I have a 98 ML320 - it will crank and run for 1 second and then die. I cannot get it to run any longer than that. I used the 5 second test(turn key to on position for 5 seconds and then turn key) to eliminate any key issues - the key works(my older 2 keys will not pass this test). I pulled 2 codes - p0110 and p0204. I've read a lot about cps sensor, maf, fuel pump. Wanted to know which way to go first. Any ideas?!?

The code p0 110 could be causing a problem. Intake air temp sensor is part of the mass air flow sensor.

P0 204 is very specific..faulty injector citcuit on cylinder #4.

Also that type of condition can be caused by a vacuum or air intake leak between the MAF sensor & the engine.

Have you tried starting with the MAF disconnected?

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I disconnected the maf - it still won't stay running for more than 1 second.

Just checked the fuel pressure on the fuel rail - holding steady at 50 psi. Does that sound right?

I tried to start the vehicle again - it ran for a couple of seconds - the tachometer moved. So I guess the cps is good?

I left the pressure gauge on the fuel line for 2 hours. It fell from 52 psi to 43 in the first 1/2 hour. Down to 36 psi in the next 1/2 hour. Then down to 30 psi in the next hour. Do I have a fuel pump or fuel regulator problem?

JessiesM1,
I am having the same symptoms (as listed in your original post) on my 1998 ML320 with 205k miles which I have owned since new. What finally corrected the problem for you?
Thanks,
Ken

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2014 E250 Bluetec 4-Matic
2014 GL350 Bluetec 4-Matic
1996 Chevy Tahoe 4 x 4
2009 ML350 (sold)
2005 SLK350 (sold)
1999 E300 Turbodiesel (sold)
1998 ML320 (sold)
1991 300D 2.5 Turbodiesel (sold)

Did this problem just start one day when you cranked it up? or after running for only a few minutes...???

Arnold,
Thanks for the follow-up. The problem started after the headlights were left on overnight and the battery was fully discharged. After fully charging the battery the vehicle would start momentarily then shut down immediately. I figured it out last night (after the flatbed tow provided by AAA). Using another key, all worked fine. Problem is in the key programming which I have to get corrected but the vehicle runs fine.
Thank you,
Ken

__________________
2014 E250 Bluetec 4-Matic
2014 GL350 Bluetec 4-Matic
1996 Chevy Tahoe 4 x 4
2009 ML350 (sold)
2005 SLK350 (sold)
1999 E300 Turbodiesel (sold)
1998 ML320 (sold)
1991 300D 2.5 Turbodiesel (sold)