97 Rocker Valve Adjustment
#11
05-17-2017, 11:58 AM
Join Date: Mar 2017
Location: Tulsa, OK
Posts: 220
OK congrats on the wedding 
so I bought compression tester gauge and fuel pressure from Harbor Freight ( see first pic ), these look about right ?
OK so now I'm trying to buy the light noid set and AutoZone wants $25 for there's ( see second pic ). Does this noid set look about right ? Can't really afford the $40 set at Harbor Freight...
so I bought compression tester gauge and fuel pressure from Harbor Freight ( see first pic ), these look about right ?OK so now I'm trying to buy the light noid set and AutoZone wants $25 for there's ( see second pic ). Does this noid set look about right ? Can't really afford the $40 set at Harbor Freight...
Last edited by Tynan Tha Real Dill; 05-17-2017 at 12:20 PM.
#12
05-18-2017, 12:36 AM
Join Date: Mar 2017
Location: Tulsa, OK
Posts: 220
OK I've gotten the light noid, fuel injection test gauge, and engine compression test gauge.
1. Tested the fuel pressure, turned on the key and the gauge immediately jumped to 60 psi, then dropped to 0 after 2 seconds.
2. Tested the injectors with the light noid, tested every injector, and they all lit up as the engine was cranked.
Lacking a spark plug socket at the moment so I can't do the compression test just yet.
So far so good ?
1. Tested the fuel pressure, turned on the key and the gauge immediately jumped to 60 psi, then dropped to 0 after 2 seconds.
2. Tested the injectors with the light noid, tested every injector, and they all lit up as the engine was cranked.
Lacking a spark plug socket at the moment so I can't do the compression test just yet.
So far so good ?
#13
05-18-2017, 05:32 PM
OK I've gotten the light noid, fuel injection test gauge, and engine compression test gauge.
1. Tested the fuel pressure, turned on the key and the gauge immediately jumped to 60 psi, then dropped to 0 after 2 seconds.
2. Tested the injectors with the light noid, tested every injector, and they all lit up as the engine was cranked.
Lacking a spark plug socket at the moment so I can't do the compression test just yet.
So far so good ?
1. Tested the fuel pressure, turned on the key and the gauge immediately jumped to 60 psi, then dropped to 0 after 2 seconds.
2. Tested the injectors with the light noid, tested every injector, and they all lit up as the engine was cranked.
Lacking a spark plug socket at the moment so I can't do the compression test just yet.
So far so good ?
Having the noid light blinking tells us the Crank sensor is "sensing", and the PCM is electronically trying to drive the fuel injectors injectors. Also means that Security is not preventing it from starting (security shuts off fuel injectors through the PCM).
Last edited by LesMyer; 05-18-2017 at 05:37 PM.
#14
05-26-2017, 07:34 PM
Join Date: Mar 2017
Location: Tulsa, OK
Posts: 220
Need to figure out where the fuel pressure is going after fuel pump shuts off. Should maintain 50psi+ pressure for some minutes. If it is going to zero immediately after fuel pump shuts off, then this is probably the cause of your no-start. Please advise fuel pressure during cranking for 5 seconds and we will know for certain if it is a problem or not.
Having the noid light blinking tells us the Crank sensor is "sensing", and the PCM is electronically trying to drive the fuel injectors injectors. Also means that Security is not preventing it from starting (security shuts off fuel injectors through the PCM).
Having the noid light blinking tells us the Crank sensor is "sensing", and the PCM is electronically trying to drive the fuel injectors injectors. Also means that Security is not preventing it from starting (security shuts off fuel injectors through the PCM).
Cylinder #1 - 150 psi
Cylinder #2 - 0 psi
Cylinder #3 - 120 psi
Cylinder #4 - 125 psi
Cylinder #5 - 0 psi
Cylinder #6 - 130 psi
I'm guessing cylinder's #2 and #5 are clearly dead, but I dont know what I'm looking for in these results. So with these results, what seems to be my problem ?
P.s. - my fuel pressure gauge sprays fuel from the hose connected to the gauge. So before I try the fuel pressure test again, im going to fix that, dont want fuel in my eye again lol
#16
05-26-2017, 09:22 PM
Join Date: Mar 2017
Location: Tulsa, OK
Posts: 220
ok cool I bought mine at Harbor Freight too, I guess I need the teflon tape too !
Last edited by Tynan Tha Real Dill; 05-26-2017 at 09:32 PM.
#17
05-26-2017, 11:27 PM
OK compression test is complete, I'm uploading the results I wrote down (see pic).
Cylinder #1 - 150 psi
Cylinder #2 - 0 psi
Cylinder #3 - 120 psi
Cylinder #4 - 125 psi
Cylinder #5 - 0 psi
Cylinder #6 - 130 psi
I'm guessing cylinder's #2 and #5 are clearly dead, but I dont know what I'm looking for in these results. So with these results, what seems to be my problem ?
