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Checking cylinder compression 

 

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 Post subject: Checking cylinder compression
Posted: Mon May 28, 2007 2:06 pm 
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I have a Gregory's guide and It's not exactly accurate and I'm looking at the cylinder compression test section.

This is the steps it says.

1. Run the engine until it reaches normal operating temperature.
2. Carefully disconnect the high tension leads from the spark plugs.
3. Remove Spark plugs
4. Remove starter relay and connect a remote satarter switch.

This is where I am lost, where can I get a remote starter switch and what exactly does it do? If it starts the engine just likje normal won't that be bad since the car is only running on 5 cylinders?

5. Set the throttle to wide open position.

Does this ean floor the accelerator? That can't be good for the engine especially on 5 cylinders???

6. Install compression guage to number 1 spark plug hole.

7. Using the remote starter switch, rotate the engine at least five turns. Observe the compression guage.

Now I never got this whole rotating thing, Does 1 rotation mean when a cylinder goes down and then back up? It says rotate it with the remote starter switch? Also how do I know when it finishes it's rotation?

I'm trying to learn DIY servicing since I'm poor and it cost $900 for a major service.

I'd also feel more confident knowing I'm dfoing it myself.
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Posted: Mon May 28, 2007 2:13 pm 
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i did it with two people, one to hold a compression tester in the spark plug hole, and one to crank the motor over. makes the job a lot easier lol.

 

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Posted: Mon May 28, 2007 2:13 pm 
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a remote strater switch is just basically a switch that you attach to the starter motor,

the motor will not run if you remove the starter relay.

when you switch the remote starter it will just crank the motor over ( no spark, so it will not run)

read compression guage....

write down your reading...

put plug back in move to next cylinder

write down reading...

so on so forth till all reading have been done..

 

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Posted: Mon May 28, 2007 8:05 pm 
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To make it easier I simply reach down to the coil and remove the coil plug on my EF. I then pull all spark plugs (label all wires to make life easier). Screw in compression gauge. Crank engine for 5 revolutions with your foot flat to the floor (if you don't hold WOT then you will get low readings). Write down number and repeat for other 5 cylinders.

Below 140 PSI is bad. A difference of 10% between lowest to highest is bad. Readings of 165 PSI or more is excellent. Mine were all within 2 PSI and all were around 170 PSI IIRC.

cheers
Scott

 

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Posted: Mon May 28, 2007 9:08 pm 
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hmmm thanks guys.

so WOT is the accelerator on full?

Won't that be bad for the engines? reving the crap outta it?

Know that I know what a starter switch does I basically get the idea.

Where can I get a starter switch form and how much do they cost?

Also on another note.

In the engine tune up section of this gregory's guide It tell me how to check and adjust ignition timing.

It tells me to connect a timing light to the 1st lead then connect a jumper wire (where can I buy this and how much?) Then start the engine.

Now that's meant to put it in self diagnostics mode which I guess means it's ok that it's running on 5 cylinders (timing light takes cylinder 1's lead).

But what if it doesn't go in self diagnostics mode if say the jumper doesn't bridge Terminal A and B.

Everything else seems ok for me to do in the tune up it's just these things that make be worry
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Posted: Mon May 28, 2007 9:18 pm 
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By accelerating, it is just opening the intake manifold to let air/petrol in. Since there is no spark going to the spark plugs (cause you take the main spark plug lead of the dizzy or the coil), the car will not fire/start.

The timing light will go between the spark plug lead and the spark plug. So it will still be running on 6 cylinders. The timing light will have 2 connections. 1 goes on the spark plug lead and the 2 one go onto the spark plug.
If u dont understand, i can draw a quick diagram with mspaint. Might be easier to understand.

 

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Posted: Mon May 28, 2007 9:25 pm 
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The point of removing the starter relay is so you can insert a manual switch so you can do it yourself at the engine bay. If you have two people, you leave the starter relay in and get them to turn the key to crank while you poke the compression guage in the spark plug hole.

I think the point you are missing is that you don't want the engine to kick over and start - you only want it to crank to build up cylinder compression, so no, WOT will not rev the hell out of it as long as you have removed the coil primary plug (You don't want sparks flying out of all those unplugged leads)

Remove all the plugs so the engine turns easier and you don't end up with a flat battery.

Quote:
EF_fairmont_guy
the motor will not run if you remove the starter relay.


