Hi guys. I am new to using labscopes. I have been using my picoscope for the last couple of weeks on cars that are not broken, just to get my feet wet. Today I used it on an 02 Ford Explorer 4.0 SOHC, eng. VIN E, that has a suspected bad fuel pump. I tried to do it like the tutorial shows how to. Please let me know what I could have done better, and please explain what the waveform shows you. I believe it is bad based on what I read in the tutorial but would like some more experienced users feedback. Thanks for your time and I hope these are not stupid questions. Andy

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sorry, let me try that again

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Shummi

I like to put more time on the screen so as to see the cranking to start and idle of the fuel pump.

This pump apears to be spinning real fast at 7326 rpm.

Mick

Mick, thank you for your response. Is this more like what you mean? I went up to 500 ms per division, and then zoomed in on it? Please excuse my ignorance, I'm watching the training videos, but slowly, as to take it all in.

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now zoomed in

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Excuse me, in the bottom left corner of the PICO is:   ms +2.0s.
         What are those, Tom, somebody?    I think I see that ms = 813.7 thru 829.3 ms

fisher,

from what I have noticed/seen that would be 2.813 thru 2.829 ms time frame.

the zoom wackes the 2 ms into the .813 part. if you zoom a capture and then scroll thru you will see when you get to 2.0 ms 999.9 it will change to 3.0ms.

Pico can zoom that close  ;)

HTH

dave

Andy_ wrote on Dec 21^st, 2010 at 5:37pm:

Mick, thank you for your response. Is this more like what you mean? I went up to 500 ms per division, and then zoomed in on it? Please excuse my ignorance, I'm watching the training videos, but slowly, as to take it all in.

Schumi

Yes thats about the time thats good

Can you post that psdata file please?

If the file is over 7MB then we have a drop site to assist in sharing large files.

The training videos are great.
The Pico presets in automotive help section are not the best setups

Did you change the pump and capture a after wave form of the new pump?
If you did the pump, did you change the filter as well?

Mick

fisher wrote on Dec 21^st, 2010 at 6:01pm:

Excuse me, in the bottom left corner of the PICO is:   ms +2.0s.          What are those, Tom, somebody?    I think I see that ms = 813.7 thru 829.3 ms

Dave and Don

The 2s is because on this file the lenght of time on the screen was 5 seconds, that would be 500ms per div.
Schumi had zommed in 813.7ms past the 2 second point to 893ms

Mick

No Mick, I didn't change the fuel pump yet, but will also change the filter, and will get an after waveform as well. Am I correct that this waveform doens't look right? How do I post the psdata file?

Andy_ wrote on Dec 21^st, 2010 at 7:42pm:

No Mick, I didn't change the fuel pump yet, but will also change the filter, and will get an after waveform as well. Am I correct that this waveform doens't look right? How do I post the psdata file?

You posted a psdata file in your first post.

How big is the 5 second file

Mick

Thank you.

Andy_ wrote on Dec 21^st, 2010 at 3:27pm:

Hi guys. I am new to using labscopes. I have been using my picoscope for the last couple of weeks on cars that are not broken, just to get my feet wet. Today I used it on an 02 Ford Explorer 4.0 SOHC, eng. VIN E, that has a suspected bad fuel pump. What is the customer concern and what lead you to believe you should of done this test? I tried to do it like the tutorial shows how to. They are a big help. They will get you up to speed faster. Please let me know what I could have done better, and please explain what the waveform shows you. I believe it is bad based on what I read in the tutorial but would like some more experienced users feedback. It's a little on the fast side but not to much from what I have seen from Fords. Thanks for your time and I hope these are not stupid questions. Andy They are not stupid questions

Thanks for posting what you have.   ;)

Spence, the customer's concern was it died out in a parking lot. It cranked but would not start. Once I got it in the shop it started. I scanned it and had P0231-fuel pump secondary low. Most of the time it runs fine, but I have had a few times where it will start for a few seconds, then the fuel pressure drops of and it dies, also a few times it blew the fuel pump fuse, so I figured this would be a good time time try to scope a fuel pump. I wasn't so worried about the speed, but on the sample waveform, the current peaks are much more even, what do you think of the one that I posted, thanks for your help.

Mick, the 5 second file is 407 KB

A new pump wouldn't look like that.

