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Old 11-15-2006, 05:45 AM
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how to check compression on 99 f250?

i have a 99 crew cab f250 that is overpressurizing coolant system, going to test for combustibles in the coolant by using block checker, was thinking i could unhook injectors at valve cover plug and run test with 1 side of motor to determine which side to tear down first, has anyone tried this before. i was also going to check compression and was wondering what the procedure to do this was. i was going to buy a diesel engine compression test kit from harbor freight tools for $17, it said it had the glow plug adapters for ford, pull all the glow plugs on that side and run compression on all cylinders. does anyone know the correct procedure? thanks in advanced.
jason
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Old 11-15-2006, 06:15 AM
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Before you remove the glow plugs use compressed air and blow the oil away from the glowplugs first, otherwise oil will enter the cylinder and give innacurate readings. I remove all the glow plugs first so the engine spins freely when cranking. I crank the the motor 6 revolutions when checking each cylinder. You should be close to 400 psi. Your lowest cylinder should be at least 75% of you highest reading. Heres a copy of Ford's procedure. It's for a gas motor but it's in there diesel section. Also included is a cylinder leak down procedure.

Compression Test—Compression Gauge Check

Make sure the oil in the crankcase is of the correct viscosity and at the correct level and that the battery (10655) is correctly charged. Operate the vehicle until the engine is at normal operating temperature. Turn the ignition switch to the OFF position, then remove all the spark plugs (12405).
Set the throttle plates in the wide-open position.
Install a compression gauge such as the Compression Tester in the No. 1 cylinder.
Install an auxiliary starter switch in the starting circuit. With the ignition switch in the OFF position, and using the auxiliary starter switch, crank the engine a minimum of five compression strokes and record the highest reading. Note the approximate number of compression strokes required to obtain the highest reading.
Repeat the test on each cylinder, cranking the engine approximately the same number of compression strokes.
Compression Test—Test Results

The indicated compression pressures are considered within specification if the lowest reading cylinder is at least 75 percent of the highest reading.


If one or more cylinders reads low, squirt approximately one tablespoon of engine oil on top of the pistons in the low-reading cylinders. Repeat the compression pressure check on these cylinders.

Compression Test—Interpreting Compression Readings

If compression improves considerably, piston rings are faulty.
If compression does not improve, valves are sticking or seating incorrectly.
If two adjacent cylinders indicate low compression pressures and squirting oil on each piston does not increase compression, the head gasket may be leaking between cylinders. Engine oil or coolant in cylinders could result from this condition.
Use the Compression Pressure Limit Chart when checking cylinder compression so that the lowest reading is within 75 percent of the highest reading.

Cylinder Leakage Detection

When a cylinder produces a low reading, use of the Engine Cylinder Leak Detection/Air Pressurization Kit will be helpful in pinpointing the exact cause.

The leakage detector is inserted in the spark plug hole, the piston is brought up to dead center on the compression stroke, and compressed air is admitted.

Once the combustion chamber is pressurized, a special gauge included in the kit will read the percentage of leakage. Leakage exceeding 20 percent is excessive.

While the air pressure is retained in the cylinder, listen for the hiss of escaping air. A leak at the intake valve (6507) will be heard in the throttle body (9E926). A leak at the exhaust valve (6505) can be heard at the tail pipe. Leakage past the piston rings will be audible at the positive crankcase ventilation (PCV) connection. If air is passing through a blown head gasket to an adjacent cylinder, the noise will be evident at the spark plug hole of the cylinder into which the air is leaking. Cracks in the cylinder block or gasket leakage into the cooling system may be detected by a stream of bubbles in the radiator (8005).
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Old 10-30-2007, 12:19 PM
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You will get better results if you follow the procedure described by djsdiesel above. If you do one side, make sure to disable the other bank. The engine will start and run on one bank.

If you are overpressuring the coolant system, you likely have cracked injector cups.
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Old 10-30-2007, 12:51 PM
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thanks for the reply, turned out it was a blown head gasket on the drivers side, head was warped .040. had head resurfaced and replaced gasket and head bolts and torqued in the 3 step sequence. thanks, been running great, 7,000 miles put on since repair now at 258100 on odometer, has been a great truck
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Old 04-17-2008, 07:21 AM
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so you go through the glow plug wholes with the adapter? Does it fit in it or do you hold it on???
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Old 04-17-2008, 07:26 AM
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Quote:
Originally Posted by krupatex View Post
so you go through the glow plug wholes with the adapter? Does it fit in it or do you hold it on???

