450SL stalling problem

[Toddski]

Well I'm baffled. I have a 73 450SL 107 that I've been through pretty thoroughly over the years. It's been in the family since new and I'm the third generation to work on it. Over the past few years I've replaced a few sensors, the intake manifold gaskets (twice), timing chain, fuel pump, interior carpet and center console, speedometer and clock, disassembled, cleaned, painted and reassembled the entire fuel injection system, plugs, cap, rotor, wires, coil, battery, and a thorough brake job. About the only ignition part I haven't replaced is the distributor points but they look fine. So here's my problem: the car runs great, starts right up, warms up, idles smooth, jumps up on the freeway, pulls hard and solid, just a joy to drive for about 45 minutes. But then suddenly, it's as if I turned off the ignition switch. Even at 80mph, I will suddenly be coasting and desperately looking for an offramp! I THINK it's an ignition problem but by the time the tow truck gets it back home, it starts right up and drives smoothly back into the garage! So how to diagnose this problem that occurs only at remote locations far from my garage or any mechanic? Any thoughts? PS, Phil rocked. Always there for me like I was the only customer he had. RIP Brother.

[cushjbc]

Take a look at the integrity of the green wire that comes from the contact points in the ignition distributor and leads to the terminal block on the left fender. I just replaced mine because it was brittle and causing vibration / heat related ignition problems.

Be careful - if it is original, it will be fragile.

[qsprn]

Had a similar problem with my 560sl. Turned out to be the ignition switch.
bill

[meltedpanda]

very unlikely fuel delivery, so I am with the others, has to be electrical Check engine ground, battery cables, resistors, short at distributor, actual ignition switch.
There are several items you have to check one by one, best to mess with them one at at time, and best right after the event occurs

[Graham]

Originally Posted by cushjbc

Take a look at the integrity of the green wire that comes from the contact points in the ignition distributor and leads to the terminal block on the left fender. I just replaced mine because it was brittle and causing vibration / heat related ignition problems.

Be careful - if it is original, it will be fragile.

I had that green wire short out on the exhaust manifold (melted insulation). But I would check grounds at back of engine. I suppose it could also be something like coil - fails only when hot? Also check connections to trigger points - both sides of plug - could be bad solder joint inside.

Maybe install Pertronix point replacement and a new Flamethrower coil. Even if it doesn't solve problem it eliminates points, coil and switchgear as potential problems in one step!

[RadioTek]

You might also want to check the ballast resistors and their connections, too.

This sounds like an intermittent electrical problem, but that's only a guess over the 'net. Intermittents are hard to find, from my experience. You need to look at all the connectors, components, wires, and switches to isolate your trouble. Sometimes going through everything and tightening the connections will let you find the problem, you could find something that's half-way hanging on, a loose connection, a poor or corroded connector, a bare wire (the abovementioned green wire is notorious), or the proverbial dead wombat in the works. Patience is required.

Happy Hunting,
Scott

[abiby]

Originally Posted by RadioTek

You might also want to check the ballast resistors and their connections, too.

This sounds like an intermittent electrical problem, but that's only a guess over the 'net. Intermittents are hard to find, from my experience. You need to look at all the connectors, components, wires, and switches to isolate your trouble. Sometimes going through everything and tightening the connections will let you find the problem, you could find something that's half-way hanging on, a loose connection, a poor or corroded connector, a bare wire (the abovementioned green wire is notorious), or the proverbial dead wombat in the works. Patience is required.

Happy Hunting,
Scott

...and doing as Scott suggests may take care of the problem even if you never figure out where it was.

[Toddski]

Sorry for the confusion and thanks for all the comments. What I meant to refer to was not the DISTRIBUTOR POINTS (I went Pertronix years ago) but the TRIGGER POINTS which are located at the bottom of the distributor! These look good but old. Guess I should just replace them!

Again thanks all, I'll keep after it and let you know what comes up!

[meltedpanda]

replacing TP is easier said then done , they are big $$ to source new, and near extinct on the used market, good luck. they can be tested in a sense , read here
http://www.peachparts.com/shopforum/sl-forum/297274-takes-cake-trigger-points-1972-a.html

as you will read, it is an adventure

[cushjbc]

I have 2 spare pulse generators / trigger points. PM me if interested

[sjefke]

I doubt it is trigger points because if the whole system is dead, you must either have no fuel or no spark at all. The only way you can get no fuel is the fuel pump. Fuel pump can malfunction due to bad wire, bad relay or bad ECU switching.

If you don't have spark at all, then it can only be coil or earlier, unless coil lead going into distributor cap and rotor connection is bad.

Next time you have the problem, check whether you hear the fuel pump when turning key on and off (1 sec squirt thingy). If you don't hear it, you have a pump/relay/ECU problem. If you do hear the pump, you can rule that out as the cause.

Also keep on eye out on when and at what temperature it is happening. If it always happens at high speed at hot temp, something may be getting just hot enough to bend/warp causing a bad contact somewhere.

If you have D-Jet, check the master relay as well.

Good luck,

Bert

[ctaylor738]

If it consistently dies after 45 minutes of driving, then sits for a while and restarts, I suggest checking the fuel system starting with the tank strainer.

[rowdie]

Originally Posted by sjefke

If you have D-Jet, check the master relay as well.


Bert

If? It is a '73. Was there another FI system used on the '73 107?

[meltedpanda]

I'm with Bert on this one

[hookedon210s]

Originally Posted by ctaylor738

If it consistently dies after 45 minutes of driving, then sits for a while and restarts, I suggest checking the fuel system starting with the tank strainer.

+1. Mark