Any one change fuel pumps for prev maintenance?

[onion]

Originally Posted By: MacGyver
In some cases yes. I have used a lab scope to look at the wave form of many fuel pumps. This allows me to "see" the condition of the brushes and commentator bars on the armature of the motor and the amps needed to run the pump. This has turned out to be a very accurate way to gauge the condition and life span of the fuel pump motor. However, not the pump gears. The taping on the fuel tank to get the pump running again is due to bad spots on the armature. Saw this many times as a no start in the parking lot. Then the car was towed to us and the car would start right up. Send the car home scratching our heads just to have it return days later with the same story. The tow truck fixes the bad pump by bouncing the car on the rear wheels only, all the way to our shop. In a way taping on the tank!!! Not to many Techs use this method because of the skill and tools required to test this way. But there are getting to be more and more of us all the time. If you can find a tech to do this you can gauge the condition of the pump with very little investment. The hardest part is back probing the wire at the fuel pump relay to get a good wave form. Or using a low amp probe - is what I prefer.
Good Luck!


I read an article a couple years ago about measuring electrical current to the fuel pump as a way to predict when it needs replacement. Never tried it myself, but the wife's Lumina has about 212000 miles on it and is due for a fuel filter (I've been changing them roughly every 50k). So I'll give that a try soon if the wiring is easy to access at some point.

 

[JustinH]

I change the fuel filters at usually half the interval of what the book suggests.

Its simple maintenance, for 9 dollars every couple years or whatever.

Also, I could see MMO helping out lubing the pump, our gas is heavy with ethanol here, and winter gas is very very dry.

 

[andyd]

My first 528e ran to 350k miles on its original main fuel pump. That said, when I went on road trips, I packed a spare and the tools to change it.

 

[George7941]

Originally Posted By: onion
I read an article a couple years ago about measuring electrical current to the fuel pump as a way to predict when it needs replacement. Never tried it myself, but the wife's Lumina has about 212000 miles on it and is due for a fuel filter (I've been changing them roughly every 50k). So I'll give that a try soon if the wiring is easy to access at some point.



The easiest way to scope fuel pump current is at the fuel pump relay (or fuse, if the fuse is more accssible). Jump the relay terminals and clamp an amp probe on the jumper.

I check the waveform of the fuel pump on my truck annually to keep an eye on it. I also listen to it occasionally for abnormal sound. For some reason, the GM pumps on trucks fail way more often than they do on GM cars.

 

[andyd]

The manual I have lists acceptable amperage draw for the pump. You can check it with a decent meter by putting it across the fuse contacts.

 

[Kiwi_ME]

What exactly are you looking for in the waveform? Perhaps gaps in the current draw related to poor conductivity through the commutator?

You would think that if brush life is the primary mode of "failure" it would be fairly predictable in term of hours of operation rather than miles.

 

[Shannow]

When you get into electrical rotating machine diagnostics, the opportunitis to make diagnoses are incredible.

 

[Silk]

Current ramping a fuel pump with a low amp probe and osciloscope is a very quick way to diagnose a faulty pump.If you know how many segments on the commutator you can calculate rpm...low rpm and high current draw is maybe a blocked filter....high rpm and low current maybe a worn pump.

I scoped a fuel pump on a Imprezza last week with a no start....a thump on the tank got the pump going and I could tell on the scope it had 2 dead spots on the com.I cut the old pump open....and found a very badly worn commutator with 2 dead segments.Good enough for me

 

[George7941]

Originally Posted By: Kiwi_ME
What exactly are you looking for in the waveform? Perhaps gaps in the current draw related to poor conductivity through the commutator?

You would think that if brush life is the primary mode of "failure" it would be fairly predictable in term of hours of operation rather than miles.



I look for three things.
1) The shape of the waveform. I have a recorded the waveform when the pump was young and running well. I now look for how much the waveform is deviating from normal.
2) The rpm of the pump
3) The current draw.

