here is how good ol' bob z. does a cranking compression check, but before i
get into it, i would like to share something with you. a cranking
compression test is just a tool used to quickly determine a difference
between the cylinders. you are looking for consistency. a leak-down tester
is the only way to know if you have engine or not:

1. warm the engine to operating temperature
2. pull all of the spark plugs (don't get burnt - be careful!)
3. prop the throttle wide open
4. screw the compression gage into the first cylinder
5. bump the starter over manually until the pressure peaks (a continuous
cranking, approximately 3 -5 revolutions) - screwdriver laid over the posts
on the solenoid or by using one of those really nice remote starter buttons
(not the starter button that you use to start your car from the house)
6. record your reading
7. continue till you finish all cylinders
8. the cylinders should not vary more than 25lbs from each other.

--
bob z.

"people with less brain power than you are doing more difficult things
everyday"©

 

here is how good ol' bob z. does a cranking compression check, but before i
get into it, i would like to share something with you. a cranking
compression test is just a tool used to quickly determine a difference
between the cylinders. you are looking for consistency. a leak-down tester
is the only way to know if you have engine or not:

1. warm the engine to operating temperature
2. pull all of the spark plugs (don't get burnt - be careful!)
3. prop the throttle wide open
4. screw the compression gage into the first cylinder
5. bump the starter over manually until the pressure peaks (a continuous
cranking, approximately 3 -5 revolutions) - screwdriver laid over the posts
on the solenoid or by using one of those really nice remote starter buttons
(not the starter button that you use to start your car from the house)
6. record your reading
7. continue till you finish all cylinders
8. the cylinders should not vary more than 25lbs from each other.

--
bob z.

"people with less brain power than you are doing more difficult things
everyday"©

 

here is how good ol' bob z. does a cranking compression check, but before i
get into it, i would like to share something with you. a cranking
compression test is just a tool used to quickly determine a difference
between the cylinders. you are looking for consistency. a leak-down tester
is the only way to know if you have engine or not:

1. warm the engine to operating temperature
2. pull all of the spark plugs (don't get burnt - be careful!)
3. prop the throttle wide open
4. screw the compression gage into the first cylinder
5. bump the starter over manually until the pressure peaks (a continuous
cranking, approximately 3 -5 revolutions) - screwdriver laid over the posts
on the solenoid or by using one of those really nice remote starter buttons
(not the starter button that you use to start your car from the house)
6. record your reading
7. continue till you finish all cylinders
8. the cylinders should not vary more than 25lbs from each other.

--
bob z.

"people with less brain power than you are doing more difficult things
everyday"©

 

If the throttle is closed the intake manifold will be at a partial
vacuum.... and the vacuum value must be subtracted from the compression
value --- and you really dont know what this will be due to all the
vacuum, etc. bleeds.
Why bother? .... just open the throttle plate so that the intake is
exposed to atmospheric pressure.

In article <btlltp$8jcmc$1@ID-193866.news.uni-berlin.de>, William
Oliveri <wuji@bigvalley.net> wrote:

> Thanks,
>
> I found in my FSM that the pressure for a 6 cylinder should be between 120
> and 140 psi.
>
> One thing I don't understand is why should the throttle be wide open
> position when fuel pump and coil are dis-engaged?
>
> What does the throttle have to do with anything when testing cylinder
> compression?
>
> Thanks,
>
> Bill
>
> "DougW" <post.replies@invalid.address> wrote in message
> news:0OlLb.57344$PK3.46808@okepread01...
> > William Oliveri did pass the time by typing:
> > > Ok, I have a compression gauge but haven't used it yet.
> > >
> > > Can someone outline the steps and what the correct compression on a 258
> > > should be?
> >
> > Dunno
> >
> > > 1. Should I remove all spark plugs when testing compression?
> >
> > You could. I usually do a quick comression test when changing plugs.
> > Removing the plugs lets the engine crank easier.
> >
> > > 2. I have the Mopar MPI kit on my 258. Do I need to unhook it so fuel
> > > doesn't go in the cylinder when testing?
> >
> > Pull the fuse for your fuel pump.
> >
> > Don't forget to disconnect the coil signal. :)
> >
> > > 3. I hook the compression gauge into the spark plug hole. How many
> times do
> > > I turn the engine?
> >
> > Till the numbers stop climbing (4-5 compression strokes)
> >
> > http://www.georgiazclub.com/tips/ztech/comptest.htm
> > is fairly good although I'm not so sure about step3
> > (running the engine with plugs loose)
> >
> > --
> > DougW
> >
> >
> >
>
>

 

If the throttle is closed the intake manifold will be at a partial
vacuum.... and the vacuum value must be subtracted from the compression
value --- and you really dont know what this will be due to all the
vacuum, etc. bleeds.
Why bother? .... just open the throttle plate so that the intake is
exposed to atmospheric pressure.

