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  #1  
Old 04-06-2012, 03:23 PM
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Default 98 4.3 vortec cranks but wont start

Ok I'm a lil lost here and hope someone thinks of something I have missed. driving the other day and at 50 mph it started a small miss/ stutter threw a code for the cam sensor or out of time and the evap can possibly soaked in fuel. then back fired loudly and when i hit the gas again back fired while driving and then lost power when i would try to give it fuel so i pulled over and the truck died. has spark off the coil and fuel to the throttle body when i looked under the truck the muffler has a 1 1/2 " hole where it looks like it blew outward. Changed the Cam sensor in the distrib. and no change. strange thing is my fuel gauge now works as before it was always on E with the light on. any help or insight would be greatly appreciated. Thanks in advance.
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Old 04-06-2012, 04:02 PM
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Looks like you pretty much covered your bases, fuel, air, and fire. But just to beat the horse, if you got fuel in your exhaust its gotta come from somewhere. check the spark at each plug to make sure you are getting fire, and check the cap and rotor for visible signs of wear, heat damage, or cracking. If thats all good and you know you are getting fuel to the cylinders I would check the timeing and make sure it didn't jump, then do a compression test. Let us know what you find.
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Old 04-06-2012, 04:31 PM
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Will have to get the tools for a pressure check and the battery charged since even with a jump on it it still wont turn over now. just a thought if the timeing chain went would the distrib still turn? i ask only because i had to bump the key to get the distrib aligned to replace the cam sensor.
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Old 04-06-2012, 04:51 PM
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As mentioned, check for a hot, blue, not orange, spark at each plug.
In most cases, problems with the distributor cap are not visible. If the distributor cap & rotor are AC Delco with 100K miles or more on them, replace them with AC Delco parts. If they're some off the wall aftermarket brand, doesn't matter how many miles, replace them with AC Delco.
Did you check fuel pressure and leakdown with a gauge? Both must be within specs or you'll have problems, guaranteed.
What diagnostic trouble codes, (DTC's) did you retrieve? Remember, DTC's never tell you to replace a part. They tell you what circuit or system has malfunctioned and it's up to you to diagnose the problem. It's not uncommon for a backfire to set a camshaft position sensor DTC.

If the timing chain jumps, the distributor will still rotate. If the chain breaks, no, it will not rotate. Timing chain problems on the 4.3L are almost nonexistant, so don't waste time with that until you check the basics mentioned above.
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Last edited by Captain Hook; 04-06-2012 at 05:02 PM.
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Old 04-06-2012, 05:22 PM
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P0340 and P0446 were the codes pulled at auto zone. The backfire happened after i had the codes pulled. Off to the auto parts store to get a gauge and new battery. When i do crank it i can hear a "woofing" sound is as best as i can describe it.. like air being pushed out from somewhere but i cant pin point where but that doesnt seem like it should be normal to me. also has a W in the vin code for the SEFI if that helps anything. Thanks for the help and tips so far. This site has been a wealth of info and help.

Last edited by 98BlazerSL; 04-06-2012 at 05:27 PM.
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Old 04-06-2012, 05:33 PM
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The P0340 is/was in fact indicating a problem in the camshaft position sensor circuit, could be wiring or the sensor itself. If the DTC doesn't show up again, ya got lucky

The P0446 is indicating a problem in the EVAP vent solenoid or its circuits.

Key ON, engine OFF, fuel pump running: fuel pressure must be 60psi to 66psi and must remain above 55psi for 10 minutes after the pump shuts off. If it passes both of those tests, fuel delivery is ok. If it fails one or both tests, more diagnosis is necessary. Post your results.
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Old 04-06-2012, 07:56 PM
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OK checked the spark at the coil..if its far from ground its orange but closer turns blue but at the plugs its orange so i can guess its the button and or cap. I also sprayed starting fluid into the intake and it wont start even then just cranks. have not had a chance to get a fuel pressure gauge on it.
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Old 04-07-2012, 01:59 PM
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Update It was the button or cap i just replaced both fires up and runs..idles at about 800 rpms atm but i think the comp just needs to re set since i had the batt disconnected.first time i ever had this issue with a truck guess there is a first time for everything. and i see now why i never see many chevys and alot of fords in front of auto parts stores..you get your buddy and his ford to run you back to get parts for your chevy. Thanks for the help Captn Hook, Prom and Swartlkk for your flow chart. Much appreciated all. hope to pass the help along to someone here in the future.
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Old 04-07-2012, 02:22 PM
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First.. notice how Capn HOOK was right?
BLUE SPark is critical. and more of a 'SNAP!' than something like 'tick'
For those of you who like to know WHY, this from an article on 'waste spark' systems:

Click the image to open in full size.

In our case here.. bad rotor / cap introduced the resistive gap represented by the graphite pencil
This pencil test can also be used to find miss-wired coil. Blue toward coil and red flare toward plug is proper polarity.
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Originally Posted by 98BlazerSL View Post
....i see now why i never see many chevys and alot of fords in front of auto parts stores..you get your buddy and his ford to run you back to get parts for your chevy. .....
ROFLMAO!!!!! Remember where you read that first, kids....
Wasting my time?

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"Unless they're driving their Ford to go pick up parts for ya"

unquote

Aint so much true as it is a good comeback to Ford haters, cuz it's true often enough.



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Now.. fix that evap code.
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Last edited by pettyfog; 04-07-2012 at 02:57 PM.
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  #10  
Old 04-07-2012, 02:47 PM
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Yeah thats showing as the valve is stuck, but after driving it around for 15 min i have no DTC's showing up (yet) but the hole it blew in the muffler needs to be patched or replaced. Never seen a backfire blow a hole in the muffler..lol.
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Old 04-07-2012, 02:47 PM
 
 
 
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2000, 43, air, bravada, chevy, crank, cranks, dpnt, fuel, olds, problems, rin, spark, start, vortec, wont


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