Author Topic: New to me 1980 280se, rough start, changing idle  (Read 4703 times)

rumb

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Re: New to me 1980 280se, rough start, changing idle
« Reply #15 on: 04 December 2019, 08:33 AM »
Speaking of spark plug wire if you have aftermarket ones on they need replaced with correct ones.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

dnaspazz

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Re: New to me 1980 280se, rough start, changing idle
« Reply #16 on: 04 December 2019, 07:30 PM »
U guys are amazing, thanks for all of the help!
Regarding the green and white vacuum check valve, it is located on the vacuum hose coming off the lower portion of the air intake. At idle, that hose is pulling constant air, but the g&w valve is completely blocked and there is no vacuum going from there into the 3 in 1 connector.

What ( who from) are the correct spark plug wires wires?

dnaspazz

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Re: New to me 1980 280se, rough start, changing idle
« Reply #17 on: 04 December 2019, 07:34 PM »
I owe a picture of the fuel cooler

UTn_boy

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Re: New to me 1980 280se, rough start, changing idle
« Reply #18 on: 05 December 2019, 07:48 AM »
You're fuel cooler has low side air conditioning lines running to it, not engine coolant lines. 

Regarding your check valve, in the first picture below it shows it, but it shows to be in a different location.  I' not certain that the parts catalog is always correct. So take it with a grain of salt.  The part number is 000-140-68-60, but that part number is no longer available.  It has been replaced by part number 001-140-16-60.  It's still available from Mercedes for around $10.00.  However, do make sure that someone didn't reverse the check valve first.  I've seen that happen on numerous occasions. 

In the second picture you'll notice highlighted parts.  Make sure all of these rubber hoses are new, as well. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex

dnaspazz

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Re: New to me 1980 280se, rough start, changing idle
« Reply #19 on: 10 December 2019, 08:53 PM »
Yep, still working. I m getting stuck, since I cant find the info about how/where the original vacuum lines went. So, anybody have pictures of  1980 280se engine bay or a link the the manual that maps out where everything is supposed to go? The 2nd picture above looks almost like how  things are laid out, but it is also off- doesnt show everything that  is in my car!

Also, I am going to take my first shot at adjusting the valve lash this weekend. I am going to do it in the morning, on a cold  engine. A bit nervous, since I doubt this car has been adjusted in many years. Any advice is  greatly appreciated

UTn_boy

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Re: New to me 1980 280se, rough start, changing idle
« Reply #20 on: 11 December 2019, 07:49 PM »
Since you have a CA emissions model you'll have to seek out an M-110 and/or W116 "Introduction into service" manual.  CA emission models are always a class all their own, and no other car in the world had the amount of unnecessary vacuum lines and connections.

Regarding you valve lash, make sure you have the wrench, a new valve cover gasket kit, and try to inspect the rocker arms when making the adjustments.  Each camshaft lobe has to be pointing away from the rocker arm before lash is measured.  Obviously, this involves having to spin the engine.  To do this either hook up a remote starter (the squeeze trigger kind), take a chance and do it by turning the ignition key, or put a 27mm socket on the crankshaft to spin the engine over by hand.  Just be sure you remove the socket before you start the engine......bad things will happen other wise. ;) 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex

dnaspazz

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Re: New to me 1980 280se, rough start, changing idle
« Reply #21 on: 18 January 2020, 08:25 PM »
Got some questions for next steps, but will give a complete update about what Ive done so far.  \
Just a reminder, I recently bought this CA 1980 280se (K-jetronic with lambda) and had a goal of fixing a very rough start idle, spewing soot on startup, and weak power/accelerations. 

