Fuel pump questions?
Thread Starter
Racer
Joined: Nov 2006
Posts: 322
Likes: 1
From: Muskego Wisconsin
Fuel pump questions?
1.) will a failing fuel pump throw codes
2.) does $95 seem right for a new pump.
Today I wanted to let the smoke out of my tires. Jumped on the gas and it just bogged, sputtered and farted. Let off the gas and it returned to an idle. Normal acceleration engine runs fine, while increasing speed if i stab the gas engine starts missing and bogging. ya know symptoms of a starved engine. Of course tomarrow I will replace the fuel filter to start, just thought 100 bucks was quite a bit high for a pump. Any suggestions anyone??
2.) does $95 seem right for a new pump.
Today I wanted to let the smoke out of my tires. Jumped on the gas and it just bogged, sputtered and farted. Let off the gas and it returned to an idle. Normal acceleration engine runs fine, while increasing speed if i stab the gas engine starts missing and bogging. ya know symptoms of a starved engine. Of course tomarrow I will replace the fuel filter to start, just thought 100 bucks was quite a bit high for a pump. Any suggestions anyone??
Le Mans Master
Joined: May 2000
Posts: 7,033
Likes: 12
Thread Starter
Racer
Joined: Nov 2006
Posts: 322
Likes: 1
From: Muskego Wisconsin
no pressure gauge. will buy one tomarrow and test. do have full tank of gas. that is exactlly what it feels like though. i started out with a break torque and it just started missing and bogging down. Once rolling I could lean on it and it seemed responsive... But, when i nailed it while rolling approx 15 mph, there was no real excelleration. fell flat on it's face. back off and it seems ok. 'course somthings not right. can fuel pumps fail to low pressure or do they normally just die?
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
fuel pump
if you think $95 is a lot of money for a pump,your gonna be doing the farting, not the car, the fuel pump gauge is $50
There are some other factors for the engine falling flat on it's face,
false air, bad ignition components, bad timing chain, timing is off,low fuel pressure, dead spots in the throttle position sensor, bad knock sensor, false air in the intake, vacuum leaks, etc.
There are some other factors for the engine falling flat on it's face,
false air, bad ignition components, bad timing chain, timing is off,low fuel pressure, dead spots in the throttle position sensor, bad knock sensor, false air in the intake, vacuum leaks, etc.
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Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
You didn't say it explicitly, but you got no error codes, correct?
1) duck tape your FP gauge to windshield when you test, since your problems are seen during hard accel. under load. Does engine "bog" if you have car in "park" and throttle it with your hand ??
2) check your TPS with a DVM and make sure there are no "dead" spots. Voltage should increase steadily from around 0.5V to almost 5V as you open Throttle from Idle to WOT. Do this with ignition on, engine off.
3) Check your MAF. Easiest way to check with voltage measurements is to dissconnect it and see if there is any change to your symptoms.
1) duck tape your FP gauge to windshield when you test, since your problems are seen during hard accel. under load. Does engine "bog" if you have car in "park" and throttle it with your hand ??
2) check your TPS with a DVM and make sure there are no "dead" spots. Voltage should increase steadily from around 0.5V to almost 5V as you open Throttle from Idle to WOT. Do this with ignition on, engine off.
3) Check your MAF. Easiest way to check with voltage measurements is to dissconnect it and see if there is any change to your symptoms.
Thread Starter
Racer
Joined: Nov 2006
Posts: 322
Likes: 1
From: Muskego Wisconsin
Havn't checked for codes yet. this just started 7-7-7 (that may be the problem 
) seriously though the engine in park reves right up no prob. I'll check TPS for dead spots. if i disconnect the MAF the engine would still run normal?
) seriously though the engine in park reves right up no prob. I'll check TPS for dead spots. if i disconnect the MAF the engine would still run normal?
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Not normal......but it will run. Your PCM will simply lack input from this sensor for AFR adjustments, but it will run.
just FYI:
In a "mass air" engine control system, as used in the 94 and later F-bodies, the PCM only needs a few pieces of information to manage the air and fuel mixture. The most important is the amount of air entering the engine, to be used for combustion with the correct amount of gasoline. More specifically, it needs to know the "mass" of air, or the number of pounds or grams of air that entered the engine to be used to burn the gasoline.
