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Matt, Engineer
Category: Mercedes
Satisfied Customers: 20385
Experience:  Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
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Crank but will not start, replace fuel pump, no gas going to

Customer Question

crank but will not start, replace fuel pump, no gas going to the engine
JA: Does the engine turn over? How old is the battery?
Customer: Battery will not hold the charge
JA: What is the model/year of your Mercedes?
Customer: MB 2003 c240
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: replace the pump
JA: Anything else you think the mechanic should know?
Customer: no idea
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Mercedes Mechanic about your situation and then connect you two.
Submitted: 3 months ago.
Category: Mercedes
Customer: replied 3 months ago.
ok so i changed the fuel pump and now is crank but don't start and i see i code MIL
Expert:  Matt replied 3 months ago.


if the battery won't hold a charge then I'd check that the ECU is getting 12V on its fuse with the ignition on as if the battery voltage is below 11V then it will never start

and if it is low then it may be time to replace the battery

Also check that the alternator is actually charging the battery in the car by taking a battery voltage reading with the engine off then another with the engine running. The 2nd reading should be higher than the 1st and climbing steadily. And also check that the alternator is secure to the engine as this provides the ground for the charging circuit and make sure that the engine / gearbox earth strap is secure and the contacts are clean and bright.

if the alternator appears not to be working - take it to a electrical specialist and ask them to test it as sometimes you can replace just the diode pack and this will repair the alternator without requiring replacement

And one last thing is – how old is the battery? – As even good quality ones need replacing every 5 years and faulty battery just won’t hold a charge