jQuery not supported.



Replaced Injectors, Now truck struggling to start

Replaced Injectors, Now truck struggling to start

Postby BowDownBowser [OP] » Mar 07 2017, 2:37am

Hey everyone, I was having an issue with my truck(07 NNBS Sierra 5.3l Flex) losing fuel pressure. When it is warm out or after I drive and the truck sits and hour or two it would have trouble starting unless I tapped the gas. A buddy and I checked the injectors and saw two leaking. I ordered a new set and today I replaced 7 of them to include the two we saw leaking. (One of the new ones was damaged and needs to be returned) After driving around everything seemed normal and I didn't notice any smell of fuel. Let the truck sit for an hour and went back to start it and it really struggled until I tapped the gas. When replacing the injectors I was sure to check to make sure I got all of the old O-Rings out and I lubed the new ones with oil and seated them. Any Ideas on what it could be? Could the new ones be bad? My fuel trim seems normal so I dont think the injector itself is leaking. Could the O-Rings not be seated properly causing leakdown? Any help is greatly appreciated.
Original Poster
BowDownBowser
Firing on 6 cylinders [L1]
Firing on 6 cylinders [L1]
Posts: 64
Topics: 10
Joined: Oct 27 2016, 3:17am
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Location: Jacksonville
Year: 2007
Make/Model: GMC Sierra
Extra Info: 1500NNBS FF 5.3L 4x4
Group Membership:
Registered users

Re: Replaced Injectors, Now truck struggling to start

Postby idrivea2005sierra » Mar 07 2017, 2:47am

Sounds to me like you're losing pressure while the truck is sitting. Have you run any pressure tests on the fuel lines? I would lean more towards a potentially failing fuel pump.
~Spencer
2005 Victory Red GMC Sierra, 5.3, Z71, CCSB
2002 Volkswagen Golf GLS 2.0, it's not stock
1991 Avanti Convertible, weekend cruiser and project OEM+ restoration
1961 Willys CJ5, currently undergoing chassis off OEM+ restoration
idrivea2005sierra
Combustion on 6 pistons [L2]
Combustion on 6 pistons [L2]
Posts: 684
Topics: 19
Images: 33
Joined: Dec 10 2016, 5:10am
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Location: Grayslake (Chicago Sub)
Year: 2005
Make/Model: GMC Sierra
Extra Info: 5.3 Z71 CCSB
Group Membership:
Registered users

Re: Replaced Injectors, Now truck struggling to start

Postby 6.2AllTerrain » Mar 07 2017, 2:48am

Maybe air in the system
2017 F**d F250 6.7 PSD Bronze Fire Metallic, 2.5" Rancho level, Fox resi's, Fuel Rampage 20X10 2 piece, Nitto Terra G2 37/12.5
User avatar
6.2AllTerrain
Armed Forces
Armed Forces
Shifting into Gear [L3]
Shifting into Gear [L3]
Posts: 1066
Topics: 31
Images: 68
Joined: Apr 10 2015, 10:10pm
Years of membership: 5 years of membership5 years of membership5 years of membership5 years of membership5 years of membership
Location: Florida
Year: 2010
Make/Model: GMC Sierra
Variant: All Terrain
Extra Info: Z71 4X4 6.2L
Group Membership:
Automotive Technicians
Servicemen
Registered users

Re: Replaced Injectors, Now truck struggling to start

Postby idrivea2005sierra » Mar 07 2017, 2:49am

When you say 2 were leaking; were they leaking from the top of injector (attached to the fuel rail) or leaking at the bottom (interface with engine)??
~Spencer
2005 Victory Red GMC Sierra, 5.3, Z71, CCSB
2002 Volkswagen Golf GLS 2.0, it's not stock
1991 Avanti Convertible, weekend cruiser and project OEM+ restoration
1961 Willys CJ5, currently undergoing chassis off OEM+ restoration
idrivea2005sierra
Combustion on 6 pistons [L2]
Combustion on 6 pistons [L2]
Posts: 684
Topics: 19
Images: 33
Joined: Dec 10 2016, 5:10am
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Location: Grayslake (Chicago Sub)
Year: 2005
Make/Model: GMC Sierra
Extra Info: 5.3 Z71 CCSB
Group Membership:
Registered users

