2004 Tahoe Hard Start

[KodiThaFox]

I don't know if this is in the right thread or not,sorry if it isn't, but I have a 2004 Tahoe that I have replaced the fuel pump, fuel filter, fuel composition sensor, fuel rail, fuel injectors, regulator, and even the pcm. When I let the truck sit for more than ten minutes it loses all fuel pressure. The only codes I can get are fuel system too rich bank 1 and 2, and whenever it does start it gives a flooded start (black smoke and rough running) to get it to clear up I have to Rev it to about 1500 for a second or two and it runs fine. And I have tried to disable a injector through my matco scanner and it will stop that injector for like 2 seconds and run back on all 8. Don't know where to go from here I'm at a complete loss

[davester]

It sounds like one or more injectors are leaking fuel into the intake.

 

I would suggest doing an injector leakdown test.  I'm not sure, but your matco scanner probably can do it, combined with a fuel pressure guage.  Basically, you get the system up to full pressure without the engine running, then the scanner will pulse the injector a number of times, and you note down the start and finish pressures.  Repeat for all injectors.    They all should drop about the same amount, and up to a certain psi drop, but I don't know what those numbers are for your engine (it's in the full service manual).  This may show one or more injectors having a problem.

 

You can also put a fuel pressure guage on the rail, run the engine, then turn the engine off and watch how the fuel pressure drops.  The full-service manual also specifies how long it should stay at close to full psi.

 

helminc.com/ebay/amazon has the paper version, or online at sites like alldatadiy.com

 

And remember, just because you put in new parts doesn't mean those parts are good.  they might be bad out of the box, or depending on where you bought them from, they could be knockoffs or factory rejects.

[KodiThaFox]

46 minutes ago, davester said:

It sounds like one or more injectors are leaking fuel into the intake.

 

I would suggest doing an injector leakdown test.  I'm not sure, but your matco scanner probably can do it, combined with a fuel pressure guage.  Basically, you get the system up to full pressure without the engine running, then the scanner will pulse the injector a number of times, and you note down the start and finish pressures.  Repeat for all injectors.    They all should drop about the same amount, and up to a certain psi drop, but I don't know what those numbers are for your engine (it's in the full service manual).  This may show one or more injectors having a problem.

 

You can also put a fuel pressure guage on the rail, run the engine, then turn the engine off and watch how the fuel pressure drops.  The full-service manual also specifies how long it should stay at close to full psi.

 

helminc.com/ebay/amazon has the paper version, or online at sites like alldatadiy.com

 

And remember, just because you put in new parts doesn't mean those parts are good.  they might be bad out of the box, or depending on where you bought them from, they could be knockoffs or factory rejects.

I just performed this test and each injector went from 56 psi down to 55 psi, over the course of roughly 10 minutes the fuel pressure drops from 60 down to 25 after running. I do have access to my.all data.com

[KodiThaFox]

I was just messing around with it and I decided to unplug each injector and the pressure stayed around 53-56 after about 30 minutes, and if anybody is wondering the only sensors that aren't new are all 4 o2 sensors, ect sensor, and the crank position sensor

[KodiThaFox]

Went ahead and put another fuel pump in it, same problem, anyone?

[rjgti]

well you could smell your oil, see if it smells like gas.  if so we are back to injectors. 

[KodiThaFox]

On 3/16/2020 at 6:41 PM, rjgti said:

well you could smell your oil, see if it smells like gas.  if so we are back to injectors. 

Oil smells fine doesn't light with a lighter

[sefiroxx]

A)Do two fuel pressure leak down tests.

1) key on 5sec, key off, monitor
2) repeat, but with all injectors unplugged.

If different results, then there is a short in the wire harness.

B) check upstream o2 voltages and fuel trim to see if the rich condition is side specific. If side specific, it could be wire harness that side or cylinder specific on that side.

[William Christopher Speight]

just throwing  random idea....PCM issues??

[KodiThaFox]

On 4/17/2020 at 3:19 PM, William Christopher Speight said:

just throwing  random idea....PCM issues??

Replaced pcm already with same results

[Duramax3oh]

I guess this thread is as good as any without starting a new one, so here goes...

 

I've got a 2006 Tahoe and looking for the specific forum for this body style... I'm not seeing anything at all. Just 1500/HD's with these model years.  Anybody got advice for where us early-mid 2000 Tahoe owners go