E55 AMG Wagon - Compression Test How?
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Junior Member
Joined: Apr 2014
Posts: 34
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From: Netherlands
2004 Mercedes E55 AMG Wagon
E55 AMG Wagon - Compression Test How?
Hi All,
I want to do a compression test on my E55 but I need a bit of guidance as it's my first time
I have a compression tester kit and my plan was the following, would this be good or am I missing something?
- Remove 1 spark plug from each cylinder
- Disconnect all coils
- Remove 2x fuel pump relay in the back right of the car
Am I on the right track here or do I need to do more or is there an easier way? I also heard depressing the gas pedal all the way might do something(don't know what exactly)?
For the spark, is just disconnecting the coils enough or do I also need to do something more? I tried search but there is really a low amount of information specific to W211 E55 AMG's and compression tests.
I want to do a compression test on my E55 but I need a bit of guidance as it's my first time
I have a compression tester kit and my plan was the following, would this be good or am I missing something?
- Remove 1 spark plug from each cylinder
- Disconnect all coils
- Remove 2x fuel pump relay in the back right of the car
Am I on the right track here or do I need to do more or is there an easier way? I also heard depressing the gas pedal all the way might do something(don't know what exactly)?
For the spark, is just disconnecting the coils enough or do I also need to do something more? I tried search but there is really a low amount of information specific to W211 E55 AMG's and compression tests.
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From: America
1999 C43 AMG, 2005 E55 Wagon
Sounds accurate to me. No idea what you've heard about the gas pedal. The starter will turn and it will not fire if the coils are unplugged.
I believe only 1 of the 2 relays in the trunk is for fuel. I forget what the other is for.
I believe only 1 of the 2 relays in the trunk is for fuel. I forget what the other is for.
Thread Starter
Junior Member
Joined: Apr 2014
Posts: 34
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From: Netherlands
2004 Mercedes E55 AMG Wagon
THanks Sulaco, at least makes me feel a bit more confident
I removed the Harman Kardon subwoofer in the back of the wagon and found 1 relay, probably because it's code 804 2004 model year with the old type relay and I've removed it. Looked good.
Question; if I just unplug the coils and leave the plugs hanging there that's fine? I don't have to do more like some ignition fuse I think?
Will first do the breather cover gasket and after that I'm doing the compression test.
I removed the Harman Kardon subwoofer in the back of the wagon and found 1 relay, probably because it's code 804 2004 model year with the old type relay and I've removed it. Looked good.
Question; if I just unplug the coils and leave the plugs hanging there that's fine? I don't have to do more like some ignition fuse I think?
Will first do the breather cover gasket and after that I'm doing the compression test.
Thread Starter
Junior Member
Joined: Apr 2014
Posts: 34
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From: Netherlands
2004 Mercedes E55 AMG Wagon
I just did the compression test as I couldn't wait. It indeed worked just removing the fuel pump relay and 1 plug from each cylinder and leaving the coil plugs just hanging. I tied them with a tierip to the surge tank and left them hanging.
I think my results are okish?
Cyl 1: 152
Cyl 2: 155
Cyl 3: 162
Cyl 4: 157
Cyl 5: 155
Cyl 6: 152
Cyl 7: 165
Cyl 8: 167
I think my results are okish?
Cyl 1: 152
Cyl 2: 155
Cyl 3: 162
Cyl 4: 157
Cyl 5: 155
Cyl 6: 152
Cyl 7: 165
Cyl 8: 167
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2005 e55 AMG
We used to do the test with the throttle pedal to the floor with Fords and this would shut off the injectors so no fuel would enter the cylinders but not sure on other model cars.
Saved the hassle of finding the fuel pump fuse or relay.
Saved the hassle of finding the fuel pump fuse or relay.
Senior Member
Joined: May 2021
Posts: 251
Likes: 73
From: North of Houston, Texas
2013 CL 63, 2002 E 55, 04 Jaguar XJ8, 66 Jaguar XKE
One would open the throttle plate to maximize the amount of air entering the cylinder, thereby increasing the volume of air compressed and giving a maximum pressure reading. In modern, drive by wire vehicles, I don't think pushing on the throttle of a non-running engine does anything at all to the throttle plate.
BTW: your numbers do look good and reasonably equal across the board. Best of luck to your project.
