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  #1  
Old 03-07-2017, 06:24 PM
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Got a 560 SEC - small list of problems

So I got just got home my 88 560 SEC, damn it's fast, really takes off when pressing the pedal, it's a 300hp engine

But apart from that, it has lots of small problems, and i need some advice on what might cause what

The car is hard to start when cold, but it comes around after trying 5-6 times, I had a similar problem with one car, and it was the ovp relay that was bad. My ovp relay looked good, and I sprayed it with contact cleaner, but still hard to start. It idles fine, but the IVC is not working, most likely the wire, removing the wire when idling had no effect, even after cleaning.
At cold you have to press the pedal slightly to keep it from dying, but after 1min it will idle on its own, but at high rpms. Timing seems fine, ignition system is newly serviced.
There is a strong smell of fuel in the car, might be the EHA, but it has no visible leaks.

The car has been sitting for a while, it's a project car, but shift fine, and drives fine. Any help with the problem I have will be much appreciated
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  #2  
Old 03-07-2017, 06:28 PM
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Check coolant temp sensor (not the inst. cluster one, the computer one)
Check idle air valve
Check for vacuum leaks

As to the fuel smell, check the gas cap seal and the rubber bib that seals the filler neck to the body if there is nothing more obviously leaking under the hood. Also, crawl under the back and check if the fuel pumps are dripping.
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1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition
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  #3  
Old 03-07-2017, 06:36 PM
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One more thing, your test of the idle air valve might be meaningless. If the computer is getting bad sensor readings, it might not even be trying to adjust the valve so unplugging it may not be revealing of anything. To test the valve, I take them off and apply 12v directly to the terminals and see with my eyes if it is working or not. Often a 9v battery will work too, and is super easy to test with since terminals line up. It's on the low side of the needed voltage though, so while I might declare a valve OK with a 9v test, I wouldn't declare it BAD until I tried it with 12v.
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1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition
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  #4  
Old 03-07-2017, 06:43 PM
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Hey, thanks for info. I am going to replace all the rubber in the engine when I get parts in the mail. Also going to use my test light tomorrow
The fuel smell was worst when driving at normal speeds, but I did fill a full tank today, but no obvious leaks. Obvious cracks in all rubber parts though, this car has been sitting in the sun for a while, so it might indeed be a seal
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  #5  
Old 03-07-2017, 06:46 PM
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One fuel pump is also bad, probably. I bought a new battery earlier today, tried to start it, but no. What I did notice though, was that the fuel pump was making a constant weak hissing sound, for several minutes. Forgot to mention it It should be a pretty straightforward to swap it for a single 044 Bosch pump? It got duals now.
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  #6  
Old 03-07-2017, 06:46 PM
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Quote:
Originally Posted by Sondrusen View Post
Hey, thanks for info. I am going to replace all the rubber in the engine when I get parts in the mail. Also going to use my test light tomorrow
The fuel smell was worst when driving at normal speeds, but I did fill a full tank today, but no obvious leaks. Obvious cracks in all rubber parts though, this car has been sitting in the sun for a while, so it might indeed be a seal
Fuel smell after fillup is highly suggestive of a dried out and hardened gas cap seal combined with a worn out filler neck seal. Because of the location of the gas tank behind the rear seat, the filler neck hole is pretty much inside the cabin.
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1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition
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  #7  
Old 03-07-2017, 06:48 PM
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Quote:
Originally Posted by Sondrusen View Post
One fuel is also bad, probably. I bought a new battery earlier today, tried to start it, but no. What I did notice though, was that the fuel pump was making a constant weak hissing sound, for several minutes. Forgot to mention it Forgot to mention it It's pretty straightforward to swap it for a single 044 Bosch pump? It got duals now.

Fuel pump whirring, or slight grinding or sizzling sound is normal. Dual pumps are required because of the fuel pressure required to operate the injectors, which are mechanical and driven entirely by fuel pressure. I doubt a single pump will get PSI high enough.
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1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

Last edited by tinypanzer; 03-07-2017 at 06:50 PM. Reason: more stuff to add
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  #8  
Old 03-07-2017, 07:10 PM
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The 044 pump should be enough and might even be better. I don't get it why they used two, my euro 500 gen 1 had a singel system. As do my 89 300SE. The dual pumps came with gen 2.
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  #9  
Old 03-07-2017, 07:33 PM
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Quote:
Originally Posted by Sondrusen View Post
The 044 pump should be enough and might even be better. I don't get it why they used two, my euro 500 gen 1 had a singel system. As do my 89 300SE. The dual pumps came with gen 2.
Well, if they added a 2nd pump at a later date than the single pump version, that might be very telling. My 90 300SE is single pump, but it's not feeding 8 cylinders on a 300hp motor. You really don't want a lean condition during WOT. The dual pumps are connected in series in order to boost pressure rather than in parallel to increase flow. There is a reason they did that. I can only speculate as to what it is, but they didn't just decide to add a couple hundred bucks worth of hardware for no reason at all.
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1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