Re: Replaced Injectors, Now truck struggling to start

Postby BowDownBowser [OP] » Mar 07 2017, 2:50am

I plan on checking fuel pressure tomorrow when I can get my hands on a pressure gauge. It may be air in the system, but once I replaced them I started it and drove it about 20 miles so I figured it wouldve gotten any air out then after sitting for an hour is when it struggled. The only reason I don't think it is the fuel pump is that it seems to struggle worse now than it did before replacing the injectors.
Original Poster
BowDownBowser
Firing on 6 cylinders [L1]
Firing on 6 cylinders [L1]
Posts: 64
Topics: 10
Joined: Oct 27 2016, 3:17am
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Location: Jacksonville
Year: 2007
Make/Model: GMC Sierra
Extra Info: 1500NNBS FF 5.3L 4x4
Group Membership:
Registered users

Re: Replaced Injectors, Now truck struggling to start

Postby BowDownBowser [OP] » Mar 07 2017, 2:51am

idrivea2005sierra wrote:When you say 2 were leaking; were they leaking from the top of injector (attached to the fuel rail) or leaking at the bottom (interface with engine)??

They were leaking from the bottom of the injector.
Original Poster
BowDownBowser
Firing on 6 cylinders [L1]
Firing on 6 cylinders [L1]
Posts: 64
Topics: 10
Joined: Oct 27 2016, 3:17am
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Location: Jacksonville
Year: 2007
Make/Model: GMC Sierra
Extra Info: 1500NNBS FF 5.3L 4x4
Group Membership:
Registered users

Re: Replaced Injectors, Now truck struggling to start

Postby idrivea2005sierra » Mar 07 2017, 2:54am

I'm leaning toward it for that very reason. The injectors only do one function, they open and close. They are really only the culprit if one sticks open. From your description you had one stuck open before and you have one now. The other option is the fuel pump is not priming correctly and is leaking down pressure as it sits. Since you had the hard start before the injector change that's where i'm leaning. Without a pressure test though i'm taking a shot in the dark.

Leaking from the bottom of the injectors would tell me the fuel pressure is staying in the system. Leaking at the bottom tells me you may have a small vacuum leak, but nothing that would cause a hard start like you're describing.
~Spencer
2005 Victory Red GMC Sierra, 5.3, Z71, CCSB
2002 Volkswagen Golf GLS 2.0, it's not stock
1991 Avanti Convertible, weekend cruiser and project OEM+ restoration
1961 Willys CJ5, currently undergoing chassis off OEM+ restoration
idrivea2005sierra
Combustion on 6 pistons [L2]
Combustion on 6 pistons [L2]
Posts: 684
Topics: 19
Images: 33
Joined: Dec 10 2016, 5:10am
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Location: Grayslake (Chicago Sub)
Year: 2005
Make/Model: GMC Sierra
Extra Info: 5.3 Z71 CCSB
Group Membership:
Registered users

Re: Replaced Injectors, Now truck struggling to start

Postby BowDownBowser [OP] » Mar 07 2017, 3:05am

idrivea2005sierra wrote:I'm leaning toward it for that very reason. The injectors only do one function, they open and close. They are really only the culprit if one sticks open. From your description you had one stuck open before and you have one now. The other option is the fuel pump is not priming correctly and is leaking down pressure as it sits. Since you had the hard start before the injector change that's where i'm leaning. Without a pressure test though i'm taking a shot in the dark.

Leaking from the bottom of the injectors would tell me the fuel pressure is staying in the system. Leaking at the bottom tells me you may have a small vacuum leak, but nothing that would cause a hard start like you're describing.

