tongster

My 1999 ML320 engine stopped while I was driving on the streets and won't restart whether hot or cold. It has about 240k miles and ran like a champ until now. Battery is good. Starter is good. The crank keeps turning over when trying to start the car, but it won't go. Maybe a fuel pump and/or fuel filter problem? I did replace the CPS once about 70-100k ago. Any suggestion on best course of diagnosis? Should I start with changing the CPS, check fuel pressure, etc...? Is there a way to verify if the CPS is working properly? Will this spit out a code? Thanks in advance.

mihir_d

If CPS is the problem, engine normally restarts when cold. Your problem seems to be fuel supply...you can have the pressure on the fuel rail tested to confirm.

tongster

Thanks for the tip. I wasn't sure if the CPS was consistent in that manner. I'll try to look on this site on the diy of checking the fuel pressure. Is there only the fuel pump in the tank or is there another somewhere else? My older VW had a prepump in the tank and a main pump outside underneath.

mihir_d

Fuel pump is in the tank..

Fuel pump has a life of about 120K miles...mine had to be replaced at that time..since you are at 240K miles..it might be time for another fuel pump.

Also, check the fuse and relay for the fuel pump before concluding on the pump itself. The fuses are starting to suffer from oxidation issues with these 15+ year old trucks..and relay malfunction is also not uncommon.

tongster

Someone suggested that if trying to start the car and the tach doesn't is an indicator for CPS problem. Therefore, I tried this method and the tach doesn't budge with the engine cranking, so I guess I need to start with replacing the CPS and go from there. Ordering one from Rockauto for $34 and hope this does the trick. I'm probably going to check the fuel pressure tonight as well just to validate the pump and filter.

mihir_d

I would not advice throwing cheap parts on critical components like the CPS. The CPS is fundamental to ignition and timing. If the non-OE/after market CPS is problematic, it will only add to the mystery of ignition failures and make you possibly replace more unnecessary parts down the road.

Dealer cost for CPS is $135. I think, it is a Bosch unit. If your CPS is at end of life and you intend to keep the truck for long, it is totally worth spending the extra $$$ on such critical sensors. If you still want to save some money, look online and try to find the OE Bosch sensor...I think, you might be able to find it for $100ish..

tongster

The part from Rockauto is a Bosch part # 0261210170 with a 1 notch tab so I guess a really good price. FCPeuro also has this exact same part for $38.

mihir_d

Yeah, I noticed, the Bosch CPS for the W163 is also $37 on Amazon..it just seems they were price gouging all these years..it was hard to find the Bosch CPS for any less than $100 just 2-3 years ago..

Good Luck with your troubleshooting! Failure to start is usually down to 1-3 things...CPS, starter or fuel delivery...other issues would normally throw meaningful DTC codes.

tongster

I changed the CPS with a Bosch part and didn't fix the problem. I should have just checked the fuel pressure first as the reading was 0 pressure with the motor cranking. Ordered a new fuel pump and fuel filter and hopefully it gets the car running by next week.

mihir_d

You did not lose anything by replacing the CPS. At $40, that is inexpensive peace of mind knowing you are good for another 60,000 miles on it.

Don't forget to test the fuel pump relay & fuse before deciding on replacing the pump.

The fuel pump once replaced should be good for 120,000 miles. Again, try & find OEM or OEM supplier fuel pump. Labor to replace & criticality of function of fuel pump is too high. Not worth investing in cheap or used parts.

tongster

Problem solved with replacement of fuel pump and fuel filter. Running strong at 220k miles!
Thanks to all that replied.