Quick observation: Cars with suspected bad, or marginal or dead, fuel pumps.. seem to start up perfectly, after being towed. At least on the turn of the key after being hooked up, and towed at some kind of angle. Why is this?
Observation on cars with bad fuel punps...
- Thread starter MalfunctionProne
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JHZR2
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bad electrical connection...
pump motor develops dead spots-old mech friend told me if pump starts to act up, keep a rubber mallet in car and tap fuel tank, oftentimes will get pump work. Of course, the pump is going to fail eventually, but this technique can often keep you from being stranded.
Kinda like the near dead starter concept. Tap it once or twice or bounce the vehicle a few times so the gas can slosh against it a few times and it fires right up.
Appreciating all replies.
Motor develops flat spots?
Motor develops flat spots?
My Vette check engine light came on in traffic during the summer and started running very sluggish. I managed to get it home and pulled the code which ended up being for lean left and right banks, so I immmediately suspected a bad fuel pump. By this time it would start ok, but bog and die when you rev'd it. I hooked up my fuel pressure gauge to the fuel rail and was barely registering, but did show a couple pounds. I couldnt hear the fuel pump however, and normally I could (very faintly). Being the middle of summer, it gave me an idea. I started it back up, and it was barely idling at this point. I then went back and removed the fuel cap... swoooooosh, the pressure released.... then it stalled and died (for good until I put a new pump in).
Maybe while being towed enough pressure built up from heat or sloshing or whatever to start yours?
Maybe while being towed enough pressure built up from heat or sloshing or whatever to start yours?
Originally Posted By: MalfunctionProne
Appreciating all replies.
Motor develops flat spots?
If it is a brush-type electric motor such as the Bosch Turbine style fuel pump, it can arc under the brushes and develop higher resistance carbonized spots. If it comes to rest under these spots (and it often does due to greater mechanical resistance), the electric motor can be harder to get turning again on the next activation. This is easily avoided by simply waiting a second or two after keying the vehicle "on" before engaging the starter.
The reason is simple physics. Electric motors have a minimum voltage at which they being to spin, and that minimum goes up as the motor ages.
While the starter is engaged, the flooded cell battery is able to deliver huge Amperage to everything that conducts, but the Voltage drops significantly. If any brushed electric motor (wipers, blower, fuel pump) is switched on but not yet turning, the Voltage may be too low to get it turning, but it will appear like a short in the circuit and the battery happily dumps huge current through it. Thus, the arc-welding spots.
I try to turn off wipers, ventilation blowers, and all other motors before starting a vehicle, and I wait a second or two between switching "on" and engaging the starter. As a result I've never had to replace any of my wiper, electric fuel pump, or vent blower motors. Ever. (And I'm not considered to be a person to have great luck with vehicle reliability). I have replaced them for other people, and those other people hop in and hit the starter immediately. I've given the above explanation as to why, but with the exception of a few engineers, no one cares. The vehicle exists for their convenience, and if motors burn out, they reserve the right to complain and not change their behavior.
Appreciating all replies.
Motor develops flat spots?
If it is a brush-type electric motor such as the Bosch Turbine style fuel pump, it can arc under the brushes and develop higher resistance carbonized spots. If it comes to rest under these spots (and it often does due to greater mechanical resistance), the electric motor can be harder to get turning again on the next activation. This is easily avoided by simply waiting a second or two after keying the vehicle "on" before engaging the starter.
The reason is simple physics. Electric motors have a minimum voltage at which they being to spin, and that minimum goes up as the motor ages.
While the starter is engaged, the flooded cell battery is able to deliver huge Amperage to everything that conducts, but the Voltage drops significantly. If any brushed electric motor (wipers, blower, fuel pump) is switched on but not yet turning, the Voltage may be too low to get it turning, but it will appear like a short in the circuit and the battery happily dumps huge current through it. Thus, the arc-welding spots.
