Failed Engine/Cyl Compression Test??, Unplugged Fuses & Impala.... :( - Page 3 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 03-11-2016, 06:39 PM   #21
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Quote:
Originally Posted by Tech II View Post
and........"WHY" were you doing a compression test in the first place?

Have you checked fuel pressure with a gage, checked for spark, checked for injector pulse, like Mike asked?

Have you scanned for codes?

Tried starting vehicle with MAF disconnected?

Check for fuel in vac line to fuel pressure regulator?
I don't know how to check the fuel gauge And Injector Pulse, YET. But, I'll Look into how to do that, Youtube it or Search For write-ups online. If You have any Resources You can send My way, I'll appreciate it.

If You read the last thread I started You'll get the whole story.
But, I was trying do the Comp. test to find out why I had a misfire in Cyl #5. (Which didn't work out well either)


Quote:
Originally Posted by REGAL GUY View Post
So before you did anything it ran fine?
All most sounds like a total plug up exhaust system now.
Yes, It ran, albeit not so well, But at least it ran.
Only thing was it had a Mild Persistent Misfire in Cyl #5. I posted a Vid of it in One of My Posts.
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Old 03-11-2016, 06:47 PM   #22
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Misfires are commonly caused by faulty ignition components.
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Old 03-11-2016, 08:54 PM   #23
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I would suggest you try unplugging the MAS like it was suggested by Tech2 if it wont start at all or have you ?
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Old 03-11-2016, 11:04 PM   #24
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You can buy a fuel pressure tester from a lot of places, Amazon has them for kind of cheap, or you can see if your local auto-parts store rents them.

Here is a guide for testing your Fuel Pressure.
https://www.gmforum.com/trouble-shoo...4/#post1392202


And something on testing injector pulse.
Part 1 -How to Do a Fuel Injector Noid Light Test (GM 3.8L)

And in case you want to test the injectors..
Part 1 -How to Test the Fuel Injectors (GM 3.8L)
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Old 03-12-2016, 04:35 PM   #25
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Quote:
Originally Posted by Mike View Post
Engines need 3 things to run.
1. Air
2. Fuel
3. Spark

We already know the engine is getting air, maybe getting fuel, but you do hear the pump prime, but are you getting spark and fuel into the cylinders?

One way to test the fuel/spark is to remove the intake duct off the throttle body and squirt a tad bit of carb cleaner into the intake while the engine is being cranked over. If it attempts to run, you now know you have spark. Now you need to find out why you are not getting fuel into the cylinders.
You meant four right?

4. Compression
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Old 03-12-2016, 04:47 PM   #26
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Excellent post by WilliamE
Auto Zone has the testing tools for rent well free.
Deposit then you get your money back
They even have the circuit tester Noid lights for the injectors
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Old 03-12-2016, 05:23 PM   #27
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Brian has a point, engines are technically glorified compressors, if there is no compression then nothing else matters.

Thanks Karl, Auto Zone was the place I had in mind, cannot remember if AdvanceAuto has them for rent as well or not..
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Old 03-12-2016, 06:46 PM   #28
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Compression only aids in the ignition of the fuel/air mixture. Otherwise, its difficult to start it.
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