james0002

hello everyone new member here, i have a 1999 tahoe and had prob. starting the other day. the truck has been running rough awhile, i have replaced cap,rotor,plugs,wires and have added injector cleaners (sea foam) in the fuel tank as well as in the main vaccum off the brake booster. it runs smooth so times and rough others. the service light does come on periodically and throws only one code (misfire on #4) on replacing the plugs i did notice the #4 cylinder plug was very dry almost rusty looking like not getting proper fuel. Possibly a injector? like i said the other morning it did not start at all (first time ever) sprayed some starting fluid and fired right up. This system single injector? 8 under the intake? ive heard two different things. Any help would be greatly appreciated thank you

ZX1100F1

The 1999 Vortec 5.7L uses a Central SFI system, the fuel meter assembly is located just under the plastic intake manifold cover.
There is a separate poppet/injector assembly going to each cylinder that can be serviced individually.

Make sure to take care to get each injector back to its original location, this is a very common error that causes a lot of heartache.

james0002

so in ur opinion the injector is the problem? is it the way to go to just replace 1 or should all of them be replaced? i am a self doer but havent wrked on this type of fuel system i take it that you just take off the intake replace the injector get a new intake gasket and bolt back, pretty much a clear cut deal? Thank you again

ZX1100F1

That is pretty much all there is to it.
If you just have the one acting up I would replace just the effected injector they are fairly pricey but before you do you may want ot see about cleaning them all.

Chevron Techron cleaner http://www.chevron.com/products/prod...ate_plus.shtml
works wonders and if you have a clogged set of injectors I recommend dumping up to six 16oz bottles of the stuff in a full tank of fuel and running the hell of the motor till the tank is nearly empty.

james0002

ok well i really appreciate the imformation i guess the spark plug (being rusty) tells the story. i think i will try the chevron stuff ur talking about first before diving into it, u say 6 bottles all together in one tank?

ZX1100F1

Yep

james0002

ok i decided to use the 6 bottles of cleaner first and it seems to run smoother at a idle and it will start now w/o useing ether. i will try to describe this if i can ,when starting in the morning after sitting all night i go to turn the key over and the motor turns quickly (as it should) but.... it wont start like that, the only way it will start is let the motor turn over like 3 times and let off the key as the revolutions of the motor slow it will fire off. its hard to describe. i am very familiar w/ the older 350 but not this type fuel system, i find it hard for single injector to cause this, to add.... once it fires it runs rough for about 2-3 minutes then clears this rough idle is only at standard engine idle any increased rpms over 1000 and it smooth as a kitten. also for the remaining of the day it seems to start right up easier. the truck takes off fineno hesitation out of the hole and like i said everything has been replaced new wires cap that kind of thing and also has a brand new fuel pump bout 6 months ago. any helpwould be appreciated thank you

james0002

i read in a post that this sysstem is pressurrized is that both running and while off? i see a box on the front driver side that has a line out that reads not to exceed 1-2 lbs pressure. if it is supposed to be pressurized where do u take the reading and what should the reading be. thanks

RonH

The fuel pressure test port is a schrader valve on the fuel rail on top of the engine. Remove the plastic intake cover from the throttle body, then lookjust to the rear ofthe throttle body and just a little to the driver's side. You will see it sticking straight up. That's where you attach the gauge to measure the pressure and relieve the pressure when needed.

Bringdanoisemik1

I've been having the same problem with my Hoe, I have to crank it 3 or 4 times in the morning or after it has been sittin off for a while. I went ahead and took ZX1100F1'sadvice and threw in 6 bottles of the Techron Cleaner, It might be to soon but lets see if I notice a difference in the AM.