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Author Topic: Could use some help (mechanically speaking)  (Read 80 times)

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Justinl350

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Could use some help (mechanically speaking)
« on: April 15, 2019, 19:10:03 PM »

Hello. New member here and could use some advice. I just bought an 04 avalanche with 160k. The truck has had some intermittent stalling issues and hard starts. Being some what mechanically inclined I began looking for the issue. I found that the fuel pressure builds slow and only hits between 50-60 psi after cycling the key a couple times. But the second I turn the key off,fuel pressure drops to zero within 2 seconds. Obviously at this point I'm leaning toward fuel pressure regulator. Now here is the kicker. After speaking with the old owner I found out that the truck had an engine swap and it seems to be swapped with an 07 motor. The 07 motor does not have a fuel pressure regulator on the fuel rail, instead its built into the fuel pump. Could it be possible the swap was done and they left the original fuel pump in and there is actually no fuel regulator on the motor period? Also if this is the case could I just put an 07 pump in and call it done? Or do you think it would be better to just put a universal fuel regulator on?  Any advise would be greatly appreciated. Truck is the z66 with the 5.3
« Last Edit: April 15, 2019, 19:20:07 PM by Justinl350 »
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enoniam

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Re: Could use some help (mechanically speaking)
« Reply #1 on: April 16, 2019, 05:49:28 AM »

I highly doubt that your problem is lack of a pressure regulator as it bleeds off excess fuel flow to limit pressure.  You most likely have a leaking fuel injector.  By checking your plugs you can likely isolate the culprit.
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2004Slickside

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Re: Could use some help (mechanically speaking)
« Reply #2 on: April 16, 2019, 10:02:03 AM »

Hello. New member here and could use some advice. I just bought an 04 avalanche with 160k. The truck has had some intermittent stalling issues and hard starts. Being some what mechanically inclined I began looking for the issue. I found that the fuel pressure builds slow and only hits between 50-60 psi after cycling the key a couple times. But the second I turn the key off,fuel pressure drops to zero within 2 seconds. Obviously at this point I'm leaning toward fuel pressure regulator. Now here is the kicker. After speaking with the old owner I found out that the truck had an engine swap and it seems to be swapped with an 07 motor. The 07 motor does not have a fuel pressure regulator on the fuel rail, instead its built into the fuel pump. Could it be possible the swap was done and they left the original fuel pump in and there is actually no fuel regulator on the motor period? Also if this is the case could I just put an 07 pump in and call it done? Or do you think it would be better to just put a universal fuel regulator on?  Any advise would be greatly appreciated. Truck is the z66 with the 5.3
Well, I would first figure out if the 2004 fuel injection system was put on the 2007 engine.  I think this is likely.  Just look for the fuel pressure regulator in the lines.  You can see it in a youtube video.

https://www.youtube.com/watch?v=rsmkroO_i14

4 possibilities for you.  Fuel pressure regulator is bad, leaking fuel through it into the return line.  Injector is leaking fuel through it, into the intake.  Check valve in pump is not holding pressure, and fuel is going back into the tank.  Fuel pump is bad.  I'm betting on the fuel pump being bad along with a stuck check valve.

See this link for how to diagnose the fuel system.  Yeah it's for a Blazer, but instructions will work for Avalanche if the fuel filter has same connections.  Photos of parts needed to make up the testing equipment to dead end the fuel pump is in post 37, 38, 39 - you will get the idea what you need to hook up to the Avalanche fuel filter.  In your case (Avalanche) ignore the 60 psi minimum specification.  Also please know that these fuel pumps put out a lot more than 60 psi if working correctly.

https://blazerforum.com/forum/2nd-gen-s-series-1995-2005-tech-41/how-check-regulated-fuel-pressure-pump-max-output-leakdown-88305/page4/
     
« Last Edit: April 16, 2019, 10:19:12 AM by 2004Slickside »
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MS03 2500

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Re: Could use some help (mechanically speaking)
« Reply #3 on: April 16, 2019, 11:52:23 AM »

That is one strange engine swap considering a 07 have AFM
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