bml320

I have a 98 ML320 with 70K miles. When the weather gets cooler (below around 50F/10C), two different starting problems sometimes occur. They may occur together or independently, but have never happened in warmer weather.

(1) The engine will start but then immediately die (within a half-second or so). I can then start it again and it runs fine. I have discovered that if I turn the key to the ON position and then fully depress the gas pedal once before turning the key to the START position, the problem doesn't occur. I also notice when doing this that the fuel gauge initially shows empty but then moves to the actual level after I depress the gas pedal. Anyway, this gas pedal routine seems to avoid the problem and I can live with that, but I would like to know what might cause this behavior and whether it might indicate that some part is on the verge of failing.

(2) I turn the key to the START position but the vehicle doesn't even think about starting. Any electrical devices (radio, etc.) that are turned on will work, but the starter doesn't turn at all, as far as I can tell (no sounds, vibrations, etc.). If I return the key to the OFF position and then try to start again, the engine fires right up, as though nothing was wrong; the cranking is not at all sluggish, nor is any extra cranking required. Usually, the no-attempt-to-start behavior only occurs on the first key turn, but on rare occasions it has occurred on two or three consecutive key turns (when it was very cold -- below 0F/-18C). So far, it has always started eventually, but it's a little nerve-wracking when I initially turn the key and nothing happens.

If anyone can shed any light on either of these problems (especially the second) I would appreciate it.

sosh

The first of your issues could be fuel pump related. Remember that the fuel level sensor is integral with the pump.

mihir_d

First turn on a cold start, the engine sometimes hesitates...to the point, where, I have to give up.

Second attempt, invariably fires fine...like a champ.

Only happens on cold starts...never on a warm engine.

No OBD fault Codes...I hadn't changed the ignition wires at 100K miles, just the plugs..I am suspecting those are the problem (Fuel pump and CPS were replaced at 120k miles)..

Will get those replaced in spring and am hoping, the problem will disappear, but I have an expert german mechanic here locally. He is confident, he can pin point the cause if I leave it overnight with him, before jumping into any conclusions...

Will post the findings in spring, when I get to repairing it. For now, its just a mild annoyance.

The 2nd attempt success like champ is confusing me as well..

I am guessing, the ECU probably records what was not right in the first attempt, and compensates accordingly for the 2nd try....

mihir_d

I would try swapping out the starter relay...the starter relay has a lot of hard work cut out for it through its lifetime...it is possible, it is aging away...

bml320

Thanks for the replies.

Sosh, any idea why depressing the gas pedal with the engine off would "wake up" the fuel pump/sensor? And why it's only necessary when the temperatures are low?

Mihir d, is the starter relay located on the starter, or somewhere else? Is there any way to test it without replacing it?

sosh

Sorry I do not know why or how. Perhaps you should have a dealer look at this issue before you are stuck where and when you dont want to be. Early ML fuel pumps and quantity gages were an issue when the cars were new. I do know that there have been improvements made in the fuel pumps.

mihir_d

Along with all the other fuses/relay. There is also a fuel pump relay that you could try swapping out, although your fuel related starting symptom do not indicate that the relay could be The problem..