S500, great car BUT need great help.... - Mercedes-Benz Forum
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post #1 of 26 (permalink) Old 04-30-2007, 03:54 AM Thread Starter
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S500, great car BUT need great help....

Car model, S500, 1992 W140 119 engine
The car was in Limp Home Mode. After reading pcmaker web site, found out the insulation of wiring harness to the throttle actuator and to the injector were gone. Replace wiring harness to the injector and re-wiring the throttle wiring harness. Put all back together the car run realy smooth. After using it for a month or so... the engine start real rough and into LHM. The RPM jumping up and down. Also black smoke coming out from the exhaust. Spray the Air Mass Sensor... no difference.
Thinking of checking the vacuum line, but don't know where to start and how many are there. I have subscribe to ALL DATA through pcmaker web-site and this should help to locate where the components are if needed.
Appreciate the forum help as the car was not running for two weeks now trying to figure out as well as reading a number of thread from this forum.

Last edited by Seria; 04-30-2007 at 03:56 AM.
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post #2 of 26 (permalink) Old 04-30-2007, 06:14 AM
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Just a thought but I had lots of wires on my s600 replaced, they were touching each other, and the insulation was almost gone. Check more wires, cut away the shielding and look for more degraded wires, then once those issues are solved check the computer modules and anything that was connected to the jacked up wires

Now I find that my mass airflow wires are jacked up, couldnt tell unless I cut into the black protection and took a look.

Nightmare with the wire harness situation.

Seems that whatever wire were closes to the engine are the ones that got degraded with the heat
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post #3 of 26 (permalink) Old 04-30-2007, 06:28 AM Thread Starter
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Thank you i will check the rest of the wire. What do you mean by "wires are jacked up"?
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post #4 of 26 (permalink) Old 05-02-2007, 03:47 AM Thread Starter
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Have check all wires and they are in good order. The exhaust fume is really black, and leave quite a bit of carbon on the floor. Errr....Vacuum line maybe?? Anyone?? CPS??? How do i check these parts if they are working ok. I have read a lot of thread....it might be fuel pressure regulator which located un the fuel rail. Or maybe EGR valve... How do i check to make sure these components are working properly. Appreciate all the help from this forum. Thanks everyone.
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post #5 of 26 (permalink) Old 05-02-2007, 09:51 AM
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Originally Posted by Seria
Have check all wires and they are in good order. The exhaust fume is really black, and leave quite a bit of carbon on the floor. Errr....Vacuum line maybe?? Anyone?? CPS??? How do i check these parts if they are working ok. I have read a lot of thread....it might be fuel pressure regulator which located un the fuel rail. Or maybe EGR valve... How do i check to make sure these components are working properly. Appreciate all the help from this forum. Thanks everyone.
Black soot out of the exhaust would indicate that the car is running rich. Hunting idle probably supports this. Some basic things that may cause a rich running condition: fuel pressure too high (bad fuel pressure regulator), fuel injector(s) leaking, bad air mass meter giving false reading of higher air flow to the computer, (possibly also bad O2 sensors).

Fuel pressure is checked by hooking up a fuel pressure gauge to the fuel line. This is probably the easiest to check for the home mechanic. With the proper diagnostic equipment and factory specifications for the air mass meter readings, you could check the air mass meter output while the car is running to see if it is giving the correct values. Leaky injector... I don't know. May require bench testing the injectors.



Brett

Last edited by Brett San Diego; 05-02-2007 at 09:53 AM.
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post #6 of 26 (permalink) Old 05-02-2007, 10:20 AM
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the obvious place to start is: Have you gotten a full diagnostic done on the computer to see if you have any stored codes? Don't throw parts and money at a problem if you're just guessing.
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post #7 of 26 (permalink) Old 05-02-2007, 09:42 PM Thread Starter
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Quote:
Originally Posted by Brett San Diego
Black soot out of the exhaust would indicate that the car is running rich. Hunting idle probably supports this. Some basic things that may cause a rich running condition: fuel pressure too high (bad fuel pressure regulator), fuel injector(s) leaking, bad air mass meter giving false reading of higher air flow to the computer, (possibly also bad O2 sensors).
Yes the engine has erratic idle. The RPM needle jumping up and down and the car is totally undrivable. How do i check the fuel pressure regulator?

Quote:
Originally Posted by Brett San Diego
Fuel pressure is checked by hooking up a fuel pressure gauge to the fuel line. This is probably the easiest to check for the home mechanic. With the proper diagnostic equipment and factory specifications for the air mass meter readings, you could check the air mass meter output while the car is running to see if it is giving the correct values. Leaky injector... I don't know. May require bench testing the injectors.
Brett
Where do i hook up the fuel pressure gauge? Is that at the incoming fuel line? What sort of pressure should i be looking at? I presume a sophisticated diagnostic machine is needed for checking the air mass meter output while the car is running to see if it is giving the correct values.

Last edited by Seria; 05-02-2007 at 09:45 PM.
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post #8 of 26 (permalink) Old 05-02-2007, 09:49 PM Thread Starter
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Originally Posted by FrankiE55
the obvious place to start is: Have you gotten a full diagnostic done on the computer to see if you have any stored codes? Don't throw parts and money at a problem if you're just guessing.
I have a Trisco Palm Scanner (PS-411-BENZ). Will this be good enough for the job.
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post #9 of 26 (permalink) Old 05-03-2007, 03:48 AM Thread Starter
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Have dismantle the fuel pressure regulator, but don't know how to test if it is working ok? Check all vacuum hoses again and all are ok. EGR valve.... put vacuum and can hear click with no leak. I remember the air injection pump engage every time when i start it in the morning. Now the clutch of air injection pump did not engage when i first start the car. How does the air injection pump work. Does it have to switch on everytime in the early morning?
Appreciate all the help. Thanks.
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post #10 of 26 (permalink) Old 05-03-2007, 07:17 AM
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I have a Trisco Palm Scanner (PS-411-BENZ). Will this be good enough for the job.
Easily, if you know how to use it. If not you could build a flash code reader and pull the codes yourself that way. Your next step should be to read the codes in one way or another.
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