1998 Z71 Fuel Pump and mass air question HELP!!!
MikeD73USA
02-22-2006, 03:46 AM
:banghead:
Hello,
First off let me say thanks for taking the time at looking at this post!
Ok here goes... Yep, The dreaded fuel pump with a twist!
I did a fuel pressure check key on, engine off. Gauge went to 50+ (did not actually see how high it got) then after the pump shut off the gauge went back down to zero. Bad Check valve right?
With the engine running it is 60 psi, and if I blip the throttle the pressure goes to 62 psi. Output is good, and goes up under load, so I know the fuel pressure regulator and associated tubing is working.
Recently now when I SHUT the engine off, the pump will run about 20 seconds and the sound will get deeper (more bass of a whine) then shut off. One time I thought I was going to have to pull the negative battery cable to shut it off!
And here is the twist. It is two fold.. nothing ever easy... : )
The truck will lead lag lose power surge in the summer, the cold doesnt seem to effect it as much. It doesnt buck like a bronco, but is definetly noticeable.
wheres the twist you say.....
I have a k&n cold air kit installed, this utilizes the old tubing that goes to the valve cover and sucks gasses from the engine which is after the mass air sensor and is not calculated as an input. I know the seal of the tubing that is at the valve cover is weak at best and is probably pulling in more air then the the math in the fuel and timing tables in the pcm thinks the mass sensor is seeing and is maybe causing a lean condition... OR does the check valve not working in the pump cause this lean lag surge? AND what would happen if I put an oil air breather cap where the tubing sucks off of the left valve cover, and plug the hole in the intake tubing that the plastic suction hose connected to? How would this effect the engine? I do not care from an emmisions point of view. The engine is 5.7, and the right side of the engine is where the tubing connects from the manifold to the pcv valve that is in the valve cover. Will the pcv valve work if the suction tubing that is on the left side of the motor is disconnected and plugged, and an oil cap breather in it's place? I want to eliminate the leaks screwing up the mass air sensor. I just need to know if what I am doing will not cause damage to the engine. Or could I get away with also capping the tubing going to the pcv valve on the right side, and stick an oil air breather on that side also???
I know.. to much at one time... Thanks for your time, patience, and experience in helping me out.
//\\//\\ikeD73USA
Hello,
First off let me say thanks for taking the time at looking at this post!
Ok here goes... Yep, The dreaded fuel pump with a twist!
I did a fuel pressure check key on, engine off. Gauge went to 50+ (did not actually see how high it got) then after the pump shut off the gauge went back down to zero. Bad Check valve right?
With the engine running it is 60 psi, and if I blip the throttle the pressure goes to 62 psi. Output is good, and goes up under load, so I know the fuel pressure regulator and associated tubing is working.
Recently now when I SHUT the engine off, the pump will run about 20 seconds and the sound will get deeper (more bass of a whine) then shut off. One time I thought I was going to have to pull the negative battery cable to shut it off!
And here is the twist. It is two fold.. nothing ever easy... : )
The truck will lead lag lose power surge in the summer, the cold doesnt seem to effect it as much. It doesnt buck like a bronco, but is definetly noticeable.
wheres the twist you say.....
I have a k&n cold air kit installed, this utilizes the old tubing that goes to the valve cover and sucks gasses from the engine which is after the mass air sensor and is not calculated as an input. I know the seal of the tubing that is at the valve cover is weak at best and is probably pulling in more air then the the math in the fuel and timing tables in the pcm thinks the mass sensor is seeing and is maybe causing a lean condition... OR does the check valve not working in the pump cause this lean lag surge? AND what would happen if I put an oil air breather cap where the tubing sucks off of the left valve cover, and plug the hole in the intake tubing that the plastic suction hose connected to? How would this effect the engine? I do not care from an emmisions point of view. The engine is 5.7, and the right side of the engine is where the tubing connects from the manifold to the pcv valve that is in the valve cover. Will the pcv valve work if the suction tubing that is on the left side of the motor is disconnected and plugged, and an oil cap breather in it's place? I want to eliminate the leaks screwing up the mass air sensor. I just need to know if what I am doing will not cause damage to the engine. Or could I get away with also capping the tubing going to the pcv valve on the right side, and stick an oil air breather on that side also???
I know.. to much at one time... Thanks for your time, patience, and experience in helping me out.
//\\//\\ikeD73USA
nafi77
02-13-2009, 05:05 PM
I would definitely take a look at that K&N filter setup and check you MAF for oil deposits from the filter. Poor MAF performance can cause the poor performance your talking about, but it could also be you MAP sensor, ignition module, or cam and crank sensors.
Have you pulled codes, or is your SES light lit?
Have you pulled codes, or is your SES light lit?
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