Need help with No Start: glow plug relay fault and low rail pressure
Thread Starter
Junior Member
Joined: Jul 2016
Posts: 56
Likes: 4
2005 E320 CDI
Need help with No Start: low rail pressure and acting like it's out of fuel
'05 E320 CDI
I've been having the Glow Plug light acting up since spring with an occasional Check Engine Light. Didn't use the car much and was really busy with life, so I ignored it. Lesson learned. Yesterday I went to start it and it didn't start. Turned over fine and battery has plenty of power. Previous to this the engine was running really well. Put it on Star Diagnostics and got the following:
Control Unit: CDI3_UP
2257-004
Check component N14/2 (Glow output stage) FAULTY
STORED
3051-001
Rail pressure monitoring via pressure control valve. The rail pressure is too low
Current and stored
Now, my understanding is that the Glow Plug Relay fails due to fuses inside it which makes we wonder if there is something causing that fuse to blow. If I replace the relay($250) am I going to blow it right away due to something else?
Is the rail pressure related? Anybody see a common thread here or can give me some direction before I start blowing a lot of money on parts that I might not need?
Thank you!
I've been having the Glow Plug light acting up since spring with an occasional Check Engine Light. Didn't use the car much and was really busy with life, so I ignored it. Lesson learned. Yesterday I went to start it and it didn't start. Turned over fine and battery has plenty of power. Previous to this the engine was running really well. Put it on Star Diagnostics and got the following:
Control Unit: CDI3_UP
2257-004
Check component N14/2 (Glow output stage) FAULTY
STORED
3051-001
Rail pressure monitoring via pressure control valve. The rail pressure is too low
Current and stored
Now, my understanding is that the Glow Plug Relay fails due to fuses inside it which makes we wonder if there is something causing that fuse to blow. If I replace the relay($250) am I going to blow it right away due to something else?
Is the rail pressure related? Anybody see a common thread here or can give me some direction before I start blowing a lot of money on parts that I might not need?
Thank you!
Last edited by danielgetsthis; Jul 20, 2020 at 06:35 PM. Reason: to focus in on the specific problem
Super Member
Joined: Jan 2010
Posts: 563
Likes: 31
From: The Villages, Florida
2006 E320 CDI
These are two different separate issues with your cdi. The glow plug controller will NOT stop your cdi from starting, unless you are in sub-zero weather. So I would address the fuel issue first.
Mike T.
Mike T.
Thread Starter
Junior Member
Joined: Jul 2016
Posts: 56
Likes: 4
2005 E320 CDI
Thank you for that information. Indeed, I checked the fuel flow at the fuel filter by removing the supply hose to the filter. It was sputtering. Looked like lots of bubbles with some small spurts of fuel. I can also hear the fuel pump outside of the car and it sounds like someone gargling mouthwash, not normal. Fuel tank is low, but still 2 bars. Do fuel pumps fail like this? As in, a partial fail?
Thread Starter
Junior Member
Joined: Jul 2016
Posts: 56
Likes: 4
2005 E320 CDI
Alright, hopefully this helps someone else. I added 5 gallons of fuel and it started right up. This matches these two threads:
https://mbworld.org/forums/e-class-w...lace-help.html
https://mbworld.org/forums/e-class-w...-1-4-tank.html
Apparently there is a hump in the fuel tank and two pumps. One pump sends fuel over the hump to the other pump which then gets sent to the filter. Does this sound right? Are both pumps accessed from the port below the rear seat?
Anybody know how to solve this problem? I can keep the car over 1/4 tank, but this will be a pain in the rear over time.
https://mbworld.org/forums/e-class-w...lace-help.html
https://mbworld.org/forums/e-class-w...-1-4-tank.html
Apparently there is a hump in the fuel tank and two pumps. One pump sends fuel over the hump to the other pump which then gets sent to the filter. Does this sound right? Are both pumps accessed from the port below the rear seat?
Anybody know how to solve this problem? I can keep the car over 1/4 tank, but this will be a pain in the rear over time.