Work done so far (learning on the go)-
1) new fuel injectors, 2) reman fuel distributor 3) reman WUR 4) Removed air intake manifold, had it cleaned (looks like new), 5) cleaned the throttle body, 6)put on a new intake manifold gasket (note- the car had an aftermarket gasket (Victor Reinz) that blocked the crank case breather hole  >:() and throttle body gasket, 7) a new fuel damper behind FD, 5) new fuel pump, filter, accumulator, and fuel tank strainer, 6) adjusted valve lash, 7) new 9 DCO plugs (old plugs were pretty fouled) Also cleaned the idle assembly, diverter valve, fuel lines, and anything else I could get to. Blew out fuel return to fuel tank (super easy!) Put on new hoses (had a hole in the breather hose!), all new rubber vacuum pieces, mostly new vacuum lines. I hooked up all of the original vacuum lines, per the CA emission tag on the car.  I did not clean the AAV ( >:(stupid of me, didnt figure out I shouldve until the mani was back on), install appropriate plug wires yet, nor have I replaced the coil. I measured the warm control pressure at 49 PSI/3.4 Bar and valve closed system pressure at 75 PSI/5.3 Bar. I didnt do the cold pressure right, but will do tomorrow. I am also going to try to use a digital oscilloscope on X11 Ports 2 and 3 to try to optimize the setting of the mixture. Then I will work on the timing.

Observations after this work- Overall better, feels like a well running car is in sight 1) Smoother start, 2) Idle not drifting all over from day to day, 3) When I start the car cold, it chugs a bit for 1-2 minutes, then speeds up quite a bit, 4) Is shifting gears early around 2200 rpm from 2nd to 3rd, 5) more power, but still not great, 6) in the driveway, the engine will randomly speed up or slow down ~100 rpm.

So here are my questions for the learned members...
1) How/when do you set the nylon idle screw, and how /whenis it adjusted relative the mixture adjustment screw and should the nylon screw be set after a cold start, or warm?
2) Timing- I know to set it at 3000 rpm first, but I am unsure what to set it to since we 93 gas in california? Any advice here for an old CA car?
3) Timing- On the harmonic balance there is a mark/pin around 8. What is that for, Is it TDC 0, or is it TDC at 0? (Stupid question I know, but I got confused by the manual...
4) Has anybody else worked with the lambda system? Is the oscilloscope the way to go, any advice appreciated...



« Last Edit: 18 January 2020, 10:22 PM by dnaspazz »

UTn_boy

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Re: New to me 1980 280se, rough start, changing idle
« Reply #22 on: 19 January 2020, 03:38 AM »
Early shift issue....renew nylon propylene bushing at transmission end of linkage going from accelerator linkage to transmission, and then adjust this linkage until you're happy with how it shifts.  The book isn't always right. 

The nylon idle screw is used to maintain engine RPM.  Sometimes you might have to adjust idle in the middle of a procedure, but for the most part it'll pretty much be the last thing you do.  Always adjust the idle with a warm engine.  When the engine is cold it'll idle high until warmed up, so setting the idle when cold is useless. 

The pin on your harmonic balancer is only for the round diagnostic socket on the left inner fender well.  When the factory tool was connected to this diagnostic socket this pin would provide an RPM reading on the factory test equipment.  It has nothing to do with setting/checking your ignition timing.  Pay attention only to the numbered graduations on the harmonic balancer and the pointer mounted to the clock opposite the graduated numbers. 

Regarding fuel, all U.S. model M-110 engines were low compression engines.  They require regular unleaded (87 octane) only.  Putting a higher octane rated fuel in will cause the car to run poorly and/or consume an inordinate amount of fuel.  If anything you'd be wasting money on expensive gas. 

If you're good with an oscilloscope then go for it.  It'll be the most accurate, but remember that the car and it's systems are too antiquated to respond to any minute readings that are off one way or the other.  If an oscilloscope is used then close is good enough.  Otherwise, use any on/off ratio detector.  They give you the dwell, or duty cycle, of the o2 sensor.  You can even use a volt/ohm meter set to the mV position. 

Did you adjust your fuel mixture after the rebuilt warm up regulator and rebuilt fuel distributor were installed?  A lean mixture can cause idle fluctuations. 

Bear in mind that a U.S. 280se was only rated at 142 horsepower at 5,750 RPM.  At the time that was somewhat tolerable, but compared to anything new we'd drive today it'll seem like a slug. 

