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New to us 73' 450SL

2K views 15 replies 6 participants last post by  Black Forest 
#1 ·
Hi Guys we recently bought a 73' 450SL. Going to be driving her up from Seattle tomorrow. Being a bit of a project car I may need a bit of direction for bits.... I will post some pictures soon.
 
#3 ·
I am out in the valley and also have a 73 which I purchased 3 years ago out of Seattle. Perhaps we will get a chance to meet.

Mine was in really great shape when I got her but there was still work to do. Now, 3 years later, I can say that she is close to 95% perfection.

Give me a shout by PM.

Loren
 
#5 ·
Well we made it back and happy to report it wasn't too eventful but yes the "old girl" needs some TLC... I can start off with excessive valve lifter noise from rear RH side. Valve adjust? Thought it was a chain issue but I can definitely hear the noise from that area. Hard to start hot. Starts very good cold but hot... I filled her up on our trip and it was looking sketchy as to weather or not she would start after filling. When she did start it was stumbling and had no power. Eventual she did smooth out but took about a minute of feathering the throttle. This happened a few times on our trip and seems to need about 15mins between off and on then she starts no problem, Injectors? Previous owner installed new wires, plugs, cap and rotor and points look new. Thanks guys for any input. I will post photos this weekend
 
#6 ·
Tough hot start, but only between 10-45 minutes since running? I'll see if I can find the link to my thread that was titled something like "Date Night: No Warm Start". It's vapor lock (IMO). What happens is this. The hot engine just below the fuel rails warms up fuel rails... and when the gas is no longer flowing, so what's left in the rails gets hotter, and turns to vapor. So when you try to start your car about 10-45 minutes after driving it, you might be running lean until you can get the fuel flowing again. This is kind of a P.I.T.A. but from what i understand there's nothing to do about it except maybe insulate the fuel rails. I think winter gas (more volatile) in warmer weather can exacerbate the problem.

I think there's supposed to be a return fuel sender that sends fuel back to the tank. I guess if there was a way to stop this when the car turns off you might keep pressure in the lines, maybe stopping the gas bubbles from forming. That sounded like too much to me. If I know about the issue, I can just be prepared for the issue and handle it better. For instance: Since the fuel pump runs for a second when you turn the key to ACC, you can do this a few times to increase fuel pressure before turning the key all the way to start the car.

I am not a mechanic, but this is just one of many things I've learned in this forum. I trust the information is true. Other guys may be able to correct my mis-statements.

Congrats on getting the car home! Now let's see some pictures!
 
#9 ·
What Mike said is pretty well correct. The problem occurs even if vapour doesn't form in the fuel rail. I can be because the hot gasoline flashes to a mixture of gas and liquid as it is discharged through the injectors.

Regardless, with winter fuel, there is a problem. We don't drive our '72 SL in winter, so no big deal except for short period in Fall and Spring when we don't have summer fuel.

I have minimized the problem by increasing fuel pressure to about 34 psig. But this makes car run rich, so I adjusted MPS (Manifold Pressure Sensor) to get back to correct mixture (Need an exhaust gas analyzer to do this).

I had intended insulating my fuel rails, but have not yet. I did polish them so they have a reflective surface - makes them less likely to absorb heat from the surroundings. And they look good :)

One other fix that MB used to suggest, was to purposely let the rail pressure down. Either through a small orifice in the regulator or via a bypass around the regulator. This allowed fresh cooler gas to come from pump when restarting.
 
#14 ·
A decent starting point.

It would be a good idea to pull the valve covers and check the timing chain. If the guides have not been changed they will be metal with a black surface material. If you don't know when the tensioner was last changed I would change it. Look for grooves in the head where the chain might have been hitting. Tensioner and chain stretch are the main failure on the early engines with the metal guides.

The valves probably do need adjusting and the cam oiling tube connectors replaced. You will need either the special valve adjusting tool or a crows foot to adjust the valves. 17MM IIRC.
 
#16 ·
Thanks for your input guys. I will be doing the valve adjust this week as I can hear them clattering on the right rear. Thanks rowdie for the info on the chain guides and tensioner. I will look for any signs of contact when I pull the covers.
The left front fender is a new fender yet to be painted but hey the whole car needs a splash. I spent most of the day today cleaning out and spraying the inner fenders. It was a long day..
 
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