In article <btlltp$8jcmc$1@ID-193866.news.uni-berlin.de>, William
Oliveri <wuji@bigvalley.net> wrote:

> Thanks,
>
> I found in my FSM that the pressure for a 6 cylinder should be between 120
> and 140 psi.
>
> One thing I don't understand is why should the throttle be wide open
> position when fuel pump and coil are dis-engaged?
>
> What does the throttle have to do with anything when testing cylinder
> compression?
>
> Thanks,
>
> Bill
>
> "DougW" <post.replies@invalid.address> wrote in message
> news:0OlLb.57344$PK3.46808@okepread01...
> > William Oliveri did pass the time by typing:
> > > Ok, I have a compression gauge but haven't used it yet.
> > >
> > > Can someone outline the steps and what the correct compression on a 258
> > > should be?
> >
> > Dunno
> >
> > > 1. Should I remove all spark plugs when testing compression?
> >
> > You could. I usually do a quick comression test when changing plugs.
> > Removing the plugs lets the engine crank easier.
> >
> > > 2. I have the Mopar MPI kit on my 258. Do I need to unhook it so fuel
> > > doesn't go in the cylinder when testing?
> >
> > Pull the fuse for your fuel pump.
> >
> > Don't forget to disconnect the coil signal. :)
> >
> > > 3. I hook the compression gauge into the spark plug hole. How many
> times do
> > > I turn the engine?
> >
> > Till the numbers stop climbing (4-5 compression strokes)
> >
> > http://www.georgiazclub.com/tips/ztech/comptest.htm
> > is fairly good although I'm not so sure about step3
> > (running the engine with plugs loose)
> >
> > --
> > DougW
> >
> >
> >
>
>

 

If the throttle is closed the intake manifold will be at a partial
vacuum.... and the vacuum value must be subtracted from the compression
value --- and you really dont know what this will be due to all the
vacuum, etc. bleeds.
Why bother? .... just open the throttle plate so that the intake is
exposed to atmospheric pressure.

In article <btlltp$8jcmc$1@ID-193866.news.uni-berlin.de>, William
Oliveri <wuji@bigvalley.net> wrote:

> Thanks,
>
> I found in my FSM that the pressure for a 6 cylinder should be between 120
> and 140 psi.
>
> One thing I don't understand is why should the throttle be wide open
> position when fuel pump and coil are dis-engaged?
>
> What does the throttle have to do with anything when testing cylinder
> compression?
>
> Thanks,
>
> Bill
>
> "DougW" <post.replies@invalid.address> wrote in message
> news:0OlLb.57344$PK3.46808@okepread01...
> > William Oliveri did pass the time by typing:
> > > Ok, I have a compression gauge but haven't used it yet.
> > >
> > > Can someone outline the steps and what the correct compression on a 258
> > > should be?
> >
> > Dunno
> >
> > > 1. Should I remove all spark plugs when testing compression?
> >
> > You could. I usually do a quick comression test when changing plugs.
> > Removing the plugs lets the engine crank easier.
> >
> > > 2. I have the Mopar MPI kit on my 258. Do I need to unhook it so fuel
> > > doesn't go in the cylinder when testing?
> >
> > Pull the fuse for your fuel pump.
> >
> > Don't forget to disconnect the coil signal. :)
> >
> > > 3. I hook the compression gauge into the spark plug hole. How many
> times do
> > > I turn the engine?
> >
> > Till the numbers stop climbing (4-5 compression strokes)
> >
> > http://www.georgiazclub.com/tips/ztech/comptest.htm
> > is fairly good although I'm not so sure about step3
> > (running the engine with plugs loose)
> >
> > --
> > DougW
> >
> >
> >
>
>