1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex

dnaspazz

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Re: New to me 1980 280se, rough start, changing idle
« Reply #23 on: 20 January 2020, 06:58 PM »
All,
UTN, thanks for the reply. California cars are bit hard to get info, so Im still trying to sort through everything. I got K jetronic with transistorized ignition.
Your right the transmission bushing is shot, and quite sloppy.
Regarding timing
Ive read all about set the timing at 3000 rpm @ 30 degrees (w/o vacuum), check at 1500 w/o vacuum, and then idle with vacuum should be TDC+/- 0-3.  With the car warm/hot I  got it set 30@ 3000rpm (the harmonic balancer was jittery?), 1500 looked right (HB was still bouncing around). I attached the vacuum lines, and 3000 rpm was about 38, but idle was still 10 BTDC.  I went through each of lines and there are no leaks. It just seems there is no retard vacuum at idle. At the distributor, I have 2 vacuum lines 1) is directly to throttle body to the back of of distributor, and 2) a yellow line that comes from a  3 way connector that is pulled from side of the manifold (below the throttle body). The other 2 lines go to the wur and a sequence of a 50 degree and 17 degree thermo valve. Any chance the CA car spec at idle is 10BTDC? I think the harmonic balancer shouldnt be jittery, so I am thinking about replacing the coil.

Regarding the mixture screw, yes I have been turning coutnerclockwise leaning it out bit by bit. In total, I have turned it counterclockwise about 3/4- 1 whole turn.  I found a point where it is running rougher/missing and went back a bit. I  played around with the oscilloscope, going to be harder than I thought. The issues are
1) i dont know if the oxygen sensor is any good- it was replaced before I got the car, but the 02 light is on in the dash.
2) the other site says that a regular multimeter with a duty cycle does not accurately measure the frequency valve modulation for 80-85 MBs. If I set it to a 50% duty cycle, (measured by the + probe in Port 3 of the X11) the car seems way too lean.

Has anybody else set the K Jet with lambda? How did you do it?

Still, lots of progress but every step is new learning experience!

rumb

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Re: New to me 1980 280se, rough start, changing idle
« Reply #24 on: 21 January 2020, 07:31 AM »

You really need to remove the AAV and clean and test it in hot water.  They get all gummed up and will not close all the way. This is what raises the idle when cold and reduces when warmed up. As mentioned adjust after it warms up. There are directions on the interweb\utube on how to do.

You have a vac advance and retard distributor. The retard works if the AC is off and comes off when the AC is on. there should be a vac line going to a little dome shaped valve with some wires going to it. Just to insure the disti is fine put a mitivac on each line and verify the plate/ timing changes. Make sure the other vac line is going to the correct port on the throttle body, there s/b one above the plate and one below, I dont remember which one you should be using.
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

UTn_boy

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Re: New to me 1980 280se, rough start, changing idle
« Reply #25 on: 21 January 2020, 08:33 AM »
If you're seeing jitters on the harmonic balancer then there are either vacuum fluctuations in the engine (due to ill-seating or burned valves....quite common), or the distributor itself is worn....another common issue. 

Under the hood somewhere, probably on the drivers side, there is a little metal box with a bi-polar plug on it that the speedometer cable runs through.  It'll have a button on it you have to manually push in to turn off the 02 sensor light.  Otherwise there is an issue with the Lambda system's electrics or the new 02 sensor wasn't plugged in.

As far as how to test the Lambda, you're looking to see what voltage it's giving off after it get hot.  The frequency valve has nothing to do with the voltage the 02 sensor is giving off.  The voltage given off can be mathematically converted into a percentage duty cycle.  If you have specific questions about something in particular regarding Lambda please ask.  The chapter on Lambda is 30-40 pages long.  I don't want to post all of those pages......it's too time consuming. 

Below are lot of pictures that should answer a lot of your questions.  Do make it a point to buy yourself an M-110 engine repair manual.  I've been working on these for around 25 years, and even I have to use the manuals often.  It's a worthy investment.  I believe this same manual is also in this forum's library. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex

dnaspazz

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Re: New to me 1980 280se, rough start, changing idle
« Reply #26 on: 26 January 2020, 10:24 AM »
Again, thanks for info! I had bought an electronic version of the service manual, but it turns out not to be complete with all of the info for the 1980. Urgh. I went through the forum library also, but didnt finid the lambda specific stuff. I would greatly appreciate it if you could post the formula for calculating the duty cycle from the voltage. I am going to have to keep going on that- the car is running well (and not spewing soot anymore) but I know I dont have the mix right yet.

