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2007 S550
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Discussion Starter #61
Let us measure your voltage at the pumps first with a voltmeter. Measure the voltage across the leads on the fuel pumps, each one separately and report on them as discussed in the post. For voltage the gauge of the wire does not matter. If you have a 10A-20A current meter let me know, we can measure your current too. I assume you know where they are etc. by the rear driver side area under the car close to the fuel tank.

I had already suggested why your car start easily when cold. The cold start valve sprays fuel into the intake and that does not need high pressure. When >40c that valve is shut off, so you need pressure for the fuel distributor to work. This is my theory any
Let us measure your voltage at the pumps first with a voltmeter. Measure the voltage across the leads on the fuel pumps, each one separately and report on them as discussed in the post. For voltage the gauge of the wire does not matter. If you have a 10A-20A current meter let me know, we can measure your current too. I assume you know where they are etc. by the rear driver side area under the car close to the fuel tank.

I had already suggested why your car start easily when cold. The cold start valve sprays fuel into the intake and that does not need high pressure. When >40c that valve is shut off, so you need pressure for the fuel distributor to work. This is my theory anyway.
Finally some good news. The voltage at the forward pump is 13,68 no matter the rpms and the aft pump is 12.89 again no matter the revs. What's next :) ?.
See link below to a manual page I found on line. I think the first system is what applies here but not sure as I don't think I have Y8, idle speed air valve. Do you think the throttle valve switch (S29/2)could be involved and if so can we test it? Thanks
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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We unpluged your IACV already and there was no improvement. So no failure due to electrical issues.It being mechanically stuck closed in the middle would be highly unusual. That is because in either end forces 1100rpm or >1500rpm idle. Closed position (very low idle, or stall) is somewhere in the middle.

The pump voltages being different probably means they are drawing different current/power. I'm not sure if that is a sign. Can you see if you can feel the forward pump (13.68V) if it is doing anything. I believe they are both supposed to draw about 10A each. They don't appear to. If you cannot measure current, see if disconnecting the electrical wire to the 13.68V one has any impact on how the car idles. Try the other one as well. One at a time.

We have already disabled your lambda control system by disconnecting EHA and IACV. So no, I do not believe the Throttle Valve Switch is involved.
 

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2007 S550
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Discussion Starter #63
I have to put it back on jack stands in the back and set up test rig again. Can you tell me where you are going with this if one pump being disconnected does change something? I don't feel it's mechanical as it only started after my brain fart while charging the battery. Thanks G:)
 

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89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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I have to put it back on jack stands in the back and set up test rig again. Can you tell me where you are going with this if one pump being disconnected does change something? I don't feel it's mechanical as it only started after my brain fart while charging the battery. Thanks G:)
Precisely Gozody, we are trying to figure out an electrical reason for your idle problem as opposed to a mechanical reason. This is why we have eliminated electrical issues with Idle control valve and EHA valve first (the easy ones) by disconnecting the electrical connectors. Both of those will cause the idle to go up above the expected 700 rpm and you ECU will not be controlling anything, it is all mechanical now. In your case this did not happen.

In this fuel injection system there are only 4 "electrical" actuators that effect idle/running/start issues.

(1) Fuel pump (effects fuel pressure)
(2) IACV (effects air bypass to control idle speed) - if disconnected electrically will be partially open
(3) EHA valve (allows more or less fuel flow to control idle speed) - if electrically disconnected will be set in the middle so disconnecting it eliminated electrical issues
(4) Cold start valve ( sprays fuel into intake during cold crank and up to 2 seconds to aid in cold combustion because the fuel pressure is also weaker for the Fuel distributor to operate properly)

It is this simple, Mercedes wanted it this way back in the day.

We have eliminated 2 and 3 with your experiments, and we know 4 sort of works because you said cold starts are pretty easy. Not sure if it being stuck open will cause running issues, probably not the way you described things.

So that leaves the Fuel pump by process of elimination. This is why I was concentrating on that. If one is not running I believe you will have all sorts of issues. The most direct way is to measure the fuel pressure to make sure it is in the range of 80psi. But requires some tools.

