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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15181
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I have a 1998 Blazer that is well maintained and

Customer Question

I have a 1998 Blazer that is well maintained and immaculate...but I began having problems a couple months ago. After sitting awhile it would not start. No codes shown. Autozone thought it most likely a ignition switch based on how it acted at the time. I did nothing and it ran fine until about 3 weeks ago I pulled into a convenience store and the check engine light came on. When I came out it would not start. Had it towed home. I have a code reader and the code P0300 came up with no other descriptions. Has not run since.
Submitted: 8 months ago.
Category: Chevy
Expert:  Jerry Newton replied 8 months ago.

P0300 isn't enough information to do anything with, unfortunately. It's a random misfire code, but misfires can occur for any number of reasons. You don't have a misfire problem now, though, you have an engine that won't run. The P0300 may or may not be related to that cause, but we can't assume that it is just because it's such a generic code.

So, we start with some solid diagnostics. Does your code reader also read any kind of live data from the vehicle?

Customer: replied 8 months ago.
No not much DTC:01 I/M No P0300 01/01 Fault 01 Pend 00
Those are all I got.
Expert:  Jerry Newton replied 8 months ago.

OK, that's not enough to work with, so let's sidestep that info, and just move into regular diagnostics.

Fuel pressure and spark are the first two big things to check. Remove a spark plug wire, have someone crank it, and see if you're getting a spark if you hold that wire near ground (or preferably, use a spark tester). Go to the parts store and ask them to borrow a fuel pressure gauge, Autozone and Advance and places like that will loan you one for free. Fuel pressure test port is on top of the engine, fuel pressure should be 55-62psi.

I commonly see fuel pump failure, coil failure, ignition cap and rotor failure, crankshaft position sensor failure. It can be any of these things, or something else entirely, so good diagnostics will save you from buying things you don't need.

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