i too am an electiical engineer-----------and have a lot of experience with dc motors----------i too own lots of electric forklifts and thousands of dc motors that operate in my manufacturing plants----------and while your math is right it is not correct in the application------with a forklift when the voltage drops you simply increase the throttle/lever to make up for the lower battery voltage------the voltage at the motor actually increases until it can no longer do the work needed at which time you recharge it-------very poor analogy that doesn't apply to this application---------a simple dc motor on a non regulated power supply will not increase current draw if the voltage drops----------the motor will run slower and do LESS work meaning it will take more time to do the task at hand--------the entire equation of ohms law tells us that for a given voltage a permanent magnet brush dc motor will draw a given amount of energy to do work------usually expressed as watts as you have stated-------lets look at your formula--------36 volts at 100 amps indeed means that the motor is consuming 3600 watts-------it also means that the motors resistance to the flow of electricity is .36 ohms---------this also means that if the voltage drops to 30 volts the current will DROP to 83 amps and the wattage drawn by the motor will drop to 2490 watts and it will run slower and COOLER--------UNLESS you have a variable power source to increase the VOLTAGE there is NO WAY to get more than 83 amps to be drawn by a resistance of .36 ohms---------there are some issues that complicate these simple assumptions that are related to EMF from the moving armature etc but the bottom line is that a dc motor on an unregulated supply is not going to suffer damage from low voltage unless it has a locked rotor and if the rotor is locked that is the problem not low voltage---------in a fuel pump application whare a liquid is being pumped into a fuel line with a return path the mechanical impedance is so mismatched that EMF is really a non issue..............RC
Premature Walbro Failure
- Thread starter t-topflyer
- Start date
i too am an electiical engineer-----------and have a lot of experience with dc motors----------i too own lots of electric forklifts and thousands of dc motors that operate in my manufacturing plants----------and while your math is right it is not correct in the application------with a forklift when the voltage drops you simply increase the throttle/lever to make up for the lower battery voltage------the voltage at the motor actually increases until it can no longer do the work needed at which time you recharge it-------very poor analogy that doesn't apply to this application---------a simple dc motor on a non regulated power supply will not increase current draw if the voltage drops----------the motor will run slower and do LESS work meaning it will take more time to do the task at hand--------the entire equation of ohms law tells us that for a given voltage a permanent magnet brush dc motor will draw a given amount of energy to do work------usually expressed as watts as you have stated-------lets look at your formula--------36 volts at 100 amps indeed means that the motor is consuming 3600 watts-------it also means that the motors resistance to the flow of electricity is .36 ohms---------this also means that if the voltage drops to 30 volts the current will DROP to 83 amps and the wattage drawn by the motor will drop to 2490 watts and it will run slower and COOLER--------UNLESS you have a variable power source to increase the VOLTAGE there is NO WAY to get more than 83 amps to be drawn by a resistance of .36 ohms---------there are some issues that complicate these simple assumptions that are related to EMF from the moving armature etc but the bottom line is that a dc motor on an unregulated supply is not going to suffer damage from low voltage unless it has a locked rotor and if the rotor is locked that is the problem not low voltage---------in a fuel pump application whare a liquid is being pumped into a fuel line with a return path the mechanical impedance is so mismatched that EMF is really a non issue..............RC
The new Walbro pump is not the same as the old "340" or "307".
Mike posted a chart for the #F20000169. The testing was done by Carl Hockman of the TI Group on 3/22/04 which shows:
60 psi @ 12 volts= 44 gph
Carl Hockman of the TI Group also tested the "307" and the "340" Walbro pumps on 12/18/00 which shows:
340 pump= 60 psi @ 12 volts= 50 gph
307 pump= 60 psi @ 12 volts= 49 gph
Of course with more voltage the output goes up in all cases.