P.s. - my fuel pressure gauge sprays fuel from the hose connected to the gauge. So before I try the fuel pressure test again, im going to fix that, dont want fuel in my eye again lol
Cylinder #1 - 150 psi
Cylinder #2 - 0 psi
Cylinder #3 - 120 psi
Cylinder #4 - 125 psi
Cylinder #5 - 0 psi
Cylinder #6 - 130 psi
I'm guessing cylinder's #2 and #5 are clearly dead, but I dont know what I'm looking for in these results. So with these results, what seems to be my problem ?
P.s. - my fuel pressure gauge sprays fuel from the hose connected to the gauge. So before I try the fuel pressure test again, im going to fix that, dont want fuel in my eye again lol
#18
05-30-2017, 06:42 PM
Join Date: Mar 2017
Location: Tulsa, OK
Posts: 220
There may be more causing a no start, but definitely need to figure out cylinders 2 & 5 before going on. Let's pop the valve covers and turn the rocker nuts out a couple of turns on both valves for both #2 and #5 cyl, and repeat compression test. If you get compression with the nuts backed off, then you know something happened when overtightening the rocker nuts to 40 ft lbs and we can deal with that. If you still don't get compression we can deal with that too. Also look at the valve action on those cylinders when cranking and note any differences. As an aside, what about the test for spark out of the coil?
I read an article about a "wet compression test" I should perform after the first test readings from those 2 cylinder's. Look :
From article - "The results you obtain from this second ‘Wet’ compression test will help you determine if the low compression you recorded in the ‘Dry’ compression test are caused by worn piston rings or worn cylinder head valves."
CASE 1: The compression value shot up.. This tells you that the piston compression rings are worn out and thus the problem is in the bottom end (block) of the engine in your GM 4.3L, 5.0L, or 5.7L equipped vehicle.
Here's why: The engine oil helped the piston rings seal better, thus bringing up the compression value almost back to normal. If the problem were in the cylinder head valves... the engine oil you just added wouldn't make a difference at all (on the compression value).
CASE 2: The compression value stayed the same.. This confirms that the problem is in the cylinder head valves.
Here's why: If the cylinder head valves and their seats are worn out (or maybe even bent from a broken timing belt), no amount of engine oil is gonna help seal the compression in, in the cylinder. So, if the compression value, for the specific cylinder you're testing did not go up (after you added oil to it)... then this is a dead giveaway that you've got cylinder head valve damage.
OK now my question is, where can I add oil to these cylinders besides the spark plug holes ? Oil leaks back out when I add it there.
#19
06-01-2017, 07:59 AM
OK, there's spark from the coil...
I read an article about a "wet compression test" I should perform after the first test readings from those 2 cylinder's. Look :
From article - "The results you obtain from this second ‘Wet’ compression test will help you determine if the low compression you recorded in the ‘Dry’ compression test are caused by worn piston rings or worn cylinder head valves."
CASE 1: The compression value shot up.. This tells you that the piston compression rings are worn out and thus the problem is in the bottom end (block) of the engine in your GM 4.3L, 5.0L, or 5.7L equipped vehicle.
Here's why: The engine oil helped the piston rings seal better, thus bringing up the compression value almost back to normal. If the problem were in the cylinder head valves... the engine oil you just added wouldn't make a difference at all (on the compression value).
CASE 2: The compression value stayed the same.. This confirms that the problem is in the cylinder head valves.
Here's why: If the cylinder head valves and their seats are worn out (or maybe even bent from a broken timing belt), no amount of engine oil is gonna help seal the compression in, in the cylinder. So, if the compression value, for the specific cylinder you're testing did not go up (after you added oil to it)... then this is a dead giveaway that you've got cylinder head valve damage.
OK now my question is, where can I add oil to these cylinders besides the spark plug holes ? Oil leaks back out when I add it there.
I read an article about a "wet compression test" I should perform after the first test readings from those 2 cylinder's. Look :
From article - "The results you obtain from this second ‘Wet’ compression test will help you determine if the low compression you recorded in the ‘Dry’ compression test are caused by worn piston rings or worn cylinder head valves."
CASE 1: The compression value shot up.. This tells you that the piston compression rings are worn out and thus the problem is in the bottom end (block) of the engine in your GM 4.3L, 5.0L, or 5.7L equipped vehicle.
Here's why: The engine oil helped the piston rings seal better, thus bringing up the compression value almost back to normal. If the problem were in the cylinder head valves... the engine oil you just added wouldn't make a difference at all (on the compression value).
CASE 2: The compression value stayed the same.. This confirms that the problem is in the cylinder head valves.
Here's why: If the cylinder head valves and their seats are worn out (or maybe even bent from a broken timing belt), no amount of engine oil is gonna help seal the compression in, in the cylinder. So, if the compression value, for the specific cylinder you're testing did not go up (after you added oil to it)... then this is a dead giveaway that you've got cylinder head valve damage.
