560 Dist Timing
 

Failed CA smog functional, crazy but passed the emisions gases with flying colors (and I have an aftermarket Cat). timing ight says 30btc. It moves up to 40, but I don't know how to bring it down to TDC.

Details: Failed idle rpm at 942, had a boken hose to the EGR (fixed that), idled at 942, and gas cap doesn't vent right (Can replace that: removes with a swoosh of, I think, pressure, could be vacuum, not sure.)

I think the idle will come down with the timing.

Looked into the dist: Is this right? only has one spring and a bushing on the inner tang where the second spring would go. No bushing on the weight tang. No debre, no spring, no marks or damage that a broken spring might cause.

Gary

did you time it w/ or w/o vacuum on the EZL? Timing is only variable via the R16 resistor. Pull the vacuum and re-test @ idle.

Your idle is most likely a vacuum leak somewhere or a sticky air idle valve.

Search rough idle etc and I'm sure you find Lots of info here, BW and MBC's.

Jonathan

EZL? Where is it, what does it look like.

When I pull the vacuum the timing should retard?

I'll check rough idle...

Looks like you are having fun with 560SEC's! I've been told I should cut the resonators out befor and after the 90* bends and replace with straight pieces. Gives better power, mpg and not much noise, just a nice V8 sound. Any input?

Gary

The EZL is the ignition control unit..it's on the drivers side fender well. Has two 4 pin plus, 1 vacuum plug and one 1 pin plug.

Yes, w/ the vacuum advance removed timing will retard.

I have fun w/ all my Mercedes...they keep me happy:)

Yes, removing the kidney beans as I call them is a good way to open the exhaust up some. Should see minor hp/mpg gains. Adds a bit of throatiness as you mentioned which is nice when you have a V8 under the hood.


Jonathan

I found the EZL. pulled the vac and idle dropped to ~750 from 950. I did't look at timing change. What's next?

what is it you are trying to change? I thought you attempting to check your timing and fiddle with it..

Pulling your vacuum advance and getting a lower idle is odd.. Have you adjusted the CO on your car?

Jonathan

The timing is 30 at idle! I need to get it to TDC. I don't know how to change it.

This may be of no consequence but I just remembered I replaced the water pump a year ago and R&R'd the distributor. Could it be off by one tooth?

Umm...yes, it looks to be... time to re-set your dist.!

I think you'll find your power and economy will come back significantly!

Jonathan

I just checked timing. It started and settled to 20. First time I've caught it there and the idle was a little lower. pulled zacuum to the ELZ and rpm fell and timing too, to maybe 5*. Repeated 3 - 4 times and noticed rpm climbing and timing came back uo to 30 from 20. took maybe a minute total with the change taking maybe 10 15 seconds. Like something warmed back up. The car had cooled slightly from a short few mile trip to the post office.

Haven't changed CO, measured .o1 at 2500 and .04 at 942.

Is there only one spring in the mechanical advance??? Anyone know??

I'll check the distributor position. I'll rotate crank to get distributor to #1 & mark on lip. And see where the crank is. Then get the crank to TDC and see where the distributor is. "Mark twice cut once."

yes, only 1 spring. Your car should have an initial timing of 3-4 degrees @ idle w/ the vacuum removed.

Where is your distributor set? Is it in the middle of it's adjustment or it is cranked one way or the other?

Jonathan

Its about in the middle. Rotating either way even all the way made little/no change.

Where do you connect a remote starter switch? I knew where on my 380, but can't find where on the 560.

it makes no change to your timing..timing is controlled via the R16 resistor.


Can't say I use a remote started on my 560's..besides, there's always someone to turn the key for me.

Jonathan

Crank is on 0 (TDC) and distributor is dead on 6 (opposite 1).

didn't pull it.

Its a little work getting both valve covers off to see where the cams are and I think their position is not involved in the spark timing.

Next?

Where is the R16 resistor. It must be a variable resistor, so I can dial in the idle timing?

Gary

Gary, cam location and is Very important when considering distributor alignment.

The R16 is located next to the fuse box, it is a small (1/2 inch) square box w/ 2481 (I think) written on it. It will also have electrical tape around the bottom where it plugs into the wiring harness. They don't make a resistor big enough to bring your timing back that far so that's not going to solve your problem.

When you are at TDC your rotor should be pointing right about 10:30-100 O'clock.

Jonathan

hey guys what about the top dead centre reference sensor at the flywheel[the single pin wire at the ezl]? they have been going bad because of time not mileage.it needs doing so put one in,a little fiddly at the trans end but might cure your problem because the alternative is another ezl[$$$$$]

I thought there should be a sensor. Is the trans at the harm. balancer? I've seen a little stud stiking up about 1/16" at about 25* on the HB. Thought that might be to cause a pulse.

Wifey need the car for the next 4 hours. When she gets back, I'll :

1. find R16, I get the impression it is a selectable/removeable fixed resistor
2. find the sensor (its probably close to the EZL?),
3. pull the v covers to see where the cams are And chain condition
4. What is the -100?? (4:30 -100). I thought the distrib could be at either 10:30 or 4:30 (one rotation of crank, exhaust, 4:30. next rotation, 10:30, compression, Wrong?). My rotor was pointing to 4:30.. the cams will tell me ex or comp and I'll put it on compression check chain, and put the dist on #1 (10:30).