BTW: your numbers do look good and reasonably equal across the board. Best of luck to your project.
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Thread Starter
Junior Member
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From: Netherlands
2004 Mercedes E55 AMG Wagon
Thanks I was hoping it looked good! At least now I know I'm not just throwing money/parts at a unhealthy engine.
When the engine is cold and the transmission is in P, when I start it up and it slowly comes down in the RPM range I'm getting what feels like small missfire and vibration. I've been chasing this for quite some time and I do not know what it is. If I switch to D / R it's gone.
When the engine is cold and the transmission is in P, when I start it up and it slowly comes down in the RPM range I'm getting what feels like small missfire and vibration. I've been chasing this for quite some time and I do not know what it is. If I switch to D / R it's gone.
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From: Republic of Texas
'99 and '05 E55 AMG
Thanks I was hoping it looked good! At least now I know I'm not just throwing money/parts at a unhealthy engine.
When the engine is cold and the transmission is in P, when I start it up and it slowly comes down in the RPM range I'm getting what feels like small missfire and vibration. I've been chasing this for quite some time and I do not know what it is. If I switch to D / R it's gone.
When the engine is cold and the transmission is in P, when I start it up and it slowly comes down in the RPM range I'm getting what feels like small missfire and vibration. I've been chasing this for quite some time and I do not know what it is. If I switch to D / R it's gone.
In my case, it was as failing motor mount causing vibration in a narrow band around 1500 rpm. You can use a borescope to check out the motor mounts. My driver's side mount was obviously wet with fluid on top.
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From: Netherlands
2004 Mercedes E55 AMG Wagon
Hi bbirdwell, thanks for your reply. I've had the motor mounts AND transmission mount replaced by my shop 1000 miles ago so that's really not it I would say?
If I hook up the diagnostic machine, smooth running values I can feel that the engine when it sometimes gives a sort of misfire feeling that some of the cylinders go out of the smooth running range. There is no error stored, I've checked with DAS and Foxwell 530NT. I did hear that certain small misfiring is not logged as code. That there is some sort of counter behind that resets and only sets misfire code above a certain value? Not sure if that is correct.
Actually there are no codes stored at all for Engine or Transmission.
I've myself replaced the:
- Fuel damper
- Spark plugs (16x NGK)
- Coil packs (8x NGK)
- Spark plug wires (16x Bosch)
- Breather hoses (Mercedes)
- Throttlebody gasket (Mercedes)
- Surge tank gasket (Mercedes)
Checked:
- vacuum hoses
- SAI relay disconnected
- Fuel pressure
Thinking about:
- Checking 722.6 oil level checking.
- Can the torque converter be broken? It feels absolutely fine in D, driving off from standing still though. Is there any valve/actuator that can cause this on the transmissions valve body
- Running engine without serpentine belt to see if that makes a difference
- MAP sensor testing?
If I drive for a bit and then set it in P, there no to almost no vibration. So it only does this when it's cold and in P. When I put it in D or R it drives off smooth and is not vibrating when standing still.
If I hook up the diagnostic machine, smooth running values I can feel that the engine when it sometimes gives a sort of misfire feeling that some of the cylinders go out of the smooth running range. There is no error stored, I've checked with DAS and Foxwell 530NT. I did hear that certain small misfiring is not logged as code. That there is some sort of counter behind that resets and only sets misfire code above a certain value? Not sure if that is correct.
Actually there are no codes stored at all for Engine or Transmission.
I've myself replaced the:
- Fuel damper
- Spark plugs (16x NGK)
- Coil packs (8x NGK)
- Spark plug wires (16x Bosch)
- Breather hoses (Mercedes)
- Throttlebody gasket (Mercedes)
- Surge tank gasket (Mercedes)
Checked:
- vacuum hoses
- SAI relay disconnected
- Fuel pressure
Thinking about:
- Checking 722.6 oil level checking.
- Can the torque converter be broken? It feels absolutely fine in D, driving off from standing still though. Is there any valve/actuator that can cause this on the transmissions valve body
- Running engine without serpentine belt to see if that makes a difference
- MAP sensor testing?
If I drive for a bit and then set it in P, there no to almost no vibration. So it only does this when it's cold and in P. When I put it in D or R it drives off smooth and is not vibrating when standing still.
Last edited by Gripen; Jul 16, 2025 at 10:03 AM.
