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Hey all, I’ve had my E55 since October if 2018, when I bought it with 68k miles. Now sitting at 101k, it’s been a blast, even through some of the frustrating repairs. We’ll probably 8 months ago or more I had an intermittent starting problem that I chalked up to a crankshaft position sensor. The problem wasn’t too bad (shame on me for waiting) and I didn’t replace until last week when I also went through the entire HVAC system.
Fast forward to a successful a/c job and the car won’t start. I filled it to the brim just yesterday and had no issues. So I first checked the pump relays which look perfect, then moved into the rear seat. The driver’s side pump has fuel pooled on top.
My question now is: could the two problems be related? The only reason I am hesitant to believe so is because the car runs flawlessly after startup.
Any ideas? I am at my wits end with this thing after just finishing my last job, just to get in and have the car fail to start. Worst feeling in the world.
The leaking fuel when full is more than likely related to the fuel tank recall. I don’t think the no start is related to the puddling on top of the sender, as both of mine ran fine but still leaked when filling the tank
The leaking fuel when full is more than likely related to the fuel tank recall. I don’t think the no start is related to the puddling on top of the sender, as both of mine ran fine but still leaked when filling the tank
Right. Well recall already done in 2008, but clearly it’s cracked again and leaking.
Nothing visually looks off about the pump or connections but of course the tank is filled to the brim and I can’t pull the housing out without getting gas everywhere. Any ideas on easily siphoning a few gallons out?
I also cranked the car several times and then checked the schrader valve on the passenger side fuel rail and there was nothing. So I’m guessing it’s a pump/sender issue. Although I’m not sure I understand what the sender specifically is.
Connect drain hose to schrader valve on fuel rail (with schrader valve open of course). Remove fuel pump relay. Jumper pins 30 and 87 (See attached). Key to position one. You'll need to drain out about 17 gallons of fuel if full. Gauge should be at three bars or less is my recommendation.
I kept a spare top hat for the fuel pumps but sold the other top hat to another member on the forum.
FWIW, I do not believe the two A/C and no-start are related. Are you getting fuel pressure to the rail? Could you have damaged a harness while under the hood working on the A/C? Any moisture in the front SAM or ECU?
Connect drain hose to schrader valve on fuel rail (with schrader valve open of course). Remove fuel pump relay. Jumper pins 30 and 87 (See attached). Key to position one. You'll need to drain out about 17 gallons of fuel if full. Gauge should be at three bars or less is my recommendation.
I kept a spare top hat for the fuel pumps but sold the other top hat to another member on the forum.
FWIW, I do not believe the two A/C and no-start are related. Are you getting fuel pressure to the rail? Could you have damaged a harness while under the hood working on the A/C? Any moisture in the front SAM or ECU?
Thanks for the info Barry. You helped me with a suspension issue last year; I am also SA based.
I don’t think the A/C is related and I don’t believe I damaged anything or got fluid into the SAM or ECU ( although my SAM does not have the rubber cover you recommended - shame on me).
My starting issue has been intermittent for almost a year, with the car coughing to life. This leads me to believe it is a fueling problem. I have what I believe is an early 2005 MY (summer 2004 production) but it looks like it has the later relays you have previously described that came on later cars.
I suppose it is most likely I have had a leaking fuel pump housing for some time now, and the starting issue is unrelated however it seems it must be a pump issue also. With the back seat cover off and the access covers off, I heard nothing when I cranked the car over. I assumed I would hear them but maybe not?
You should hear the pumps prime for one second when you turn the key from "off" to "run" (position one). After one second, the power to the pumps cuts off until the Motor Electronics see a signal from the CPS indicating the crankshaft is rotating, at which time the pumps are re-energized. If it would help, I wouldn't mind dropping off my in-line circuit tester for the fuel pumps for you to use. It just plugs into the circuit and provides a visual display of voltage and current for each pump. If interested, text me; you should still have my number in your phone.