Mike posted a chart for the #F20000169. The testing was done by Carl Hockman of the TI Group on 3/22/04 which shows:
60 psi @ 12 volts= 44 gph
Carl Hockman of the TI Group also tested the "307" and the "340" Walbro pumps on 12/18/00 which shows:
340 pump= 60 psi @ 12 volts= 50 gph
307 pump= 60 psi @ 12 volts= 49 gph
Of course with more voltage the output goes up in all cases.
mike--------i'm going to put a new 340 on a car this weekend and put it on a 8 volt power supply and park it for at least a few days and let it run--------i'm gonna see what happens----- i'll let it run for weeks if need be to see what happens------i personally don't believe this as i don't believe there is a valid basis for it in eletrical/mechanical theory...............RC
- Joined
- May 28, 2001
RC, being that you are an EE, maybe you'd explain what caused the brush holders to melt, the contactors to fail, since the explanation I received from the engineers at work, seems to be "incorrect"???
the forklift analogy is a TOTALLY different issue than one of these fuel pumps--------melted brushes and related parts in an electric forklift are usually due to bad connections/contactors or worn brushes that make poor contact-------the increased resistance results in excessive voltage drop across the bad connection and creates heat in a place not designed for adequate dissipation-------the operator just increases the "throttle" to compensate and this just worsens the situation------under these conditions even more voltage is dropped across the bad connection due to heating and the armature windings get even less voltage---------evenutally something gives and its time for repair-------adequate maintenance and service intervals prevent this---------attempting to run the lift when the battery is discharged can also create similar problems since the motor is heavily loaded and running at speeds less than designed for normal operation---------melted brushes in a fuel pump would almost certainly be from armature blockage--------something jamming the gear cogs that actually pump the fluid, or something in the gas that is causing the cogs to not turn easily would cause quite a heating effect if it slowed the armature and adequate voltage was still available---------simple fact is that power decreases by the square of the voltage and at lower voltages the dissipated power drops very rapidly------i am not saying this is not possible------just that it seems VERY unlikely-------the pump is designed to be cooled by the gasoline actually flowing by the armature and brushes-------it seems to me that these designs cannot run very long in free air without damage since primary cooling is the gasoline-------that said if the pump wasn't flowing gasoline adequately it would not cool properly and excessive heat would build up--------i would also assume that if it wasn't pumping gasoline adequately the car would also not be running adequately and it would be shut down--------every pump i have found to be bad has had a clear history of mechanical and or contamination failure that caused armature slowing and melting due to ADEQUATE current still being available................RC
if all it can do before regulation is 60 psi that would be dangerously marginal for a TR pump..............RC
I would think they would be capable of more than there base line spec being regulated...say that is 60lbs. What's the stock setting for a TR....40 with line off. That gives you 20lbs of boost room. I'm not saying it would work, just curious. Can't believe someome hasn't tried this. If it did work, at least it would provide an alternative.
Rich and Chuck,
I had in the past, done considerable engineering work in the material handling industry for many years and have designed and produced SCR controllers for electric DC drive motors (and lift motors). In addition, I have also designed and produced battery discharge indicators under the trade name of Sentinel and Charge Guard that monitor the battery voltage, rate of discharge, depth of discharge and ultimately disable the lift contactors once the lead-acid battery reached an 80% depth of discharge. I have seen thousands of silver contacts, SCR's, and FET components fail due to overly discharged batteries. Rich, you are correct in your assertion that the conditions are much different in a lift truck as opposed to a fuel pump. The fuel pump slows, and simply does not deliver the desired fuel since the operator has no input in the functions (only battery voltage, no variables). On the lift truck, the operator calls for more demand, creating an additional load on the battery and components. When the contactors' voltage is reduced, the contacts open and close much slower, causing "arc" conditions across the tips, rapidly self-destructing the contacts. The arc causes excessive spikes that destroy SCR's and FET's. And to top it off, the battery plates self-destruct due to sulfation, causing early battery cell failure. This all happens when the battery voltage drops below a particular threshold.
I used, in my designs, a typical voltage of 2.18 volts per cell at 100% charge, and 1.97 volts per cell at 20% charge. Below that, virtually every electrical component would self-destruct. But that's because the load requirements stayed the same (still must travel and lift the rated load of the vehicle) and the lift truck operator has control of these load requirements via controls.