Andy_ wrote on Dec 21^st, 2010 at 8:35pm:

Spence, the customer's concern was it died out in a parking lot. It cranked but would not start. Once I got it in the shop it started. I scanned it and had P0231-fuel pump secondary low. Most of the time it runs fine, but I have had a few times where it will start for a few seconds, then the fuel pressure drops of and it dies, also a few times it blew the fuel pump fuse, so I figured this would be a good time time try to scope a fuel pump. I wasn't so worried about the speed, but on the sample waveform, the current peaks are much more even, what do you think of the one that I posted, thanks for your help.

All of the symptoms you described are typical ford fuel pump failure symptoms, although I am unable to see the fuel pump initial ramp the amp draw is high and so is RPM, and the comutators do not look good at all. I would never condem a fuel pump based on a bad waveform, but if the symptoms pointed me in a fuel pump direction and I saw that waveform I would be putting in a fuel pump.

Andy_ wrote on Dec 21^st, 2010 at 8:47pm:

Mick, the 5 second file is 407 KB

Then you can post it here

please do that

Mick

Schumi,

There is something wrong in the image posted of the fuel pump the current should start high since it is not moving and then the current should drop to a stabilized pattern once the pump is moving.

Each vehicle is a little bit different on what a normal amperage reading is.  Some like to use 1 amp per 10 psi.  I can not say with authority on the FP posted, to me the current seems high.

If you can post the psd file or at least zoom in on the turn on and post it that would be awesome.

Here is an example of a typical fuel pump turn on:

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Thanks for the replies. I will post the whole file when I get off work.

Here is the 5 second file.

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Schumi

It is most unusual to see the pump speed up and Amps increase.
There is a 2000 RPM difference, so I would have to say that this pump would have worn/tight bearings and the pump chamber must be leaking fuel back into the tank.
Fuel volume must be low.

Mick

I changed the pump and the filter. The filter was quite plugged. Also, I took apart the pump and the magnet was cracked into a few pieces. I will post the waveform from after it was changed because I still have a few questions.

Quote:

It is most unusual to see the pump speed up and Amps increase. There is a 2000 RPM difference, so I would have to say that this pump would have worn/tight bearings and the pump chamber must be leaking fuel back into the tank. Fuel volume must be low.

Mick   Wouldn't low voltage create low speed and low current flow
Usually when I see low current and low speed I suspect a voltage drop problem either the circuit or the pump itself. This one may have been on the verge of getting it started by slapping the bottom of the tank

Rick Hill wrote on Dec 23^rd, 2010 at 10:38am:

Quote: It is most unusual to see the pump speed up and Amps increase. There is a 2000 RPM difference, so I would have to say that this pump would have worn/tight bearings and the pump chamber must be leaking fuel back into the tank. Fuel volume must be low. Mick   Wouldn't low voltage create low speed and low current flow Usually when I see low current and low speed I suspect a voltage drop problem either the circuit or the pump itself. This one may have been on the verge of getting it started by slapping the bottom of the tank

Rick

Fords usually run at 5 amps and a speed of 6000 rpm so his start up is some what normal even though its not.

I have never seen one that increases  in speed and amps that was good.

It would have been right if we had instructed Suhumi to hook up to voltage and grouind at the pump before he had replaced it.


Mick

Here is the pump after being replaced. Please, correct me if I'm wrong and I probably am, but doesn't the overall waveform look similar to what it did before?  When I zoom in on it though, the waveform looks much more like the good sample waveforms I've seen.

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Zoomed in.

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Andy_ wrote on Dec 23^rd, 2010 at 1:57pm:

Here is the pump after being replaced. Please, correct me if I'm wrong and I probably am, but doesn't the overall waveform look similar to what it did before?  When I zoom in on it though, the waveform looks much more like the good sample waveforms I've seen.

There appears to me that there is alternator ripple wave mixed in with this fuel pump.

How were you hooked up Schumi?

How is the charging system?

Can you take a wave of alternator ripple?

Did the car work as expected after pump/filter replacement?

Mick

Mick, I was hooked up around the pink/black wire coming out of the inertia switch. The vehicle seemed to work as expected. Sorry, but it's gone now, so I can't get a wave of the alt. ripple. Is it possible that I had it hooked up wrong?

Hey there, I was wondering if this ford uses the fuel pump module. If so the fuel pump is pwm, it can vary the press. accordingly. The module recieves a pcm control input, pwr. and ground. It ouputs to the fp. It reports diagnostic info back to the pcm in 3 states, 25%, 50%, and 75% duty cycle. Each duty cycle % corresponds to a "normal op." pid or dtc. ATG has some pretty decent material on these, not sure about All Data or Mitchell. Ford started using these back in 99, so it may be on this explorer. The sedans usually have them located in the rr side of the trunk. Not sure about the suv's. Thought this may be useful to you if your'e not already aware of it.

