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07 Starting issue

tazman1

New Member
Joined
Jan 19, 2016
Messages
7
Hey All,

Ok so this just started happening to me. I've had the avy since January of this year and never had this until now. Sometimes when I go to start it, the starter engages but it never starts. I let it go for a few seconds and then turn the key back. Don't want to be frying a starter. This usually takes 3 times before it will start. Other times it is fine and starts normally. Any ideas?

Thanks!
 
Usually it is low fuel pressure, have it checked.
 
Agreed. If it is turning over, then it isn't the starter.

I have the same issue. Using a pressure regulator (rented from Autozone) the pressure built up while the fuel pump primed, but then sank immediately afterwards. The more times I let the pump prime, but didn't start, the higher the pressure became. This would eventually allow the engine to start.
 
What a coincidence.  My '07 started doing the exact same this week after a 10 hour road trip.  Runs 100% fine once it fires up, but getting it to start is difficult -- nearly left me stranded at a gas station.

I haven't gotten around to working on it yet, but I suspect it's either the fuel pressure regulator or a check-valve in the fuel pump bleeding off fuel pressure.  Hopefully it's just the regulator -- I'm going to pull the vacuum control hose from it and see if I smell fuel.  If memory serves, this truck doesn't have an externally-replaceable fuel filter (it's in the tank with the fuel pump).

At this point, I doubt it's fuel injectors hanging open and bleeding off fuel pressure / flooding the engine, as I don't notice any black smoke or anything once it fires up, but I'm not certain yet.

I'll post back if/when I get it figured out.

[Edit] Doesn't look like these 2007s use a rail-mounted fuel pressure regulator -- just looked, and I don't see one.  That's probably in the tank as well?  Great!
 
I did confirm that it's a fuel pressure issue.

There doesn't appear to be any priming at key-on -- my fuel pressure stays at zero and doesn't move.  It only builds fuel pressure slowly while cranking.  Once it builds up enough, the engine sluggishly starts up (at around 20~25psi), and then fuel pressure builds to 50psi while the engine is running.  The instant I shut off the engine, fuel pressure bleeds off immediately to 0 psi.

I really don't feel like dropping the fuel tank, but that's probably the next step.  I'll try to find a fuel system schematic to make sure I'm not missing anything, but as of now, it's looking to me like everything that could cause this problem is in the fuel tank.
 
You could always cut a hole in the floor >:D
 
Did you rent a fuel pressure tester to find the problem? I think that will be my next step. I suspect it is the same problem you are having and everything is in the tank grrrrr.  :E:
 
tazman1 said:
Did you rent a fuel pressure tester to find the problem? I think that will be my next step. I suspect it is the same problem you are having and everything is in the tank grrrrr.  :E:

You can buy a fuel pressure test gauge from your local autoparts store.  (Ask if they offer a tool-rental program in which you get your money back when you return it -- you could quickly test it there in the parking lot).  The fuel pressure testing port (schrader valve) is located on the passenger-side fuel rail.  You'll need to remove the top plastic engine cover (pulls up and out) as well as unscrew a black plastic protective cap from the schrader valve.  Be careful not to put any lateral load on the schrader valve -- they can crack and snap off the fuel rail.  Helps to have a second person to either start the engine or watch the gauge.

I haven't yet replaced my fuel pump assembly because I just filled up my fuel tank prior to this happening, and I don't want to wrestle a 200-pound fuel tank (gas weighs about 6.3 pounds per gallon * 31 gallons).  I'll run out this tank of fuel before I drop the tank.  In the meantime, I might still try to pull up the fuel rail and see if the injectors are leaking, just to be certain.

It appears that replacement fuel pump assemblies are only $200~300 from the local parts store (I was expecting more like $500~800, so that's a relief).  I'd recommend getting an AC Delco brand replacement if you attempt the replacement yourself.  However, it appears that there are two versions of the pump assembly -- one vs two electrical bulkhead connectors -- and I won't know which one fits our 2007 until I drop the tank.

Installation should be similar to the following video.  You'll have to decide whether or not you feel comfortable performing the replacement yourself.  Biggest difficulty will be safely attaining sufficient ground clearance to drop the tank and reach the connections -- it's not worth killing yourself if you don't have a lift:

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

 
:laugh: plenty of us have cut a hole in the floor to get at it. Just make sure it's sealed good afterwards.


http://www.chevyavalanchefanclub.com/cafcna/index.php/topic,100699.msg2125124.html#msg2125124
 
MS03 2500 said:
:laugh: plenty of us have cut a hole in the floor to get at it. Just make sure it's sealed good afterwards.


http://www.chevyavalanchefanclub.com/cafcna/index.php/topic,100699.msg2125124.html#msg2125124

I know, I've done it before on other vehicles.  I'm an engineer who builds engines for fun.  I cut a similar access panel on my 383ci D1sc-procharged Trans Am with a custom dual-255lph pump assembly, because dropping the gas tank requires dropping the rear axle (and the filler neck is fixed which is a pain in the ass).  It frequently burns out pumps, so I need quick access.  

To each their own pleasure, but I would never personally cut the bed of a truck when the tank drops out so easily.  Plus I want to wash out the fuel tank.

[Edit] Correction: Looks like the access panel would be cut in the rear seat area, not the bed.
 
No worries not too many people want to do it. But it does allow access when you are on the side of the road dead
 
MS03 2500 said:
No worries not too many people want to do it. But it does allow access when you are on the side of the road dead

Well, it appears that 13 pages' worth of people have done it, which is quite a bunch.  And yes, it would allow road-side access, which is good.  I suppose I probably would do it myself, but only after cleaning out the fuel tank once, as it's entirely possible that a decade's worth of contaminants are what caused the failure in the first place.

To the OP, should you decide to cut the access panel, I'd recommend painting the exposed edge of the cut (to prevent rust from moisture).  Naturally, don't make a deep cut, as you'll hit the fuel lines.  You can buy bare sheetmetal from the hardware store to fabricate a new cover panel, but you'll want to paint it first.  Attach with silicone/RTV and short self-tapping sheetmetal screws.

MS03 -- do you know offhand whether the fuel filter is separate from the pump assembly, or is it combined?  Or is the "fuel filter" merely a filter sock on the pump inlet?  I'll find out eventually, just thought I'd ask.  Thanks in advance.
 
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