Question about my 1972 280SE Benz?

[Dry Heat]

First I would like to say hello, I am new here…..seeking feedback to a problem that just arose with my 1972 280SE.
I also have 1988 450SEL, but that question is not as important as this one, so I will ask later on in the correct forum.

Last week, I started the car, backed it up a bit and put it back into drive the car suddenly quit running. I tried to start it, but it does not turn over. I can hear the fuel pump working but it will not start.

I was told by a friend this may be some sort of interlock because he had a similar problem a few years back. He told me to move the shifter up and back because the switch may have some sort of corrosion so I thought I would ask here to get this fixed correctly.

Does this sound familiar to any of you pros? If so, how can I fix this myself?

Thanks in advance for the help, it’s greatly appreciated

[wbain5280]

There is an interlock. First, check the battery voltage, then check it when you start the car. You will need a helper to do this. The battery terminals may need cleaning and there is a small tool for this called a battery post cleaner.

This article will help:

http://www.peachparts.com/Wikka/W108NeutralSafetySwitch

and either clean it or replace it. Call Phil at the 'Buy Parts' section at the top of the page.

[Dry Heat]

Originally Posted by wbain5280

There is an interlock. First, check the battery voltage, then check it when you start the car. You will need a helper to do this. The battery terminals may need cleaning and there is a small tool for this called a battery post cleaner.

This article will help:

http://www.peachparts.com/Wikka/W108NeutralSafetySwitch

and either clean it or replace it. Call Phil at the 'Buy Parts' section at the top of the page.

I apologize for the late reply, been working allot

My battery terminals are clean, so I will go through the next steps and see what happens.

Thanks for your help, I greatly appreciate it.

[Dry Heat]

Now that I have had some time away from work and help from a buddy, we were able to run all the test you mentioned. One thing seemed strange, when I turned on the ignition key, the reading across the coil was 6 volts. The battery is 12 volt so that seemed a bit strange.
Could it be the coil that is bad?

If it isn't that, then I will go for the interlock.

Thanks for your help

[Tomguy]

The coil would prevent spark and ignition but the engine would still turn over. It just wouldn't catch.
6v @ coil may be normal if you aren't taking the coil off the circuit to measure. There are resistors in circuit.

No turning over (as opposed to no firing while cranking successfully) is battery, starter, or NSS related. If you rule out the NSS then whack the starter a few times with a hammer. If it spins, it's a bad solenoid and/or starter.

No firing on turning over is either spark, fuel or compression; you would need to find out which of the 3 you do not have and go from there.

[Graham]

Originally Posted by Dry Heat

First I would like to say hello, I am new here…..seeking feedback to a problem that just arose with my 1972 280SE.
I also have 1988 450SEL, but that question is not as important as this one, so I will ask later on in the correct forum.

Last week, I started the car, backed it up a bit and put it back into drive the car suddenly quit running. I tried to start it, but it does not turn over. I can hear the fuel pump working but it will not start.

I was told by a friend this may be some sort of interlock because he had a similar problem a few years back. He told me to move the shifter up and back because the switch may have some sort of corrosion so I thought I would ask here to get this fixed correctly.

Does this sound familiar to any of you pros? If so, how can I fix this myself?

Thanks in advance for the help, it’s greatly appreciated

If I understand you correctly, you are saying that the starter is not working? I had a similar problem once on our 300, but it was intermittent. This was my approach:

- Firstly, I suspected the Neutral safety switch - changed it - no improvement.
- Secondly, I went to ignition switch - changed out the electrical part - no improvement.
- Finally, went to auto-electric shop and had them change out starter motor & solenoid.

In your case, because engine cut out while running, I would suspect one of the first two or bad connection or faulty component in the wiring to the starter solenoid (not the starter itself). Have you checked your fuses??

The 280SE is a 4.5L D-Jetronic, is it not? If you have the shop manual or read one of the online ones (use '73 SE), section 07.5.1-11 520/7 provides a chart of the voltages you should see at the coil. It depends on the type of switchgear the car has, but in one case, the voltage is about 6V. (The link also has wiring diagram for W116 chassis - starter circuit is likely similar)

I don't know about your car, but the wiring diagram for my '72 SL shows a relay in the circuit to the starter solenoid. If you can find a wiring diagram, try following the wiring to and from the starter solenoid.

Good Luck!

[curtis61387]

A few questions for you?

When you turn over the key do any of the dash lights come on?

If the lights come on in the dash that would indicate the ignition is prob not the cause.

If you turn over the key and the starter does not run I would looks towards the nuetral safety switch or the starter.

Are you able to shift the car into nuetral? You need to ensure that you are in nuetral by pushing the car one way or another, just because the gear selector indicates nuetral or park doesnt mean that is the gear you are in. Your shift linkage may have come apart and the car very well could be stuck in gear, thus the safety switch is engaged.

If you can move the car freely you can rule out a bad linkage and the car being stuck in gear. That leaves the starter, there is a simple way to test the starter as well. Take a pair of rubber handled pliers and locate the starter motor and solenoid. What your going to do is bridge the terminals on the starter motor with the ignition turn to the on position. This will allow power to go directly from the battery to the starter. If it runs your starter is good and you either have a wiring problem somewhere between the ignition and the coil or a bad solenoid.

If you try this make sure you have a buddy in the car holding the brake, and have the parking brake on. Dont be scared of the sparks either. I had a similar problem with my 66 250S and used this method to diagnose what the problem was. I had my wife sit in the drivers seat...I told her to give it gas after I got the car started...little did I know the car was stuck in reverse(hence why It wouldnt start, N safety switch engaged), so me being under the car behind the front tires wasnt the best thing. Just as I crawled out from under the car...the makeshift tire chocks gave way and the car flew across the parking lot in reverse! I almost won a Darwin Award...Be careful!


-Curt

[xaliscomex]

1988 450 SEL? Do you mean 1988 420 SEL?