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so i go out for a nice 2 hour cruise around town. Car is running fine. No check engine lights. Pulls real hard. Life is great. Well i wake up in the morning and the car wont start. It cranks but does not even try to start. I decided to check my ignition and fuel pump fuses and everything seems to look good. Did some online searching and saw the crank position sensor seemed to be a problem for some people so i went ahead and replaced it. unfortunately that was not the issue. I pressed the nipple on the fuel rail and no fuel sprayed out. Worried, i rip out my backseat and put my ear to the top of the fuel tank. I can clearly hear the fuel pump in the rear passenger area priming when i turn the key to the on position. So i hooked up a fuel pressure gauge and of course there is no fuel at the rail at all. I just had the recall done on the car about 8-9 months ago for the fuel tank and im pretty positive the fuel pump, filter and lines were replaced. So im stumped as to why there is no fuel pressure when i can hear my fairly new pump turning on?! Someone Please help!
Did you listen to both pumps for priming while key is in position two? most likely a pump issue if fuses/relays were checked. CPS is typically a failure that occurs when the engine is warm/hot. Pump can be a DIY, see below, write up is pretty good. Definitely troubleshoot a bit more before going ahead with it. Dumb question but, is there gas in the tank?
For the OP, when the dealer replaces the fuel tank, the fuel pump relay and socket is not touched as they are not considered a part of the tank.
First thing I would do is pull the cover off the inside of the trunk on the fuel filler cap side and inspect the relay. Multiple instances where the relay melts and will only work for a few seconds to a few minutes. If the relay is bad, look for my post on replacing the stock 40-amp relay with a 70-amp relay with larger connectors.
Depending upon year you will find one to three relays. 2003 and 2004 had fuel pump relay only. Early 2003 model had the relay with integral fuse; later models had the fuse separate from the relay. In 2004/2005, the air pump relay was moved into the trunk next to the fuel pump relay. After 1 June 2005, the MY2006 has two fuel pump relays plus one air pump relay. Amazingly, the 2006 version doesn't melt fuel pump relays like the earlier versions.
PS. While you have the metal cover off over the fuel pumps, if the pumps part number ends in 00-00, ensure the dealer installed the adapter cable. With the 00-00 pumps, power should be on pins 2 and 3; look for the striped wires. I'm personally aware of at least 4 members of this forum who had the tank and pumps replaced but the adapter cable was not installed. In that case, one pump runs backward, fuel pressure drops at high rpms, and potential engine damage/destruction can occur.
For the OP, when the dealer replaces the fuel tank, the fuel pump relay and socket is not touched as they are not considered a part of the tank.
First thing I would do is pull the cover off the inside of the trunk on the fuel filler cap side and inspect the relay. Multiple instances where the relay melts and will only work for a few seconds to a few minutes. If the relay is bad, look for my post on replacing the stock 40-amp relay with a 70-amp relay with larger connectors.
Depending upon year you will find one to three relays. 2003 and 2004 had fuel pump relay only. Early 2003 model had the relay with integral fuse; later models had the fuse separate from the relay. In 2004/2005, the air pump relay was moved into the trunk next to the fuel pump relay. After 1 June 2005, the MY2006 has two fuel pump relays plus one air pump relay. Amazingly, the 2006 version doesn't melt fuel pump relays like the earlier versions.
PS. While you have the metal cover off over the fuel pumps, if the pumps part number ends in 00-00, ensure the dealer installed the adapter cable. With the 00-00 pumps, power should be on pins 2 and 3; look for the striped wires. I'm personally aware of at least 4 members of this forum who had the tank and pumps replaced but the adapter cable was not installed. In that case, one pump runs backward, fuel pressure drops at high rpms, and potential engine damage/destruction can occur.
thanks for the help everyone.
Bbirdwell thank you so much for the reply. The link you gave me isnt working but i assumed it was the link for one of your older threads and have looked through a couple. Sure enough i have the new pumps and the old connector! Iv been driving like that for the past year and have put 40,000 miles on it! Does this sound like what my problem could be linked with?? Im worried about my engine now i hope i was not leaning out up top since i drive my car very.. very hard.
Definitely overheating. With the wires on the connector melted like that it is a good bet the relay looks like this:
I recommend re-pinning the connector on the OEM harness; remove pins, cut the wires back, crimp on new pins and insert into connector (new one if possible. use an extra adapter cable for a connector if possible). The dealer screwed up; the parts listing shows multiple additional parts to be installed with the 00-00 fuel pumps. Don't forget the little piece of foam that goes on the underside of the metal cover over the fuel pumps; this is intended so, when the insulation overheats and falls off the wires, the conductors will not short out against the underside of the metal lid. You certainly need the adapter cable. The pins can be purchased from the dealer. If you are not confident with this, you will need to take it to the dealer or an indy.
