is there a quick plug to disconnect the fuel injectors somewhere?

also if you know what do these run at on average psi cranking, and anything else unusual about the procedure for this car.

thanks.

 

oh gosh come on guys, nobody?

 

Have not done a true "compression test"

But have used HPT to run the dynamic cyl test, when we had a car come in that had an odd rough idle. (Turned out to be the factory spark plug wire had an internal short somewhere, replaced wire, problem solved)

 

cylinder balance test? how far off was the problem cylinder?

 

Yes, Cyl balance test...

It was off by 7% at idle, and obviously underload you could feel something a little "odd" Not a flat out misfire, but a lame cly.

Obviously due to the lack of spark energy getting to the plug.

Literally, new wire, no issues.

 

anyone with a physical compression test?

 

TTT! want to put this thought to bed

 

still looking.

 

Out of curiosity, how would an actual leak down test on a C7 be performed any differently than any other car? In other words, are you seeking information about how to perform a leak down test on a C7?

 

i just need to know how to disable the fuel system.. along with what the 'usual' numbers are.

 

you could depressurize the fuel line and pull the fuse to the in tank electric pump

so if you pull the fuse and run the car it should "pump out" the di side and run out of fuel

I'd see what the service manual says,

 

This is how I've always done it, pull the fuse.

 

I would definitely find the service procedure for this before experimenting. In general high pressure DI pumps do not like being run without a fuel feed.

 

I'm surprised with all the people that bought the helms service manual nobody has posted what it says about doing this..

 

Alldata states

Fuel Pressure Relief

Warning

Fuel that flows out at high pressure can cause serious injury to the skin and eyes. ALWAYS depressurize the fuel system before removing components that are under high fuel pressure.

Note:
If a scan tool is not available, WAIT at LEAST 2 hours after the engine has been run, before removing the high pressure fuel line.

1. Install a scan tool to the vehicle and command the fuel pump relay OFF, allowing the low pressure fuel pump to shut off.

2. Start the vehicle and allow the engine to idle until the engine stops. The engine will stop in approximately 20-30 seconds.

3. Turn the ignition OFF.

4. Using the scan tool, verify that there is little to no fuel pressure, if there still is fuel pressure repeat step 2.

 

is there a fuse covering all 8 injectors?

 

After much wait we got this car strapped up last night, its making a bunch of blowby which i will follow somehwere with a vid as it really exercises my catch cans good. Ran the dynamic compression cylinder balance test 3 times. Worst of all 3 was cyl 8 at 97% and best was usually cyl 4 at 102%

my cyl #2 which was only plug that looked abnormal (stock heat range plug was in it turns out) was hanging right with the rest of them.

so the % are close but we weren't sure what to make of the rpm drop tps adv. as it did not seem to directly correlate.

i know this isnt the most 'tech' forum but anyone with more info i would love to hear!

the car made 508 after we split up the barometer from the maf and put the 3 bar in the intake. lots of false knock peak at max rpm of 11# boost.

drivability and power tuning this eve unless we run into something else first.

 

So did you do a psi compression test while you had the plugs out, and what are the numbers?

 

Yes, pull spark plug and then use a remote start switch. You will not be turning the ignition on so there will be no fuel. This will make a fast one man job because you can turn the engine over while holding the gauge.

 

Engine Compression Test
Removal Procedure
 1. Run the engine until it reaches normal operating temperature.
 2. Ignition key in the OFF position.
 3. Remove air cleaner resonator outlet duct. Refer to Air Cleaner Outlet Duct Replacement.
 4. Remove the spark plug wires. Refer to Spark Plug Wire Replacement.
 5. Remove the spark plugs. Refer to Spark Plug Replacement.
Note: In order to perform the compression test it will be necessary to use the scan tool in order to set up the compression test function.

 6. Put vehicle into compression test mode using the scan tool.
 7. Without compression gauge attached crank the engine using the ignition key to remove any foreign substances from the cylinders.
 8. Return the ignition key to the OFF position.
 9. Install a compression gauge to the cylinder to be tested.
10. Start with the compression gauge at zero and crank the engine through 4 compression strokes, 4 puffs using the ignition key.
11. Return the ignition key to the OFF position.
12. Repeat starting at step 9 for all remaining cylinders. All cylinders must be tested to obtain valid test results. Record the readings.
13. The minimum compression in any 1 cylinder should not be less than 70 percent of the highest cylinder. For example, if the highest pressure in any 1 cylinder is 862 kPa (125 psi), the lowest allowable pressure for any other cylinder would be 607 kPa (88 psi). (862 kPa x 70% = 607 kPa) (125 psi x 70%  = 88 psi).
◦Normal — Compression builds up quickly and evenly to the specified compression for each cylinder.
◦Piston Rings Leaking — Compression is low on the first stroke. Compression builds up with the following strokes, but does not reach normal. Compression improves considerably when you add oil.
Valves Leaking — Compression is low on the first stroke. Compression usually does not build up on the following strokes. Compression does not improve much when you add oil.
◦If 2 adjacent cylinders have lower than normal compression, and injecting oil into the cylinders does not increase the compression, the cause may be a head gasket leaking between the cylinders.
14. If a cylinder has low compression, inject approximately 15 ml (1 tablespoon) of engine oil into the combustion chamber through the spark plug hole. Measure the compression again and record the reading.
Installation Procedure
 1. Turn ignition key is in the OFF position.
 2. Remove compression gauge.
 3. Install the spark plugs. Refer to Spark Plug Replacement.
 4. Install the spark plug wires. Refer Spark Plug Wire Replacement.
 5. Install air cleaner resonator outlet duct. Refer to Air Cleaner Outlet Duct Replacement.
 6. Using the scan tool, clear all diagnostic codes.