will now rev to 3000 at start up without much problem. After about 30 seconds it's like a governer kicks in and speed drops to 1700-2000. If I drop back down to idle it will rev to 1700-2000 but not much higher. If I shut the car off and let it sit for a few min. it will do the same thing all over again. Any more ideas?

Thanks 4speed, I've got the cruise control unplugged for now until I can get everything else working properly.

Chuck,

Have you got a diagram/picture of where the coolant temp sensor is located? The car is the 500SL (Euro).

Thanks!

I think that an '85 would have plain K-Jet rather than KE-Jet injection. So enrichment is controlled by the warm-up regulator, not the actuator controlled by the computer with input from a coolant temp sensor.

Again, I think that your only temp sensor is the one in the back of the right head which tells the idle relay to have more rpm's when the engine is warming up. You might have an oil temp sensor near the filter housing if you have the lambda setup with an O2 sensor and frequency valve. This sensor tells the lambda computer that the engine is warm enough to go into closed loop.

Sorry if this is TMI.

Chuck,

If the above is directed to me, I do have a warm-up regulator on the car. Been chasing a stumbling problem for months now and the WUR seems, at this point, to be the cause of the problem. Don't want to hijack this thread, so will post an update on the problem on another thread. Thanks.

BUMP, thanks

Maybe WUR, but the only way to tell is to put a gauge on it and see what system and control pressure are doing.

What do the plugs look like?

You could also be running out of fuel. Suggest a volume test (you should get at least a liter in 30 seconds from the fuel return line, disconnected at the FD.

Maybe you are getting into closed loop and the computer is getting an input that causes it to tell the frequency valve to go lean. That would sort of explain the "switch" symptom. What happens if you unhook the oxygen sensor?

You could also be lean because someone screwed with the mixture. Try going a max 1/2 turn CW in 1/8 increments and see what that does. Be sure to track what you do so you can get back to where it at least starts and sort of runs.

Just replaced the top vac hose on the WUR near the 2 elec connections
it was taped & found it severed half way thru.

What would lose of vacumn at this point do to the engine at atartup?
high idle or low?

:confused:

The vacuum connection on top is a vent and should not be connected anywhere it it's like anything I've ever seen.

On the WUR, you should have a connection on the back that goes to the intake manifold just below the FD via a three-way connector and a temp switch, and one in front that goes to a four-way connector.

I'll have to check
but this is the pic & the car is a Euro prod date 5/10/82 but listed A 83

tHERE is a vac hose on top and its listed in 83 500 sec parts manual
also the one in fron & back are alo plain either 45 or 60 vac hoses
no tris coming off

haven't traced them yet but they go under intake manifols area

I do have a 4 way in fron of manifold
have to check thats where it goes

I boutght the 4 way vac hose yesterday
but only got to do the one on top so far

reply to 500sec revving issue
 

My 84 euro 500sel had an issue w/ starting when warm but started well when cold. And on start up it wouldn't rev up until it ran for at least 10 seconds. Sometimes when hot i'd have to crank on it for at least 5-12 seconds. Quite embarrassing. It also kind of had a lack of power. Goofy me i gambled $100.00 took it to the closest benz dealer and he said fuel accumulator. Well the issue was the fuel accumulator was leaking back fuel pressure into the tank. Thus we weren't getting enough fuel. He temporaryily clamped the hose to the accumulator and it immediately had like another 10 horse and always started up and ran great. So i immediately removed the clamp and put a good accumulator on it. Hope this helps.

Wow!

Didn't notice any power problem but I;m new to the car & used to a 4 cyl.

Starts right up cold
but idles hi 1300 to 1500 until it reaches 80C in park then maybe 800 to 1000

in drive its 650 ish

could that be the accumulatortoo or just the warm/hot start problem
?
Thanks
Have to find it & clamp it.

Would be nice to fix that
:D

A broken vacuum fitting certainly won't help your starting or running. I have no idea what connecting in that top fitting would do, except maybe to increase control pressure, which would lean the mixture in high vacuum situations, like coasting. Where does it connect to the vacuum system?

Another thing to check is to put your Mityvac on all the fittings of the WUR. They should hold vacuum briefly and then slowly lose it. If it's a dead leak, then you need to fix it because not only do you have a vacuum loss, you're not getting any enrichment when you need it.

