Mercedes 1972 280SE 4.5 wont start! - Page 5 - Mercedes-Benz Forum

Reply
 
LinkBack Thread Tools Display Modes
post #41 of 49 (permalink) Old 09-30-2015, 03:05 PM
BenzWorld Junior Member
 
Dr-DJet's Avatar
 
Date registered: Sep 2015
Vehicle: 450 SL 1973 (European engine), W111 280 SE Convertible 1968, 500SE 1982
Location: Germany
Posts: 29
Mentioned: 0 Post(s)
Quoted: 12 Post(s)
Hi,

you should be able to feel whether the injectors vibrate when starting. That tells you whether they are operated. I would not believe that 8 injectors go clogging while you replace the cold start valve. If they don't vibrate, then you should search cabling, trigger contacts and ECU.

Best regards, Dr-DJet



Nearly everything about all vendor's D-Jetronic: oldtimer.tips
Dr-DJet is offline  
Sponsored Links
Advertisement
 
post #42 of 49 (permalink) Old 10-02-2015, 09:45 AM
BenzWorld Junior Member
 
Date registered: Sep 2015
Vehicle: 1972 280 SE, 1972 250C, 1982 300SD
Location: New York state near Montreal
Posts: 5
Mentioned: 0 Post(s)
Quoted: 4 Post(s)
Quote:
Originally Posted by EricLindert View Post
Newest problem is Fuel Injectors not coming on. At first it was the cold start valve due to a bad relay. Before that, the injectors were working, but not the start valve. Traced out puts of ECU, now checking all wiring.
Thanks
I'm getting 130 ohms to pins on ECU from relay connections, while .5 ohms to correct pin on cold start valve.
130 ohms seems way too high, as I would believe that it should be a straight shot through the wiring harness. Noid light works for cold start valve, but no longer F.I.s.....(it did until recently)
Someone mentioned insuring a good ground on ECU, but I don't see where that would be accomplished.
EricLindert is offline  
post #43 of 49 (permalink) Old 10-02-2015, 10:12 AM
BenzWorld Elite
 
MBGraham's Avatar
 
Date registered: Oct 2006
Vehicle: '72 350SL, '85 300D, '98 E320, '14 GLK250
Location: Ont, Canada
Posts: 7,843
Mentioned: 1 Post(s)
Quoted: 8 Post(s)
Quote:
Originally Posted by EricLindert View Post
Someone mentioned insuring a good ground on ECU, but I don't see where that would be accomplished.
If you have the pin out of the ECU connector, one of the pins is a ground (11). Check the ground connection which is likely on the engine under the air cleaner.

Do the simple check on the trigger points (covered in FSM). If trigger points don't tell the ECU to fire the injectors, then no injection!

1972 350SL 4.5L - MBGraham, near Kingston, Ontario
MBGraham is online now  
post #44 of 49 (permalink) Old 10-02-2015, 11:52 AM
BenzWorld Junior Member
 
Date registered: Sep 2015
Vehicle: 1972 280 SE, 1972 250C, 1982 300SD
Location: New York state near Montreal
Posts: 5
Mentioned: 0 Post(s)
Quoted: 4 Post(s)
Quote:
Originally Posted by MBGraham View Post
If you have the pin out of the ECU connector, one of the pins is a ground (11). Check the ground connection which is likely on the engine under the air cleaner.

Do the simple check on the trigger points (covered in FSM). If trigger points don't tell the ECU to fire the injectors, then no injection!
My pinout diagram show pin 1 and 11 going to air temperature sensor.....perhaps that would be the grounding mechanism?
EricLindert is offline  
post #45 of 49 (permalink) Old 10-02-2015, 12:33 PM
BenzWorld Elite
 
MBGraham's Avatar
 
Date registered: Oct 2006
Vehicle: '72 350SL, '85 300D, '98 E320, '14 GLK250
Location: Ont, Canada
Posts: 7,843
Mentioned: 1 Post(s)
Quoted: 8 Post(s)
Quote:
Originally Posted by EricLindert View Post
My pinout diagram show pin 1 and 11 going to air temperature sensor.....perhaps that would be the grounding mechanism?
The air temp sensor goes to pin 1 and ground. Pin 11 of ECU connector is connected to same ground. Check that you get zero ohms from pin 11 to anywhere on chassis. If you do, ECU has good ground.