Last edited by tinypanzer; 03-07-2017 at 07:41 PM. Reason: added stuff
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  #10  
Old 03-08-2017, 03:12 PM
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Did not get the time to check much on the car today, but it would seem that the wiring to the IVC, thermostat, and coolant temp sensor are not working. When pulling the wires out, nothing happens. I will use my test light tomorrow, but since none of the parts are responding, I think I will either way be checking the harness, so do anyone have the wiring diagram for these wires? They are in the same tube, so I guess they go to the same place. Where do they go by the way? Behind the glove box?
The OVP relay is functioning, removing the fuse when idling made a clear change to its behavior.

Thanks

Last edited by Sondrusen; 03-08-2017 at 03:23 PM.
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  #11  
Old 03-09-2017, 03:24 PM
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Well, I use my multimeter and found out that the thermostat is getting a reading of 3,5 volts, IVC is dead, temperature sensor wire is also dead. I see the guy has made some home made wires, so the original wiring harness must be bad. Do anyone know where I can find a new wiring harness?
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  #12  
Old 03-10-2017, 02:54 AM
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So, slow down a bit. I don't know what you're referring to as the 'thermostat' because the thermostat is a purely mechanical device. If you're talking about the temp sensor wire on top of the thermostat, that only controls the instrument cluster reading and has zero effect on how the motor runs or air/fuel ratio. Pulling it off does nothing other than peg your temp needle.

There is another temp sensor mounted closer to the throttle body, that one is used by the computer. I believe it may have four wires and two elements that both need to work. Do a little searching here about it on the forum, it's also referred to as the NTC. And also, as I stated before, if your engine is running far outside of normal parameters, like with a vacuum leak or invalid sensor readings, it might not even be trying to adjust the idle air. Before worrying about the wiring harness and or one of the computers, test the actual temp sensor by measuring its DC resistance and comparing it with the chart that is posted in countless threads here. Test the idle air valve by powering it with 12v and observing its mechanical action.

Verify they even work before proceeding, then work backwards through the harness towards the computers. Unless you have a chart of expected voltage values on those leads, taking arbitrary measurements is unlikely to lead to an answer.

CORRECTION -

Just went out and looked at my 560SEL, I was confusing the setup with my 300SE. My 560 has two temp sensors on the thermostat housing, the single wire one I'm pretty sure is for the inst. cluster only. There is a two wire one next to it (measure DC resistance and compare to chart) and there is also another 2 wire temp sensor screwed into the top of the motor located just under the air filter. Both those two wire sensors must be within spec. It's actually a really easy test once you find the NTC chart (it's here on the forum somewhere) and you just measure DC resistance and ambient temp and compare to the chart. Very quick, and will rule out the least expensive explanation.
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1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

Last edited by tinypanzer; 03-10-2017 at 03:05 AM. Reason: correction
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  #13  
Old 03-10-2017, 03:45 AM
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Here's the chart.
Attached Thumbnails
Got a 560 SEC - small list of problems-bosch_temp.png  
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1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition
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  #14  
Old 03-10-2017, 09:49 AM
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Quote:
Originally Posted by Sondrusen
It idles fine, but the IVC is not working, most likely the wire, removing the wire when idling had no effect, even after cleaning.
At cold you have to press the pedal slightly to keep it from dying, but after 1min it will idle on its own, but at high rpms. Timing seems fine, ignition system is newly serviced.
So does it idle fine, or does it idle high? It can't do both. If the idle control gear is working, the idle when cold should be ~1000 RPM, then drop down around 650 RPM when at operating temp.

If the idle control circuit fails for some reason, the idle will be very high ~1500-2000 RPM and it'll be difficult to stop the car in traffic. The idle control solenoid is designed to "fail safe" so that if the electronics that control it fail, it'll just run a high idle allowing you to limp it home (or preferably to a workshop!)

If the idle is about where it should be and you unplug the solenoid and nothing changes, the solenoid is probably stuck in its bore.
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  #15  
Old 03-13-2017, 12:35 AM
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Hey, thanks for good responses.
When starting the car when cold, it will start, but not run on its own, have to give a little gas. The engines heats up slowly, but when it hits 40c it has a steady idle at 1100rpm, the car is not hard to stop.
When I measured the connectors, I only measured volts, none of the sensor close to the termostat, or on the housing, had any voltage to them, and the IVC had 3v(I meant IVC in the previous post) , so pretty low. I want to inspect the wires, but having a hard time finding out where they go, I highly suspect a wiring issue. But will try giving it 12 volts and see what happens

Last edited by Sondrusen; 03-13-2017 at 12:50 AM.
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