# 1995 Chevy Blazer won't start



## Guap0_ (Dec 2, 2017)

A compression test would tell you a lot. Possible causes of a backfire: cracked/bad/moisture in distributer cap - blown valve - bad timing chain/belt 
Is the backfire out if the exhaust pipe or throttle body?


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## de-nagorg (Feb 23, 2014)

Help: You need to post your location in the profile page, this gives us clues.


Now there needs to be three things to occur simultaneously for an engine to run, First there needs to be fuel, then compression of the air fuel mixture, and ignition of that mixture all at the same time.

Any variances will shut it down, in my experiences on GM engines, these symptoms that you speak of are caused by a worn timing chain or gears.

Of course I am a little rusty on a 1995 , so someone else might have another take on this.

I would begin by putting a timing light on the engine, and cranking it, to see if the timing marks are " floating", or are steady, if " floating", your timing is bad, and needs new parts, ( chain or belt, gears, or pulleys.)

If steady, then check the distributor cap for cracks, the rotor for burned contacts, the wires for bad spots.

And the list goes on, and on.


ED


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## treesloth (Jul 27, 2018)

Thanks for the replies. As it happens, the local Autozone has tools to borrow (buy/get refunded, really) that should help. I think I should be able to check compression with those. I'll have to see about checking timing, though.

As for the fuel pump, I know that sometimes you can check that it's operating (and entertain the neighbors) by starting the electric on the car and then putting your ear up to the open gas inlet. However, I never thought to try this with the Blazer when we got it. Anyone know if I should be able to hear that?


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## Guap0_ (Dec 2, 2017)

I never heard of a fuel pump causing a backfire.


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## de-nagorg (Feb 23, 2014)

I think you are going up the wrong tree, chasing a fuelpump problem, with backfire.

Backfire is improper timing, allowing the fuel to get ignited at the wrong time, sending the explosion into the intake, or the exhaust at the wrong time.

So therefore you must have fuel in the mix, or it wont ignite.

There are so many things that can be wrong in the timing system, that it would take a book to explain them, 


Wait there is already books out there, Chilton's, many college textbooks, Haine's, etc.


ED


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## treesloth (Jul 27, 2018)

Thank you. I find the points of the last couple of posts compelling. I need to get a timer, but I'll see what I can find out along those lines. I guess I'm about to learn about timers and, possibly, distribution caps.


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## raylo32 (Nov 25, 2006)

Had something similar on my old S-10 4.3L pickup. T'was a stuck open EGR valve. It needs to be closed at idle and will only open under throttle if it is working properly.


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## Bigplanz (Apr 10, 2009)

Backfire followed by loud knocking=sell to salvage yard.


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## Brainbucket (Mar 30, 2015)

Sounds like the timing chain took a dump.:vs_cool:


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## BigJim (Sep 2, 2008)

Another way to check your timing is to take the #1 plug out, hold your finger over the plug hole, turn the engine over until it blows your finger out of the hole, and the timing mark on the harmonic balancer are at, or real close to both marks lining up. (If you have small fingers, don't stick it inside the hole)

Now take a screw driver and put inside the plug hole and turn the engine over by hand, when the piston is at top dead center, look to see where the rotor in the distributor is pointing, it should be pointing dead at #1 post. Also make sure the rotor isn't broken.


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## Oso954 (Jun 23, 2012)

> there is a pretty loud knocking with each turn


That usually means that two metal parts are beating each other to death. I’d quit playing with it and someone with a lot of mechanical experiance listen/trouble shoot it.

Every time you hear that knock, there is a bit more damage to one or both parts.


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## Bigplanz (Apr 10, 2009)

When my timing chain broke, it broke in half. Starter just spun. Anytime you hear KNOCK, KNOCK, then things are BAD.


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## Oso954 (Jun 23, 2012)

> Anytime you hear KNOCK, KNOCK,


Who’s there ?
Rod.
Rod who ?
Rod bearing.


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## de-nagorg (Feb 23, 2014)

I have saw 3/4 of the fiber teeth on the gears bust off, and the chain falls into the bottom. 

Time for all steel timing gears, and new chain. 

Knock: knock:

Who's there?

Cam.

Can who?

Cam Shaft busted into three pieces.

Saw that once too.

ED


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## Bigplanz (Apr 10, 2009)

de-nagorg said:


> I have saw 3/4 of the fiber teeth on the gears bust off, and the chain falls into the bottom.
> 
> Time for all steel timing gears, and new chain.
> 
> ...


I replaced the crank and camshaft gear, timing chain and tensioner set. Miraculously, the engine was back to life. This was after the chain broke in half at 60 MPH on the expressway.

GM 3.1 V6 was robust!


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