Hello Everyone,

I have a 2000 ML 320, and for months now it will not start on the first attempt. The starter just "times out". However, on the second attempt it will start right up with no problems. Once the engine starts there are no problems. If I turn off the vehicle (after running) and I start it up, it will start up right away. The hard starting will occur if the vehicle sits for 20mins. or longer. There are no codes.
The fuel filter has been replaced (the hard starts were occuring before replacement) and the fuel injectors have been cleaned, flow tested and blueprinted (I highly recommend this service), the fuel pump relay was replaced and the CPS was also replaced. I doubt the fuel pump is bad, I would think if the fuel pump were defective, the vehicle would not start or run at all.
Has anyone experienced anything like this? And if so, does anyone have any recommendations as to what I should look at next before going to the STEALER or mechanic?
Thanks in advance for your help, Happy Holidays everyone!

If the CPS (crank position sensor) hasn't been replaced yet I would suspect it to be failing. Common problem that leaves no codes. My 2 cents.

I had the exact same problem and after replacing the CPS, I had NO improvement. I read some more and found that it could either be the Fuel Pump/Filter or the MAF sensor. I chose to try the MAF first and Voila! The problem was cured and the vehicle now starts on the first try. I found the MAF on EBay for $68.00 which is a great price compared to the $200-$300 that it was priced at other stores online.

Good Luck!

Thanks for the great info!
I finally took the vehicle to the "stealer" $242 later, they claim it was the CPS (even though I already changed it!) so I replaced it with another one and no change!!!
One of the service advisors said that it could be the fuel check valve, which makes sense, but that would require changing the whole fuel pump, so I just may try the MAF and see what happens. BTW, was the MAF you purchased an OEM unit or a Chinese copy that I keep hearing about? Thanks again...

Hello,
My wife is having the same problem now with her 1999 ML320. We purchased it new in 99 and have had absolutely no issues until a couple months ago. The car has 98k on it. It started right after the engine belt idler pulley came apart and we had all that replaced . Coincidence maybe but a week later it sputtered and lost power while going to town and she babied the throttle at lights to keep it from dieing to get it back home. Once home she switched it off and it started and ran fine with no check engine lights coming on during the whole thing. A few days later it seemed to turn over a long time before starting but it would eventually start. Now it's hit and miss wether or not it will start at all. After reading the forum I ordered and replaced the CPS with no change. I have since replaced the fuel filter and hoses with the upgraded parts,still with no improvement. I have changed the fuel pump relay with no results but I did notice one thing when testing the fuel pump relay. If I probe the fuel pump relay fuse it shows the pump receives power for a couple seconds when I turn the key on and then it remains on during cranking when things work correctly. The problem seems to be the probe indicates it receives power late in the crank sequence when it takes a long time to start and power "Blinking" on and off during the times the car will not start. Does this tell you anything that can direct me to the most likely cause ?

Thanks so much for any help.

By description, you most likely have a fuel bleed-off issue.

Either the fuel pump or fuel filter is allowing that bleed-off.

Checking with a pressure gauge at the fuel rail should give you better info on the problem.

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Thanks. Would that cause the power switching on and off at the fuel pump relay though ?