2004 E320 has run great since purchase with 95K miles, but now at 175K it has faltered a few times on start up and now will not run. It was trying with the start valve shooting fuel and then died but the battery was low so I replaced with an AGM, and no more low voltage!
Now there is no firing at all so Im checking for pressure at the fuel rail. The fuel pumps arent on fuses are they? And maybe some other FP issues like the filters or hoses?
I was doing some jump starting and charged my off-grid batteries when the system got low with jumper cables, and it brought the voltage right up but hopefully no damage to electronics. At one point I did have a very high draw from the Positive post..due to connecting to a dead lithium which pulled high amperage. OK off to check for fuel pressure and to listen for the fp hum in the tanks..(after checking out some video advice on you-tube)
Thanks in advance for any wise counsel.

Fuel pump fuse and relay are in the panel in the trunk on the left side. Relay is the bottom one. Fuse may be the 4th one up from the bottom, 20 amp?

Fuel pump is in the tank, remove the bottom of the rear seat for access.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Thanks SugarBear, Yes.
I checked the fuse and relay and was checking the one above, corrected. Thanks. And I tried to 'jump' the pump leads to power the pump and no success, no power going to the fuel pump pins. (but I was jumping the wrong pins I see from your comment about the relay) The big red one on the left pump, right? Nothing, no power to the pumps, no fuel pressure.
I was suspicious of the SAM but I see there is a fuse block by the battery on the passenger side which may be at fault. and I possibly blew one with some arcing during a jump recently.
I know the sam has been faulty BC when I purchased originally, the gas gage showed nothing, but then it began working. Now the wiper spray is dead and I also have a bad tail light on the right side but the bulb is good. So I ran a jumper. But this may also be a SAM fault..
I'll keep updated with results for benefit of all.

PS. I'm a great fan of Hoffer and love your quote.

To continue the no fuel pressure issue, I jumped the correct pins on advice and yes, now find power at the fuel pump red lead but the pumps do nothing. It could still be a SAM issue since with the key in run position there is no power showing on the red lead. the relay seems okay and has continuity on its electromagnet.

So Im feeling new pumps are in order and what a Bt* dealing with the hoses and tank seal. And there should be notes about emptying the tanks prior to work. A tilt puts the low pump below fluid level and yikes. Gas everywhere!

Yet another reason the old 124 was to be preferred over the W211. These pumps are a nightmare of complexity and fragile and dont really fit through the opening.

Off to harbor freight to get a fuel transfer pump and jerry cans to empty the tank!

OK I was confused thinking there were dual pumps, the second cover is just the siphon I suppose. The old 124 had dual pumps. So they say 'just slide the tubes off' !!! "JUST" with a tube welded onto the hose barbs and set since 2004, 21 years! This is major extraction of hardened plastic...

At 179K I suppose failure is normal...

Not much to changing it out.

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Jim

Thanks Jim. Im glad to hear its not bad. Hopefully get those hoses off without breaking anything. I normally use heat on a hard plastic hose to soften but not at the fuel tank!

On my '08 the pump failed without any warning around 140K. I'd suggest replacing the fuel pump relay when replacing the pump even if it tests good due to its age and the potential it was subjected to a high current load before the pump failed. I know it is fuse protected but they are also quite inexpensive.

Was able to use a topsider oil changer on mine to empty the fuel tank. On the '08 the cap on the left side gave easy access to remove the fuel.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

So now with 15 gallons removed I can get into the system and yes, its easy to unclip the lines and connectors. And the old pump was clearly dead. On recalling events it began not running but tried to start on the low residual fuel pressure. So Im optimistic the only issue is the fuel pump. Hopefully the SAM is okay.
Yes I agree about the relay for two bucks, good idea replacing and Im going to do both sides so I will have a fresh fuel filter and sending unit.
I was confused because the car was full of gas and I could only open the left side and thought the pump was there needing all those hoses removed. But no, they unclip easily and its not hard.
I siphoned the left side and still the right side was below fluid level so I had to jack up toward level and then siphon another 10 gallons even to get into the covers and do the work..clearly the pump is bad testing the two pins on the motor w/ direct jump plus/minus, nothing. Pump kit on order!

cool

I changed the fuel pump and filter on the 2014 GLK350 at around 290k miles as a preventive measure. Just got back from a 2200 mile road trip (I had the honor to have lunch with Tom W in Auburn, In) where the car turned over 300k. I think they last longer if you never let the tank get below 1/4 full. Reason being you are not concentrating all that trash/debris into the suction filter on the pump unit. I don't have any scientific proof that this is true but I did change one that was still operating properly at 290k.

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Jim

The Pelican co-founder, cool. It was just occurring to me that a pump change could save a tow bill.
Its really inconvenient when the pumps go and you are dead somewhere. Fortunately I was at a friends who happened to have a spare car which Im using now to get back in business.
Good thoughts on fuel issues killing the pumps. Makes sense to me!
Im just looking forward to being back in operation with the comfy E320 with tons of room in back for my dog.

One more question, is there a reason for no power appearing at the large red lead to the pump? Key on in run position. I see the little wires to sensors, probably the tank float and pressure sensors. Would low fuel level kill the 12 volts or possibly a disconnected pressure sensor? Hopefully this is why there is nothing there currently. I doubt that the relay is bad, could be but it does click.

With the engine not running the fuel rail is pressurized maybe 2 seconds then the power is removed awaiting confirmation the engine had started, (tac signal) before re-energizing the pump.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

Thanks Dieselbenz1, I would think recycling the ignition key would energize again. maybe it does and then shuts off in the 2 seconds you mention.
Very helpful forum and worth ten times the $20 Just answer dialogues.
Thanks to all! Looking forward to the new parts and added note, the suspension collapsed over the three days now its been sitting and with no engine will not recharge. I have a fresh air pump so Im sure it will be fine. (bad pump and blown fuse when I got the car, but the suspension was up and it was not detected on inspection. so I know how to troubleshoot the air shocks.)