Topic: New to me 1980 280se, rough start, changing idle

[dnaspazz]

All,
This is a great site and I appreciate all of the info in it. I have read through so many posts, and it has been incredibly helpful for learning about my first Mercedes.

So, I bought a 1980 W116 280se, which is in very good shape. It was laid up awhile, and I have been having fuel problems that I have been slowly working through. I have replaced the pump, screen, accumulator, and injectors. For a bit, the car ran great with exception of  a very rough idle till the engine warms up. Then, the car lost all power (felt choked) and I cleaned the K-jetronic fuel distributor. Fixed that problem, but then then I could not get the idle set. Really rough start idle, but would run well on freeway and than stall the second I came to a stop. Started again fine, but needed more gas. Anyhow, anytime I would adjust the mixture it would be fine for a bit but  then go out of adjust. So, I am having the fuel distributor rebuilt currently.

Anyhow, I am wondering if I am going down the right road. At a start, the car spews black particulate/spray from the exhaust and I am sure it is running way too rich at a start. So, I while I have the distributor out, are there other points that make sense to tackle now? I  am not  an expert, but in the process of enjoying learning. My read of many of the posts seems to suggest that a bad WUR could explain the rough idle at start, but after that I am out of ideas. Any suggestions?

[dnaspazz]

Forgot to mention that it starts fine, just  idles very, very rough until it is warmed up. Also, at times it feels like it "surges" and I can hear the pump seems to pick up at that the same time.

[UTn_boy]

Well, you're definitely on the right track.  A rebuilt fuel distributor AND warm up regulator are in order.  Unless is an odd situation always have those two things rebuilt at the same time. I hope you send them to Larry Fletcher.  There's just no one else in the U.S. that can do it right. ......even though many claim they can.  Anyway, While you're waiting on those to be rebuilt I'd definitely address the following:

-Check and correct valve lash
-Renew EVERY piece of rubber on the intake manifold....boots, idle air hoses, hose connectors, etc. 
-Remove distributor to clean/lubricate the centrifugal weights and check for excess wear in the lower housing bushing
-Make sure you have the correct NON RESISTOR sparking plugs (still available from Mercedes)  If there is an "R" in the spark plug nomenclature then they're the wrong
  ones
-Address the high tension leads if necessary, but do not buy Bosch or BERU
-Check ignition coil or just buy a new one if you're suspicious of anything
-Check and clean all electrical connections that look dirty or suspicious
-Test your coolant temperature sensor to make sure it's not bad.....or just buy a new one given the age of the original
-Make sure that your cold starting valve isn't sticking open
-Make sure that the catalytic converter isn't plugged up (if equipped)
-Make certain that both the supply and return fuel lines are unobstructed

The surging of the engine is likely what's causing you to hear the fuel pump surge, (alternator current surging) but if the new fuel pump is a Bosch you shouldn't be able to hear it unless you're close to it.  Also, did you inspect the inside of the fuel tank for rust and debris?  These fuel tanks are bad about rusting inside when left to sit. I'm certain someone will chime in and make mention of something I've left out.....and I hope they do so we can be thoroughly helpful to you!   

[TJ 450]

Yes, spewing black soot out the exhaust is a good indicator that it's running too rich, surging and black smoke might also occur when driving.

Once you have the FD back, make sure the airflow meter plate is centered/ not binding and the arm moves freely.

When reinstalled you will need to adjust the mixture screw to get it to idle smoothly if this can be achieved.

Another trick if it’s running roughly and you suspect a mixture issue, you can manually lift the plate (if running rich) or push it down if running lean, if it smooths out then you know what the deal is.

For further troubleshooting you need to have a suitable fuel pressure gauge to measure the control/ system pressure. This is why you should ideally have both the FD and WUR rebuilt at the same time as this means they can be calibrated to achieve the proper pressures.

Try the rebuilt FD and see how it goes.

Tim

[Peter]

Also check and clean the EGR and congrats on your first W116 - the late model 280Se is a wonderful car, 

[daantjie]

Also replace the fuel pressure damper at the fuel distributor.  You should see a small can shaped vessel in the circuit with the Warm Up regulator.

Here is a pic:

[dnaspazz]

All, t

Thanks for the input, it has been helpful to figure out what I can tackle immediately vs having to figure out how to do it etc. I really appreciate the help and you taking the time bring a newbie up to speed. As I mentioned, I love the car- already did the injectors, shock absorbers, FD, seatbelts.  Gotta get the engine running tops, then the screaming speedometer, etc. Would be great to get it back to top condition. Super enjoyable to drive already!

