Cranks Longer on First Attempt Alwnays
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GLC300
Cranks Longer on First Attempt Alwnays
Good afternoon,
Every time I start my car, after sitting for some time, it takes longer than it should to start. If I shut it off and retry, it's instant. After an hour, it is back to taking longer to start, sometimes up to 7 seconds of cranking. Put a new battery (did the registration) and a new auxiliary battery, as I was getting a message. No other codes exist when I connect it to my scanner. Runs fine and has never not started (yet). At this point, I am thinking fuel pump assembly in the tank and feel as though it is losing its prime or pressure as it sits, not sure if there is a stuck valve or something. First time owning a Benz and I love it, besides this aspect. Took it to a local shop that supposedly works on European stuff, and they noticed it took longer to start, but found nothing on the scanner, and should take it to the dealer. I can do the installation myself if I knew the issue, but I don't want to just start bolting on random parts. It's a 2016, btw, with 147km on it. I can't really hear the pump much, but I'm not sure what to be listening to, and I have pressed the button twice, not starting it, and waiting 30 seconds for the pump to build pressure, but I am getting mixed results.
Has anybody had similar situations?
Thank you very much for reading.
Every time I start my car, after sitting for some time, it takes longer than it should to start. If I shut it off and retry, it's instant. After an hour, it is back to taking longer to start, sometimes up to 7 seconds of cranking. Put a new battery (did the registration) and a new auxiliary battery, as I was getting a message. No other codes exist when I connect it to my scanner. Runs fine and has never not started (yet). At this point, I am thinking fuel pump assembly in the tank and feel as though it is losing its prime or pressure as it sits, not sure if there is a stuck valve or something. First time owning a Benz and I love it, besides this aspect. Took it to a local shop that supposedly works on European stuff, and they noticed it took longer to start, but found nothing on the scanner, and should take it to the dealer. I can do the installation myself if I knew the issue, but I don't want to just start bolting on random parts. It's a 2016, btw, with 147km on it. I can't really hear the pump much, but I'm not sure what to be listening to, and I have pressed the button twice, not starting it, and waiting 30 seconds for the pump to build pressure, but I am getting mixed results.
Has anybody had similar situations?
Thank you very much for reading.
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From: New Orleans Area
2015 E400 Sedan
check fuel pressure at rail. with key off in the AM before you start.
Then once you get running watch how high it goes...
Then turn off and watch gage to see if it stays steady or leaks down.
Sometimes as car sits the fuel system has an internal leak so pressure drops in rail...
This means when you start the fuel pump has to run longer to get pressure up to where i needs to be.
Then once you get running watch how high it goes...
Then turn off and watch gage to see if it stays steady or leaks down.
Sometimes as car sits the fuel system has an internal leak so pressure drops in rail...
This means when you start the fuel pump has to run longer to get pressure up to where i needs to be.
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11 E550, 16 AMG GTS, 13 S550
This is not very helpful but it's a known GLC300 thing. There is not a definitive answer thus far that I can find.
https://www.google.com/search?q=glc3...h=1285&dpr=1.5
https://www.google.com/search?q=glc3...h=1285&dpr=1.5
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Amsoil Independent Dealer #7236674
Thread Starter
Junior Member
Joined: May 2025
Posts: 15
Likes: 2
GLC300
check fuel pressure at rail. with key off in the AM before you start.
Then once you get running watch how high it goes...
Then turn off and watch gage to see if it stays steady or leaks down.
Sometimes as car sits the fuel system has an internal leak so pressure drops in rail...
This means when you start the fuel pump has to run longer to get pressure up to where i needs to be.
Then once you get running watch how high it goes...
Then turn off and watch gage to see if it stays steady or leaks down.
Sometimes as car sits the fuel system has an internal leak so pressure drops in rail...
This means when you start the fuel pump has to run longer to get pressure up to where i needs to be.
What would be the cause of the fuel pressure loss? Could it be any part of the fuel system? Or a particular part, like the fuel pump assembly, is more likely to be it?
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'21 AMG53 wDPP & ARC, 19 GLC300 - Former-03 C240,2 ML BlueTecs,20 GLE450 E-ABC,15 Cayenne D,17 Macan
On one of my cars, it's a check valve. On another, it's a check valve contained in the fuel pump. Both of those are VW's. Both also have a over-pressure relief valve that can be weak.
May not apply to a GLC, but that's the gist of troubleshooting.
Need the correct procedures.
MBWorld Fanatic!
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From: New Orleans Area
2015 E400 Sedan
Fuel pressure leak down causes due to leaks from one or more of:
- Fuel injector
- Fuel Lines
- Pressure regulator(s)
- Fuel pump
- anything really between pump and injectors.