I try to turn off wipers, ventilation blowers, and all other motors before starting a vehicle, and I wait a second or two between switching "on" and engaging the starter. As a result I've never had to replace any of my wiper, electric fuel pump, or vent blower motors. Ever. (And I'm not considered to be a person to have great luck with vehicle reliability). I have replaced them for other people, and those other people hop in and hit the starter immediately. I've given the above explanation as to why, but with the exception of a few engineers, no one cares. The vehicle exists for their convenience, and if motors burn out, they reserve the right to complain and not change their behavior.
Originally Posted By: HangFire
I've given the above explanation as to why, but with the exception of a few engineers, no one cares.
I care. Thank you for posting. Much appreciated.
I've given the above explanation as to why, but with the exception of a few engineers, no one cares.
I care. Thank you for posting. Much appreciated.
Originally Posted By: HangFire
Originally Posted By: MalfunctionProne
Appreciating all replies.
Motor develops flat spots?
If it is a brush-type electric motor such as the Bosch Turbine style fuel pump, it can arc under the brushes and develop higher resistance carbonized spots. If it comes to rest under these spots (and it often does due to greater mechanical resistance), the electric motor can be harder to get turning again on the next activation. This is easily avoided by simply waiting a second or two after keying the vehicle "on" before engaging the starter.
The reason is simple physics. Electric motors have a minimum voltage at which they being to spin, and that minimum goes up as the motor ages.
While the starter is engaged, the flooded cell battery is able to deliver huge Amperage to everything that conducts, but the Voltage drops significantly. If any brushed electric motor (wipers, blower, fuel pump) is switched on but not yet turning, the Voltage may be too low to get it turning, but it will appear like a short in the circuit and the battery happily dumps huge current through it. Thus, the arc-welding spots.
I try to turn off wipers, ventilation blowers, and all other motors before starting a vehicle, and I wait a second or two between switching "on" and engaging the starter. As a result I've never had to replace any of my wiper, electric fuel pump, or vent blower motors. Ever. (And I'm not considered to be a person to have great luck with vehicle reliability). I have replaced them for other people, and those other people hop in and hit the starter immediately. I've given the above explanation as to why, but with the exception of a few engineers, no one cares. The vehicle exists for their convenience, and if motors burn out, they reserve the right to complain and not change their behavior.
Great explanation. I knew some but not all of this. But then, I am a Mechanical Engineer!
Originally Posted By: MalfunctionProne
Appreciating all replies.
Motor develops flat spots?
If it is a brush-type electric motor such as the Bosch Turbine style fuel pump, it can arc under the brushes and develop higher resistance carbonized spots. If it comes to rest under these spots (and it often does due to greater mechanical resistance), the electric motor can be harder to get turning again on the next activation. This is easily avoided by simply waiting a second or two after keying the vehicle "on" before engaging the starter.
The reason is simple physics. Electric motors have a minimum voltage at which they being to spin, and that minimum goes up as the motor ages.
While the starter is engaged, the flooded cell battery is able to deliver huge Amperage to everything that conducts, but the Voltage drops significantly. If any brushed electric motor (wipers, blower, fuel pump) is switched on but not yet turning, the Voltage may be too low to get it turning, but it will appear like a short in the circuit and the battery happily dumps huge current through it. Thus, the arc-welding spots.
I try to turn off wipers, ventilation blowers, and all other motors before starting a vehicle, and I wait a second or two between switching "on" and engaging the starter. As a result I've never had to replace any of my wiper, electric fuel pump, or vent blower motors. Ever. (And I'm not considered to be a person to have great luck with vehicle reliability). I have replaced them for other people, and those other people hop in and hit the starter immediately. I've given the above explanation as to why, but with the exception of a few engineers, no one cares. The vehicle exists for their convenience, and if motors burn out, they reserve the right to complain and not change their behavior.
Great explanation. I knew some but not all of this. But then, I am a Mechanical Engineer!
I've been doing the key turn to "on" for years now. I believe in it.
Seems like if you wait a second or two, the fuel pressure builds higher, & the engine starts faster (especially on a cold, overnight start). I agree with the rubber mallet (or regular hammer if you are gentle)-saved more than a few tow bills!
Originally Posted By: Merkava_4
Originally Posted By: HangFire
I've given the above explanation as to why, but with the exception of a few engineers, no one cares.