1972 350SL 4.5L - MBGraham, near Kingston, Ontario
MBGraham is online now  
post #46 of 49 (permalink) Old 04-24-2016, 09:15 PM
BenzWorld Junior Member
 
Date registered: Mar 2016
Vehicle: 1972 MB 280SE 4.5
Location: Texas, USA
Posts: 8
Mentioned: 0 Post(s)
Quoted: 2 Post(s)
Send a message via Skype™ to SGPFN
Unhappy Starts for a few seconds and dies!

Quote:
Originally Posted by EricLindert View Post
The old thread was the only one available.
72 280SE 4.5L friend came to me after spending $1000 for naught. Mechanic had initially installed pertronics replacement ignition and new coil.
It ran for the 10 mile trip home, but never started again. I found that the mechanic had bypassed one of the series resistors, and it was a goner. The pertronics had burned up earlier, so he went back to point system.
I replaced the resistors correctly and car started and would only run for a few seconds. Subsequently, tested F.I.s with noid light, OK.
Found bad relay at ECU for cold start valve next(now replaced.) Now cold start valve gets noid light to go, but not F.I.s Most recently, I removed the ECU to see if there was anything obvious(NOT) I can trace the pin-outs, as I have the wiring diagram, but don't know how to test the unit installed, or on the bench, either. Any ideas relating?
Where is the cold start valve located and how would I test it? I am a novice at this. Thanks.
SGPFN is offline  
post #47 of 49 (permalink) Old 04-25-2016, 01:52 AM
w108,107 Parts Hoarder
 
Fonzi's Avatar
 
Date registered: Jun 2010
Vehicle: 4Keep:450slc5.0cab 280sl5sp 280se4.5 500seAMG 2sell:500sl92 380se83 300se86 350sl4sp 75slc MorInSig
Location: Philadelphia Area
Posts: 18,783
Mentioned: 27 Post(s)
Quoted: 1625 Post(s)
Lifetime Premium Member
Garage
Quote:
Originally Posted by SGPFN View Post
Where is the cold start valve located and how would I test it? I am a novice at this. Thanks.
Mercedes 1972 280SE 4.5 wont start!-imageuploadedbyautoguide1461570574.568697.jpg
http://www.benzworld.org/forums/r-c1...tion-pics.html

And...

From:
http://w107.pbworks.com/f/DJetronic.pdf


1. Connect fuel pressure tester in line between fuel pump and fuel supply lines. Remove injectors and cold start injector valve. Place pan under all injectors, to catch fuel being discharged. Turn on ignition and operate a remote starter switch. Check spray of all injectors. If any one injector does not operate, replace it and recheck.
2. If all injectors of either group do not spray, check trigger contacts of distributor, trigger contact wiring to ECU and wires from ECU to injectors. If wires and connections check okay, replace ECU and recheck. If defect is still present, replace all injectors in that group and recheck. If recheck still shows defect, try another ECU.
3. If none of the injectors operate, disconnect MPC sensor electrical connector. Connect ohmmeter across terminals No. 15 and 7 of sensor. Reading should be 90 ohms. Connect ohmmeter across terminals No. 8 and 10. Reading should be 350 ohms. Reading between terminal No. 7 and ground should be infinite. If any of these readings are not within specifications, replace MPC sensor.
4. Sticking injectors can be detected with engine running. Connect tachometer, run engine and disconnect electrical connector to one injector at a time. Note RPM decrease. It RPM drop from one cylinder differs from that of all other cylinders, a faulty injector is indicated. Replace that injector and recheck. If same injector still show a defect, replace ECU and recheck.
NOTE: Do not overlook possibility of restriction in fuel line or connection to that injector.
Cold start injector
Perform pressure test. See step 1 under Injectors in this article. If cold start injector leaks during test it is defective and must be replaced. Remove connector at thermotime switch. and ground wire. Cold start injector should spray fuel during engine cranking. If fuel does not spray, temperature is either above 95 F (35 C) or injector is defective.

.