It's an adapter that screws in. You won't be able to hold it.
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Old 11-11-2008, 06:06 PM
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Was about to start a new post but I might as well revive an old thread.

So I saw in the tech files this video: Cylinder Compression Test

Is the adaptor that they use for the ford glow plugs come with all compression testers, or is there a specific diesel compression tester? Can I trust a Harbor freight tester, or should I buy one at a parts store like Oreilly?

I am planning on testing my compression while I am under the valve covers next week putting in my Stage 2s from DIY, and will be changing the glow plugs while I am at it, might as well see how this 240,000 mile motor is holding up.

Also, what is the easiest way to disable the injection to keep the motor from firing? I am going to be pulling the injectors anyways, so should I just unplug the UVC harnesses or unplug something else to kill the injectors or PCM to compression test?

I dont have any issues, not burning or leaking any oil, besides now an HPOP line O ring is leaking, so I should add that to the list of things to change. I am pretty confident that the motor will be good, just want to verfiy, like the fact that I know my model year is a forged rods but I pulled the plug today just to take a look and smile knowing I have decent rods.


Also while I am ranting, what specficially is the contribution test? Correct me if I am wrong its testing the injector intensity through the OBDII port? If thats the case and I am putting in reman injectors I should have to bother with testing this, they should all be good?

Last edited by AFBLUE; 11-11-2008 at 06:14 PM.
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Old 11-11-2008, 06:25 PM
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Quote:
Originally Posted by AFBLUE View Post
Was about to start a new post but I might as well revive an old thread.

So I saw in the tech files this video: Cylinder Compression Test

Is the adaptor that they use for the ford glow plugs come with all compression testers, or is there a specific diesel compression tester? Can I trust a Harbor freight tester, or should I buy one at a parts store like Oreilly?

Also, what is the easiest way to disable the injection to keep the motor from firing? I am going to be pulling the injectors anyways, so should I just unplug the UVC harnesses or unplug something else to kill the injectors or PCM to compression test?

I am planning on testing my compression while I am under the valve covers next week putting in my Stage 2s from DIY, and will be changing the glow plugs while I am at it, might as well see how this 240,000 mile motor is holding up.

I dont have any issues, not burning or leaking any oil, besides now an HPOP line, so I should add that to the list of things to change. So I am pretty confident that the motor will be good, just want to verfiy, like the fact that I know my model year is a forged rod block but I pulled the plug today just to take a look and smile knowing I have decent rods.


Also while I am ranting, what specficially is the contribution test? Correct me if I am wrong its testing the injector intensity through the OBDII port? If thats the case and I am putting in reman injectors I should have to bother with testing this, they should all be good?
specific tester and specific adapter for the powerstroke. I think a tester and adapter is around $150.

On your superduty, leave the keys out of the ignition. Remove the top wire from the starter solenoid on the passenger fender (top wire is a small, single, covered wire). After connecting the compression adapter to the head and the tester, make sure that the adapter is clear of the valve train. Use a jumper wire from the positive battery terminal to the solenoid terminal you just uncovered. Let the motor crank over a few times. You should be in the 400psi range.


Cylinder Contrib/balance is nothing more than the scanner telling the pcm/idm to "listen" or "cut" out each cylinder and monitor RPM changes. It also messes with fuel flow to do this.

Don't worry about different injectors unless you are going above stage 3.
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Old 11-11-2008, 06:32 PM
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To add, PLEASE remember to remove all oil away from the glow plug before removing. I'll try to keep watching the thread if you have anymore questions.
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Old 11-11-2008, 06:32 PM
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Quote:
Originally Posted by Dirk View Post
specific tester and specific adapter for the powerstroke. I think a tester and adapter is around $150.

On your superduty, leave the keys out of the ignition. Remove the top wire from the starter solenoid on the passenger fender (top wire is a small, single, covered wire). After connecting the compression adapter to the head and the tester, make sure that the adapter is clear of the valve train. Use a jumper wire from the positive battery terminal to the solenoid terminal you just uncovered. Let the motor crank over a few times. You should be in the 400psi range.


Cylinder Contrib/balance is nothing more than the scanner telling the pcm/idm to "listen" or "cut" out each cylinder and monitor RPM changes. It also messes with fuel flow to do this.

Don't worry about different injectors unless you are going above stage 3.
On that note does anyone have a tester I can borrow if its going to run me $150?
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