no start

[david smith]

help, i have a 94 c220. once in awhile after the car sets it cranks but refuses to start. the time it sets doesnt really matter, it could be anywhere from a few minutes to days. could this be the fuel check valve or am i barking up the wrong tree? my son usually drives this car and he waits for the fuel pump to run awhile before he tries to crank it over. at least we think the noise in the back is the pump. he almost always has good luck with this method.

[forp]

Pull the vacuum line off of this, http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1QF0V26SB1UX0O8OB1&year=1994&make=MB&model=C-220-001&category=All&part=Fuel+Pressure+Regulator

It should be easily visible near the front of the engine. If it's moist with gas, the regulator is bad.
Good Luck, Dan

[ILUVMILS]

Don't forget to check the OVP.

[david smith]

could you please tell me how this relates to my problem, so i can understand better? :

[forp]

Do a search for "OVP". Tons of info on what it is and what it does.
Was the vacuum line to the regulator dry?
Dan

[david smith]

Vacum Line Was Dry, Thanks Also New To Site And M-b

[Arthur Dalton]

Next time condition exist, tap OVP relay lightly with a screwdriver handle and retry..
If OVP is Siemens brand, just change it

[ILUVMILS]

Originally Posted by david smith

could you please tell me how this relates to my problem, so i can understand better? :

It's simple. The OVP protects some expensive control modules (engine management, ABS, traction control, etc.) from being damaged by high voltage conditions. A typical over-voltage situation could be caused by a faulty voltage regulator, jump-starting, or reverse polarity. Without OVP, the repair bill would be astronomical. In your case, it sounds like the OVP is intermittently cutting power, or at least lowering the voltage to the engine control module, resulting in the crank/no-start condition. This is a very common problem. Follow Arthur Dalton's advice.

[shandy]

Originally Posted by david smith

help, i have a 94 c220. once in awhile after the car sets it cranks but refuses to start. the time it sets doesnt really matter, it could be anywhere from a few minutes to days. could this be the fuel check valve or am i barking up the wrong tree? my son usually drives this car and he waits for the fuel pump to run awhile before he tries to crank it over. at least we think the noise in the back is the pump. he almost always has good luck with this method.

The noise you hear is the fuel pump and should cut off after about 5 seconds when it has brought the fuel pressure up to normal, if it continues to run afterwards without you starting the engine I would think it is probably worn out and due for renewal.
Although the Seimens OVP relays on these cars are unreliable and should be replaced as a precaution I can't see that being the problem in this case as you say it usually starts when your son lets the pump run for a time.