Screwed on craigslist purchase

[spyderg0d]

Gotcha. But a cracked head wont cause every cylinder to be low on compression, just the cylinder(s) with a crack, and even then they will leak compression not just be at half value right off the bat. Even if indeed it is cracked, the engine is unsellable the way it is anyway with low compression. No one really buys engines that dont run for more than maybe 200 with the full intentions of a rebuild. That's why your best and only hope is to just try the compression test again. Ive had 3 m5_ engines that had washed cylinders or stuck rings that eventually loosened up with oil and compression tests. I know its a bitch to do, but you got your options my man. Rest is really your discretion.

[zohaibrose]

Gotcha. But a cracked head wont cause every cylinder to be low on compression, just the cylinder(s) with a crack, and even then they will leak compression not just be at half value right off the bat. Even if indeed it is cracked, the engine is unsellable the way it is anyway with low compression. No one really buys engines that dont run for more than maybe 200 with the full intentions of a rebuild. That's why your best and only hope is to just try the compression test again. Ive had 3 m5_ engines that had washed cylinders or stuck rings that eventually loosened up with oil and compression tests. I know its a bitch to do, but you got your options my man. Rest is really your discretion.

Oh ok didn't know adding oil in could maybe revive the Piston rings n bring back compression, I don't even think the head is cracked or overheated, never saw a clue of oil n coolant mixed in cooling system, n dipstick smelled like oil. There was another forum member on here who had the same case as me except his was a 318, his cylinders had only 50-70 psi each cylinder and he went to get the head resurfaced, installed the head back on n compression tests were identical,

Gotta be something with the block or something. I think at this point it's time for an engine swap because there's no point in trying to fix the current engine if the oil trick doesn't work.

Car has 180k miles anyway

[E36328Coupe]

Oh ok didn't know adding oil in could maybe revive the Piston rings n bring back compression,

It was clearly covered in post 9.

[zohaibrose]

It was clearly covered in post 9.

well i get it will bring compression up for the time being, thought it would bring it back forever. M52 arent common for piston ring failure tho thought it was only m54.

[gdavid]

well i get it will bring compression up for the time being, thought it would bring it back forever. M52 arent common for piston ring failure tho thought it was only m54.

Rings can fail in different ways, some are terminal and others aren't too bad.

One is the ring getting stuck tight to the piston and not expanding against the cylinder wall, it can be due to carbon build up or corrosion from extended lack of use. Both result from lack of use or overextended oil life which any car of this age could have experienced but they can usually be overcome with use, frequent oil changes and some engine treatments. A little oil in the cylinder will help diagnose this and sometimes the rings are freed up with use (movement and heat) so it isn't a band aid or temporary measure but a diagnosis tool and first step in what may be a permanent fix.

Rings can simply wear down to the point of being too loose a fit, which is rare in a modern engine, the materials and manufacturing tolerences are too good.

Rings can be overheated to the point of over expansion where the ends of the rings touch and have no more room for expansion so it expands against the piston until the piston breaks at the ringland. This is a pretty dramatic failure usually associated with a botched engine build, poor turbo set up or both. Not likely unless someone went out of their way or the cylinder ran way lean.

Rings can fail to seal because the cylinder wall is worn or damaged which also isn't common on these iron blocks unless there was some foreign material or a bad rebuild.

Since your low pressure is consistent across all cylinders I would consider a cause that would be likely to influence them all rather than accute failure, this could also be explained by poor measurements which is why multiple guys questioned your testing, they aren't ribbing you but looking for a plausible explaination. If you had a valve failure I would expect very different pressures from cylinder to cylinder. At this point, aside from retesting compression you may as well pull the head and see what you have. If the head is good you are in good shape because a good one is worth more than a complete used engine of questionable condition.

[spyderg0d]

Il +1 myself again along with gdavid.

[zohaibrose]

Rings can fail in different ways, some are terminal and others aren't too bad.

One is the ring getting stuck tight to the piston and not expanding against the cylinder wall, it can be due to carbon build up or corrosion from extended lack of use. Both result from lack of use or overextended oil life which any car of this age could have experienced but they can usually be overcome with use, frequent oil changes and some engine treatments. A little oil in the cylinder will help diagnose this and sometimes the rings are freed up with use (movement and heat) so it isn't a band aid or temporary measure but a diagnosis tool and first step in what may be a permanent fix.

Rings can simply wear down to the point of being too loose a fit, which is rare in a modern engine, the materials and manufacturing tolerences are too good.

Rings can be overheated to the point of over expansion where the ends of the rings touch and have no more room for expansion so it expands against the piston until the piston breaks at the ringland. This is a pretty dramatic failure usually associated with a botched engine build, poor turbo set up or both. Not likely unless someone went out of their way or the cylinder ran way lean.