Thanks everyone. Anymore ideas??
Gary

Sorry, I wasn't logged in and missed the flywheel location for the sensor.

assuming the chain hasnt jumped or anything like that you can just look in through the oil cap to see what cyl 1's cam is at.

the reference sensor is mounted on the bell housing and has a single ground shielded wire running to a single pin plug at the ezl.

Still trying to get timing down to near TDC.

EZL sensor measures 833 ohms.

Looked through the oil fill hole: #1 is in exhaust lobes down, 'dizzy' is under center of #6 plug: ~4:30.

If everything is "right", the cams should be at zero (the scribed lines which you can't see without removing the valve covers), the distributor rotor should point to a scribed line on the body of the distributor, and the pointer on the water pump should point to the harmonic balancer's zero mark. It is possible to get the distributor 180 out of phase, which, incredibly, seems to want to run (terribly).

Recap & where we are
 

Its running great! Passes emissions. Dist is in right. W/vac removed from EZL: R16 works; open 16 btdc, r16 (750 ohms) 6-8btdc, shorted 6-8atdc.

But with vac connected R16 has no effect and timing is at ~22 btdc cold and it goes up to ~30 btdc once warm.

This is all in Park

Thanks

i think your missing my point.you say that as temp climbs so does timing and it has been my experience that these sensors go bad with heat.unlike most sensors that just go out these give some warning.

I get it!
 

David, not at all. Thanks to you, I and anyone watching, know about the sensor. I measured it at 833 ohms, but not temp. I'll do that next. There should be a change hot and cold if it change signal as the engine warms (Could, because the change is in a just few seconds, fast like electrical, that doesn't eliminate a circuit in the EZL either.)

Jonathan led us to the EZL, the glories of variable timing through R16. (I can go to Radio Shack and get a little 2.5K pot, put in place of the actual R16 and easily adjust my timing for gas or altitude!!)

But so far, we are 50/50 Sensor or EZL:
A) Sensor is wrong and maybe changes some with temp.
B) EZL is overpowered by Vacuum
C) EZL is overpowered by Vac and temp sensitive
D) My Luck: A&B

It couldbe A&C but no dif in solution.
Can you help a little more? what does the manual say about checking the sensor any measurement values? Do yu have a bad one and a good one to measure resistance. I suspect ohms will not be right if sensor is not giving right signal -but of course maybe not. I ordered the MB CD manual but it willtake a week to get it

Johnathan said he would check the EZL to see how it responds to vacuum and R16.

Sure I can buy a sensor and get it in a few days, but what if its the EZL, or both. I don't have a spare to swap to break this 50/50.

Thanks to both of you and this board!!
Gary

Sorry missed 2 people
 

Strife what and how is the home brew 1st gear start? And Johnhef for the hole trick. That's helped eliminate the mechanical timing. The emissions being so good point away from that too: valves operating at the wrong time or spark at 180 should be knoticable. I thought perhaps dist could be off one tooth, but seems too close to right on. I would think that if a mechanical is causing this: one or both cams jumped a tooth or the chain stretched, it would cause a failure in emmisions. combustion could not be that good to pass nearly perfectly.

What I think I see:
An EZL that without vacuum can get put timing anywhere it is needed at idle, between 8btdc and 16atdc. That seems to be exactly what it should do with the sensor signal and R16.
A sensor that for the most part is catching the tdc at the right time, but I also see a temperature shift.
Both devices could change results with temp, but it is more likely EZL would respond linearly with a gradual shift in timing.

JMO FWIW: I would guess the sensor output would not shift in time but in amplitude (signal strength, amount, value, voltage) Its probably a coil that feels a magnet passing on the flywheel. It acts like a generator and responds with a signwave pulse as the magnet passes. the signal is probably a small voltage 0 to 1V, and that explians the shield on the cable to keep the low voltage signal clean.

If its output changes I would suspect it falls in volts and the EZL looses it in the noise and would respond with a window of irratic timing and sputtering or rough idle.

Lov this stuff,
Gary

Update: The best I could do with R16 was 300 ohms gave me 0 tdc with no vac. Vac on still pulls timing up to 12. Idle was still about 900. Not sure this is the way it should be, at least its closer.

Got brave and adjusted idle mixture at the air horn. CCW leans so I went 1/4 and got a nice reduction in rpm. It took 3 or 4 of those 1/4 turns (slowly and waiting for stabilized idle) to get too far, a rough stumbling idle. Good news idle came down to about 600 and timing down to 10.

Looked at signal at X11 (I think pin 3) with ac meter and pure rms meter. My scope would'nt trigger on this signal. It would trigger on pin 1 but I think that is tach signal. Voltage started near 5V and came down to 4.1 (about 70%) where I left it. That point is about 1/2 turn from where I had the 950 idle. It is very repeatable. idle is about 700, timing is still 12 advanced with vac. Vac off drops to the R16 setting of 0tdc.

One more: I found a post on adjusting the mix on a 91 560, that discribed a button and LED on a diagnostic connector back by the battery. Mine doesn't act that way. With the ignition on and engine off, led is lit, pushing it does nothing. With engine running led is off but pushin button turns it on only as long as button is pushed.

:dizzy2: What next.