As you turn the key to on postion (but do not start) it floods the engine. It's like the injectors are on all the time. When you start the truck normally, it acts like you've just poured raw fuel down the intake. The exhaust fumes also smell like raw fuel. I put new injectors in about 1 year ago. New plugs, cap, rotor, & wires were installed about 2 weeks ago. I took the truck to my local Chevrolet dealer and they told me it was the fuel pump. When I tested it, it had 60 psi. I went ahead and installed a new fuel pump. This didn't fix my problem! I took it back to the dealer and they said they would look at it again. That was a joke. I was told 3 different people drove it and it ran fine. I have read thru the repair manual, but cannot figure out the problem. If you have any insight to this problem, I would really appreciate your help. Thank you,
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Re: fuel injectors are dumping fuel
Sounds like the fuel pressure regulator diaphragm has ruptured. When this happens fuel is drawn in from the manifold vacuum and if the leak is severe enough the fuel pump pressure will push it in as well. The unit is a small component that resides on the fuel injector rail and will have a vacuum hose running to it. Remember you are working with GASOLINE and lots of it so be careful!
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Suspect (potentially) either a stuck injector, or a failed/failing fuel pressure regulator. One sign of a failed fuel pressure regulator can be gas in the oil. (I suffered that side effect, along with bogging, and black smoke rich running, worsening as warmed up, turned out to be fuel pressure regulator). If the injector is loose in the throttle body, or has bad o-rings, can also cause some wonky behavior. Good luck.
Most likely is the temperature sending unit/sensor. Nobody ever thinks about how it works. When engine is started, and cold, the temp sensor tells the computer to put the engine into cold start mode, putting more fuel into the engine and to a bit higher idle. Once it warms up to operating temp, said sensor tells the computer to turn off cold start mode and it stops dumping excess fuel in. If the sensor puts it in cold start mode, malfunctions and doesn't take it off cold start mode, it's still dumping excess fuel in and flooding the engine. Sometimes a re-start will reset the computer, but not always. Makes sense now, doesn't it. Find the temp sensor and replace it like you did all the others.
Well the pump would not be able to flood the engine unless the pressure regulator failed or one of the injectors was stuck open. Have you checked the regulator and injectors ? The pump relay should power the pump for 3 seconds when you turn the key switch on, and you should have around 40psi of fuel pressure in the injector line.
Fuel pressure regulator probabaly flooding it when you turn the key forward it primes but the regulator just dumps to much fuel into the cylinders flooding the plugs pull a plug out after you try starting it if it dont start and see if there full of gas
Pumping the gas pedal and turning the key on and off would not have any affect on the problem. And the fuel pump runs as long as you are cranking the engine, the fuel pressure regulator allows the extra pressure back into the tank. The excess fuel came thru the injectors or the pressure regulator and probably would have even if you had just turned the key and nothing else. The injectors are turned on by the computer based on several things including coolant temp and air temp. The fuel mixture should have been very rich if the air temp was 35 below zero, but it should have leaned out once the engine warmed up. The longer you crank an engine in any weather and it does not start, the more fuel is dumped into the cylinders. Its possible you had one or more injectors that were stuck - froze open when you first cranked the engine. I hope you did not damage the catalytic converter or the O2 sensors.
'pumping' a fuel injected engine is NOT like the old days (like with a carb)-if you hold the petal to the floor, it shuts off the injectors-NO petal, the injectors pulse (and dump fuel to an engine that is slow to start). If you are having hard starting, chances are good you have a flooding condition-leaking injectors, leaking O-rings, a damaged fuel pressure regulator could all be re3asons for your hard starting (and backfiring from a flooded engine). You should try to HOLD the petal to the floor and see if that helps-if it does, you should get the fuel regulator checked, replace the injector o-rings, check fuel pressure and might even need to consider replacing injectors themselves (or having them cleaned).
Sounds like you have an injector leaking. Have someone just cycle the key on and off to run the fuel pump but don't crank the engine. If you see fuel dripping from the injectors, unbolt the injector cover on the throttle body, remove the injectors and replace the orings around the injectors.
SOUND LIKE A INTAKE MANIFOLD LEAK.WHICH WILL CAUSE BACK FIRING.FUEL INJECTORS COULD BE STUCK OPEN DUE TO CARBON BUILT UP ON INSIDE OF THE TIPS.TRYING CLEANING INJECTORS ADDING A BOTTLE OF FUEL INJECTOR CLEANER IN A FULL GAS TANK.ONCE YOU GET ENGINE STARTED DRIVE TRUCK AROUND TO LET THE INJECTOR CLEANER CLEAN INJECTORS.IF THIS DONT WORK.YOU COULD HAVE A BAD INJECTOR STAYING OPEN.HAVE TO BE REPLACED.
When trying to start an engine that you feel might be "flooded" , hold gas pedal down to the floor while cranking . This will stop the injectors from triggering. You might have to remove spark plugs to clean and dry out from fuel. Hope this helps