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HAve a clk550, had both fuel pumps replaced by a Mercedes…

Customer Question
HAve a clk550, had...

HAve a clk550, had both fuel pumps replaced by a Mercedes specialist, on two separate occasions wen to start the car, it turns but does not fire. Took it back to the garage and they told me they have replaced the relay. what is causing this?

Mechanic's Assistant: How many miles are on the car? Has the car been starting normally?

132,000 kms, yes been starting normally

Mechanic's Assistant: What year is your CLK550?

2007

Mechanic's Assistant: Are you fixing your CLK550 yourself? What have you tried so far?

Been taking it too the garage, they said it could be the ecu

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Replaced engine fan as its been running high, but still experiencing the same thing with the fan

Submitted: 28 days ago.Category: Mercedes
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Customer reply replied 28 days ago
Also, the keyless go is not working on the door handles, I removed the fuses to reset but nothing, works on the gear stick.
Customer reply replied 28 days ago
I changed the relay after the second time but, I could not start it; so not sure what they did to start it, maybe an ecu reset????
Customer reply replied 28 days ago
I plugged in the carsoft reader and it highlighted the relay as the issue.
Customer reply replied 28 days ago
They have advised me to change the ECU at a cost of $3000
Answered in 2 days by:
3/30/2018
Mercedes Mechanic: Danny, ASE Certified Technician replied 26 days ago
Danny
Danny, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 4,282
Experience: ASE Master Technician with L1 advanced engine performance, VW Certified, former US Army mechanic
Verified
Anytime that you change the fuel pump you should change the relay so that should have been done initially.The reason is that when the pump fails it causes an excessive amperage draw that causes damage to the relay and you to the way electricity works if you don't replace the relay when you put the new pumps in you can still have an issue where now the new pumps aren't getting the proper amount of voltage which causes them to again draw high amperage and then that can ruin the brand new pumps.Can you please give me the actual fault code numbers that the vehicle has in memory. I would be extremely worried about trusting the recommendations of a scan tool like that because it's a generic recommendation that's not even based on what type of vehicle you drive it's more important to just know what the actual fault code number is.So I'm a little bit confused your story kind of sounds like after they replaced the relay it was starting normally again, so did it start failing to start again? Or what is the exact problem now?Who told you to replace the cooling fan because it was running on high? That's generally caused by a faulty coolant temp sensor or cooling system malfunction that is in memory.When the engine cranks but does not fire does the tachometer show that the engine is running at a couple hundred RPM? The most common thing that's going to cause a crank with no start would be a crankshaft position sensor that is faulty, when the engine computer doesn't that the engine is spinning due to a faulty crank position sensor it will shut the fuel pump relay off and it will stop pulsing the fuel injectors and cut the coils off as well. That generally will throw a fault, however occasionally it doesn't.I would probably start with the crankshaft position sensor, and then I would investigate whether the ignition switch is faulty.Diagnosing sporadic deficiencies like this can be very difficult if the shop can't verify the concern, the best course of action would be if you knew how to use a voltmeter then next time that it wouldn't start for you you could actually test and see if the ignition switch is out putting the proper voltages on the proper wires, ignition switches have multiple circuits so it's possible that even though the crank signal is being sent out of it it's actually the starter that it's not powering up the wires necessary to power the fuel pump relay and the fuel pump relay Powers the injectors oxygen sensors and most of the other sensors and actuators necessary to run the engine.If I've answered your question to your satisfaction please remember to hit accept next to my name because that's the only way I get paid.If you need any further assistance please don't hesitate to ask, you can ask follow-up questions even after accepting.
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Danny
Danny, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 4,282
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Experience: ASE Master Technician with L1 advanced engine performance, VW Certified, former US Army mechanic

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