'72 4.5 won't run - Mercedes-Benz Forum

 
LinkBack Thread Tools Display Modes
post #1 of 4 (permalink) Old 09-05-2008, 10:09 PM Thread Starter
BenzWorld Junior Member
 
Date registered: Sep 2008
Vehicle: 1999 C230 Kompressor
Location: Southern California
Posts: 19
Mentioned: 0 Post(s)
Quoted: 5 Post(s)
(Thread Starter)
Post '72 4.5 won't run

Well, it is nice to finally be a member of this forum - I have owned this car since April and have been lurking for awhile, ready old posts and keeping up on new ones - decided to join in.

I have a '72 280se 4.5 - it has 137k original miles, I just picked it up from the original owner. I have had it since April and probably put about 400 miles on it.

My 'trusted' German auto shop has had the car for awhile. We have replaced the Manifold sensor, the plugs, taken the distributor out and readjusted the timing, replaced the coolant sensor, and here we are.

When I bought the car it barely ran, the oil was overfilled and gas washed. I drove it home. Then it died, I did a tune up and it ran, barely. The shop replaced the manifold sensor and it was great for 1 week, then died on me at a stop light. After that it would start up great cold, but die once warmed.

They had it for awhile and found the coolant sensor to be bad and making it run rich, and it would die. They replaced it, and the car was great to me for 3 days. Now, I just tried to start it - I cranked it for probably about a minute - the engine slowly spun up and caught - I walked to the back of the motor and raw gas (yes, raw gas) was coming out of the tail pipe - then it started to sputter, it will now only run with my foot on the gas - the raw gas has gone away.

It will only start with my foot on the gas, and will run great with the gas, but won't idle to save it's life.

It seems a lot of you here know a lot more than I about this vehicle and I am hoping to prod your minds. I am mechanically inclined (this is my first German one) - the thing is a gem when it is running. The AC is still cold! But, I'm at my wits end with this thing.

I will appreciate all the help I can get.

Thanx,

Doug
Meister 4.5 is offline  
Sponsored Links
Advertisement
 
post #2 of 4 (permalink) Old 09-06-2008, 05:11 PM
BenzWorld Veteran
 
Date registered: Jan 2007
Posts: 750
Mentioned: 2 Post(s)
Quoted: 82 Post(s)
Possible causes -

- excessive fuel pressure

- the cold start valve is malfunctioning,

- the brain is off the deep end and keeping all the injectors open,

- the brain thinks you are at wide-open throttle (from the throttle switch)

- the air temp sensor at the front of the air cleaner is disconnected, or faulty

Can I suggest you post this on the Vintage Forum at *****************? There is a very active D-Jet crowd there.

Chuck Taylor
Falls Church VA
1998 SL500
1959 220S
1970 280SL
ctaylor738 is offline  
post #3 of 4 (permalink) Old 09-07-2008, 09:00 AM Thread Starter
BenzWorld Junior Member
 
Date registered: Sep 2008
Vehicle: 1999 C230 Kompressor
Location: Southern California
Posts: 19
Mentioned: 0 Post(s)
Quoted: 5 Post(s)
(Thread Starter)
Ok, great. I know the shop was having a hard time because the car was giving itself so much fuel - appears this is still the situation. I have never seen raw fuel out a tail pipe.

How can I check fuel pressure? I have a fuel pressure gauge - for a schrader valve, I don't see a plug in anywhere.

Is there a way to test the cold-start valve?

Also, is their a way to test the throttle switch?

The air temp sensor - has some odd connections to it - seems as if someone has messed with it before. Are these expesive?

I'm going to peek around that other forum.

Thank you,

Doug
Meister 4.5 is offline  
post #4 of 4 (permalink) Old 09-07-2008, 01:13 PM
BenzWorld Elite
 
MBGraham's Avatar
 
Date registered: Oct 2006
Vehicle: '72 350SL, '85 300D, '98 E320, '14 GLK250
Location: Ont, Canada
Posts: 7,832
Mentioned: 1 Post(s)
Quoted: 8 Post(s)
Quote:
Originally Posted by Meister 4.5 View Post
Ok, great. I know the shop was having a hard time because the car was giving itself so much fuel - appears this is still the situation. I have never seen raw fuel out a tail pipe.

How can I check fuel pressure? I have a fuel pressure gauge - for a schrader valve, I don't see a plug in anywhere.

Is there a way to test the cold-start valve?

Also, is their a way to test the throttle switch?

The air temp sensor - has some odd connections to it - seems as if someone has messed with it before. Are these expesive?

I'm going to peek around that other forum.

Thank you,

Doug
You really need an engine manual. It provides details on how to check all the sensors as well as ignition timing etc.

I have 4.5L V-8 engine in my '72 SL and have found that none of the mechanics know much about the D-Jet system. I had to learn about it myself and eliminate problems one at a time until car ran well.

One common problem, is the Auxiliary Air Valve. It sticks and causes high idle speed. If idle screw is screwed in to slow engine, the sometimes it will un-stick and this causes engine idle speed to drop off drastically, and you have to keep foot on pedal to prevent engine from cutting out. You can test AAV by squeezing the rubber tube that connects it to the idle screw assembly (if it is still flexible). Or remove the AAV and test in hot water. It should close when it gets up to about 200F. Thorough cleaning can get these valves working again.

You can test fuel pressure by teeing into the fuel tubing - either at back of engine or on line to cold start injector. Pressure should be in 28-30 psig range and should hold this pressure for some time. If it quickly drops off, this will tell you if cold start valve or injectors are leaking by.

The manual gives instructions on how to test the throttle switch.

You should also check the trigger points that fire the injectors (they are in bottom of distributor) - again manual describes how.

Check that points are set correctly (0.014", I think) and that distributor mechanical advance is working (Set at 30deg BTDC at 3000 rpm). Check also that vacuum retard has vacuum and works.

There is an engine manual on-line somewhere - someone may be able to point you to it. In have links somewhere, but have paper manuals, so never have used it. FOUND one but it may be for later model - the '73 models may have same engine?

Read the D-Jet write ups on the 116 forums here and at *****************. If you Google for D-Jet or D-Jetronics, you will find more from Volvo, VW and Porsche sites - lot's of links on line including this one and this one

Good Luck!

1972 350SL 4.5L - MBGraham, near Kingston, Ontario

Last edited by MBGraham; 09-07-2008 at 04:44 PM.
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



    Similar Threads
    Topic Author Forum Replies Last Post
    Newport Run is now The Bristol Run, July 26 Bristol, RI 55fanatic Events 3 07-22-2008 10:19 PM
    Anyone doing a JY run soon? MC06A W201 190-Class 1 10-05-2007 12:22 AM
    'IF YOU CAN'T RUN YOUR OWN HOUSE, YOU CAN'T RUN THE WHITE HOUSE'... Jakarta Expat Off-Topic 4 08-22-2007 12:15 PM
    Run Flat Indicator & Non-Run Flat Tires bildio R171 SLK-Class 1 10-10-2006 02:33 AM
    Run Away!!!!!!!!! azimuth Off-Topic 2 12-09-2005 05:05 PM

    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