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97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel


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E.B.
User

Oct 9, 2012, 4:29 PM

Post #1 of 28 (2078 views)
post icon 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

Cylinders no 2&4 dumping fuel. Wash down and compression tests have been done, all came back good. Lower intake pulled gaskets good, tried new injectors, still the same. Fuel pressure tests were good. Any thoughts?


(This post was edited by E.B. on Oct 16, 2012, 4:21 PM)


Hammer Time
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Oct 9, 2012, 5:22 PM

Post #2 of 28 (2048 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

Is it holding rest pressure?



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E.B.
User

Oct 9, 2012, 5:24 PM

Post #3 of 28 (2044 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

Sorry not a mechanic, I have it at the shop now. What is rest pressure?


Hammer Time
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Oct 9, 2012, 5:27 PM

Post #4 of 28 (2038 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

It means, does it maintain correct fuel pressure for a period of time after the key is shut off or does it drop off considerably in the first 5 minutes?



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E.B.
User

Oct 9, 2012, 5:29 PM

Post #5 of 28 (2034 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

Talking to mechanic and he said it holds good pressure.


Hammer Time
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Oct 9, 2012, 5:36 PM

Post #6 of 28 (2026 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

That means you don't have a leak so now you have to look at injector controls and wiring. You can test each individual injector trigger with a noid light to see if any are shorted to ground which would keep the injector open all the time. This would also show up as a fuel pressure drop when the key is on, engine off.



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E.B.
User

Oct 9, 2012, 5:40 PM

Post #7 of 28 (2021 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

So if it is going to ground then the injector would be open all the time causing the overfueling?


Hammer Time
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Oct 9, 2012, 5:43 PM

Post #8 of 28 (2014 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

Yep. The injector receives power all the time when the key is on and the computer pulses the ground to fire it off. The amount of ground time determines the "on" time for the injector called the "pulse width"



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E.B.
User

Oct 9, 2012, 5:47 PM

Post #9 of 28 (2010 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

The mechanic told me his scan tool is able to fire each injector, and he knows that they are all functioning.


Hammer Time
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Oct 9, 2012, 5:49 PM

Post #10 of 28 (2006 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

OK, if you say so. You just eliminated all possible cause of fuel washdown so apparently you don't have a problem.



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E.B.
User

Oct 9, 2012, 5:55 PM

Post #11 of 28 (2001 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

I had just called him relaying messages back and forth. Is that something you have never heard of before?


E.B.
User

Oct 9, 2012, 5:58 PM

Post #12 of 28 (1996 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

Could it be a head problem? Or are you convinced it is an injector problem?


Hammer Time
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Oct 9, 2012, 5:59 PM

Post #13 of 28 (1993 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

As I just told you, either your test results are tainted or incorrect or you don't have a problem at all because according you you, it passed all the tests so i'm pretty much done here. Fuel can only get into the cylinders either through the injectors or around them and you supposedly eliminated both.



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E.B.
User

Oct 9, 2012, 6:03 PM

Post #14 of 28 (1989 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

That makes sense, I know there is a problem. Fuel in the oil, and popping out the exhaust. The only problem I have had with the motor is intakes gaskets in the past, been very dependable.


Hammer Time
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Oct 9, 2012, 6:04 PM

Post #15 of 28 (1985 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

Check engine light on? What are the code numbers?



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E.B.
User

Oct 9, 2012, 6:08 PM

Post #16 of 28 (1981 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

Waiting on a reply from the mechanic.


E.B.
User

Oct 9, 2012, 6:32 PM

Post #17 of 28 (1976 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

The only code that came up was a p0300.


nickwarner
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Oct 9, 2012, 6:37 PM

Post #18 of 28 (1970 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

Thats a random cylinder misfire. Has he looked at the misfire counters?


E.B.
User

Oct 9, 2012, 6:40 PM

Post #19 of 28 (1969 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

That I do not know, last time I talked to him, he said the only thing that did not check out was that bank of the engine was runnin rich.


Hammer Time
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Oct 9, 2012, 6:49 PM

Post #20 of 28 (1961 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

I don't know how he's concluding that because there are no rich codes so the computer isn't seeing 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.



E.B.
User

Oct 9, 2012, 6:52 PM

Post #21 of 28 (1955 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

That I cannot answer.


Discretesignals
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Oct 10, 2012, 8:15 AM

Post #22 of 28 (1922 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

Just curious, but how did you determine cylinders 2 and 4 were dumping fuel?





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E.B.
User

Oct 10, 2012, 6:28 PM

Post #23 of 28 (1907 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

No 2&4 plugs were wet with gas, the rest were dry.


E.B.
User

Oct 10, 2012, 6:31 PM

Post #24 of 28 (1906 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

I think we have it narrowed down to crossfire in the cap. Frustrated spending a fair amount of money for a simple fix.


Discretesignals
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Oct 10, 2012, 6:59 PM

Post #25 of 28 (1900 views)
Re: 97 gmc sierra 1500 5.7 cylinders 2&4 dumping fuel Sign In

It wasn't dumping fuel. It was injecting fuel, but because of no spark your plugs were wet. I don't think I have seen a CMFI injector hang open as of yet. It would be even rarer for two injectors to do that, but you never know what you'll run into. Glad to see you figured it out.





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 Oct 10, 2012, 7:00 PM)






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