However, with the fuel pump, the load requirements drop in accordance with the available voltage, i.e. lower fuel pressure and lower fuel volume.
So, as I see it, a low battery voltage won't adversely affect a fuel pump. It will only deliver less. And unless you are seeing a "locked rotor" condition, the pump won't self-destruct with lower voltage.
There is my .02
I had in the past, done considerable engineering work in the material handling industry for many years and have designed and produced SCR controllers for electric DC drive motors (and lift motors). In addition, I have also designed and produced battery discharge indicators under the trade name of Sentinel and Charge Guard that monitor the battery voltage, rate of discharge, depth of discharge and ultimately disable the lift contactors once the lead-acid battery reached an 80% depth of discharge. I have seen thousands of silver contacts, SCR's, and FET components fail due to overly discharged batteries. Rich, you are correct in your assertion that the conditions are much different in a lift truck as opposed to a fuel pump. The fuel pump slows, and simply does not deliver the desired fuel since the operator has no input in the functions (only battery voltage, no variables). On the lift truck, the operator calls for more demand, creating an additional load on the battery and components. When the contactors' voltage is reduced, the contacts open and close much slower, causing "arc" conditions across the tips, rapidly self-destructing the contacts. The arc causes excessive spikes that destroy SCR's and FET's. And to top it off, the battery plates self-destruct due to sulfation, causing early battery cell failure. This all happens when the battery voltage drops below a particular threshold.
I used, in my designs, a typical voltage of 2.18 volts per cell at 100% charge, and 1.97 volts per cell at 20% charge. Below that, virtually every electrical component would self-destruct. But that's because the load requirements stayed the same (still must travel and lift the rated load of the vehicle) and the lift truck operator has control of these load requirements via controls.
However, with the fuel pump, the load requirements drop in accordance with the available voltage, i.e. lower fuel pressure and lower fuel volume.
So, as I see it, a low battery voltage won't adversely affect a fuel pump. It will only deliver less. And unless you are seeing a "locked rotor" condition, the pump won't self-destruct with lower voltage.
There is my .02
JDSfastGN
Well-Known Member
- Joined
- Jun 16, 2001
I got another speciman today. I went to meet a customer to change out his 1-2 accumulator on a transmission i recently rebuilt for him and his car died on the way there. He managed to limp it to the shop and it was the fuel pump. It had less than 500 miles on it.
I'm on number 3 in less than 2 years. I removed a working stock pump (20 years old with over 100k on it) in favor of a 340 about 2 years ago. It got louder and louder over the course of about 2 months and finally stranded me. New pump, louder and louder over about 10 days and then quit. Number 3 is holding on, but I've noticed that I can hear it whine at idle now, when I couldn't hear it before. I assume that it's on it's way out as well.
Maybe the real solution is a sumped tank and an external pump. Ramchargers sells sumps for $20, and most any welder can Mig one onto the bottom of your tank. You'd have to mod some fuel lines and buy a more expensive fuel pump, but at least it would be the last time you had to buy a pump.
Maybe the real solution is a sumped tank and an external pump. Ramchargers sells sumps for $20, and most any welder can Mig one onto the bottom of your tank. You'd have to mod some fuel lines and buy a more expensive fuel pump, but at least it would be the last time you had to buy a pump.
Rodney87GN
Well-Known Member
- Joined
- Feb 1, 2004
Maybe I'm lucky here but I'm going on 3 years with my Walbro 340 from Racetronix.
That's still nothing really especially when OEM pumps can last for 10 years or more...so you would expect these pumps to last more than a couple of years. I've read that you should replace your pump every 2 or 3 years for good insurance but with all these bad pumps showing up I'll just stick with my "old" Walbro 340, who knows if I'll end up with a bum pump.
