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2001 mercedes c320 fuel pump was in backwards car was

2001 mercedes c320 fuel pump was...
2001 mercedes c320
fuel pump was in backwards car was running fine just didn’t know if i was empty or not. i flipped it around. car started fine gas gauge went up not all the way. i didn’t shit car off i pulled fuse for fuel pump to reset. it did not reset turned car off then it did not start again. did get car to start but running like it wanted to keep on dying and making sucking sound. i put the new fuel pump on and relay and car will not start it sounds like no compression just turns over. i put on computer and got a po450 code. i do t know what is going on car worked fine before.
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Answered in 3 minutes by:
10/16/2017
Pete
Pete, Mercedes Mechanic
Category: Mercedes
Satisfied Customers: 32,616
Experience: Over 15 years experience as a Mercedes dealer technician
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Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

If you loosen the gas cap does it start and run properly then at all?

Let me know,thanks Pete

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Customer reply replied 8 months ago
no pete it won’t start anymore but more importantly it sounds weird turning over like no compression
Customer reply replied 8 months ago
i get the po450 code.

The P0450 is an evap emissions fault code.This is an evap fuel tank pressure sensor fault code.If you connected hoses incorrectly at the tank this can cause this code as well as cause a vacuum in the fuel tank causing this issue here.

The first thing that needs to be done is to check the hose connections at the pump and the tank to make sure nothing was damaged.Make sure all electrical connections are plugged in as well at the pump.If this is all checked or was all checked already and found o.k. let me know.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated ( should be a link to click on here or above).You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

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Customer reply replied 8 months ago
can you tell me what wire i test to see if i have power going to the fuel pump on this car
Customer reply replied 8 months ago
looks like the big brown one. i don’t here fuel pump running and my buddy that i’m trying to help with this did not have fuel sending tight or hoses so that could have made car go into limp mode

The brown wire is a ground to the pump.The red/green wire is power to the pump.Make sure these are all o.k. then have the fault codes cleared out to see if this resolves the issue.

On the passenger side fuel level sender there is the fuel tank pressure sensor.Make sure this is plugged in properly.It is shown below as B4/3.

https://www.dropbox.com/s/zv3afciirjmxxx2/ftp-10-16.gif?dl=0

Let me know if you need anything else and feel free to rate my help here or above ( should be a link to click on ) as this is how I receive credit for my time,this can be done at any time and you can still come back here and reply if needed.Your 5 star rating is appreciated

Thanks Pete

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Customer reply replied 8 months ago
sorry to be a pain. i’m in drivers side i have two plugs on drivers side. small 3 plug and the bigger 4 plug. i have power to little red green wire very dim. i can find power after that can you explain what i should be getting? do i have to turn car over completely to get power because i have no power on any other wires that head over to passenger side fuel pump
Customer reply replied 8 months ago
someone else put the fuel pump on new two months ago it is on passenger sidde.

The fuel pump wire ( red/green wire) should have around 12 volts DC with the key first on the first 2 seconds or when cranking over the engine.

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Customer reply replied 8 months ago
ok the red green wire i’m using a light tester it lights it up. when i connect back to sending unit where does it transfer power to. i get no more power anywhere after i plug in small plug
Customer reply replied 8 months ago
i’m only getting 5 amps

Unfortunately my diagrams are not as complete as I would like.I will have to see if anyone else here has this info to assist further on this.

I will open your question up for others here to see if someone else can assist further on this as there may be others here that may have more info on what to check or do with this issue.I hope you can get this resolved with ease.No need to reply to my last post here unless it is a last resort as it will keep your question locked to me and others will not be able to view it.If you feel you want to continue to work with me on this feel free to reply at any time but keep in mind in some cases it can be difficult to fully diagnose or help repair this without seeing your vehicle.

Thanks Pete

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Customer reply replied 8 months ago
thank you
Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 6,016
Experience: 20 years Master Certified excellent fix rate and have access to factory wiring, and instructions.
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Hello, Lou Here.

checking over your info.

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ok i have a problem with the wiring diagram info you were sent.

the 4 pin connection .

brown is ground.

black wire with green stripe is the fuel pump power .

do you have those 2 wires?

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Customer reply replied 8 months ago
red green is with the small plug with two other wires. i get 5 volts with key on and it stays constant. i was getting no reading out of the plug with the brown and other black wires. i will have to check black with green but it should be with the plug with brown wire correct? i should have 12v for only couple seconds until car is turned over then constant. i get no reading of power for. that 4 plug harness. i replace relay in trunk plus checked number 4 fuses are good. i’m getting no power and car worked fine before hast to be a fuse am i missing one somewhere??

i cannot answer that until you check the wiring i described, i think before you were checking the fuel tank pressure sensor wire.

that is the only 5volt signal you will have back there.

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Customer reply replied 8 months ago
i did check the other black wires in that plug and i got nothing for voltage.
Customer reply replied 8 months ago
i checked number 4 and the relay they seem to be fine i get 12v and the relay is new

ok the fuse is BEFORE the relay so the only way to know if the relay is being activated is to check for power and ground across terminal 1-2 or 85-86 of the relay, not sure what the underside is labeled as.

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but if you jump a wire across where 3-5 or 87-30 are for the relay the fuel pump should get power on the wire i specified.

think it was black with green stripe.

check the connection for burn marks.

the under side of the plate will have the same color wires leading to the pump.

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but with that info you should be good to go.

if you need more help in the morning let me know

have a good night.

Please take a second and click the STARS at the top of the screen to rate my service 5 stars if you feel I have been helpful , rating is just as important to me as your issue is to you. Please request me in the future. Keep in mind that when you rate it does not end our conversation, you can still return here to me for follow up information if needed, Thanks for choosing just answer. Also , if you feel I deserve one , BONUSES are GREATLY APPRECIATED! Thanks again ,
Lou P.
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Lou P. master tech
Lou P. master tech, Mercedes Technician
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