I want to do a compression test On my car.
I have removed the fuel pump fuse (54)
what other fuses do I need to remove?
I have removed the fuel pump fuse (54)
what other fuses do I need to remove?
mujjuman
Yup, I did it myself. Someone told me i may have done it wrong though... for those steps, I will write a "Is this the correct way?" next to it. I will remove it once someone can confirm it is correct.
Np, I'll write a step-by-step guide on how I did it... (and a how-to).
I'll go into some detail, since I dont know the experience level of people that will be reading this thread.
I'd rather go in detail and explain, than attempt to lead someone who will be blinded by my vagueness.
Make sure the car is warm... Some people like to just start their car and idle for 5 mins, I did this right after an entire day of driving (100 miles). Also, make sure your battery is healthy and not dying on you... if thats the case, then plug it into a generator or something.
Turn the car off, go into fusebox in the glovebox compartment, and remove the fuse for the fuel pump. In my car, it was fuse number 54. Read the fuse card in your fusebox to confirm which fuse(s) power the fuel pump.
Now try to start the car, it may or may not run for a few seconds... do this to clear out as much fuel from the fuel lines as possible. My car wouldnt run for more for than a couple seconds, but it still did run a bit, so I kept trying to restart 5 times (just to be sure).
Now open up the hood. Undo the cabin air filter cover and remove the filter. Carefully open the plastic cover that covers the 2 engine harness cables in the front of the cabin air filter housing. Remove the 2 cables from the clips. Unscrew the 4 torx screws holding the cabin air filter housing tray thing. Remove the cabin air filter tray. Now you have easier access to the last two spark plugs.
Unscrew and remove your engine covers... remove the caps that cover the bold/nut, and unscrew the bolts/nuts (depends on which cover). It uses a 10mm socket. To remove the left engine cover, the one that covers the spark plugs and ignition coils, first unscrew and remove the oil cap. Dont forget to screw the oil cap back on once you remove the cover...
Now you will see all 6 ignition coils, covering the spark plugs. Depending on whether you have a M52 or a M54, and whether or not your ignition coils were recalled, the removal of the ignition coils is a bit different... but not that much. I have the M54 with the updated ignition coils. I simply had to pull the edge of the cover up, and the connector just released. To reconnect the connector, just push the plug back in, and snap the cover close (if need be, otherwise it will close on its own). BMW did that right. Disconnect all of the ignition coils connectors. In my non-technical opinion, it will be easier on the battery if it is not sending spark to plugs for this process... since you will be using your battery for quite a while. You can choose to remove all the coils at this point, or remove only the one for the cylinder you are currently testing. I did the former. (Is this the correct way?)
Most guides I read told me to leave all the spark plugs in the car, except for the cylinder you are testing. So what I did was remove the spark plug for the cylinder I was testing, test the compression, and then replaced the spark plug when I was done. (Is this the correct way?) I used a torque wrench, an extension, and a spark plug socket to unscrew the spark plug. Then I used a magnetic tool to take the spark plug out (and put it back in when I was done).
I bought a compression tester kit from Advance Auto for $27ish including tax. I screwed the hose for the gauge in place of the spark plug, attached the hose to the gauge, and proceeded to start my car. I held the key in the start position for 5 seconds (1 mississippi, 2 mississippi, etc) while holding the gas pedal all the down (Is this the correct way? Someone told me this was specifically wrong) then turned it off. I checked the gauge, wrote the number down, and pushed the button on the side of the gauge to release the pressure. I unclamped the gauge from the hose, since it was easier to screw/unscrew the hose from the spark plug hole, and unscrewed the hose from the s.p. hole. I re-installed that spark plug, and repeated this process for the next cylinders.
I'm going to do this again later this weekend... without holding the pedal down to see if I will get different results. In my opinion, I dont think it should, but another thread I looked at stated that it is a way to make sure the cyl gets as much air as possible.
Oh yeah this process was also written so that anyone with a lot more experience than me can tell me if I did something wrong.
Np, I'll write a step-by-step guide on how I did it... (and a how-to).
I'll go into some detail, since I dont know the experience level of people that will be reading this thread.
