Cold Start

[BRIAN123]

My 1990 500SL , 107k , never starts the first time in the morning. Second time , every time I turn the key VOROOM, starts just fine. When warmed up, one crank is all it needs.
The two tries do not concern me, it is what the future may bring. Is this something I should live with or a warning of a problem down the road? What should keep an eye on ?

[ctaylor738]

Does it fire and die on the first try? Or does it just crank?

Does the outside temperature have an effect?

What happens if you turn the ignition on, but don't crank, turn it off and then crank?

[BRIAN123]

Originally Posted by ctaylor738

Does it fire and die on the first try? Or does it just crank?
just crank
Does the outside temperature have an effect?
no
What happens if you turn the ignition on, but don't crank, turn it off and then crank?

gonna try tomarrow to see if any diffrence, my guess is needs to crank 1 time to start the 2nd time

[BRIAN123]

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Quote:
Originally Posted by ctaylor738
Does it fire and die on the first try? Or does it just crank?
just crank
Does the outside temperature have an effect?
no
What happens if you turn the ignition on, but don't crank, turn it off and then crank?

gonna try tomarrow to see if any diffrence, my guess is needs to crank 1 time to start the 2nd time


I guessed wrong , when cold , turn key not to crank, back to off, then crank, starts fine. What does that tell you ?

[ctaylor738]

Fuel pump relay would be my first guess. My hypothesis is that for some reason it needs a second signal from the ignition to get going.

So I would do a first time crank and have someone put their hand on the fuel pump to see if it vibrates while you're cranking. If it doesn't do anything, replace the FP relay.

If it vibrates, then I would suspect the same sort of thing with the ignition module.

[Cliff Thompson]

I have researched the threads and have the same symptoms with my '91 500 SL. Has anyone else run into this? From a cold start the car will fire but die. Then upon restart it fires fine and keeps running. I have tried just turning the key on then off prior to cranking as suggested but same result. I have new plugs new caps and rotors and new wires along with a new fuel filter. The car runs fine otherwise but this nuisance may get worse. Thanks for the help.