A few quick follow questions- where is the location of the EGR and cold valve start on a 1980 280se? Ive been poking around trying to figure which they are, but not so simple. Once i find the EGR I am going to clean it, but it seems like there are not any new ones available if it has failed. Is that true?  I am going to get the WUR rebuilt, but have to get the numbers of the  current one to see if I can find a core so that I can keep driving while it is being rebuilt.


Also, what is the best way to confirm/clean the return fuel line from the distributor? I read just putting the fuel intake and return on loop and cycle carb cleaner through the lines for an hour? Is that the best way to clean that out?

One last question- to the right of the engine bay, there is cylinder shaped unit wrapped in foam, mounted on the top of the wheel well. It has multiple hoses going into it, including from the water pump and the fuel distributor.  What is that called?

Again- thanks!

[UTn_boy]

The EGR valve will be located in one of the exhaust manifolds.  It'll also have a metal line attached to it from the intake manifold.  The EGR valve itself, part number
000-140-58-60, is sadly no longer available.  That's not to say that someone doesn't have a new one lying around somewhere.  They usually don't fail unless the diaphragm inside ruptures.  Then again, it's better that the EGR system is disabled, as they cause a lot of carbon build up in the intake manifold.  I know you're in CA, but given that your car is a 1980 you shouldn't have to worry about passing any kind of an emissions test. 

The cold start valve is located in the intake manifold.  It'll have a metal fuel supply line going to it from the fuel distributor.  There will also be a bi-polar electrical connection that plugs to it, as well.  It'll look like the electrical connection that connects to the warm up regulator.  The cold start valve should also have some blue or black plastic on it right below where the electrical connection goes. 

If you suspect varnish build up in the fuel lines then the looping of carburetor cleaner, lacquer thinner, or methyl ethyl ketone will definitely clean the lines.  Otherwise just ensure that they're not blocked or restricted in any way. 

The device on top of your inner fender well with the cooling lines and fuel lines going to it is a fuel cooler.  It was put in place to prevent vapor lock, and rarely gives any problems.  If any of the cooling lines or fuel lines going to it are suspect or hard/cracked definitely replace them.  I'm at odds about it being connected to the cooling system though, as the cooling usually came from the fuel cooler being connected to the A/C system's low side line. 

[rumb]

I'd like to see a picture of the fuel cooler.

[dnaspazz]

Guys, thanks a lot for the help so far. I got the new fuel distributor on, the car is idling at start much, much better and seems to be rounding smoother.  On flats, the car runs incredibly well. I still have the issue with losing power going up hill ( nochugging, backfiring, missing etc , the car just loses power and goes much slower), so I’m still trying to sort that out. It’s not the cat, I had that checked already.  Any ideas greatly appreciated.

Here is a picture with the fuel cooler in it.

 

[UTn_boy]

Well, wait until the warm up regulator has been repaired before anything else is done.  And don't forget to check the most important things beforehand......things like valve lash adjustment, ignition timing, and insuring that there are absolutely zero vacuum leaks.  If these things aren't in order beforehand you'll chase your tail over and over again.  And don't forget that after a warm up regulator and fuel distributor rebuild the fuel mixture/co must be checked/reset as needed.  It's not a plug and play ordeal.  Each fuel distributor is tuned to each individual engine.  Granted, when new they were all adjusted alike (according to the car's domicile).  However, as engines wear, and as the cars find their final region of residence, the fuel mixtures are adjusted accordingly.  We could almost say that now two are alike.....or tuned alike, that is. 

So, I reiterate, check and adjust your valve lash, ignition timing, and repair any/all vacuum leaks, check and double check your fuel delivery/return system.  Dampers and accumulators can and will cause issues if they're compromised. Get your warm up regulator rebuilt.  Then an ONLY then can you start making adjustments. 

[raueda1]

Also replace the fuel pressure damper at the fuel distributor.  You should see a small can shaped vessel in the circuit with the Warm Up regulator.

Here is a pic:

Can you or anybody explain what this thing actually does?  And why there's a vacuum line on it?  I've been wondering for the last 2 years and others may wonder as well.   

[dnaspazz]

Working on the vacuum system now- and found the green and white vacuum check valve is blocked. I’ve looked for replacements but can’t find any. Advice on where to source?