OK now my question is, where can I add oil to these cylinders besides the spark plug holes ? Oil leaks back out when I add it there.
If loosening the nuts doesn't restore compression, then you need to remove the rockers completely and attempt to pressurize the cylinder with compressed air (yes at that point you would need to borrow an air compressor and a hose to adapt to the spark plug hole). Be careful when plugging the air into the cylinder - the crankshaft will turn as much as almost 180° as the piston goes to the bottom of its travel and you don't want any fingers cut off in the belt pulleys. Simply listen to where air comes out - if it blows out the intake it is intake valve, if air blows out exhaust it is exhaust valve, if air blows out the crankcase it is a piston. This a crude leak-down test.
As an aside, true leak down testing uses a leak-down testing device that measures pressure drop across a small restriction in a 100psi regulated air supply flowing into the cylinder through a 0.040" orifice. The more the cylinder leaks past valves or rings, the more the pressure drops across the orifice. Less than 10% pressure drop across a 0.040 orifice due to cylinder leakage is considered excellent. Race engines can get less than 5% and sometimes even lower (better seal = more power). Over 25% leak-down is considered bad. Again, you can tell where the leak is by listening and comparing cylinders.
As for valve adjustment on a 1997 Blazer - once you are sure valve train is OK, you want to simply torque the stop-nuts down against their stops at 20 ft lbs. Nothing more, nothing less. Easy-peasy!
Last edited by LesMyer; 06-01-2017 at 10:37 AM.
#20
06-01-2017, 08:46 PM
Join Date: Mar 2017
Location: Tulsa, OK
Posts: 220
It's a typically valid test that you have found, but I think it does not apply very well to your particular situation. The test assumes low compression is found (not zero compression). If you have zero compression in a cylinder, then either you have a hole in the piston or a serious valve problem. I'm betting on a valve problem after tightening those nuts to 40 ft lbs. So please do the tests I described in post #17 (backing off the rocker nuts a couple of turns on those two cylinders) and report. Also don't forget to observe valve action while cranking. If we find any rocker stud/nut damage, these are screw-in rocker studs that can be easily changed!!
If loosening the nuts doesn't restore compression, then you need to remove the rockers completely and attempt to pressurize the cylinder with compressed air (yes at that point you would need to borrow an air compressor and a hose to adapt to the spark plug hole). Be careful when plugging the air into the cylinder - the crankshaft will turn as much as almost 180° as the piston goes to the bottom of its travel and you don't want any fingers cut off in the belt pulleys. Simply listen to where air comes out - if it blows out the intake it is intake valve, if air blows out exhaust it is exhaust valve, if air blows out the crankcase it is a piston. This a crude leak-down test.
As an aside, true leak down testing uses a leak-down testing device that measures pressure drop across a small restriction in a 100psi regulated air supply flowing into the cylinder through a 0.040" orifice. The more the cylinder leaks past valves or rings, the more the pressure drops across the orifice. Less than 10% pressure drop across a 0.040 orifice due to cylinder leakage is considered excellent. Race engines can get less than 5% and sometimes even lower (better seal = more power). Over 25% leak-down is considered bad. Again, you can tell where the leak is by listening and comparing cylinders.
As for valve adjustment on a 1997 Blazer - once you are sure valve train is OK, you want to simply torque the stop-nuts down against their stops at 20 ft lbs. Nothing more, nothing less. Easy-peasy!
If loosening the nuts doesn't restore compression, then you need to remove the rockers completely and attempt to pressurize the cylinder with compressed air (yes at that point you would need to borrow an air compressor and a hose to adapt to the spark plug hole). Be careful when plugging the air into the cylinder - the crankshaft will turn as much as almost 180° as the piston goes to the bottom of its travel and you don't want any fingers cut off in the belt pulleys. Simply listen to where air comes out - if it blows out the intake it is intake valve, if air blows out exhaust it is exhaust valve, if air blows out the crankcase it is a piston. This a crude leak-down test.
As an aside, true leak down testing uses a leak-down testing device that measures pressure drop across a small restriction in a 100psi regulated air supply flowing into the cylinder through a 0.040" orifice. The more the cylinder leaks past valves or rings, the more the pressure drops across the orifice. Less than 10% pressure drop across a 0.040 orifice due to cylinder leakage is considered excellent. Race engines can get less than 5% and sometimes even lower (better seal = more power). Over 25% leak-down is considered bad. Again, you can tell where the leak is by listening and comparing cylinders.
As for valve adjustment on a 1997 Blazer - once you are sure valve train is OK, you want to simply torque the stop-nuts down against their stops at 20 ft lbs. Nothing more, nothing less. Easy-peasy!
Last edited by Tynan Tha Real Dill; 06-01-2017 at 08:49 PM.