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Pete, Mercedes Mechanic
Category: Mercedes
Satisfied Customers: 29112
Experience:  Over 15 years experience as a Mercedes dealer technician
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I have a 2000 ml320 that is hard to start. If it sits

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I have a 2000 ml320 that is hard to start. If it sits overnight it might start on the 3rd or 4th try

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Have you had the fault codes checked to see if any codes are set in any of the computers in the vehicle at all?

Let me know,thanks Pete

Customer: replied 1 month ago.

Unfortunately I am unable to place a call on this here myself but others see you have requested a call and may still call on this here.I can however continue here.

Was the pressure tested when it would not start and is this the pressure you had when it would not start?

Customer: replied 1 month ago.
55 psi
Customer: replied 1 month ago.
When engine starts it reads 58psi

If you unplug the mass air flow sensor with the key off then turn on the key when this happens and try and start it will it start then?Keep in mind the key has to be off before unplugging this sensor.If it does start then the mass air flow sensor needs replaced which is a common component to cause this issue here.

This isnt a crank sensor issue since you have spark and injector pulses and your fuel pressure is o.k.Since it runs good when it does start then this isnt an excessive back pressure fault either due to the common restricted catalytic converter issue.But I have seen the mass air flow sensor cause a false signal needing replaced for this issue here.I would check this and let me know.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated ( should be a link to click on here or above).You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 1 month ago.
Ok Pete my problem is it may not act up until later today or tom. Once it starts it seems to run fine for a period of time. Can i get back to you

No problem.

Just come back here to this post and reply when your ready.

Thanks Pete

Customer: replied 1 month ago.
Thanks Pete and i will get back i really need to clear this up. Thanks again

Your welcome

Pete and other Mercedes Specialists are ready to help you
Customer: replied 1 month ago.
Hi Pete no start observed. Disconnect maf with key off still no start

Have you tested spark at at least 4 spark plugs/cylinders as well as injector pulses?

Customer: replied 1 month ago.
Hi Pete just got back to this ml. Checked spark on more cyls. Seems very weak almost no spark at times.When it does run tester shows strong spark. Injecter pulse never goes away.
Customer: replied 1 month ago.
Checked spark on more cyls. Seems weak almost no spark at times. When it does run tester shows strong spark. Injector pulse never goes away.

I apologize for the delay as I have been offline the past few days.

If you wiggle the wiring harness leading to the coils when you have weak spark does spark then come back at all?