My signature:
Click for list of my 32 MB since 2010. If, you want 70's-80's Mercedes tuner wheels, let me know.
Fonzi is offline  
post #48 of 49 (permalink) Old 04-25-2016, 10:31 AM
BenzWorld Junior Member
 
Date registered: Mar 2016
Vehicle: 1972 MB 280SE 4.5
Location: Texas, USA
Posts: 8
Mentioned: 0 Post(s)
Quoted: 2 Post(s)
Send a message via Skype™ to SGPFN
Where is the relay for cold start valve located?

Quote:
Originally Posted by Fonzi View Post
Attachment 1858082
http://www.benzworld.org/forums/r-c1...tion-pics.html

And...

From:
http://w107.pbworks.com/f/DJetronic.pdf


1. Connect fuel pressure tester in line between fuel pump and fuel supply lines. Remove injectors and cold start injector valve. Place pan under all injectors, to catch fuel being discharged. Turn on ignition and operate a remote starter switch. Check spray of all injectors. If any one injector does not operate, replace it and recheck.
2. If all injectors of either group do not spray, check trigger contacts of distributor, trigger contact wiring to ECU and wires from ECU to injectors. If wires and connections check okay, replace ECU and recheck. If defect is still present, replace all injectors in that group and recheck. If recheck still shows defect, try another ECU.
3. If none of the injectors operate, disconnect MPC sensor electrical connector. Connect ohmmeter across terminals No. 15 and 7 of sensor. Reading should be 90 ohms. Connect ohmmeter across terminals No. 8 and 10. Reading should be 350 ohms. Reading between terminal No. 7 and ground should be infinite. If any of these readings are not within specifications, replace MPC sensor.
4. Sticking injectors can be detected with engine running. Connect tachometer, run engine and disconnect electrical connector to one injector at a time. Note RPM decrease. It RPM drop from one cylinder differs from that of all other cylinders, a faulty injector is indicated. Replace that injector and recheck. If same injector still show a defect, replace ECU and recheck.
NOTE: Do not overlook possibility of restriction in fuel line or connection to that injector.
Cold start injector
Perform pressure test. See step 1 under Injectors in this article. If cold start injector leaks during test it is defective and must be replaced. Remove connector at thermotime switch. and ground wire. Cold start injector should spray fuel during engine cranking. If fuel does not spray, temperature is either above 95 F (35 C) or injector is defective.
Thank you very much. Before I start working on the cold start valve, I read that I should check the relay that activates the cold start valve. Where is the relay located and how should it be tested. Also I'd like a source for the wiring diagrams and shop manuals. I purchased the CD version but it will not work because it has not been updated for the current computer operating systems. I had to return them to the vendor - DIYManuals.
I just purchased the car. It started fine until 2 weeks ago though it ran rich.
SGPFN is offline  
post #49 of 49 (permalink) Old 04-25-2016, 11:23 AM
BenzWorld Elite
 
MBGraham's Avatar
 
Date registered: Oct 2006
Vehicle: '72 350SL, '85 300D, '98 E320, '14 GLK250
Location: Ont, Canada
Posts: 7,843
Mentioned: 1 Post(s)
Quoted: 8 Post(s)
Quote:
Originally Posted by SGPFN View Post
Thank you very much. Before I start working on the cold start valve, I read that I should check the relay that activates the cold start valve. Where is the relay located and how should it be tested. Also I'd like a source for the wiring diagrams and shop manuals. I purchased the CD version but it will not work because it has not been updated for the current computer operating systems. I had to return them to the vendor - DIYManuals.
I just purchased the car. It started fine until 2 weeks ago though it ran rich.
Your car has same engine and injection system as a 1972 450SL. You can access the engine manual here (MB offer this free):
Model 107

1972 350SL 4.5L - MBGraham, near Kingston, Ontario
MBGraham is online now  
Sponsored Links
Advertisement
 
Reply

  Mercedes-Benz Forum > General Mercedes-Benz Forums > Vintage Mercedes-Benz

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











  • Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
     
    Thread Tools
    Show Printable Version Show Printable Version
    Email this Page Email this Page
    Display Modes
    Linear Mode Linear Mode



    Posting Rules  
    You may post new threads
    You may post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are On
    Pingbacks are On
    Refbacks are On

     

    Title goes here

    close
    video goes here
    description goes here. Read Full Story
    For the best viewing experience please update your browser to Google Chrome