Alternatively, the fuel hose clamp did not seal the connection or fuel is leaking around the pins for the float signals (unlikely but possible). If the later, clean and use a *very little* bit of epoxy around the pins; let cure prior to reinstalling the connector.
If you have two relays in the trunk, only one is for the fuel pumps on the model year 2005; the other relay power the secondary air injection pump located under the driver's side front bumper. Model year 2006 have three relays in the trunk; two for fuel, one for air.
You should hear the pumps prime for one second when you turn the key from "off" to "run" (position one). After one second, the power to the pumps cuts off until the Motor Electronics see a signal from the CPS indicating the crankshaft is rotating, at which time the pumps are re-energized. If it would help, I wouldn't mind dropping off my in-line circuit tester for the fuel pumps for you to use. It just plugs into the circuit and provides a visual display of voltage and current for each pump. If interested, text me; you should still have my number in your phone.
Alternatively, the fuel hose clamp did not seal the connection or fuel is leaking around the pins for the float signals (unlikely but possible). If the later, clean and use a *very little* bit of epoxy around the pins; let cure prior to reinstalling the connector.
If you have two relays in the trunk, only one is for the fuel pumps on the model year 2005; the other relay power the secondary air injection pump located under the driver's side front bumper. Model year 2006 have three relays in the trunk; two for fuel, one for air.
Thank you very much! Is there any alternative to draining fuel if the pumps aren’t working?
edit: stupid question obviously, I can siphon with a pump. Will report back with findings when I can actually pull everything out!
Last edited by JakeAndBake; Oct 3, 2020 at 12:59 PM.
Jumping the relay worked. I plugged the relay back in and it worked first try. So even though the relay looks fine it is most definitely shot. First step is to replace the relay. Second step is replacing relevant fuel pump parts. The top hat is leaking, is there a way to source just that part rather than the entire assembly? FCP Euro has a fuel pump replacement kit with what looks like that hat and some other things for $344. All I really need is the hat with the two connections and fuel line. Any ideas on that end?
Heck, all that you need is the top hat. If anyone on this forum has an old fuel filter assembly, you could purchase it from them, remove the top hat, and install on yours. You'll still have to pull it from the tank (my opinion) but would be much cheaper than buying a new filter/regulator assembly. A new assembly may be what you have to go with but, if so, I would keep the old assembly and transfer the top hat at the next change (Just perused prices and was shocked!). Any top hat from the three generations of fuel filter/regulator assemblies (drivers side, LHD) will fit.The versions for the E320 and E500 appear to be different (much lighter construction of the body) and hard to tell how the top hats attach. I would think the top hats would be interchangeable in all three models if only to save tooling costs. Might be worth the $63 for an Ebay E320 unit just to see if the top hat is compatible. If yes, you saved over $500; if wrong, in for a dime, in for a dollar. EDIT: Never mind; found some better photos and the top hats on that version appear to be significantly taller and molded into the body of the filter holder. The E55 version has some serious ribbing added for the additional pressure encountered.
See photo for how to remove top hat. Right line is where it is locked and you have to depress the tab to rotate the top hat; left line is unlocked and you can remove the top hat. I had to use a vise (carefully!) and a strap wrench to remove the top hat. Reassembly I recommend some sort of lube on the O-ring to ease assembly.
Last edited by bbirdwell; Oct 3, 2020 at 07:49 PM.
Thank you for the insight! I wasn’t sure how the hat came off when looking at it. I wonder if there are any wrecker E55’s around to scavenge from. Most likely not. Leave it to Mercedes to package the entire unit together instead of offering individual parts. That is my biggest complaint! I guess I will be making a post in marketplace and deciding on how much I’m willing to spend to move forward more quickly. Quarantine has had at least one upside: less mileage on the E!
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EDIT: Never mind; found some better photos and the top hats on that version appear to be significantly taller and molded into the body of the filter holder. The E55 version has some serious ribbing added for the additional pressure encountered.
