Fuel delivery issues 5.7 vortex gmc suburban any techs online?

Question

Hi, I am stuck I have sucsessfuly narrowed a no start situation to my fuel delivery. Engine will crank but not start v-8 Vortex so I sprayed some gas into the throttle body and it fired right up. Now before I start tearing down my upper intake plenium, how can i verify if the PCM is powering up the metering device I am a marine technition by trade. I only have a haynes manual to reference, and a Blue Pointe hand held code reader. There is no stored codes on PCM so what are the odds of all 8 injecters to stop working? Im thinking maby a bad pressure regulator or the filter behind it may be clogged. The vehicle has a new fuel filter new fuel pump and pump is pushing plenty of pressure its in spec. Im hoping this is a common problem or if you can tell me a way to verify my pcm output voltage to fuel injectors metering unit, its the sequencial type system. I would be greatly apriciative if you would share your knowledge and get me out of this jam Im in. Also how can i bench test a pressure regulator?Thank you in advance

Answer 1

do not hook up a voltmeter to your computer it can fry it i dont know about your pressure... unhook the fuel line at the fuel rails and crank the motor over... if a lot of fuel comes out its some injectors...

Answer 2

If the engine was hard to start and back fired occassionally and then when it did start it would barely go----That sounds like a bad Fuel pressure regulator.Crank the engine and then pull the pressure regulator vacuum line off,If fuel comes out the diaphram is defective .Injector pulse can be checked with a noid light purchased at auto parts dealer.May have a problem with the crank possition sensor.The computor has to know the crank position of the piston before it will inject and fire.Who worked on it right before the problem occured? It could just be a damaged Quad driver in the computor that controls the injectors.It should probably be taken in for a tech. to fix.

Answer 3

The vortec has a main injector and 8 poppets in the intake runners. pinch off the return line with a fuel pressure guage attatched and see what it's doing.The added pressure may give you some sign of firing.

On top of the intake is the connector for all that goes on with injectors. Without a good diagram, it's going to be tough to diagnose. Check your haynes manual and see what they offer.Good luck. Keep us updated.

The "spider" in the intake is a known offender. They do fail.

Answer 4

by the way how much fuuel pressure you have vortex motors due require a certain amount of fuel pressure to fire and havent seen regulators go bad on these just the spider under pletium cause the way you explain i would say fuel pump

Answer 5

A fuel pressure gauge is a MUST.   Fuel pressure is very critical, you MUST have 60-65 PSI  key ON Eng. OFF,,  watch the gauge for the next few minutes make sure it doesn't drop below 55 PSI

If that's not what you have, then the PUMP is bad. (yea I know you changed the pump, did you install a GM pump or aftermarket ????

I agree with Chev M , the regulator is not your problem, even if it's leaking down (truck will start on 2nd or 3rd try)   unless it's wide open but you'll see it on the gauge. Not injectors either.

AS far as PCM output to injectors,

the PCM does not provide voltage but rather a ground path to the proper injector. PCM has to see a crank signal for it to do this.

Voltage is applied through the ECM 1 fuse 20A  (power is always present at the injectors with key on  , this fuse powers all 8 injectors.)