Changing Fuel injectors on 8.1

[pound41]

2003 GMC 2500HD 8.1 125k miles
at times hard to start and idling erratic. When it doesn't start I smell gas. I will have the injectors checked. I have changed fuel pressure reg, plugs and wires,
coolant temp senor, crankshaft positioning senor. So some think its a leaking injector I looked at it today seems pretty simple but I have never done this type of job before. Any insight or help is appreciated
Thanks

[DirtyLarry]

Originally Posted by pound41

2003 GMC 2500HD 8.1 125k miles
at times hard to start and idling erratic. When it doesn't start I smell gas. I will have the injectors checked. I have changed fuel pressure reg, plugs and wires,
coolant temp senor, crankshaft positioning senor. So some think its a leaking injector I looked at it today seems pretty simple but I have never done this type of job before. Any insight or help is appreciated
Thanks

Injector issues on L18’s are pretty rare, although they do happen.

Are there any codes present?

I would first remove the air induction pipe from the throttle body and look for heavy carbon deposits inside the bore. Clean it well with carb cleaner and a rag and see if that helps any. Another thing you can do to somewhat confirm a leaking injector is to install a fuel pressure gauge then cycle the pump and watch the gauge after the key is turned off. If fuel pressure bleeds off quickly would be indicative of a leaking injector (or regulator problem but you already replaced that). It is normal for fuel pressure will drop to zero overnight. If pressure falls significantly within a few minutes would confirm an injector leak issue, then you have to figure out which one.

You can also remove the fuel rail from the engine and just lay it on top the engine where you can see them then cycle the key to ON in order to prime the fuel pump (without cranking the engine!). You will want to do this on a COLD engine because if there is a stuck or leaking injector you will see it dropping fuel. Not a good thing on a hot engine! This is the easiest way to confirm a leaking injector, just BE CAREFUL and don’t burn your house down!

Here is the list from the GM service manual for Rough, Unstable, or Incorrect Idle and Stalling.

- Engine oil contaminated by fuel
- An evaporative emission (EVAP) canister purge condition
- Incorrect fuel pressure
- Leaking fuel injectors
- An inaccurate mass air flow (MAF) sensor
- Blockage on the inlet screen of the MAF sensor
- Vacuum hoses that are split, kinked, or improperly connected
- An air intake duct that is collapsed or restricted
- An air filter that is dirty or restricted
- Water intrusion in the heated oxygen sensor (HO2S) connector

I attached the fuel rail R&R instructions for you

[pound41]

thanks for the information. When it got around 90k on it it started but it would only do it in the winter time. Last year it sent a code that was related to the mass air flow. I took it a part and cleaned it. It was about now or early march so the problem appeared gone but the temps outside were getting warmer. It would always start but cut off. Now it acts like its not getting fuel/or spark/ or maybe flooded. My dad was a professional mechanic for decades but he has passed on so I don't have him to help me. My Dad would use the phrase its not catching"
The example I would give you if a car had a bad fuel pump and when you spin it over it has a different sound than a motor that has gas and fire but just isn't catching. Thats what it sounds like then it will eventually start and you smell gas--the idle will fluctuate but once I get it going it runs ok sometimes sitting at a light the rpms move up and down between 5-7.5 or so. It was extremely cold one morning last week the Check engine light came on but it ran ok. Hooked up the scan tool. said Oxygen sensor bank 1 sensor 1 P0143. So I will cleaner the air duct as you suggested. If I hook a pressure gauge where do I hook it up.
Thanks again

[DirtyLarry]

Originally Posted by pound41

thanks for the information. When it got around 90k on it it started but it would only do it in the winter time. Last year it sent a code that was related to the mass air flow. I took it a part and cleaned it. It was about now or early march so the problem appeared gone but the temps outside were getting warmer. It would always start but cut off. Now it acts like its not getting fuel/or spark/ or maybe flooded. My dad was a professional mechanic for decades but he has passed on so I don't have him to help me. My Dad would use the phrase its not catching"
The example I would give you if a car had a bad fuel pump and when you spin it over it has a different sound than a motor that has gas and fire but just isn't catching. Thats what it sounds like then it will eventually start and you smell gas--the idle will fluctuate but once I get it going it runs ok sometimes sitting at a light the rpms move up and down between 5-7.5 or so. It was extremely cold one morning last week the Check engine light came on but it ran ok. Hooked up the scan tool. said Oxygen sensor bank 1 sensor 1 P0143. So I will cleaner the air duct as you suggested. If I hook a pressure gauge where do I hook it up.
Thanks again

Sorry to hear about your dad. I lost mine in 2010….no fun!

You could very well have a MAF issue as well. The solder joints inside break near the sensing probe that can exhibit an intermittent issue. Typically more noticeable during drastic temperatures, either extremely cold or extremely hot as the metal expands and contracts.

I feel you are more on the right track with a possible leaking injector as they will cause a long crank due to the pump having to build pressure at key on, as well as overcome the leak (leaking injector) before it will fire. In the meantime the leaking injector is enriching the problem cylinder badly. Probably why the O2 codes were thrown and you smell fuel.

This one is a long shot but I have seen this too, although a fuel smell usually isn’t noticed as much…. I’ve seen several occasions where the nylon fuel lines inside the fuel module (the lines that run from the top of the module to the pump hanging at the bottom) rub on each other until a hole appears in the supply or return line. This will cause an internal leak where fuel pressure is lost at key off then the pump struggles to build the correct fuel pressure at key on as well as overcome the leak resulting in a long crank. The pump will eventually overcome an internal fuel leak but it take a noticeable amount of time for it to do so. The engine will run fine once fuel pressure is built but can run low fuel pressure at idle and at wide open throttle while normal cruising is not affected. Often lean bank 1, lean bank 2 codes are dropped but not always. This is also something you can check with the fuel pressure gauge by looking to see if the pressure instantly starts tanking once the key is turned off, just like a leaking injector.

The fuel pressure port is on the fuel rail on the passenger’s side under the engine cover. You will need to remove the engine cover to access it.

The P0143 code you mentioned is not a valid code per the GM service manual