Autonerdz forums

sorry, let me try that again

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.

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

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


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

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?

Thank you.

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.

A new pump wouldn't look like that.

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


Then you can post it here

please do that

Mick

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

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

Quote:




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

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.

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


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

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.

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


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

Mick

Hello.

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


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?

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. 

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.

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:


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