1986 300sl won't stay running

[greg walsh]

Hi,I posted this in the tech. help but since it's an SL,maybe somebody in this section could give me advice. I went to start my car this morning and it ran for about three seconds and died. It's got 25 dollars of gas in it. Last time I was able to drive it I thought it smelled like it was running rich. Could it be a fuel pump? Please help. Greg in Florida.

[nobby]

Originally Posted by greg walsh

Hi,I posted this in the tech. help but since it's an SL,maybe somebody in this section could give me advice. I went to start my car this morning and it ran for about three seconds and died. It's got 25 dollars of gas in it. Last time I was able to drive it I thought it smelled like it was running rich. Could it be a fuel pump? Please help. Greg in Florida.

Do you hear ANYTHING when you first turn the key (before the start position) like a buzz from the fuel pump?

That first 3 seconds sounds like the cold start valve is working which means it is getting fuel.

Maybe it's your FPR....has it ever been replaced? I always carry a spare....it's just a matter of time.

[greg walsh]

Thanks for the reply. I took off the aircleaner and noticed some unconnected vacuum lines. I think one was going to the vacuum assist euro headlights it once had[ before I got it] and another coming from what looks like a fuel filter on top by the fuel distributor. I blocker off the one going to the lights and it started up. I thought that was the problem but now it runs if the lines are connected or not! One thing I did before I messed with any vacuum lines was that I pushed down on the big diaphram to make sure it was working,could that have somehow been stuck?The cold start valve,is that the thing that looks like a filter and does it have to have vacuum going ti it? Thanks!

[nobby]

Originally Posted by greg walsh

from what looks like a fuel filter on top by the fuel distributor.

Without a PICTURE I will assume it is a fuel pressure damper / regulator.
Does it have a fuel line in and out with a vacuum nipple on it? If so the vacuum nipple should have a vacuum line into some passive vacuum connection on your air cleaner housing, I'm guessing. That vacuum line is only to reroute a fuel leak if the regulator fails.

Originally Posted by greg walsh

The cold start valve,is that the thing that looks like a filter and does it have to have vacuum going ti it? Thanks!

Cold start valve is basically another injector mounted on the intake opened by an internal solenoid, triggered by an electrical charge if engine temps are at a certain low temp.

[meltedpanda]

your movement of the pressure plate may have solved your issue

Remove air filter and gently apply pressure to the sensor plate. it should float back up , If the plate does not move, there may be an internal problem. or Look for any possible cause for the binding
externally.