Be carefull! It will not crank if you turn the key, but it could start if you are jumpering the starter relay base and the key is already in the ignition position.

Removing the starter relay is a safety measure if you are going to have your hands in bad places and you don't want someone turning the key on you while they are there.

You can make your own start jumper by poking wires in the terminals that correspond to pins 87 and 30 of the base. Connect these to a 10 amp momentary switch and you have yourself a remote. Use crimp spade terminals to poke in the holes instead of bare wires to avoid a short.

Alternatively, gut an old relay and solder a swith to its innards.[/quote]

 

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Posted: Mon May 28, 2007 9:32 pm 
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Compression tester screws into the spark plug hole anyway. So you dont need another person.

Edit. lol didn't make sense.

 

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Last edited by shnoza on Mon May 28, 2007 10:05 pm, edited 1 time in total.

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Posted: Mon May 28, 2007 10:01 pm 
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Also, you can run the engine on 5 cylinders fine while checking compression. It is called a dynamic compression check. You start and run the engine, releasing pressure from the gauge. You blip the throttle and note the readings at different rpm's and that can tell you a WHOLE lot about your engine.

Also get a timing light that has an inductive pickup with a xenon bulb. They are much brighter and are a whole lot easier to use. Around $30+ depending on quality at Super Cheap.

cheers
Scott

 

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Posted: Mon May 28, 2007 10:13 pm 
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EBGizmo wrote:
The point of removing the starter relay is so you can insert a manual switch so you can do it yourself at the engine bay. If you have two people, you leave the starter relay in and get them to turn the key to crank while you poke the compression guage in the spark plug hole.

I think the point you are missing is that you don't want the engine to kick over and start - you only want it to crank to build up cylinder compression, so no, WOT will not rev the hell out of it as long as you have removed the coil primary plug (You don't want sparks flying out of all those unplugged leads)

Remove all the plugs so the engine turns easier and you don't end up with a flat battery.

Quote:
EF_fairmont_guy
the motor will not run if you remove the starter relay.


Be carefull! It will not crank if you turn the key, but it could start if you are jumpering the starter relay base and the key is already in the ignition position.

Removing the starter relay is a safety measure if you are going to have your hands in bad places and you don't want someone turning the key on you while they are there.

You can make your own start jumper by poking wires in the terminals that correspond to pins 87 and 30 of the base. Connect these to a 10 amp momentary switch and you have yourself a remote. Use crimp spade terminals to poke in the holes instead of bare wires to avoid a short.

Alternatively, gut an old relay and solder a swith to its innards.
[/quote]

Hmmm I think I get it now.

The engine doesn't start, the starter motor just turns the crankshaft so it's running on electricity and not fuel?

The gregory's doesn't mention anything about removing the leads at the main point only the boots off the spark plugs so how do I remove the primary coil plug?


I'll be doing this with 2 people so I leave the starter relay in and get one of us to attempt to start the engine by key as we always do, but the engine won't start since the leads aren't connected and can't spark the fuel on the piston head?

It sounds pretty dangerous, once the leads are removed there's no way it can start yeah? I don't wanna somehow runover the guy holding the compression guage. Also this is my first car and I'm preparing it for when I'm 18 (2 months away). It's an Auto so is Park a brake as well as neutral? I was thinking of putting it in neutral so if it somehow starts it aint going anywhere? But is park also neutral but plus a brake?
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Posted: Mon May 28, 2007 10:18 pm 
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Yes as long as there is no spark going to the spark plugs, the car wont started. Think you got the idea now.
Leave it in park. Its like a brake. It lets the engine rev but holds/stops the gears from moving. well something like that. Correct me if im wrong.

 

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Posted: Mon May 28, 2007 10:21 pm 
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What car do you have?

 

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Posted: Mon May 28, 2007 10:24 pm 
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ED falcon classic.

So Park disconnects the engine from the gears like neutral so there's no way it'll start moving?
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Posted: Mon May 28, 2007 10:30 pm 
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No way it will move.
No sure where the coil is on a ED but the on the coil (if it looks the same as a el), the leads will be connected around the top of the coil while the main lead which sends electricity to the coil will be in the center.
Think the coil should be under the intake manifold. But not to sure.

 

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Posted: Mon May 28, 2007 10:36 pm 
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Do you mean the distributer cap?

So there should be 7 leads 6 ot the cylinders and 1 that supplies the power that I disconnect?
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