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99 yukon. no fault. no start.
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fng
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Feb 17, 2014, 3:58 PM
Post #1 of 18
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99 yukon. no fault. no start.
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OK. So this thing got its tranny rebuilt about 500 miles ago. No problems. Wife drove to town.came home. Parked. Next day no start. Has fuel at intake. Spark at plugs. No codes reading. After testing good while, disconnected air sensors and choked out by hand. We got it to fire this way. Idled OK. Seemed fine. Shut down and tried to restart. No good. Tried similar choking. No good. Wore down batt. Disconnected and charged batt. Left disconnected to reboot. 3 days I retried. Still no good. 5 days later she started up. Drove around 3 days. Numerous starts and stops. Now she's dead again. Tried using start fluid. No go. Please help.
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Hammer Time
Ultimate Carjunky
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Feb 17, 2014, 4:09 PM
Post #2 of 18
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Re: 99 yukon. no fault. no start.
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All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.
Every engine requires spark, fuel and compression to run. That's what we have to look for.
These are the basics that need to be tested and will give us the info required to isolate a cause.
1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.
2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.
3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.
Once you have determined which of these functions has dropped out,
you will know which system is having the 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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fng
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Feb 17, 2014, 4:20 PM
Post #3 of 18
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Re: 99 yukon. no fault. no start.
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Yes. Thank you. I already read that. Fuel pressure held at 52 lbs. And remained after shutting off key. After 10 min tho it started to bleed. I was told this was common with this rig. And as soon as key is cycled it re-primes and holds. there is pulse at my injectors.
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Hammer Time
Ultimate Carjunky
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Feb 17, 2014, 4:39 PM
Post #4 of 18
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Re: 99 yukon. no fault. no start.
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Oh really?
Tell me, exactly how did you test for injector pulse on that engine?
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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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fng
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Feb 17, 2014, 5:18 PM
Post #5 of 18
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Re: 99 yukon. no fault. no start.
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Well that was enlightening. Apparently my "buddy" "helping" me was totally fine just blow in smoke at me. After a very heated conversation he admitted to not testing and just telling me to say yes. Now I feel like I need to start at ground zero.
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Hammer Time
Ultimate Carjunky
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Feb 17, 2014, 5:24 PM
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Re: 99 yukon. no fault. no start.
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OK, I knew it was a lie and I usually get very pissed when people do that to me when I'm trying to help them but I'll let you off the hook on this one since somebody else did the lieing.
Your problem is the fuel pressure. That pressure is way too low and this engine is very pressure sensitive. the spec is 60 to 66PSI and they usually won't run under 55. It's probably a bad fuel pump but could be a bad regulator. You would need to find a way to test the "dead head" pressure to be sure. You can usually just pinch off a return line but this truck uses plastic lines so I wouldn't recommend that.
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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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fng
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Feb 17, 2014, 5:35 PM
Post #7 of 18
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Re: 99 yukon. no fault. no start.
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I understand. Lying about this stuff would be a waste of your time and completely unhelpful to me. So I just did my own pressure test. It read 58 lbs at prime and now has dropped to 51 after 10 min. Is that normal? (The dropping I mean). And I don't know the best way to dead head a vortec
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Hammer Time
Ultimate Carjunky
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Feb 17, 2014, 5:39 PM
Post #8 of 18
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Re: 99 yukon. no fault. no start.
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No, that's not normal but may not be a big issue in this case. Try squirting a little starting fluid in the intake. If it momentarily fires right up, then we know fuel is the issue. I'm pretty confident you have a bad fuel pump.
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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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fng
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Feb 17, 2014, 5:41 PM
Post #9 of 18
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Re: 99 yukon. no fault. no start.
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I already tried that. I unhooked air sensors and shot a 3 sec blast down her throat. She didn't even hiccup. ????
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fng
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Feb 17, 2014, 5:44 PM
Post #10 of 18
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Re: 99 yukon. no fault. no start.
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I left the gauge hooked up and now down to 48 lbs.
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Hammer Time
Ultimate Carjunky
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Feb 17, 2014, 5:45 PM
Post #11 of 18
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Re: 99 yukon. no fault. no start.
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Unhooked what sensors? You can't leave anything disconnected. You have to keep the snorkel on when you try to start it. The best way is to just pull off the small breather tube and squirt some in there and then stick it back on before starting it.
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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 Feb 17, 2014, 5:46 PM)
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fng
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Feb 17, 2014, 5:52 PM
Post #12 of 18
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Re: 99 yukon. no fault. no start.
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Oh. I had the air flow send unhooked and snorkle off. Will try this way
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fng
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Feb 17, 2014, 5:59 PM
Post #13 of 18
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Re: 99 yukon. no fault. no start.
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Damn. Still no start. But I am coughing back thru intake
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Hammer Time
Ultimate Carjunky
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Feb 17, 2014, 6:04 PM
Post #14 of 18
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Re: 99 yukon. no fault. no start.
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You are? Did you mess with the distributor position in any way?
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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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fng
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Feb 17, 2014, 6:08 PM
Post #15 of 18
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Re: 99 yukon. no fault. no start.
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Not since I did my lower intake gasket 4k miles ago
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Hammer Time
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Feb 17, 2014, 6:18 PM
Post #16 of 18
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Re: 99 yukon. no fault. no start.
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Backfiring means an ignition issue.
I believe it's time to get back to basics in testing. Run through that list of tests. Testing injector pulse will be tricky on that engine because the injectors are not accessible. That's how I knew you didn't test them. In order to check pulse you have to access the wires at the harness going to the injectors and use a noid light or diode light to test for pulse, never an incandescent bulb as that will damage the computer.
Here is the diagram to pull wire colors. You don't need to test all cylinders, just one.
Use an adjustable spark tester to check spark so you can test how strong the spark may be.
Noid light
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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 Feb 17, 2014, 6:19 PM)
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fng
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Feb 17, 2014, 6:29 PM
Post #17 of 18
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Re: 99 yukon. no fault. no start.
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Is there anyway to do this test w/ a multimeter? Since earlier heated discussion many tools are no longer here
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Hammer Time
Ultimate Carjunky
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Feb 17, 2014, 6:33 PM
Post #18 of 18
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Re: 99 yukon. no fault. no start.
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Not really. You can get a spark tester and noid light for under $10 most of the time. You could use a test light as long as it uses an LED and not a regular bulb.
The injector receives constant power on one side and pulsing ground from the computer on the other side.
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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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