In other news, I put  the bushing on the transmission control rod lever. There was no old bushing left, and the new one made an such an enormous difference. Most impactful $2 spent yet. Also found me leak in the trunk- water is going in around the tail lights. So, going to be doing that next.

UTn_boy

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Re: New to me 1980 280se, rough start, changing idle
« Reply #27 on: 26 January 2020, 03:02 PM »
So.....were any of the previous pictures any use?  Were you able to straighten out what was amiss an/or understand better the set up for your particular model? 

Reading the o2 sensor duty cycle isn't how you set the mixture....it's what you adjust last as a fine tune to the mixture.  The O2 sensor’s sensing ability comes about by producing a small voltage proportionate to the exhaust oxygen content. For example, if the oxygen content in the exhaust is low the o2 sensor will produce a high voltage (0.90 Volts - Rich mixture) and if the oxygen content is high it produces a low voltage (0.10 Volts - Lean mixture).  Theoretically, the O2 sensor should cycle between 0.00 volts and 1.00 volts, but in reality it cycles between 0.10 volts and 0.90 volts.  It is easier for an O2 sensor to go from rich to lean than vise-versa.  O2 sensors tend to fail on rich bias. In other words, they tend to shift their cycling to the upper side or rich side of the voltage scale. 

An O2 sensor with a high voltage reading does not necessarily mean that the mixture is rich or high in fuel content. An EGR valve problem will send the O2 signal high as well.  So ensure that the EGR system is in good working order or completely disabled.  A stuck open EGR valve will create a lack of oxygen in the exhaust, since the re-circulating exhaust has all its oxygen already burnt . Your Lambda control unit sometimes uses the O2 sensor to check for proper EGR operation and sets a code if necessary. On a W116 thi "code" would be the illuminated o2 sensor light. So be aware of the fact that a vehicle might be running lean because the Lanbda control unit sees a rich O2 signal due to a defective (stuck open) EGR valve. Since the Lambda control unit sees a rich signal, it will try to correct with a lean command and try to lower the O2 sensor’s high voltage signal.

To directly answer your question, and to use the formula, you're going to have to know the pulse width the o2 sensor is giving off.  If you don't know it you'll have to hook an oscilloscope up to it to determine the pulse width.  To do this, connect the output of the signal to the input of an oscilloscope. (Be sure that the lead to the oscilloscope you're using is attenuated with a 10MΩ lead input) The oscilloscope screen will show a series of pulses oscillating at the frequency of the signal. Note the width, in seconds or microseconds, of each pulse. This is the pulse width, or PW, of the signal.  Next, you'll need to calculate the period (T) of the frequency (f) using the formula T=1/F.  For example, if the frequency is 20 hz, then T = 1/20, with a result of 0.05 seconds.  You now know what the pulse width (PW) and the period of the frequency (T) is.  At this point you can now determine the duty cycle (D) through the formula D = PW/T. As an example, if PW is 0.02 seconds and T is 0.05 seconds, then D = 0.02/0.05 = 0.4, or 40% duty cycle, or on/off ratio. 

Bear in mind that the period of the frequency will change with engine RPM, so do one test at idle (750 RPM) and one at, say, 2,000 or 3,000 RPM.  You'll have to recalculate the period of the frequency with the different RPM's. 

The aforementioned is a very time consuming way to do what you're wanting to do, but will work just fine.  If you want to save time maybe consider using a hand held duty cycle tester by tapping into the pins 2, 3, or 6 of the diagnostic test plug.  I don't remember which of those is ground, hot, and from the o2 sensor.  You'd have to play around and figure it out.

Last, When you are adjusting mixture and go a certain amount (rich or lean) it'll stumble making you think you've gone too far.  Sometimes that's true and sometimes it's not.  When it stumbles goose the throttle and see if it clears up.  If it does then you haven't reached a maximum or minimum. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex

dnaspazz

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Re: New to me 1980 280se, rough start, changing idle
« Reply #28 on: 08 February 2020, 07:47 AM »
Yes, thos pictures were exactly what I needed.  Fiddling around more today with mixture.  The car is running great, just need to optimize. 

A follow up question about the 02 light reset. Where is it again? I followed the o2 wire up to a plastic connector, which then extends into the passenger compartment.  I looked around under the passenger foot compartment and ECU but don’t haven’t be able to find the reset switch.