Hi Irwin, this vehicle does not have the electronic returnless with the FPDM on it, but I have dealt with those on other vehicles. Thanks for your help though, I appreciate it.

Andy_ wrote on Dec 23^rd, 2010 at 6:44pm:

Mick, I was hooked up around the pink/black wire coming out of the inertia switch. The vehicle seemed to work as expected. Sorry, but it's gone now, so I can't get a wave of the alt. ripple. Is it possible that I had it hooked up wrong?

It sounds as if you hooked the amp probe up ok,
I dont have a diagram right now.

Mick

Irwin wrote on Dec 23^rd, 2010 at 7:06pm:

If so the fuel pump is pwm, it can vary the press. accordingly

i see an opportunity here to derail the thread for just a moment  ;D.  

for anyone that hasn't messed with the electronic returnless systems, check this out:  http://members.iatn.net/forums/search/search.aspx?action=viewthread&m=18379&t=18372&forum=forum13&ft=1&fv=4&qv=1

good thread by some whacked out "cult leader"  ;)

Hello.


Mick wrote on Dec 21^st, 2010 at 4:30pm:

This pump apears to be spinning real fast at 7326 rpm.

I am wondering Mick, how do you know how fast the pump is rotating by looking at the waveform? Is it a math formula you could share? Or something I don't know about the scope's software?

Randy H. wrote on Dec 28^th, 2010 at 8:15pm:

how do you know how fast the pump is rotating by looking at the waveform?

i know i'm not mick  :), but figure it's safe to answer this one.  the easy way to get rpm is to pick the two similiar looking humps in your waveform and place your cursors on them.  then simply look in your rpm box on the lower right.  these two humps will generally be around 8 humps apart (representing 8 commutators in the fuel pump).  
the two images below illustrate this.

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Thanks CC. I know you aren't Mick that was just a generalization. I meant basically anyone that could answer my question. I never knew that - and honestly never noticed that on the screen before! Thanks man.  :)

Randy H. wrote on Dec 30^th, 2010 at 1:25am:

Thanks CC. I know you aren't Mick that was just a generalization. I meant basically anyone that could answer my question. I never knew that - and honestly never noticed that on the screen before! Thanks man.  :)

Have not had a chance to use the Pico software for a fuel pump current yet, I am use to the good old calculator method! :)

It just keeps getting better

I am surprised there was so much discussion on this. The waveform provided in the first post is all over the place.
What you are looking at in a motor current waveform is the change in current as the brushes move from segment to segment on the armature commutator. Each winding should have approx the same resistance so current for each segment should be very close..
A rule of thumb that I use is the difference in peak current from lowest to highest shouldn't exceed .5amp. and us usually much less.

Hello techs;

I hope it is OK to post this here instead of starting a new thread.
It is a very similar case for another Ford (98 Faclon AU 4.0L VIN. W) "Australia"

The image file is for the fuel pump amp. (I think it is a candidate for a replacement) the customer is going for a cross state trip.
The data file is for the volt and amp for both the pump and the alternator.

What do you think?

P.S. whenever I use the filter the sample rate drops to 2MS no matter how high I set it. Is that OK?

thx

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sorry guys i know its a bit on the late side to reply to this thread though what i was wondering was

if we had fuel cavitation such as fuel pump drawing air into the system wouldn't we get a waveform like the above which showed amps up and down though am i right in thinking that if there is no pattern in the wave noticeable then that could be a drawing air problem  :)

sory to be such a newbie  :)

kennyp wrote on Jan 16^th, 2011 at 1:24pm:

sorry guys i know its a bit on the late side to reply to this thread though what i was wondering was if we had fuel cavitation such as fuel pump drawing air into the system wouldn't we get a waveform like the above which showed amps up and down though am i right in thinking that if there is no pattern in the wave noticeable then that could be a drawing air problem  :) sory to be such a newbie  :)

No, you have to look at the timing as well as the waveform.. That pump is turning approx 1 turn every 20 ms. You can see the current draw from each segment on the armature and in my opinion that pump is no good. If there was a varying  load on the pump it couldn't vary the pressure at such a fast rate. You would have to take a capture at a longer time base to read what you are talking about.

kennyp wrote on Jan 16^th, 2011 at 1:24pm:

fuel cavitation such as fuel pump drawing air

I think that will make the pump run faster and draw less amps. "Tom's Nerds DVD series" has an example of such.

cool guy's thanks for that :)