 

[mechjames]

I think its a good idea, but I can't afford it as preventative maintenance. The factory pumps are way too expensive, and I wouldn't want to put in an aftermarket right before a long trip, just incase for some reason it isn't up to snuff, and isn't as superior as the factory might be.

I'd prefer to use my BCAA service, because they cover repairs up to $1000 under trip interruption benefits. Therefore I could get a shop to change my fuel pump for free, not costing me anything but time.

(Although I have done the Fuel Pump on my Explorer and Stratus once, due to failure.)

 

[highmilegeguy]

Seems like a lot of in depth diagnosis that'll tell ya the same thing as a pressure test and volume test.

Weak pumps definately put out a reduced pressure. No wave forms needed.

As for preventive, if it gives you peace of mind driving, do it.
My 96 s-10 needs 64 psi to run good and a minimum of 55 psi to fire the injectors.
Needless to say, trying to maintain that level of pressure destroys pumps. Experience has taught me that it needs replacing at 50k miles. It still works exceptit simply weakens to a point that it can't fire the injectors.

To make life easy, I cut out my own access hole under the bedliner. I can change it out in an hour.

 

[Shannow]

Originally Posted By: highmilegeguy
Seems like a lot of in depth diagnosis that'll tell ya the same thing as a pressure test and volume test.


Not necessarily the same, and not really that hard or complicated a test.

Know plenty of techs who can tell within seconds what a circuit is up to.

 

[Silk]

Originally Posted By: highmilegeguy
Seems like a lot of in depth diagnosis that'll tell ya the same thing as a pressure test and volume test.


By the time you've hooked up your pressure gauge and flow meter,a low amp clamp and scope will have everything you need to know,without hardly touching the vehicle.

 

[MacGyver]

Flow and pressure tests are great, for only flow and pressure. The intermintant no starts and loss of performance during hard to duplicate driveability problems is where the wave form with a low amp probe comes in. Both tests have there place and reasons for passing or failing a eletric fuel pump.

 

[PT1]

I have never had a fuel pump fail yet. But I use techron or redline fuel systems cleaner every 20,000 miles to keep the fuel system clean. So far...never an issue.

 

[paulo57509]

I used to...when I had vehicles with mechanical fuel pumps. I used to carry an AC universal in-line electric fuel pump in the trunk as a back-up just in case. Came in handy on I-15 in Idaho one winter.

I just cross my fingers with the new in-tank electric pumps now.

 

[severach]

I replace a lot of stuff to make old cars reliable but a fuel pump isn't one of them. The scope techniques here sound nice but they won't work because you can't be there testing when failure is imminent. Many fuel pumps fail in ways that no amount of testing can predict. Pumps would fail unexpectedly even if someone were to designed a chip to monitor the electrical waveform. Some fuel pumps fail often and some last beyond the life of the car without any help from top oil.

Unless there is a clear precursor such as excessive noise, occasional no starts, low pressure, or poor flow, there's no way to beat the game with electric fuel pumps. Replace if you want to but you really aren't fixing anything. What you put in might have a shorter life than what you are taking out.

Electric fuel pumps will leave you stranded every few hundred thousand or less. There's no way around it. Save your money for the tow truck.

 

[Greaser]

Changed my fuel pump out on the Jeep Cherokee with 283,000km due to the fact when I go moose hunting my life could depend on my rig.My four year old Exide battery was dumped for an Interstate before I left for the same reason.Every and anything that could go wrong that I can foresee at my garage will be done here before I go!

 

[johnd]

I monitor fuel pressure at the injector rail annually, checking the current draw sounds like a very good additional test to determine function as well.

 

[ncguy]

Originally Posted By: paulo57509
I used to...when I had vehicles with mechanical fuel pumps. I used to carry an AC universal in-line electric fuel pump in the trunk as a back-up just in case. Came in handy on I-15 in Idaho one winter.

I just cross my fingers with the new in-tank electric pumps now.


Pardon my ignorance if this is a dumb question but is there any way to replace an in-tank pump with an aftermarket electric pump installed in the fuel line outside of the gas tank? Would it work if the old pump is shot inside the tank?