I'd be willing to also be that if you remove the connector from the fuel pumps, the plastic around the contacts will be burned and melted. Again, read the full thread. You can recover from this; is just depends on how it will cost you and if the dealer will acknowledge they screwed up when the tank was installed. You could always try negotiating with them for a reduced price for them to perform the repair since their repair work could have resulted in a blown engine.
FWIW, you make #5 on this forum of whom I am aware the adapter cable was not installed when the fuel tank was swapped.
PS. plastic melts around 300 F so you have an idea how hot the relay gets....
bbirdwell, you can count number 6. I had this issue. I, however, did not have any issues with melting plastic or burnt relays. Instead, my AFR was just totally out of whack and unsafe. Didn't even realize it until getting the car on the dyno.
Definitely overheating. With the wires on the connector melted like that it is a good bet the relay looks like this:
I recommend re-pinning the connector on the OEM harness; remove pins, cut the wires back, crimp on new pins and insert into connector (new one if possible. use an extra adapter cable for a connector if possible). The dealer screwed up; the parts listing shows multiple additional parts to be installed with the 00-00 fuel pumps. Don't forget the little piece of foam that goes on the underside of the metal cover over the fuel pumps; this is intended so, when the insulation overheats and falls off the wires, or the conductors will not short out against the underside of the metal lid. You certainly need the adapter cable. The pins can be purchased from the dealer. If you are not confident with this, you will need to take it to the dealer or an indy.
I'd be willing to also be that if you remove the connector from the fuel pumps, the plastic around the contacts will be burned and melted. Again, read the full thread. You can recover from this; is just depends on how it will cost you and if the dealer will acknowledge they screwed up when the tank was installed. You could always try negotiating with them for a reduced price for them to perform the repair since their repair work could have resulted in a blown engine.
FWIW, you make #5 on this forum of whom I am aware the adapter cable was not installed when the fuel tank was swapped.
PS. plastic melts around 300 F so you have an idea how hot the relay gets....
ohh my.... Thanks again for your reply. I looked at my relay and to my surprise everything was fine! The white plastic looked a slight brown but not like anything had melted. I wanted to check the fuel tank for possible lines that would have fallen off and sure enough when i pull off the connector to the pump its burnt and melted! What are my options? Do you think they will fix this? This is definitely their fault. I had no idea the connector was not changed.
Dang! Davednconfused makes six! I wonder if Plutoe knows how to get this systemic error into the Mercedes repair system so any fuel tank replacement requires acknowledgement of installation of the adapter cable on the fuel pumps? Plutoe? Plutoe? Plutoe?
For Gsean430, the harness issue can be solved relatively cheaply. (The pumps and filter not so much but that is another matter.) Purchase two each of the adapter cables; one for the final installation, one to use as a donor to repair the OEM harness in the car. Cut the adapter cable so as to remove the "fuel pump" end of the harness, call it 3" to 5", each wire cut 1/2" shorter/longer than the one next to it. On original harness, cut the wires one at a time. Slide shrink tubing over the wire. Use a copper crimp sleeve (14 gauge) and crimp the ends of the wires together (done properly, it will micro-weld the wires to the sleeve). Slide the shrink tubing over the sleeve and heat it so as to shrink the insulation onto the sleeve. Do this one at a time. Then use a final wrap of electrical tape around each individual wire and then the entire harness. Insert the second adapter cable in between the newly repaired harness and the fuel pumps and that part of the system is good to go.
Now, if pumps and filter need to be replaced, do so. Inspect the relay and socket in the trunk. If melted or showing signs of damage, upgrade from the 40-amp to the 70-amp relay and socket as shown in my thread. Or use the three-relay circuit as shown in the schematic I posted.
I would argue one pump was carrying the full load due to the failure of the technician to install the adapter cable. One pump is forced to supply all the fuel because the other is running backwards, The melted plastic tells you which pump was wired correctly and your previous photo shows this to be so. Pins 3 and 4 were correct and carrying the full load of both pumps and melted.
