P0171 and P0174 CODES

[ATL]

darrell, mine did that for 2 yrs before the pump went out. that delay is from the check valve in the pump going bad. once the fuel pump turns off, it lets the fuel gravity feed back to the tank. so once you put the key in, you have to prime the lines with a few turns of the key before itll make enough pressure to fire up

 

[RedRocker]

Today the only code I got was the P0171 and the scanner was able to clear it. I did add a bottle of 'restore' fuel system cleaner/treatment last night and my symptoms seem to be diminishing some, but not completely. I will attempt to clean the MAF this evening and might rent a fuel pressure guage to check fuel pressure. Im hoping it's just a tank of bad gas, or gummed injectors that will work itself out with the fuel additive. A fuel pump replacement just sounds like a bad expensive weekend to me.

 

[ATL]

pump swap isnt that bad, not fun by any means but not bad. it can be done with basic tools and only takes an afternoon. i got my acdelco pump for just under $300 at my local parts store. you can get them for around $250 on ebay if you plan ahead. try seafoaming everything too, vacuum line, fuel tank, and crankcase if youd like

 

[Devious02]

So then if it was a bad pump why would it only give me problems when its cold outside? In the spring or summer starts just fine.

 

[ATL]

only explanation i can think of for that is intake gasket. i know you said you checked it, but thats the exact explanation of what they do. once it warms up the gasket swells alittle and closes the leak

but its worth borrowing a fuel pressure gauge to check that as well. check the pressure when you go out in the morning, before you start it up. maybe it can make the right pressure but has hard time doing it in lower temperatures...??? but its free to check

 

[Clean07Burb]

Im having these same 2 codes - my only symptom, not including the check engine light, is having trouble starting (hot or cold). It will turn for 4-5 seconds to no avail - I have to repeat 3-4 times before it lights off. Once started it runs like it always has. I tried the remote start via key fob and it didnt even turn the motor at all, I do hear the fuel pump making what I consider normal sounds. Any ideas?

@RedRocker

I hate to bring this thread back from the dead, guys, but I'm going to anyway.

RedRocker, I quoted your post above because it describes the EXACT same symptoms I've been having with my '07 Suburban for the last couple days. When I say exact, I mean even down to the same two codes. Mine also cranks for an extended period of time before starting, but always starts and runs fine once running. The only difference between what you described with your truck and what I'm experiencing with mine is that my remote start still works, but again, cranks for a couple extra seconds before it actually fires up.

It has already been mentioned more than once in this thread, but I was thinking about what could cause this issue, and my conclusion, at least in my head, is that the fuel system is losing its prime or having trouble priming at start-up. Although, this happens to me whether the truck has been sitting, or not. I can drive 35 minutes down the road, stop, turn the truck off, then immediately try to restart and it still cranks those extra couple seconds before starting. You'd think if it was an issue with losing its prime it would only happen after sitting for extended periods of time, but who knows.

Unfortunately, I don't have access to my fuel pressure tester right now because I loaned it out and never received it back. I manage a local auto parts store and I was actually dumb enough to loan out a personal tool to a random customer. So much for people being trustworthy these days, huh? What a shame. Anyway, did you ever figure out what was causing your extended cranking before starting issue? I'd like to get mine resolved as soon as possible because this is currently my only vehicle and I'd rather not have it leave me sitting some day!

I appreciate any help you can provide, RedRocker. Anyone else feel free to chime in if you've experienced this problem and found a resolution!

---------- Post added at 06:59 PM ---------- Previous post was at 06:50 PM ----------

As I suspected, it looks like a fuel pump replacement or fuel pressure regulator might be in my future. I just found some more folks with the same issue. It seems GM even issued a TSB because its apparently a common problem. Check out this thread. A couple guys said a new pump fixed their extended crank issues. I'm gonna run out to my truck in a few minutes and pull the vacuum line off my FPR and see if any fuel is getting past the diaphragm and into the line. I'm kind of hoping it is, because its an inexpensive and easy repair.

http://chevroletforum.com/forum/tahoe-suburban-25/long-crank-start-up-dealer-blames-k-n-48295/

 

[RedRocker]

I ended up replacing the in tank fuel pump - it's comprised of pump, regulator, sensors, gauge sending unit (all in one). I debated on doing it myself, cause labor is the real burden in this issue. I had a shop do it, and very glad I did because the first swap ended up being defective and the shop had to "eat" labor to replace it again, I feel I dodged a bullet there for sure. Oddly enough the exact same thing happened this week to my daughters HHR, a new fuel pump assembly and her HHR starts like new again. I also have read where utilizing remote start seems to help a struggling fuel pressure issue, however it didnt help with my HHR at all. Hope this helps

 

[Clean07Burb]

I ended up replacing the in tank fuel pump - it's comprised of pump, regulator, sensors, gauge sending unit (all in one). I debated on doing it myself, cause labor is the real burden in this issue. I had a shop do it, and very glad I did because the first swap ended up being defective and the shop had to "eat" labor to replace it again, I feel I dodged a bullet there for sure. Oddly enough the exact same thing happened this week to my daughters HHR, a new fuel pump assembly and her HHR starts like new again. I also have read where utilizing remote start seems to help a struggling fuel pressure issue, however it didnt help with my HHR at all. Hope this helps

Thanks a lot, RedRocker. I really appreciate your response. I'm glad you got your issue resolved with a new pump. I'm hoping my issue is with the FPR and not the pump. Just seems odd that there are no issues once it starts and I don't want to drop the tank if I don't have to. Normally, a problem with the pump would cause issues running and starting, or not running at all, but I see with your situation this is not always the case. I'll report back once I figure it out.

---------- Post added at 08:39 PM ---------- Previous post was at 08:04 PM ----------

Well, I'll be dropping the tank to replace the pump assembly after all. The FPR is built into the fuel pump module assembly on my NNBS Suburban. Figures...

 

[RedRocker]

From my understanding, it takes upwards of 30% more PSI of fuel pressure to start then it does to run. Both my Tahoe and HHR ran absolutely perfect after I finally got them started. The Tahoe had me baffled for several days, trying this and that, to no avail, but I diagnosed the HHR literally the second my daughter complained about it and showed me what it was doing. Good luck

 

[MSGKUNERT]

Has anybody had any recent problems with these two codes? This is the first I have experienced these and cleaning the MAFS only worked for a couple of hundred miles.