I care. Thank you for posting. Much appreciated.
Originally Posted By: Corvette Owner
Great explanation. I knew some but not all of this. But then, I am a Mechanical Engineer!
You're both welcome, and thanks for the kind remarks.
I in turn learned something, that I might be able to avoid a tow bill by thumping on the gas tank. That's a handy bit of knowledge to tuck away.
Originally Posted By: HangFire
I've given the above explanation as to why, but with the exception of a few engineers, no one cares.
I care. Thank you for posting. Much appreciated.
Originally Posted By: Corvette Owner
Great explanation. I knew some but not all of this. But then, I am a Mechanical Engineer!
You're both welcome, and thanks for the kind remarks.
I in turn learned something, that I might be able to avoid a tow bill by thumping on the gas tank. That's a handy bit of knowledge to tuck away.
However, with the new "push button to start" cars, we won't be able to turn on the key, wait a few seconds, and then turn on the starter. My 2014 Impala for example.
Last edited:
Originally Posted By: Corvette Owner
However, with the new "push button to start" cars, we won't be able to turn on the key, wait a few seconds, and then turn on the starter. My 2014 Impala for example.
Good point. Hopefully, the correct sequencing will be built in. For example, I have an aftermarket remote starter on my Corolla, it turns the car on a few seconds before engaging the starter. It is a higher-end unit (long story there) and adjustable six ways to Sunday, I bet that is one of the adjustable parameters.
If not, just try to leave all the accessories "off"... which reminds me, when I arrive at work in the Winter, I leave the vent fan and heat/defrost "on" so I can remote start my car from the office and it'll be 1 minute closer to defrosted when I get to it. In my defense the fan has time to spin up before the starter engages, due to the thoughtful remote starter design.
However, with the new "push button to start" cars, we won't be able to turn on the key, wait a few seconds, and then turn on the starter. My 2014 Impala for example.
Good point. Hopefully, the correct sequencing will be built in. For example, I have an aftermarket remote starter on my Corolla, it turns the car on a few seconds before engaging the starter. It is a higher-end unit (long story there) and adjustable six ways to Sunday, I bet that is one of the adjustable parameters.
If not, just try to leave all the accessories "off"... which reminds me, when I arrive at work in the Winter, I leave the vent fan and heat/defrost "on" so I can remote start my car from the office and it'll be 1 minute closer to defrosted when I get to it. In my defense the fan has time to spin up before the starter engages, due to the thoughtful remote starter design.
Don't most vehicles these days cut off accessory power when the key is turned to the start position. Seems to me most things shut off while cranking the engine.
Originally Posted By: Corvette Owner
However, with the new "push button to start" cars, we won't be able to turn on the key, wait a few seconds, and then turn on the starter. My 2014 Impala for example.
I am adding your comment to my list of reasons to avoid push button start cars.
However, with the new "push button to start" cars, we won't be able to turn on the key, wait a few seconds, and then turn on the starter. My 2014 Impala for example.
I am adding your comment to my list of reasons to avoid push button start cars.
Being devil's advocate here .. in the end every brushed motor has to start from stationary and the conditions of no back EMF and therefore high current through the commutator are always going to be present. I find it difficult to accept that the conditions of low starting voltage (say 9V) does more damage to the commutator than 12.5 V or higher, and that it doesn't just start turning anyway since there is nearly zero load.
The HVAC fan almost always starts at a low voltage due to the speed select resistor (or PWM) set to the low air flow setting, and the commutator is not immersed in gasoline like the fuel pump is.
I would venture a guess that most people don't pause long between "on" and "start" and most people also don't have fuel pump problems.
