Engine will not start

Tiny
LASURVIVOR47
  • 2003 GMC SONOMA
  • 120,000 MILES

I have a 2003 Gmc sonoma 4.3. The engine cranks, but won't start. I have a Innova Scan tool and only one code appeared. (P0102). It also read, Mass or volume air flow circuit low input. At the top of the screen, there were little letters flashing. C, EV, O, OH. Thank you for your help! Paul

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Monday, December 31st, 2012 AT 1:50 PM

13 Replies

Tiny
HMAC300
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Check to see if your duct work has holes in it/dirty air filter detiroating filter, blocked exaust. Then check fue pressure should be 60-66 psi

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Monday, December 31st, 2012 AT 2:26 PM
Tiny
LASURVIVOR47
  • MEMBER

Thanks for your reply. I did a fuel pressure test the other day and when I was cranking the engine the psi was 60. When I stopped cranking the pressure went to 57 psi and stayed there. I installed a new air filter the other day. Two questions: How do I check for a blocked exhaust? And what do you mean by, "see if duct work has holes in it?" Thanks. Paul

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Monday, December 31st, 2012 AT 2:54 PM
Tiny
HMAC300
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The duct work going from maf to throttle body or any valve cover with a grommet if they have holes it will set it. I am not familiar with the in nova tool so have no ideas what your letters mean. Fuel pressure seems okay as it needs to hold within 5 pounds after shutdown. Check crank and cam sensor for resistance they won't set a code sometimes and car won't start. Also make sure to check all your fuses in under hood box. We have no specs for those though

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Monday, December 31st, 2012 AT 4:01 PM
Tiny
LASURVIVOR47
  • MEMBER

I appreciate your time helping me. Yes the fuel pressure remained at 57 psi for more than five minutes after I shut the key off. I also checked all the fuses under the hood a little while ago and they we're all good. I will check the other things you mentioned. Forgive me, but how do I check the crank and dcam sensor and where is it on the 4.3? Thanks again. Paul

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Monday, December 31st, 2012 AT 7:01 PM
Tiny
HMAC300
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The cam sensor is in the dist and the crank sensor is in the timing cover on bottom pass side.

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Monday, December 31st, 2012 AT 8:07 PM
Tiny
HMAC300
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Ya know just for the heck of it take some choke cleaner and spray down throttle body see if it starts. If it does then it's a fuel problem.

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Monday, December 31st, 2012 AT 8:08 PM
Tiny
LASURVIVOR47
  • MEMBER

I found the crank sensor, and I will check the cam sensor. Forgive me, I forgot to tell you I tried fuel down the throttle body a few days ago and it ran until the fuel ran out in the throttle body. So i'm getting 60 psi when cranking and 57 psi with ignition off. Pressure holds at 57 psi for more than 5 min: I'm thinking, if it's holding pressure there's nothing wrong with the fuel pump or filter, and the spider injectors, fuel regulator are not leaking too. What do you think? Thanks you sir! Bye the way, if I don't talk to you this year, I'll talk to you next year! Lol! Happy new year! Paul

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Monday, December 31st, 2012 AT 10:36 PM
Tiny
HMAC300
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If you sprayed fuel and it ran then it's a fuel problem not ignition. Try a fuel filter replacemnet if you haven't already then it wil probably be a fuel pump even though your pressure seems good

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Monday, December 31st, 2012 AT 11:00 PM
Tiny
LASURVIVOR47
  • MEMBER

Ok thank you. I will try that. Happy new year!

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Monday, December 31st, 2012 AT 11:12 PM
Tiny
RICHARD SONNER
  • MEMBER

Thank God for the internet! If you have this issue, replace the distributor cap and rotor first. Cost about $40. I read numerous recommendations and everyone was talking fuel pressure, spark, crank sensor, etc. I had tried to check the spark, but one of the wires broke at the plug so I started replacing the wires and since I was there I went ahead and replaced the plugs. I did have spark, but still did not help. I did try gas in the carburetor, but did not start. This led me to believe it was electrical. I found a thread that indicated that GM had an issue where the AC line condensation would drip on the cap and corrode it. I replaced the cap and rotor and it started right up. There are horrible stories of people spending $850 for a new fuel pump and they still would not start, Even if this doesn't fix yours, it's a very inexpensive starting point. It does take a fairly short T20 screwdriver to access the rear screw. If this doesn't work, you'll have to try all those other things referenced in the various threads. Fuel pressure, fuel pump, crank and cam sensor, fuses, ECM. Good Luck, as I was prepared to have it towed to a mechanic and take it in the shorts.

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Tuesday, January 24th, 2017 AT 6:37 PM
Tiny
2CARPROS KEN
  • ADMIN
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Hey RICHARD,

Yes the internet is a good thing, it helps people like us communicate to get our cars back on the road, thanks for the additional information please feel free to add to 2CarPros anytime.

Best, Ken

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Sunday, January 29th, 2017 AT 3:48 AM
Tiny
LASURVIVOR47
  • MEMBER

I wrote this thread about four years ago and didn't finish it. My apologizes! The end result was I tried everything I could and finally had to take it into the garage. Their diagnosis was the Intake manifold gasket was worn, and After repeatedly trying to start it I flooded the cylinders which had to be drained. $900.00 later the truck was running good. Ouch! I still have the truck and been a good truck to this day. Some minor repairs I've done myself. Hope this helps someone!

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Sunday, January 29th, 2017 AT 8:02 AM
Tiny
2CARPROS KEN
  • ADMIN
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Hey LASURVIVOR47

Thanks for getting back to us with a conclusion, please use 2CarPros anytime.

Best, Ken

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Sunday, January 29th, 2017 AT 8:35 AM

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