The Mass Air Flow (MAF) sensor measures the mass of air entering the engine, expressed in "grams per second" or "pounds per minute".
The MAF sensor works by internally measuring the temperature of the air coming into the system. It then uses the wires to heat the small amount of air that is actually touching the wires, a fixed number of degrees above the incoming air. By measuring the electrical power required to heat the air, and knowing the specific heat of air, the MAF sensor can calculated the "mass" (or roughly "pounds") of air entering the engine. It then converts this signal to a variable frequency output. Inside the PCM, there is a calibration table that converts the frequency to a "mass air flow" rate.
just FYI:
In a "mass air" engine control system, as used in the 94 and later F-bodies, the PCM only needs a few pieces of information to manage the air and fuel mixture. The most important is the amount of air entering the engine, to be used for combustion with the correct amount of gasoline. More specifically, it needs to know the "mass" of air, or the number of pounds or grams of air that entered the engine to be used to burn the gasoline.
The Mass Air Flow (MAF) sensor measures the mass of air entering the engine, expressed in "grams per second" or "pounds per minute".
The MAF sensor works by internally measuring the temperature of the air coming into the system. It then uses the wires to heat the small amount of air that is actually touching the wires, a fixed number of degrees above the incoming air. By measuring the electrical power required to heat the air, and knowing the specific heat of air, the MAF sensor can calculated the "mass" (or roughly "pounds") of air entering the engine. It then converts this signal to a variable frequency output. Inside the PCM, there is a calibration table that converts the frequency to a "mass air flow" rate.
Last edited by MikeC4; Jul 8, 2007 at 11:00 AM.
Thread Starter
Racer
Joined: Nov 2006
Posts: 322
Likes: 1
From: Muskego Wisconsin
Coupeguy,
Don't think it's timing prob. can still be agressive, had it a little sidewasy in a turn, left a little rubber. just when i go WTO from dead stop. also it just seems the minute u say you got a vette they go right to the price adjusted parts book.
Don't think it's timing prob. can still be agressive, had it a little sidewasy in a turn, left a little rubber. just when i go WTO from dead stop. also it just seems the minute u say you got a vette they go right to the price adjusted parts book.
Thread Starter
Racer
Joined: Nov 2006
Posts: 322
Likes: 1
From: Muskego Wisconsin
The good news: The car ran o.k. all afternoon cold and hot. responsive acceleration, spinning tires the shoot'n match. 
So I took her home and gave her a wash.
I did pick up a fule pressure gauge and the components for the OBDII cable 'cause I know were not thru.
The bad news: I know were not thru.
I still sensed a little somthing; hesitation, maybe a caugh or hiccup.
So today I will connect the pressure gauge and drive around a bit, see what's up and get some #'s
To effn hot yesterday to do anything but play with cold water..105* AND humid.
So I took her home and gave her a wash.
I did pick up a fule pressure gauge and the components for the OBDII cable 'cause I know were not thru.
The bad news: I know were not thru.
I still sensed a little somthing; hesitation, maybe a caugh or hiccup.
So today I will connect the pressure gauge and drive around a bit, see what's up and get some #'s
To effn hot yesterday to do anything but play with cold water..105* AND humid.
Melting Slicks
Joined: Oct 2004
Posts: 2,510
Likes: 4
From: Austin Texas
Stay cool, hope your AC is running well in your vette!!
Thread Starter
Racer
Joined: Nov 2006
Posts: 322
Likes: 1
From: Muskego Wisconsin
Heat wave was sweltering. official temp at lakefront was 97*. I'm 20 mi away, usally 10* difference out in country.
AC in car currently not working but recharge kit from JCWhittney on it's way.
and as far as the filter goes 
...it has gott'n cooler-i have no excuse. i have noticed that my average milage has dropped fron 20~21mpg to 17.5 however, I have been going to a different G-Station as there gas is still $3.29 for premium vs. $3.71..so...when this tank is dry I'll bite the bullet,their may be more ethonal causeing the problem.
AC in car currently not working but recharge kit from JCWhittney on it's way. and as far as the filter goes ...it has gott'n cooler-i have no excuse. i have noticed that my average milage has dropped fron 20~21mpg to 17.5 however, I have been going to a different G-Station as there gas is still $3.29 for premium vs. $3.71..so...when this tank is dry I'll bite the bullet,their may be more ethonal causeing the problem.