I shouldn't have any leaking now. The only one I left in was one that didnt seem to be leaking when checked before so hopefully that one isn't, but who knows. Tomorrow I plan on pulling the rail to look for leaks and to do a pressure test. If I don't see any leaks and pressure is still dropping I guess it would have to be the pump. One thing that gets me and I'm not sure if its still a symptom is that It would only struggle to start when the air temp outside was warmer than like 60 or if I drove it, let it sit for an hour or two, then started it. If it was cold out it wouldn't struggle after sitting overnight
Original Poster
BowDownBowser
Firing on 6 cylinders [L1]
Firing on 6 cylinders [L1]
Posts: 64
Topics: 10
Joined: Oct 27 2016, 3:17am
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Location: Jacksonville
Year: 2007
Make/Model: GMC Sierra
Extra Info: 1500NNBS FF 5.3L 4x4
Group Membership:
Registered users

Re: Replaced Injectors, Now truck struggling to start

Postby sudden_impulse » Mar 07 2017, 3:13am

Not sure how these trucks are, but a failing fuel pressure regulator would show those symptoms on my last car (GM 3400). Maybe check that?
sudden_impulse
Combustion on 4 pistons [L2]
Combustion on 4 pistons [L2]
Posts: 424
Topics: 3
Joined: Jan 14 2015, 3:44am
Years of membership: 6 years of membership6 years of membership6 years of membership6 years of membership6 years of membership6 years of membership
Location: East Bethel, MN
Year: 2003
Make/Model: GMC Sierra
Extra Info: SLE 1500 Z71 4x4
Group Membership:
Registered users

Re: Replaced Injectors, Now truck struggling to start

Postby idrivea2005sierra » Mar 07 2017, 3:13am

How difficult is the start? Are you talking like 5-8 seconds of holding the key or more like 45-50 seconds? If you twist the key, turn it off, then twist again does it start better? It could be the pump isn't priming correctly. That may be an electrical issue.

I mean, the truck runs which means all 3 major systems work. The question is; which is slacking off when it's warm; fuel, air, or spark. Air is a possibility as you said it starts better if you give it gas pedal, could be the airway is dirty. Is the filter clean? How about the MAF and the Throttle Body?

A pressure is a good free test to run. If nothing else it will confirm the pump is working correctly. When you use the fuel pressure gauge, leave it connected for a drive and after you stop. Give it a watch and see how quickly the pressure drops. It will go to 0 eventually, but it shouldn't be instantly.

Also, I say leave it connected based on my NBS 5.3 which has a specific fuel test port. I assume yours has one as well. If not, make sure the connection is secure. You should see about 60psi.
~Spencer
2005 Victory Red GMC Sierra, 5.3, Z71, CCSB
2002 Volkswagen Golf GLS 2.0, it's not stock
1991 Avanti Convertible, weekend cruiser and project OEM+ restoration
1961 Willys CJ5, currently undergoing chassis off OEM+ restoration
idrivea2005sierra
Combustion on 6 pistons [L2]
Combustion on 6 pistons [L2]
Posts: 684
Topics: 19
Images: 33
Joined: Dec 10 2016, 5:10am
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Location: Grayslake (Chicago Sub)
Year: 2005
Make/Model: GMC Sierra
Extra Info: 5.3 Z71 CCSB
Group Membership:
Registered users
Next

Return to Vortec 5300 5.3L V8

 

  • Similar topics
    Replies
    Views
    Last post

Common search terms

truck think injectors replaced struggling start work sierra back help

It is currently Feb 24 2021, 8:48pm

  • Sponsor
Login  •  Register
Vortec 5300 5.3L V8 Forum
Vortec 5300 5.3L V8 specific.
To create a new topic in Vortec 5300 5.3L V8, click this button:
Previous topic Next topic
Sitewide News Sitemaps & Feeds

Who is online

Users browsing this forum: No registered users and 57 guests