Also found that the frequency valve isn’t “buzzing or clicking”. It tests at 3 ohms, but no sign of activity. Trying to figure what it actually does!

Update 1 hour later- So, I had removed the instrument cluster at the same time as having the FD rebuilt (because of the speedometer cable screaming)  Turns out, once I realized the frequency valve wasn’t firing but still at 3 ohms, I checked the fuse #4.  It was blown- a simple replacement and the car power is now way better ( at least manageable). Now back to getting the wur rebuilt, fixing the vacuum lines and figuring out the valve lash adjustment.

[daantjie]

Dave to my knowledge this is in fact not a vacuum line but a leak line, in case you get diaphragm rupture inside this accumulator, so fuel does not go spewing out over a hot engine but rather just gets dumped into the valve cover.

Maybe more learned friends will chime in but I am pretty sure there is no vacuum working in on this unit.

[UTn_boy]

Also replace the fuel pressure damper at the fuel distributor.  You should see a small can shaped vessel in the circuit with the Warm Up regulator.

Here is a pic:

Can you or anybody explain what this thing actually does?  And why there's a vacuum line on it?  I've been wondering for the last 2 years and others may wonder as well.   

^^What Daniel said.  It's not a vacuum line.  It's a leak line in the event of a ruptured diaphragm inside.  While the leak line will prevent raw fuel from spraying all over the engine bay and exhaust preventing potential fires, the other issue is that the inside of the engine will fill with fuel.  So if you ever notice your oil level rising it'll likely mean the damper has ruptured. Also, the oil will smell of petrol and be very thin in consistency. 

The damper itself is there to absorb pulsations from the fuel pump so there is a constant pressure on the fuel distributor and injectors.  If pulsations aren't alleviated then the engine will run rough, drive worse, and deliver poor fuel economy.  Some of the earlier models (D-Jet cars and some early K-Jet) had a primary damper at the fuel pump, as well.  On this one there is no diaphragm inside.  It's only a metal housing shaped to lessen pulsations. 

Regarding your valve lash adjustment, you'll need a valve cover seal kit, part number 110-010-08-30, and you'll need a special wrench, part number 110-589-01-01-00, to turn the adjusters on the pivoting assembly that the rocker arms pivot on.  The wrench is still available new from Mercedes for around $60-$65.  While doing this job, do take note of the rocker arm surfaces where the camshaft strikes them.  The rocker arms are notorious for becoming score due to the top metal layer being too soft (a factory mistake).  I make note of this because if this issue is left to it's own devices the scored rocker arms will damage your camshaft lobes.....and then you have to buy new rocker arm AND camshafts.  Rocker arms from Mercedes, part number 110-055-09-01, are $206 each as of right now, and if you had to buy all of them you'd have $2,500 just in rocker arms.  By all means seek out aftermarket if any of them need replaced.  Thankfully, any aftermarket rocker arms made for an M-110 engine are old stock and are made well.  Anything new or recently made be very suspect of. 

I make mention of these part numbers so you can research them on Google or take them to your local dealership and have them order the part numbers.  Most dealerships will have no knowledge of the older models or that they can even still get parts for them.  Heaven forbid you ask for a special tool.....they'll instantly tell you that it's no longer available.  So use the aforementioned part numbers to your advantage and outsmart the others. 

One other thing I want to touch on is sparking plugs.  Be certain that you have non resistor type sparking plugs.  You can still buy the correct, non resistor, sparking plugs from Mercedes for your car. Every place else will sell you the wrong plug.  There are two choices you can use for your car, a Bosch W 9 DCO or a W 8 DCO.  The W9 will be a hotter running plug, and is meant for normal driving because it has high heat dissipating characteristics.  Short jaunts to and from destinations in which the engine might not get fully up to operating temperatures would require the W8 plug since it won't dissipate as much heat.  The W8 part number is 003-159-11-03, and the W9 plug is part number 003-159-10-03.  In essence, if when reading the nomenclature on the side of the sparking plug you see an "R" in the description then it's the wrong plug.  The "R" stands for resistor.  Your high tension leads already have a resistor in the metal housing that goes over the sparking plug.  The ignition system does not need another resistor to overcome.  It causes rough idle, lessened fuel economy, and puts a strain on the coil and switchgear box (Ignition control module) long term.

Regarding your check valve, which one are you referring to?  There are a handful of check valves on your car all in different locations.