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car hard starting issue! driving me nuts. help!
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trekvana
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Dec 31, 2011, 12:57 PM
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car hard starting issue! driving me nuts. help!
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so i got a 98 2.2L auto gmc sonoma with 160k miles that is quite temperamental when it comes to starting. when the engine is cold or has been sitting for a while she starts just fine (2-3 cranks) however when shes been running long and i stop to go inside a store or get gas (anywhere from 5-20 minutes) i have to crank over about 7-10 times for her to start up.
ive replaced the starter, plugs, wires, fuel filter, and fuel pressure regulator. ive checked the ignition coils and primary and secondary resistance is good. i checked the fuel pressure: when the pump starts, the pressure is about 44 psi and after two seconds when it stops pressurizing it sits at about 38-40 psi. With the car at idle pressure oscillates rapidly between 34-36 and when i pull the regulator vacuum line the pressure jumps about 8-10 psi. Also I dont have any fuel pressure leaking (pressure holds steady at 38-40 with key off). So it looks to me like the pump and regulator are working fine.
I checked engine vacuum and im getting steady vacuum around 18 Hg.
I dont know what else to check or what else it could be. Lots of posts I've read on others with this issue said to replace the pressure regulator but that still didnt help in my case.
Any thoughts?
(This post was edited by Double J on Dec 31, 2011, 1:46 PM)
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Discretesignals
Ultimate Carjunky
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Dec 31, 2011, 1:04 PM
Post #2 of 10
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Re: car hard starting issue! driving me nuts. help!
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Did you make these fuel pressure checks and ignition system operational checks when the problem was occurring?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 31, 2011, 1:05 PM)
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trekvana
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Dec 31, 2011, 1:09 PM
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Re: car hard starting issue! driving me nuts. help!
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I let the motor warm up to operating conditions and then performed my tests. While performing my tests, I took note of the fuel pressure when the motor started just fine. Once the motor did the hard starting symptom again, i watched the fuel psi and it was still holding steady at 38-40 psi while cranking so I'm pretty sure its not a fuel pump issue. I even depressurized the fuel system and cranked the car without waiting for the pump to prime and it started just fine.
The only thing i can think of is a faulty EVAP purge valve letting fuel vapors into the engine??
(This post was edited by trekvana on Dec 31, 2011, 1:11 PM)
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Hammer Time
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Dec 31, 2011, 2:32 PM
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Re: car hard starting issue! driving me nuts. help!
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Although all your testing is on the right track, unless you do it at the exact moment when the problem is occurring, you haven't tested anything.
Also....
Your pressure is too low. The spec for this engine is Key On Engine Off 41-47 psi..... You aren't there.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Dec 31, 2011, 2:34 PM)
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trekvana
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Dec 31, 2011, 2:43 PM
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Re: car hard starting issue! driving me nuts. help!
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Hammer - just check the fuel pressure while the engine was acting up and im getting the same readings as under normal operation - 44psi while priming and 38-40 after priming. As far as the pressure, I have the GM manual in front of me and it says pressure should be between 41-47 for the two seconds it takes the pump to prime itself. Then it says after the pump stops priming pressure should not drop more than 5 psi in 10 minutes. After priming my pump holds steady at about 40 with no leak downs. So pretty much I'm right on the cusp of the allowable PSI.
Any other suggestions except for the pump - pump runs about $200 so I'd like to rule out everything before making that purchase?
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trekvana
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Dec 31, 2011, 3:05 PM
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Re: car hard starting issue! driving me nuts. help!
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Put in new plugs and wires. Tested them with a spark tester and they look nice and strong. Ignition coils are good. How to test injector pulse?
One question/observation: once the car starts the engine runs like a pro. No misfire, no rough idle, no erratic anything. The vacuum gauge says 18Hg and it holds steady (albeit a little low - most likely from worn piston rings given the motor has 160K on it) so i dont think its a valve train / missing spark issue. Would the motor still run nice and smooth if the injectors were bad?
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Hammer Time
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Dec 31, 2011, 3:09 PM
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Re: car hard starting issue! driving me nuts. help!
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None of that matters at all. Your truck needs spark, fuel pressure, injector pulse and compression to run. We have ruled out fuel pressure and compression. Now you have to find out which of the other two you are missing at the moment it won't start. Nothing matters once the truck starts.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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trekvana
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Dec 31, 2011, 3:38 PM
Post #9 of 10
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Re: car hard starting issue! driving me nuts. help!
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Got it. Thanks Hammer. Ill take a look at the injectors and sparkers and report back.
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Hammer Time
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Dec 31, 2011, 3:41 PM
Post #10 of 10
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Re: car hard starting issue! driving me nuts. help!
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You test injector pulse by plugging in a noid light bulb to one of the injector plus and crank the engine. If the bulb flashes, you have pulse and power. If not, you have a problem.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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