Negotiation time. I would offer to pay the cost of the two adapter cables and the technician time to re-wire the melted pins/connector if the dealer will pick up the cost of the fuel pumps and filter. If not, you can do it yourself but it will run you ~$1000 in parts. I see no reason a qualified technician could not perform the work in four labor hours or less.
ohh my.... Thanks again for your reply. I looked at my relay and to my surprise everything was fine! The white plastic looked a slight brown but not like anything had melted. I wanted to check the fuel tank for possible lines that would have fallen off and sure enough when i pull off the connector to the pump its burnt and melted! What are my options? Do you think they will fix this? This is definitely their fault. I had no idea the connector was not changed.
Even if the relay looks fine, replace it. And if you can upgrade it, do so. Otherwise this will just happen again. One of the weakest, if not *the* weakest areas in the 2003 to 2005 E55 vehicles. The MY2006 manufactured on or after 1 June 2005 have the dual relays which reduce the problem to a manageable level.
"I'm personally aware of at least 4 members of this forum who had the tank and pumps replaced but the adapter cable was not installed"
Bbirdwell, I would be number 7 then I guess. Had my pumps replaced in the CLS55 also without adapter cables. Took us a while to figure out wtf was going on... Thanks Mercedes
Even if the relay looks fine, replace it. And if you can upgrade it, do so. Otherwise this will just happen again. One of the weakest, if not *the* weakest areas in the 2003 to 2005 E55 vehicles. The MY2006 manufactured on or after 1 June 2005 have the dual relays which reduce the problem to a manageable level.
Thanks so much for the info bbirdwell. I would have never found this issue if you had not replied to my thread. Im going to the dealership tomarrow i already talked with them about it. They didnt have much to say but was already willing to cover the towing fee’s. Ill keep u guys updated with what going on.
Originally Posted by C32owner
"I'm personally aware of at least 4 members of this forum who had the tank and pumps replaced but the adapter cable was not installed"
Bbirdwell, I would be number 7 then I guess. Had my pumps replaced in the CLS55 also without adapter cables. Took us a while to figure out wtf was going on... Thanks Mercedes
If you dont mind me asking, What exactly was going on and how was it resolved?? Kinda curious to know what happend on your end so i know what to expect tomarrow lol
Thanks so much for the info bbirdwell. I would have never found this issue if you had not replied to my thread. Im going to the dealership tomarrow i already talked with them about it. They didnt have much to say but was already willing to cover the towing fee’s. Ill keep u guys updated with what going on.If you dont mind me asking, What exactly was going on and how was it resolved?? Kinda curious to know what happend on your end so i know what to expect tomarrow lol
Your issue is strange indeed as I believe if it was just your adapter cables not being installed your car would not have run from the moment the new pumps were installed, ie: I don't believe you would have been running these months like that. When my new pumps were installed without the adapter cable the car would prime and start but after a few seconds it would die, loosing fuel pressure at the rail, so there was no way of driving it. Only once we figured out the polarity was incorrect on the pump did that issue get resolved simply. This was after going through a lot of tedious fault finding digging into fuses, relays blockages etc... I'm guessing you have connected up a fuel pressure gauge to your fuel rail and checking fuel pressure with just ignition on then start her up and monitor what's happening?
My car ran fine without the adapter cable. Only way I knew was AFR's were in the 13-14 range under full throttle. Swapped pins after reading Barry's post and back to normal.
Originally Posted by C32owner
Your issue is strange indeed as I believe if it was just your adapter cables not being installed your car would not have run from the moment the new pumps were installed, ie: I don't believe you would have been running these months like that. When my new pumps were installed without the adapter cable the car would prime and start but after a few seconds it would die, loosing fuel pressure at the rail, so there was no way of driving it. Only once we figured out the polarity was incorrect on the pump did that issue get resolved simply. This was after going through a lot of tedious fault finding digging into fuses, relays blockages etc... I'm guessing you have connected up a fuel pressure gauge to your fuel rail and checking fuel pressure with just ignition on then start her up and monitor what's happening?
Okay update! Thanks for the reply everyone all your input has helped tremendously. They knew they were at fault. I even put everything back to see if they would come up with some BS but they didnt. they said the connector melted and the fuel pump burnt out because they had not installed the right connector with the fuel pump. And they will replace it all free of charge. All i can do now is hope they install this correctly.
My car ran fine without the adapter cable. Only way I knew was AFR's were in the 13-14 range under full throttle. Swapped pins after reading Barry's post and back to normal.
Hmmm interesting this case. I must have some other stuff going down then as well.. Only difference is my car is the CLS but I doubt that has much to do with it...
CLS is the same. When I bought fuel pumps, I only ordered 1 adapter cable. It turned out to be for the sensor side, so I just swapped two pins in the plug.
09-01-2018, 03:56 AM