- Fuel injector
- Fuel Lines
- Pressure regulator(s)
- Fuel pump
- anything really between pump and injectors.
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check fuel pressure at rail. with key off in the AM before you start.
Then once you get running watch how high it goes...
Then turn off and watch gage to see if it stays steady or leaks down.
Sometimes as car sits the fuel system has an internal leak so pressure drops in rail...
This means when you start the fuel pump has to run longer to get pressure up to where i needs to be.
Then once you get running watch how high it goes...
Then turn off and watch gage to see if it stays steady or leaks down.
Sometimes as car sits the fuel system has an internal leak so pressure drops in rail...
This means when you start the fuel pump has to run longer to get pressure up to where i needs to be.
Hard to say without following a step by step procedure to isolate culprits.
On one of my cars, it's a check valve. On another, it's a check valve contained in the fuel pump. Both of those are VW's. Both also have a over-pressure relief valve that can be weak.
May not apply to a GLC, but that's the gist of troubleshooting.
Need the correct procedures.
On one of my cars, it's a check valve. On another, it's a check valve contained in the fuel pump. Both of those are VW's. Both also have a over-pressure relief valve that can be weak.
May not apply to a GLC, but that's the gist of troubleshooting.
Need the correct procedures.
I want to ask OP: Does the long crank still happen when you have foot off the brake and press the ignition button twice (so basically key in position 2 in essence) into accessory mode, then, wait like 10 seconds for the fuel pump to do its thing, Once done, foot on the brake while still in accessory mode, and press the ignition button again, does it still do long cranks? What is the ambient temperature? Does it do long cranks only when in cold temperatures or when the outside temperature is warm as well? If possible also record a video of the cranking.
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GLC300
Sounds like a concern for sure.
I want to ask OP: Does the long crank still happen when you have foot off the brake and press the ignition button twice (so basically key in position 2 in essence) into accessory mode, then, wait like 10 seconds for the fuel pump to do its thing, Once done, foot on the brake while still in accessory mode, and press the ignition button again, does it still do long cranks? What is the ambient temperature? Does it do long cranks only when in cold temperatures or when the outside temperature is warm as well? If possible also record a video of the cranking.
But hypothetically let’s say it’s losing fuel pressure, what is there to be done, if no Schrader valve, is it needing a scanner to watch the pressure after the engine is turned off? As the individual mention earlier there is a lot of points it could leak at and maybe too difficult for a non-technician like myself. There wouldn’t happen to be spots to plug in a gauge and watch it manually?
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I can get a video tomorrow morning after letting it sit over night, I clicked it twice and waited 10 seconds before and have not noticed a difference too much. Temperature doesn’t really seem to make much of a difference right now between 6-18 Celsius a day.
But hypothetically let’s say it’s losing fuel pressure, what is there to be done, if no Schrader valve, is it needing a scanner to watch the pressure after the engine is turned off? As the individual mention earlier there is a lot of points it could leak at and maybe too difficult for a non-technician like myself. There wouldn’t happen to be spots to plug in a gauge and watch it manually?
But hypothetically let’s say it’s losing fuel pressure, what is there to be done, if no Schrader valve, is it needing a scanner to watch the pressure after the engine is turned off? As the individual mention earlier there is a lot of points it could leak at and maybe too difficult for a non-technician like myself. There wouldn’t happen to be spots to plug in a gauge and watch it manually?
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Thread Starter
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GLC300
Since you mentioned the 43, I was reminded of this thread: https://mbworld.org/forums/c450-c43-...ld-starts.html
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GLC300
I’m starting to lean towards installing this, probably not a good idea to get one off Amazon? My thinking is a check valve that’s integrated into this pump maybe causing my issues? I’m gonna call the dealer to price one shipped to me.
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GLC300
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Thread Starter
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GLC300
Sounds like a concern for sure.
I want to ask OP: Does the long crank still happen when you have foot off the brake and press the ignition button twice (so basically key in position 2 in essence) into accessory mode, then, wait like 10 seconds for the fuel pump to do its thing, Once done, foot on the brake while still in accessory mode, and press the ignition button again, does it still do long cranks? What is the ambient temperature? Does it do long cranks only when in cold temperatures or when the outside temperature is warm as well? If possible also record a video of the cranking.
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Thread Starter
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GLC300
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https://youtube.com/shorts/ozFTsW5ZJ...r-fjRt_78bbs7f
there’s the link, hopefully brings u to the short. For the starter do you mean just like the physical condition of it?
there’s the link, hopefully brings u to the short. For the starter do you mean just like the physical condition of it?
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Junior Member
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GLC300
yeah I turn it off when I get in 90% of the time, other than that I stop, it activates, then I turn it off lol.