Took the aircleaner off
stiill didn't have access to my vac hoses behind the warm up regulator
I'm very short
I couldn't see behind it & the dist wires were also blocking
but there are at least 5 or 6 back there
one off the back of the WUR
then 4 somehow coming out of something else


So maybe this engine is set up different;y

I took pics to help identify

I did find a hose not attached
bad broken end I cut to expose a good hose & attached it

It was a plastic cann9ister valve connected to a quad in fron that went onto a stem ouut of the manifold...I think

It couldn't have gone anywhere else
& why put a elbow hose on soemthing if it wasn't supposed to go somewhere..

put it back together

Started fine

Think it did run smoother
& started with lower idle 1200 then crept up then down to about 900

Ignition wire boots on distrib cap are shot
I was going to move them to get to the vac hoses better
but saw a break on top
I was afraid if I moved those something might crack so

I'm thinking its beyond me.

I did not see anything that resembles an acumulator

a 82 might not have it

I'll post some pics later maybe someone can figure the setup///

Thanks

weird 82/83 500 euro sec
 

pic
green/yellow valve was disonnectedc
I connected it after cuttin goff broken end

I wanted to change those vac hoses behing wur
there is one
I can't get oo it
then there is another 4 or 5
behind a old brittle ing wires I don't want to move

So, don't knoe where to start first

but think car runs better w the new vac hose on top wur & connecting the disconnecter

is the acumlator here?

I didn't see anything that looks like it unser the air assembly

Is the idle control vavle or acululator in these photos?

Thanks

sounds like the piston in the fuel distributor is stuck.[from sitting] buy a new o ring and take off the f.d. clean out with carb cleaner and free up the piston.

It accelerates smnoothly & has power but
I'll make a note of that since taking off a fuel distributor is beyond the scope of my ability.

Vac lines on this car seem to be different

I have a sec engine part breakdoen & it seemed to be hooked differently...

Don't see those 2 douvle ports coming out of front pass side of engine on intake in any diagrams .


I;ll have to see how it responded to the new vac hose & the reattached one which is bridging a small plastic valve marked pier or something to a vent from intake.

Thanks every bit helps guess the euros do have more problems when it comes to repair

etc finding parts

etc if you look up american specs you don't find the parts on car
I have these

water pump 117 2001 330

dist cap 0290004 505

Air Inject Check Valve was disconnected
 

Found out what the green & yellow plastic valve is a
Air Inject Check Valve

How would it being disconnected affect the engine?

I better get it a new vac hose as its really bad
had to cut the one end straighte agsin as it was all cracked & broken.

Also found reference to a T vac connector to warm up regulator
I have no such.

The Air ICV igoes into the intake man
but is also connected to a 4 way & where they do is not clear

Thanks

I have seen a few 82 84 etc car & theyt have the top vac hose on the vent of the WUR so it seems it has some function on the older models

My car is a 5/82 Euro

Ok...After a long study of the WUR traced most of it

The top vac hose goes to a vent off of a rubber hose that connects the air idle control valve into the intake.
Mine is not the electric ICV
Its a bosch upright air idle control valve

Front of reg vac tubing is red but can't trace it

Back of WUR is a vac hose that goes into the top of a T vac hose which connects to one vent of a Thermo vac valve switch
the other t arm goes to the back of the intake next to the fuel distrib area.

Sharing that TVV is another vac hose that connects to the 4 way vac hose in the front.
That 4 arm hose also goes to a air inject valve before going into the intake
Also connects to distibutor valve & a red line I can't trace...

It has bee suspected somewhere in this line is the EGR???

Anyway car runs flawlessly

Starts like a dream when stome cold
I have started it 2 times ok when warm if I restart with 5 minutes.

Still having a bad warm/hot sa=tart after the car is driven
You can leave the car and hour or 2 hours & when you try to restart
its crank city

Yesterday one restart took 2 long cranks
The other was lots of cranking many times
until finally I sat a while
Then it started a died a time or two before it finally got running...

The car did sit for 4 years
& I have only driven it say 125 miles so far
but this is the only problem I have with it...

Will asks mechanic tomoorow

Its going in for plugs & to replace the broken Tvv which is bypassed
Still car runs fine
even better
but that warm/hot start is still the same
or maybe even worse since the tvv broke but I don't think thats the cause of it.

Closet I have come to understanding this is
after the car has been run
when its shut there is a slight residual fuel leakage
it pools & creates a sort of flooded situation...

Now thats fuel injectors
old
as they are
& $$$$
so trying to see what I can do to minimize this & live with it...
Hoping maybe its even something else.

Accumulator helped warm start
 

On advise of mechanic got a new fuel accumulator.
Was a $100 part so it was worth a shot

Does help the warm/hot starts but they still on not instantaneous like a cold start & do need a lil gas

Least there is much less cranking involved so its alot better.

Thing is I also had new plugs & wires & thermo vac switch installed
at same time so maybe those could have made for better warm/hot starts too.

Anywayits starting much better on hot/warm starts
so thats a good thing...

:D

Found this site
http://www.k-jet.org/articles_dbkjet.html#34

Difficulty starting engine only when warm