I am suspicious that the pump that is running at 13.68 volts may not be running at all (open circuit) or the one with 12.89 volts is drawing too much current and not pumping effectively. Either indicate an issue with the pump. So you can disconnect the fuel pump "electrically" one at a time to observe cause and effect. You should not have to jack up the car for this.

But if you want to physically observe the IACV valve to make sure it is not in a fully closed position when disconnected, you can take it out and see if the orifice/slit is partially open (should be about ~2mm or 1/10th inch). That is the only inspection you need to completely vindicate the IACV for causing the stalling during idle with it being disconnected.
 

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Discussion Starter #65
Precisely Gozody, we are trying to figure out an electrical reason for your idle problem as opposed to a mechanical reason. This is why we have eliminated electrical issues with Idle control valve and EHA valve first (the easy ones) by disconnecting the electrical connectors. Both of those will cause the idle to go up above the expected 700 rpm and you ECU will not be controlling anything, it is all mechanical now. In your case this did not happen.

In this fuel injection system there are only 4 "electrical" actuators that effect idle/running/start issues.

(1) Fuel pump (effects fuel pressure)
(2) IACV (effects air bypass to control idle speed) - if disconnected electrically will be partially open
(3) EHA valve (allows more or less fuel flow to control idle speed) - if electrically disconnected will be set in the middle so disconnecting it eliminated electrical issues
(4) Cold start valve ( sprays fuel into intake during cold crank and up to 2 seconds to aid in cold combustion because the fuel pressure is also weaker for the Fuel distributor to operate properly)

It is this simple, Mercedes wanted it this way back in the day.

We have eliminated 2 and 3 with your experiments, and we know 4 sort of works because you said cold starts are pretty easy. Not sure if it being stuck open will cause running issues, probably not the way you described things.

So that leaves the Fuel pump by process of elimination. This is why I was concentrating on that. If one is not running I believe you will have all sorts of issues. The most direct way is to measure the fuel pressure to make sure it is in the range of 80psi. But requires some tools.

I am suspicious that the pump that is running at 13.68 volts may not be running at all (open circuit) or the one with 12.89 volts is drawing too much current and not pumping effectively. Either indicate an issue with the pump. So you can disconnect the fuel pump "electrically" one at a time to observe cause and effect. You should not have to jack up the car for this.

But if you want to physically observe the IACV valve to make sure it is not in a fully closed position when disconnected, you can take it out and see if the orifice/slit is partially open (should be about ~2mm or 1/10th inch). That is the only inspection you need to completely vindicate the IACV for causing the stalling during idle with it being disconnected.
I am with you now:). I'll get to it this week and report back to you. Thanks
 

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Discussion Starter #66
I am with you now:). I'll get to it this week and report back to you. Thanks
Here is an idea I am unsure of. When I first got the car in 7/18 it would only cold start and the owner said it just needed the CO adjusted. I leaned the air/fuel mixture slowly and it began to run better, then blew black smoke (rich) and eventually would start cold and hot and run/drive fine. Total counter clockwise turns were 1 and 9/16 rotations. When the summer gas hit the pumps it didn't like it so I richened it 1/4 turn clockwise and ran much better. Could all the new parts, IACV, MAS, and EHA require me to fatten up the mixture now as some type of new baseline in the electronic part of the system? Keep in mind it runs now just won't idle or hot start. Just a wild idea I wanted to run by you guys. Thanks as ever, G:)
 

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89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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The current state of your warrants no adjustments to the lambda adjustment screw. This is because your car is all messed up at the moment. I doubt you can even do a proper adjustment without a sniffer. What I would suggest though is see where it is at by measuring the duty cycle/average voltage at pin 3 / 2 inside the diagnostic connector. That will tell you at least what the car "thinks" about your mixture. But the MAS/sensors maybe sick so I'm not sure how much you can trust the diagnostic port. But try and measure it if you can. And see what the car is telling you. I would not adjust it.

