hey everybody its Justin welcome back to the BTR Garage today we're going to be
doing a little bit of work to my 1994 325is this is my full-time track car I
actually just gotten my time trials evaluation completed with the NASA Auto
Club so we're ready to take this car into Time Attack and time trials so
we're trying to get it set up here in the offseason get some work done to it
but first we kind of make sure that the engine is in good shape so this video is
actually going to go over a compression test for the engine and from there once
we figure out the engine is good we can go forward with the rest of the upgrades
and modifications that I want to do during the off season so we're going to
show you how to do that particular process let's go ahead and get started
now to get started the first thing we have to do is get all of the spark plugs
pulled out of the engine we need to get these little clips pulled up right here
these little silver clips they just slide right up we can pull the plugs out
of the little ignition harness so we do that for each one of the plugs
next grab your wrench with a 10 millimeter socket on it we're going to
use that to loosen all of the nuts on the little ignition packs on each one of
the cylinders with all of the nuts loosened up we can now start sliding the
coil packs they just kind of pull straight out pretty straightforward I do
like to keep them in the order that they came out so we'll just lay them over
here onto the intake manifold next up we'll grab our wrench with an extension
on it and a spark plug sockets and we're going to remove all of our spark plugs
and again making sure we keep them in the proper order
that they came out
all right now that we have the spark plugs and the ignition packs out of the
car we're gonna take that stuff off of the engine move it over to the bench the
next thing we have to do is actually get at the fuse box here and take out the
fuse for the fuel pump we don't want any fuel pumping into the engine when we're
cranking it over doing the compression test so we'll locate the fuel pump fuse
in the little fuse panel or reference and it is fuse number 18 and again
looking at the fuse panel reference down here fuse number 20 is right there
so we got 19 and 18 so we're gonna remove this little blue fuse that is our
fuel pump fuse and set that aside now I have everything moved over to the bench
here we'll get this stuff cleaned up the spark plugs and the ignition coils
before they go back into the car now we can go ahead and start with the
compression test so this is our compression testing tool it's just a
little gauge as you can see with a hose attached to it and an attachment to
screw into the spark plug hole it comes with a few different size adapters for
different sized spark plugs and different types of vehicles or even
motorcycles if you want to use it so what we'll do is actually remove this
quick disconnect on here take the hose off and then we can stick this into the
first cylinder and then go ahead with the compression test process so here we
go take our hose slide it down into place and start threading it in
get that hand tight and then put our gauge back on to the end now once we get
to this points you can just set your gauge off to the side as shown here and
leave it as is and then what we're gonna do is actually jump into the car and
start the compression test process which basically means we're gonna put the gas
pedal to the floor and then crank the ignition over for about five or six
seconds what that will do is fill up the gauge with pressure readings will come
back out and see what it is at will record that number and then go down the
cylinders all the way to the back of the car and basically rinse and repeat till
we get every cylinder tested and then we'll compare the numbers at the end all
right we're in the car we'll go ahead and give this a shot so key in clutch in
and neutral so gas pedal to the floor and we'll crank it over for five or six
seconds
all right that sounded kind of nasty let's go check and see if we got any
readings on the gauge all right so it looks like everything worked okay I do
have some pressure on the gauge it looks like right around 150 a little bit
higher than 150 reading on the gauge so what we'll go ahead and do now is take
the compression tester out of there actually we want to bleed the gauge
before moving on there's a little button just like a tire pressure where you push
and it believes the air out of the gauge so make sure you do that between each
cylinder so we'll go down do the rest of the cylinders in order and again we're
going to record the values on my little chart over here and then see what we
have at the end
all right everybody the compression testing process is complete everything
looked good so far at an initial check but I'm going to go ahead and throw
everything back together real quick put the spark plugs in and the ignition
packs back on I cleaned everything up everything looks fine so we'll get that
back together and then take a look at the data itself
so naturally I forgot to start the time lapse when I put everything back
together but basically it goes back together the way that it came apart
again you want to make sure you put the spark plugs back into the holes that
they came out of and then the ignition packs also into the same spot that they
came out of we also don't want to forget to reinstall our fuel pump fuse which is
this blue guy here in the number 18 spot like so and now we can go ahead and get
to the results of the compression test all right so I have recorded all of the
values from my compression tests on this piece of cardboard here each cylinder
has its own value now the compression test is basically
going to tell us how healthy our engine is what you want to see with a
compression test is all of your numbers for each cylinder should be roughly the
same or within a certain percentage of each other if you have a number that is
really really low compared to some of the other numbers or some of the
averages that's gonna tell you you have a problem in that cylinder likely the
piston rings have worn out and it's not holding any compression in that
particular cylinder therefore you have a lower compression test value so looking
at my compression test results for the number one cylinder in the front of the
car we have 171 for number 2 we have 170 for number 3 on the high end we have 178
number 4 is showing 160 psi number 5 169 and again 160 on number 6 I went ahead
and redid the tests multiple times for each cylinder just to get a good level
of baseline for each cylinder or a good average and then recorded them here and
again what we're looking for in these results is that our low end on the
compression test and our high end on the compression tests are not too far apart
so my low end is at 160 my high end is at 178 so an 18 psi difference roughly
between the low and the high everything else is pretty close so that is really
good the compression tester manual actually says your low-end should be at
least 75 percent of your high end and when we do the quick math on my number
is 160 divided by 178 we end up with 89% so 160 is 89% of the 178 so we're in
good shape if we're going below that 75% value you know that is not good in other
words if I had a cylinder here that read about 130 psi and my high end was at the
178 psi that 130 psi cylinder is only 73 or 74 percent of the high end so we have
a big gap between what the norm was or what the high end was and that really
low cylinder so therefore you can kind of deduce that you have a problem in
that particular cylinder your engines not gonna run as well it's not going to
make the power that it should be making and it's probably time for a rebuild so
there we have it for the e36 compression test things are looking good on my motor
for two hundred and seven thousand miles on this engine and all of the abuse that
I've put on the car through Auto cross and track driving over the years it's
holding up pretty well the bad news is is I can't swap an m3 engine into it
just yet I'm gonna run this one pretty much until it's dead we'll see how long
it goes it might be a while so the next issue that I got a
troubleshoot on this car is the clutch I've had a lot of issues with the clutch
slipping out on the track even just starting out in first gear you can tell
it's slipping and not holding power very well so either the clutch is bad or we
have oil leaking on to the clutch from the crankshaft seal so we're gonna have
to drop the transmission out of the car either way to find out we're gonna be
doing that here in the near future all right everybody we're gonna wrap it up
compression test process for an e36 bmw this process applies to pretty much any
other type of car as long as you have easy access to where the spark plugs are
and you know how to shut off the fuel system so we're not squirting fuel into
the cylinders while we're doing the compression test I'll put some links
down in the description for the compression test or tool
that I used you can also find them at your local auto store sometimes they
even rent them out as well and I hope you all enjoyed the video I
hope it was helpful and you learned a little bit of something if you have any
thoughts or comments leave them down below as well I'd love to hear from you
like I said stick around for more videos on the e36 BMW hopefully we've got a lot
of stuff happening with this car this offseason so stick around stay fast out
there I am checking out talk to you all next time
you