I'd rather go in detail and explain, than attempt to lead someone who will be blinded by my vagueness.
Make sure the car is warm... Some people like to just start their car and idle for 5 mins, I did this right after an entire day of driving (100 miles). Also, make sure your battery is healthy and not dying on you... if thats the case, then plug it into a generator or something.
Turn the car off, go into fusebox in the glovebox compartment, and remove the fuse for the fuel pump. In my car, it was fuse number 54. Read the fuse card in your fusebox to confirm which fuse(s) power the fuel pump.
Now try to start the car, it may or may not run for a few seconds... do this to clear out as much fuel from the fuel lines as possible. My car wouldnt run for more for than a couple seconds, but it still did run a bit, so I kept trying to restart 5 times (just to be sure).
Now open up the hood. Undo the cabin air filter cover and remove the filter. Carefully open the plastic cover that covers the 2 engine harness cables in the front of the cabin air filter housing. Remove the 2 cables from the clips. Unscrew the 4 torx screws holding the cabin air filter housing tray thing. Remove the cabin air filter tray. Now you have easier access to the last two spark plugs.
Unscrew and remove your engine covers... remove the caps that cover the bold/nut, and unscrew the bolts/nuts (depends on which cover). It uses a 10mm socket. To remove the left engine cover, the one that covers the spark plugs and ignition coils, first unscrew and remove the oil cap. Dont forget to screw the oil cap back on once you remove the cover...
Now you will see all 6 ignition coils, covering the spark plugs. Depending on whether you have a M52 or a M54, and whether or not your ignition coils were recalled, the removal of the ignition coils is a bit different... but not that much. I have the M54 with the updated ignition coils. I simply had to pull the edge of the cover up, and the connector just released. To reconnect the connector, just push the plug back in, and snap the cover close (if need be, otherwise it will close on its own). BMW did that right. Disconnect all of the ignition coils connectors. In my non-technical opinion, it will be easier on the battery if it is not sending spark to plugs for this process... since you will be using your battery for quite a while. You can choose to remove all the coils at this point, or remove only the one for the cylinder you are currently testing. I did the former. (Is this the correct way?)
Most guides I read told me to leave all the spark plugs in the car, except for the cylinder you are testing. So what I did was remove the spark plug for the cylinder I was testing, test the compression, and then replaced the spark plug when I was done. (Is this the correct way?) I used a torque wrench, an extension, and a spark plug socket to unscrew the spark plug. Then I used a magnetic tool to take the spark plug out (and put it back in when I was done).
I bought a compression tester kit from Advance Auto for $27ish including tax. I screwed the hose for the gauge in place of the spark plug, attached the hose to the gauge, and proceeded to start my car. I held the key in the start position for 5 seconds (1 mississippi, 2 mississippi, etc) while holding the gas pedal all the down (Is this the correct way? Someone told me this was specifically wrong) then turned it off. I checked the gauge, wrote the number down, and pushed the button on the side of the gauge to release the pressure. I unclamped the gauge from the hose, since it was easier to screw/unscrew the hose from the spark plug hole, and unscrewed the hose from the s.p. hole. I re-installed that spark plug, and repeated this process for the next cylinders.
I'm going to do this again later this weekend... without holding the pedal down to see if I will get different results. In my opinion, I dont think it should, but another thread I looked at stated that it is a way to make sure the cyl gets as much air as possible.
Oh yeah this process was also written so that anyone with a lot more experience than me can tell me if I did something wrong.
On a cable operated throttle you press the pedal down to open the throttle. I'm thinking that on the drive by wire M54 that pressing on the pedal while the car is off, isn't going to open the throttle.
I seem to recall something about pinning the throttle butterfly open while doing the test but I'll check my bentley tonight.
I seem to recall something about pinning the throttle butterfly open while doing the test but I'll check my bentley tonight.
Update (for records etc.)
Put in my new engine from a 330Ci. Finally got around to doing a compression test. These were the results:
cyl1: 190
cyl2: 190
cyl3: 190
cyl4: 170
cyl5: 200
cyl6: 210
Those numbers seem very bad to me... I used the same exact method.
