2005 Chevrolet Tahoe Z71, 5.3 non flex fuel. Hard starting.

kylebnoris · Jul 30, 2024

Afternoon y'all.

Back at it again.

Hard or long start with sputtering then runs fine after on.

So fuel pump was dropping pressure when I tested via the fuel feed line on the gauge, replaced fuel pump and now the gauge holds steady. Reconnecting the fuel feed line to the fuel rail and then, testing at the fuel rails shows pressure dropping.

Alldata says faulty injector. So I put a extension to the injectors while it was running and all 8 are clicking, sounds consistent etc. I'm currently doing the knock sensors and harness but when I put it back together, I'd like to replace the faulty injector while I'm in there.

Only clue I have so far (might be unrelated) was that cylinder 5's spark plug was wet with oil / and or fuel when I replaced it and the plug wires. Spark plug was DRY on the interior of the plug, only wet on the exterior of the threads, thought it was a valve cover leak but it seems to be seeping out of the spark plug hole etc, so I'm thinking that cylinder has the leaking injector but no proof as of yet.

Any ideas? Test I can perform? I think I can check for a misfire with my Autel MX900 when I put it all together, didn't think about that. I'll also Ohm out all 8 injectors when I have them out.

Thanks!

Fless · Jul 30, 2024

You can do an injector balance test to see if one is leaking down -- pretty sure your Tech 2 can do that. And I don't recall if that engine has a fuel pressure regulator on the fuel rail but if it does, you may want to test it or replace it with an OE regulator.

Be sure to use new o-rings on the injectors when you put them back in.

Sparksalot · Jul 30, 2024

kylebnoris said:
Afternoon y'all.

Back at it again.

Hard or long start with sputtering then runs fine after on.

So fuel pump was dropping pressure when I tested via the fuel feed line on the gauge, replaced fuel pump and now the gauge holds steady. Reconnecting the fuel feed line to the fuel rail and then, testing at the fuel rails shows pressure dropping.

Alldata says faulty injector. So I put a extension to the injectors while it was running and all 8 are clicking, sounds consistent etc. I'm currently doing the knock sensors and harness but when I put it back together, I'd like to replace the faulty injector while I'm in there.

Only clue I have so far (might be unrelated) was that cylinder 5's spark plug was wet with oil / and or fuel when I replaced it and the plug wires. Spark plug was DRY on the interior of the plug, only wet on the exterior of the threads, thought it was a valve cover leak but it seems to be seeping out of the spark plug hole etc, so I'm thinking that cylinder has the leaking injector but no proof as of yet.

Any ideas? Test I can perform? I can check for a misfire with my tech 2 when I put it all together, didn't think about that. I'll also Ohm out all 8 injectors when I have them out.

Thanks!
View attachment 434045

Ever time, or just when it’s been sitting a bit?

I had this happen with my K2 last year. It turned out to be a pinhole in the fuel line from the tank to the engine. If it sat for a few hours or longer it took a while longer to start.

kylebnoris · Jul 30, 2024

Fless said:
You can do an injector balance test to see if one is leaking down -- pretty sure your Tech 2 can do that. And I don't recall if that engine has a fuel pressure regulator on the fuel rail but if it does, you may want to test it or replace it with an OE regulator.

Be sure to use new o-rings on the injectors when you put them back in.

10-4, should rephrase, it's an Autel MaxiCheck MX900, I'll see if it's capable tomorrow.

Sparksalot said:
Ever time, or just when it’s been sitting a bit?

I had this happen with my K2 last year. It turned out to be a pinhole in the fuel line from the tank to the engine. If it sat for a few hours or longer it took a while longer to start.

It's very intermittent. Sometimes it's non existent, then sometimes it's every crank, cold or hot.

justirv · Jul 31, 2024

kylebnoris said:
Afternoon y'all.

Back at it again.

Hard or long start with sputtering then runs fine after on.

So fuel pump was dropping pressure when I tested via the fuel feed line on the gauge, replaced fuel pump and now the gauge holds steady. Reconnecting the fuel feed line to the fuel rail and then, testing at the fuel rails shows pressure dropping.

Alldata says faulty injector. So I put a extension to the injectors while it was running and all 8 are clicking, sounds consistent etc. I'm currently doing the knock sensors and harness but when I put it back together, I'd like to replace the faulty injector while I'm in there.

Only clue I have so far (might be unrelated) was that cylinder 5's spark plug was wet with oil / and or fuel when I replaced it and the plug wires. Spark plug was DRY on the interior of the plug, only wet on the exterior of the threads, thought it was a valve cover leak but it seems to be seeping out of the spark plug hole etc, so I'm thinking that cylinder has the leaking injector but no proof as of yet.

Any ideas? Test I can perform? I think I can check for a misfire with my Autel MX900 when I put it all together, didn't think about that. I'll also Ohm out all 8 injectors when I have them out.

Thanks!
View attachment 434045

I'm guessing #5 injector could be leaking. That would explain the (static) pressure loss, #5 sparkplug being wet (fuel), and the hard starting. Once running, the demand for fuel is there, and it activates normally. I wouldn't count on a nice clean cone of fuel spray from that one.

Fless · Jul 31, 2024

Could also be an intermittent evap purge valve on the engine. If it stays open while the engine is shut off, it can let fuel vapor into the intake which can cause a flood condition.

Have you tried the "clear flood" procedure -- floor the gas pedal while cranking -- when it acts up? If that works it indicates over-fueling, which could have a few things causing it.

kylebnoris · Jul 31, 2024

I'm gonna remove the intake again, set up some water bottles unter each injector and run the test via the MX900, then replace from there. She's having a real long time starting today. Gonna have to replace the A/C compressor while I'm at it too.

Side note, I have a EBCM (w/JL4) that I replaced, prior to getting it I had zero communication etc. However I need to program it, as it isn't programmed correctly. I noticed that when (they intermittently illuminate) the ABS/Parking Brake lights are on, I loose cruise control and my wiper controls.

When the lights are off I have all functionality. Is the DTC that sets the ABS and Parking lights disabling Cruise and subsequently my wipers? New wiper motor as the old one was groaning pretty bad and thought maybe that was it, but before I got trying to parts cannon the turn signal stock I think those DTC's are disabling Cruise and wipers lol.

kylebnoris · Aug 9, 2024

Update,

found during injector test via Autel, sputtering from injector 5.

Replaced it, plus the intake gasket.

So far no hard starts.

West 1 · Aug 19, 2024

Nice work, you tracked it down and fixed it. That always feels good.

2005 Chevrolet Tahoe Z71, 5.3 non flex fuel. Hard starting.

kylebnoris

Member

Fless

Sparksalot

kylebnoris

Member

justirv

Member

Fless

kylebnoris

Member

kylebnoris

Member

West 1

Member

Similar threads

Forum statistics

Latest posts