Other possibilities, from NHTSA:
Quote:
Vehicle Component: Fuel System, Gasoline
elivery*
Summary: An engineering analysis has been opened to further investigate the scope, frequency and potential safety-related consequences of the alleged defect.General Motors (GM) has identified an issue with accelerated motor brush wear in the fuel pump assembly of model year (MY) 2001 through 2003 Chevrolet vehicles that can cause the pump to stop operating.General Motors indicated that peroxide or sulfur, which are both present in varying amounts in gasoline, can react with the copper commutator of the pump motor and corrode/roughen the surface.a rough commutator surface increases the rate of brush wear.the increased electrical resistance caused by degradation of the brush-commutator interface inhibits current flow through the motor windings.according to GM, the condition will usually result in a no-start condition because of the high current required during start-up.when the alleged defect does cause a stall while driving incident, the vehicle typically cannot be restarted.GM's analysis of warrant claims showed that no start/hard start was the most common condition and the frequency of claims associated with stall while driving incidents was too low to warrant field action. This investigation has been upgraded to an engineering analysis (EA07-015) to further assess the complaint and warranty claim data and the analyses provided by GM.
Also, casual research shows that ethanol can cause issues. CRC Research
The HVAC fan almost always starts at a low voltage due to the speed select resistor (or PWM) set to the low air flow setting, and the commutator is not immersed in gasoline like the fuel pump is.
I would venture a guess that most people don't pause long between "on" and "start" and most people also don't have fuel pump problems.
Other possibilities, from NHTSA:
Quote:
Vehicle Component: Fuel System, Gasoline
elivery*Summary: An engineering analysis has been opened to further investigate the scope, frequency and potential safety-related consequences of the alleged defect.General Motors (GM) has identified an issue with accelerated motor brush wear in the fuel pump assembly of model year (MY) 2001 through 2003 Chevrolet vehicles that can cause the pump to stop operating.General Motors indicated that peroxide or sulfur, which are both present in varying amounts in gasoline, can react with the copper commutator of the pump motor and corrode/roughen the surface.a rough commutator surface increases the rate of brush wear.the increased electrical resistance caused by degradation of the brush-commutator interface inhibits current flow through the motor windings.according to GM, the condition will usually result in a no-start condition because of the high current required during start-up.when the alleged defect does cause a stall while driving incident, the vehicle typically cannot be restarted.GM's analysis of warrant claims showed that no start/hard start was the most common condition and the frequency of claims associated with stall while driving incidents was too low to warrant field action. This investigation has been upgraded to an engineering analysis (EA07-015) to further assess the complaint and warranty claim data and the analyses provided by GM.
Also, casual research shows that ethanol can cause issues. CRC Research
Originally Posted By: another Todd
Don't most vehicles these days cut off accessory power when the key is turned to the start position. Seems to me most things shut off while cranking the engine.
Yes but the fuel pump is essential for running so stays on with start.
When I wired my saturn for remote start, I found the ignition "ON" had two wires-- essentials (spark, fuel) and non-essentials (blower motor). The non-essentials get muted at "start". ACC also runs non-essentials, but not the blower motor.
Don't most vehicles these days cut off accessory power when the key is turned to the start position. Seems to me most things shut off while cranking the engine.
Yes but the fuel pump is essential for running so stays on with start.
When I wired my saturn for remote start, I found the ignition "ON" had two wires-- essentials (spark, fuel) and non-essentials (blower motor). The non-essentials get muted at "start". ACC also runs non-essentials, but not the blower motor.
Originally Posted By: Corvette Owner
However, with the new "push button to start" cars, we won't be able to turn on the key, wait a few seconds, and then turn on the starter. My 2014 Impala for example.
You can on my Challenger and wifey's JGC. To start the JGC, you have to have your foot on the brake and to start the Challenger you have to have the clutch to the floor. If you don't press the pedal then pressing the starter button turns the ignition "on," runs the fuel pump, etc. but doesn't start the engine. Then press the pedal, push the button again, and the engine starts.
However, with the new "push button to start" cars, we won't be able to turn on the key, wait a few seconds, and then turn on the starter. My 2014 Impala for example.
You can on my Challenger and wifey's JGC. To start the JGC, you have to have your foot on the brake and to start the Challenger you have to have the clutch to the floor. If you don't press the pedal then pressing the starter button turns the ignition "on," runs the fuel pump, etc. but doesn't start the engine. Then press the pedal, push the button again, and the engine starts.
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