Rings can fail to seal because the cylinder wall is worn or damaged which also isn't common on these iron blocks unless there was some foreign material or a bad rebuild.

Since your low pressure is consistent across all cylinders I would consider a cause that would be likely to influence them all rather than accute failure, this could also be explained by poor measurements which is why multiple guys questioned your testing, they aren't ribbing you but looking for a plausible explaination. If you had a valve failure I would expect very different pressures from cylinder to cylinder. At this point, aside from retesting compression you may as well pull the head and see what you have. If the head is good you are in good shape because a good one is worth more than a complete used engine of questionable condition.

The only thing I feel I did wrong was not doing a wet compression, when it was dry I snugged up the compression hose tight as i could, I could even take video of the results. I will update here what the results are with bit of oil in each cylinder and if the compression goes up I'll try add the fuel fuse back in n see if it will start because none valves are bent, no signs of overheating, must be just washed with gasoline.

[somebody5788]

It's highly likely that there is a fueling issue caused by unmetered air that caused the car not to start and flood the cylinders as others have stated. This is the most common issue on these cars and is also about the easiest thing to fix. Try getting the compression up by using the oil trick and then unplug the mass air flow when you try to start it. This will default the ecu to an estimated air flow instead of the measured number and will compensate to an extent for any air leaks in the system. My car has 209k miles with over 400 wheel hp now and the engine still purrs like it's a brand new one.

[MIKYZZ4]

Try test with a different pressure gauge for verification.
They are notorious for erroneous readings.

[zohaibrose]

It's highly likely that there is a fueling issue caused by unmetered air that caused the car not to start and flood the cylinders as others have stated. This is the most common issue on these cars and is also about the easiest thing to fix. Try getting the compression up by using the oil trick and then unplug the mass air flow when you try to start it. This will default the ecu to an estimated air flow instead of the measured number and will compensate to an extent for any air leaks in the system. My car has 209k miles with over 400 wheel hp now and the engine still purrs like it's a brand new one.

Just as I thought, left fuel injector cleaner down the cylinders, compression tested it next morning n now they have each around 150 psi, does this mean I need a rebuild, it actually cranks like a healthy engine now, before it would crank like something was wrong in the engine but I'll go ahead n put everything back together to see if it starts up

[gdavid]

According to the Bentley Manual, minimum pressure is 10-11 bar (142-156psi) so as long as they are even, it should be adequate.

[MIKYZZ4]

Upper Engine Cleaner if your rings still seem to be sticking after you put everything back together:https://www.youtube.com/watch?v=_Vo4fm0JDPY,
but it seems your fuel injector cleaner was sufficient.
Btw, drain the crap in there and use fresh fuel for startup!

[zohaibrose]

Well i tried starting it up multiple times today and it just keeps cranking and cranking but wont actually fire up, i tested for fuel and the pressure seems to be good at 50psi, not sure about spark but compression is at the same psi, One thing i found wrong is the check engine light doesent come on after putting key in position 2, and when i try to scan for codes it doesent connect, even after a new bulb it stiill wont come on, Any ideas? could this be the reason the car wont start up.

[XnWarden]

Well i tried starting it up multiple times today and it just keeps cranking and cranking but wont actually fire up, i tested for fuel and the pressure seems to be good at 50psi, not sure about spark but compression is at the same psi, One thing i found wrong is the check engine light doesent come on after putting key in position 2, and when i try to scan for codes it doesent connect, even after a new bulb it stiill wont come on, Any ideas? could this be the reason the car wont start up.

If you can't pull codes from the dme then the dme itself may be shot.

Sent from my VS987 using Tapatalk

[zohaibrose]

If you can't pull codes from the dme then the dme itself may be shot.

Sent from my VS987 using Tapatalk

Do you mean it may be shot or may be dead, meaning there's a way to revive it, I know the dme isn't getting power so I could try the dme relay or what others have said is the fusible link, which I'm not sure where it is. If I can get the dme to turn on I can most likely turn on the car

[MIKYZZ4]

Check engine chassis grounds, also your DME may have an external ground wire,search for it.

[Nanniepoo]

Do you mean it may be shot or may be dead, meaning there's a way to revive it, I know the dme isn't getting power so I could try the dme relay or what others have said is the fusible link, which I'm not sure where it is. If I can get the dme to turn on I can most likely turn on the car

Going out on a limb here but if you know the DME isn't getting power I'd probably start there.

[zohaibrose]

Gonna start a thread because am really stumped on this.

[Nanniepoo]

Gonna start a thread because am really stumped on this.

That wood be a good idea.

Hope it treets you well.