There was also lots of oil on my spark plugs and ignition coils.
I checked my oil level and it was well below low!!! I had to add more oil. So it seems my engine is burning oil.
What causes this?
Put in my new engine from a 330Ci. Finally got around to doing a compression test. These were the results:
cyl1: 190
cyl2: 190
cyl3: 190
cyl4: 170
cyl5: 200
cyl6: 210
Those numbers seem very bad to me... I used the same exact method.
There was also lots of oil on my spark plugs and ignition coils.
I checked my oil level and it was well below low!!! I had to add more oil. So it seems my engine is burning oil.
What causes this?
A few issues with your method. First pull the DME relay & fuel pump fuse.
Next, pull ALL spark plugs out, no plugs in motor when you do test. Yes,
motor should be warm, while one person cranks with the throttle wide open
(YES the throttle will open up, while you crank) the second person is manning the gauge. Crank engine 10 times per test, this means 10 needle swings or "spikes" on your gauge. While looking at gauge, its NOT the highest number you see, but the average number. So if your gauge is swinging between 180 & 200, your compression number is 190. Repeat for all cylinders. If you end up within 10% or less that's considered ok, 5% or less would be
very good. If you get numbers above 10%, that's a problem, depending on
how much of a difference there is, you might be looking at some sort of rebuild/or freshen-up.
Good Luck,
Next, pull ALL spark plugs out, no plugs in motor when you do test. Yes,
motor should be warm, while one person cranks with the throttle wide open
(YES the throttle will open up, while you crank) the second person is manning the gauge. Crank engine 10 times per test, this means 10 needle swings or "spikes" on your gauge. While looking at gauge, its NOT the highest number you see, but the average number. So if your gauge is swinging between 180 & 200, your compression number is 190. Repeat for all cylinders. If you end up within 10% or less that's considered ok, 5% or less would be
very good. If you get numbers above 10%, that's a problem, depending on
how much of a difference there is, you might be looking at some sort of rebuild/or freshen-up.
Good Luck,
thanks man.
i have no idea wherethe DME relay is.. i did pull the fuel pump fuse (fuse #54)
i did this the same exact way i did my first test, for consistency.
and yes, i had the throttle wide open.
my gauge is different... it doesnt provide the avg psi it gives the max psi.
my engine was warm... took it for a 40 min drive, parked in my garage, took a 30 min break, and proceeded to work
i have no idea wherethe DME relay is.. i did pull the fuel pump fuse (fuse #54)
i did this the same exact way i did my first test, for consistency.
and yes, i had the throttle wide open.
my gauge is different... it doesnt provide the avg psi it gives the max psi.
my engine was warm... took it for a 40 min drive, parked in my garage, took a 30 min break, and proceeded to work
To solve the throttle not opening problem, you can just pull the DISA valve out, that makes a nice gaping hole in the intake manifold.
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</quote>
If you didn't have a leak on your VCG before, then changing it would not help. Cylinder 4 compression is >10% lower than the other cylinders. This indicates you have a problem there. Whether it is a valve issue, a cylinder ring issue, a head gasket issue, or a combination of three, you'll need more diagnostics to find out. HG leak usually causes overheating due to gas entering the cooling system. If you don't have overheating, then only two possibilities remain. Since you have a oil consumption issue, I would say your most like problem is bad rings on cylinder 4.
</quote>
I replaced my VCG soon after the new compression results. I checked recently and the plugs do NOT have oil on them, and the ignition coils are clean (no oil).
My oil is black, but still smooth (not gritty, still lubricating, etc) basically feels like new except its not gold.
My car does not drip oil anywhere. The engine is def NOT overheating either. and no water is noticable in the oil either.
However, my VCG was leaking in several places before and when I noticed it, I promply replaced it.
My oil is black, but still smooth (not gritty, still lubricating, etc) basically feels like new except its not gold.
My car does not drip oil anywhere. The engine is def NOT overheating either. and no water is noticable in the oil either.
However, my VCG was leaking in several places before and when I noticed it, I promply replaced it.
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