EHA replacement does trigger a minor adjustment sometimes. When I replaced mine due to a leaky EHA I did not adjust it. The car got a little more "lively" so I let it be. A year later I measured the duty cycle and sure enough it went from 50% to about 30%. So that explained it. Never though did the car have any running issues. So do not expect miracles unless the duty cycle is way off at the moment. And I mean way off like 20% or 80%.
 

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Discussion Starter #69
Did the duty cycle test. Pin 2 and 6 were 11.86 about same voltage as direct from battery. Pin 2 am 3 zero voltage and this should be helpful to you. ThE car started fine even with low voltage. Ran as usual and won't idle.
I didn't do fuel pump test as I am hoping the duty test results will be significant in pointing you to the trouble point. Thanks as always :)
 

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89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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Was the car running when you measured 11.86V on pin 6 to pin 2?

So Pin 3 to pin 2 is showing 100% duty cycle (or 0 V).
Are you sure you turned on the diagnostic?
I do not recall where the car is located but needs the diagnostic signal turned on by pushing the LED button near the battery. Did you do that?
 

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Discussion Starter #71
Was the car running when you measured 11.86V on pin 6 to pin 2?

So Pin 3 to pin 2 is showing 100% duty cycle (or 0 V).
Are you sure you turned on the diagnostic?
I do not recall where the car is located but needs the diagnostic signal turned on by pushing the LED button near the battery. Did you do that?
This is a CT car and I am in NY so no diagnostic button to push. The car was not running when I measured Pin 6 to pin 2. Hope this helps.\
FYI I had charged the battery the day before so there is either a voltage drain or the multiple starting attempts are quickly draining the battery which is only 1 yr old. With all the ground issues it had before any of this started a voltage drain is my best guess as to why the battery is low. Many of the features like power locks and rear washer pump no longer work. The car had a lot of water under the carpets that may have acted to complete bad grounds but since I have dried it out and sealed the leaks I could find, the features no longer work. Those are of no concern to me at this point.
 

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89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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Seems you have a lot of electrical issues. You will need to sort those out before anything else.
A new battery should not drain to under 12V overnight. My 6 year old battery maintains over 12V after a week.

Did you report on your running voltage before? When you start the car in the morning and 10 minutes after running.

Sounds like your mishap perhaps fried other vital components.

I do not trust your dignostic port measurement. Absence of a voltage does not tell us anything and can be misleading. You will need to measure the current going in to your EHA valve. Connect your ammeter in series and tell us how many milllamps you are seeing. should be between -20mA to +20mA. 0mA and not changing means the ECU is not controlling your lambda. This is the direct way to measure your lambda control anyway.

For this you need to unplug the EHA and connect one side directly (do not reverse the connections by mistake) and connect the other side thru your ammeter. The polarity of the current does not matter at this point.
 

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Discussion Starter #73
Seems you have a lot of electrical issues. You will need to sort those out before anything else.
A new battery should not drain to under 12V overnight. My 6 year old battery maintains over 12V after a week.

Did you report on your running voltage before? When you start the car in the morning and 10 minutes after running.

Sounds like your mishap perhaps fried other vital components.

I do not trust your dignostic port measurement. Absence of a voltage does not tell us anything and can be misleading. You will need to measure the current going in to your EHA valve. Connect your ammeter in series and tell us how many milllamps you are seeing. should be between -20mA to +20mA. 0mA and not changing means the ECU is not controlling your lambda. This is the direct way to measure your lambda control anyway.

For this you need to unplug the EHA and connect one side directly (do not reverse the connections by mistake) and connect the other side thru your ammeter. The polarity of the current does not matter at this point.
Three strikes and your out. This is it for real. I tried to diagnosis the electrical issues when I first got the car but couldn't. Infinite thanks to all of you who took the time to try and get the car back in working order. I have had no responses to my ads. I have offered it to the local MB club for free and and waiting to hear if any of their members want it fora parts car or a project. Some pipe dreams are just that. Sincerely RG:(
 
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