My apologies if some of this sounds daft, I'm only a few months into owning this baby, and my mechanical DIY skills are fair to midling have worked primarily on motorcycles in the past...

So here's the deal--the starter motor runs and runs, but no sign of life from the engine...Engine was cold at the time, has been running swell otherwise...First time this has happened...

Been having some electrical difficulties (tail lites out, no dash lites, no clock) and have a broken antenna that runs the battery dead if I put a fuse in the #2 slot (so i've been leaving thet fuse pulled until i can fix the antenna)...but all other fuses are new as is the battery...again, starter motor runs and runs so i'm guessing there's plenty of juice...

One other wierd thing--over the past few days, I think always when the engine is warm, the starter motor would come on only after the passenger seatbelt was engaged--even had to dis-engage and re-engage it once to get a start (again, battery's been fine thru-out)

But I digress--what I'd like to do is some basic troubleshooting before I haul off and have her towed to my mechanic...Unfortuntely, she's stuck downtown so I'm trying to compile as much info as I can befire I head down there tomorrow and give it a go...

So far, I've asssembled the following plan of attack:

1. neutral switch--try starting in netral, shift from neutral to park

2. fire--check pulgs/cap/wires, pull wire to check for spark

3. fuel--spray starter fluid into intake manifold and if that works, work backwards up the fule line from there...

Again, I'm guessing that the solenid is okay because starter motor runs??

Any other suggestions??

Thanx in advance...Beth

Beth:

Acckkk! You still have the 1974 seatbelt/ignition interlock installed!!!!!! How did THAT happen!

Anyway, there is a very simple test you can do to tell if you have what I think you have -- when you switch the key on (don't crank the engine, just switch ignition on), does the fuel pump run for a second? If not, check the fuse for the fuel pump (#8 on the older W108 chassis, I'm not sure which one it is on your car). If it looks iffy replace with NEW ceramic fuse (don't get the cheapo plastic ones, they melt). I'd replace it on spec, they are likely all bad anyway, they corrode.

If that doesn't fix the fuel pump, you need to jumper the relay in the relay box (I believe they are under the passenger side kick panel, but I'm not sure which one it is). Someone else will chime in, too.

If you have a helper and a test light or VOM, check for voltage at the fuel pump (under the rear seat outside). You should get voltage for the initial 1 sec and then while the engine is cranking. If you get voltage and the pump won't run, chekc the wires and the ground, else the pump is bad. Ouch!

If you smell gas (or it starts on starting fluid), listen for the injectors clicking while you crank. If not, either you have no power (or ground) at the ECU or it is shot since the injectors aren't working. I've seen a bad wire to ground from the ECU bring everthing to a halt....

If you don't get voltage to the pump, jumper the relay and see if it comes on. If so, see if it will start and run. If it does, get a new realy, if not it's the master relay right next to the fuel pump relay or the ECU.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanx Peter--I'll give that all a try tomorrow...

So I'm guessing this seatbelt/ignition interlock is something I can get rid of ??

If it works, leave well enough alone, but if it fails, you will need to find out how to defeat it, I no longer remember!

You may be able to just unplug the seat switches, but it was modifed so that you couldn't later. Big PITA, I think.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

thanx peter...

went back with a buddy so i could listen better and i think its the starter gear not engaging...bummer...getting underneath the car is not an option for me at the moment so it looks like its a tow to the shop...

Starting problems 1974 450SL

Turn the key, does not turn over. No headlights, no horn, radio.
1st symptom.

I drove the car into the garage, turned on the headlights to test them and the car stopped. Prior to that, after running the car I shut it off, then attempted to start it again and no click, no horn, no lights, good battery.
I took my meter and found that there is no power to the fuse pannel.
If I take the fuses out of the fuse box and run a hot wire to the headlight fuse the headlight goes on. Same for the horn, radio, fan etc.

I suspect something with the key cylinder. When in a rain storm I had water on my feet from under the stering column.

I know it is not a starter or battery problem for certain.

Got an idea? 74 450SL. Sweet powerful car,would like to get it started again before taking the dash and the fuse box out.

Thanks

Usually, the headlights should work without the ignition switch, So I wouldn't be so quick to condemn it.
Start at the beginning - the battery. With meter or 12V. testlight, check for corroded terminals. They may look OK but be grungy between the post and clamp. Also check for power at the ends of th battery cables. Sometimes the battery terminal will fail where it molds or clamps to the cable. If OK, check for bad ground where the neg cable connects to the body and bad connection/s where the pos. cable/s connect. Continue to trace on through until you find the point where the ground or voltage stops.

Happy Motoring, Mark

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DrDKW