That's still nothing really especially when OEM pumps can last for 10 years or more...so you would expect these pumps to last more than a couple of years. I've read that you should replace your pump every 2 or 3 years for good insurance but with all these bad pumps showing up I'll just stick with my "old" Walbro 340, who knows if I'll end up with a bum pump.guys i did some serious fuel pump testing this weekend-----i measured the amperage/wattage of a stock low mileage 87 pump and a new 340 at several voltages and pressures------i will post the data tomorrow when i can stop by the shop and get a disc of the data-----while i had the equipment set up i also did quite a few tests of popular fuel pumps-----i did pressure vs flow vs voltage and have both charts and graphs of the data-----from the general lack of good data i felt a lot of you guys would find it useful and interesting-----here's what i tested and why and how i did it in case anyone has any comments or questions-----to answer the question about the low voltage issue i did the following test------i took a dyno stand mounted GN engine with stock fuel rail and regulator and measured the rail pressure vs voltage vs amperage-------here is what it was measured with------powersupply was a Raytheon DCR 40-40B with remote sensing regulation feedback that guarantees terminal voltage of the test item to .01% accuracy reguardless of wire and connector voltage drops-----voltage was measured with an Audio Precision System Two with DCX-127 option that displays voltage to 5 decimal places with .00005% accuracy------current was also measured on the DCX with a Snap-on EETA 308-A low current probe-----while this device is not of the same class as the rest of the equipment used in the test we carefully calibrated it before each test with a Hewlett Packard 6902B amperage calibrator before each series of tests so the accuracy could be considered good to two decimal places-------pressure was measured with a Snap on Modis with the EEPV 302 AL pressure transducer with accuracy to .1%-------I do all my fuel related flow tests with actual "regular shell 87 octane gasoline" to eliminate the need for correction factors needed with test fluids-------the entire data will be posted tomorrow but for a brief here are some numbers--------stock pump @ 60PSI -- 9 volts --6.51 amps = 58.59 watts--------18 volts --9.10 amps = 163.8 watts -------walbro 340 @ 60 PSI 9 volts--7.78 amps = 70.02 watts-------18 volts---10.01 amps = 180.18 watts---------the charts will show all the data in one volt increments from 9V to 18V for 40, 50 and 60 PSI---------i also did complete fuel pressure curves for the following pumps-------two 86 stock pumps picked at random from a crate of about a jillion as well as a pair of 87 stock pumps from the same pile--------i tested several walbro pumps from what appears to be the three main groups-----from what i can tell there is the 242-250-278 series-----the 307-315-317 series and the 340-341-342 series ???????-------at any rate i tested a 242----a 307 and several 340's-------- flow tests on these used some of the previously mentioned equipment as well as a Dwyer model TF 1072 flowmeter and TM-2 totalizer------it reads in gallons per hour and is accurate to: 100 GPH 0.02%, 50 GPH 0.20%, 20 GPH 1.2%-----"it has been calibrated with Gasoline"-------stay tuned............RC
83ttypecooled
Active Member
- Joined
- Sep 14, 2003
Hi,
I have been following your posts assiduously.One thing has escaped all of you, regarding the Walbro pumps;There is an obvious failure problem, so why not Change manufacturers? With a small amount of effort,an external Bosch pump can be installed,and I guarantee you will never replace it again. These pumps are tough, and have enough output to power any turbo Buick.It doesn't take much to install these! Think about it....
I have been following your posts assiduously.One thing has escaped all of you, regarding the Walbro pumps;There is an obvious failure problem, so why not Change manufacturers? With a small amount of effort,an external Bosch pump can be installed,and I guarantee you will never replace it again. These pumps are tough, and have enough output to power any turbo Buick.It doesn't take much to install these! Think about it....
Mike Licht
I was here first
- Joined
- May 23, 2001
I would be interested in the outcome of that since I tend to agree with you, I am only relaying the info given to me by Walbro
Mike
Mike Licht
I was here first
- Joined
- May 23, 2001
you have the groups correct, of course :smile: , Walbro will only flow test in 10 pump groups to aviod the pump to pump variation which is fairly significant IMO. If you need any pumps or hardware, filters, harnesses let me know and I will see what I can get you.
Mike
I agree with Mike too, this should be interesting...
Mr. Clark is such a huge asset to this community!
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