fuel pump current ramp

[rdaleyj]

Okay got the low amp probe set at 100 Mv/a
The dso set at 10mv. I tested a few different locations on the feed wire and before clamping the wire the red line on the scope is at zero line, once i clamp the wire the scope trace rises up off the screen and by playing with the zero button on the probe it finally comes down and shows around 2-3 amps 14.6 ms. To be sure enough voltage was getting to the pump i ran a jumper from b+
Straight to pump +. The trace shot off the screen again.
Now im thinking that my probe is shot so i hooked the fp feed wire to my toyota and got a perfect fp wave. 4 amps 9.6ms.no problems with the trace.
All humps are even. So now what could possibly be the problem with the vans fuel pump? Brand new boshe put in last year. Thnx in advance.

 

[Stick]

Sounds like you have a couple problems. By fooling around with the zero button, you aren't getting an accurate reading of how many amps the pump is drawing. Re-adjust your scope until you see how many amps the pump is really drawing (without trying to re-zero). I would guess that it is pretty high, in the 7.5A+ range, enough that it is working hard, but not so hard that it blows the fuse. Most likely you have a clogged fuel filter somewhere in the line or another sort of restriction somewhere upstream of the pump (pinched line, debris in the line, etc).

Any time you restrict the output of the pump, the speed that the pump rotates goes down, and current demand goes up. If the restriction is on the intake side, pump rotation speed goes way up, and current goes down (because it is effectively working in a vacuum).

If I had to guess, the pump was replaced, but the inline filter was not. It could also be a bad pump, but without seeing the waveform it's hard to call it that way. Just because it's a new part doesn't mean that it is known good.

 

[rdaleyj]

Thnx stick when I put the high pressure pump also did the inline filter soon after did the intank pump and sock 308 dollars. Back a few months ago I could hook onto the FL feed wire and instantly drew a decent waveform. Now yesterday I hooked to the Toyota and it did the samething that it did with the van when i clamp around the wire the ground trace would shoot straight up off the screen, now im beginning to think that there is something loose inside the clamp probe.
Well i started pushing in the zero button and the waveform came back down to where it belongs. Is it possible and cheaper to send it in to be checked and or repaired?
Oh and the amp draw on the Toyota is 4amps and the van is 2 to 3amps. Thnx again. .

 

[rdaleyj]

Thnx stick when I put the high pressure pump also did the inline filter soon after did the intank pump and sock 308 dollars. Back a few months ago I could hook onto the FL feed wire and instantly drew a decent waveform. Now yesterday I hooked to the Toyota and it did the samething that it did with the van when i clamp around the wire the ground trace would shoot straight up off the screen, now im beginning to think that there is something loose inside the clamp probe.
Well i started pushing in the zero button and the waveform came back down to where it belongs. Is it possible and cheaper to send it in to be checked and or repaired?
Oh and the amp draw on the Toyota is 4amps and the van is 2 to 3amps. Thnx again. .

And the real kicker of this thing iz when i first put the brand new pump in I didn't like the waveform, from now on when i check the waveform on a new pump if i don't like it too bring it back.

 

[bgott]

A lot of times you need to run a fuel pump for a while to get a decent wave form out of them.

 

[SpiderGearsMan]

is it dead ? no pressure ? GM ?
the aftermarket carters don't seem to last 18 months in GM
what is the fuel pressure ?

 

[Stick]

And the real kicker of this thing iz when i first put the brand new pump in I didn't like the waveform, from now on when i check the waveform on a new pump if i don't like it too bring it back.

A lot of times you need to run a fuel pump for a while to get a decent wave form out of them.

I've never seen a pump that needed runtime to get a good waveform. All the waveform is, is the current ramp of the commutators in the pump, which shouldn't change much unless the pump is on it's way out.

The waveform should give you an indication of what the pump is doing, but it's not the end all be all of tests. Normally you would see high current demand with a slow rotational speed, or high rotational speed with low current demand, not low current and low speed like in your case. Like SpiderGearsMan said, you probably need to check pump output pressure, and a volume test isn't out of the question either. My guess is that both are going to be on the low side of things if you have accurate readings, especially with such a low current demand, and a slow rotational speed.

It would still be interesting to see the waveform capture if you have a way to get it off your scope.

 

[rdaleyj]

I can snap a pic but then don't know how to upload it the only way i figure is through email, my email is [email protected] send me an email and i will send an email with the pics in the attachment. I will send one from the Toyota which is decent all even humps and around 9 1/2 ms per 1 rotation. The van however i have to adjust the voltage settings down to get a good shot of it.thnx again

 

[rdaleyj]

Oh and if the brushes were worn out in the fp wouldn't that cause the amperage draw to go down and rotational speed slower?

 

[rdaleyj]

Ahh im having a problem with the fp gauge showing anything, the needle won't move, the pump sounds strong for a second after turning the key on, it starts and runs but surges at idle.

 

[rdaleyj]

Here are fp waveforms via photobucket

HTTP://s1126. Photobucket. Com/albums/161. HTTP://1126.photobucket. com/albums/1610/rdaleyj/2010-10-30131128.jpg

 

[rdaleyj]

Here are fp waveforms via photobucket

HTTP://s1126. Photobucket. Com/albums/161. HTTP://1126.photobucket. com/albums/1610/rdaleyj/2010-10-30131128.jpg

Here's the van two frames later
HTTP://i1126.photobucket.com/albums/1610/rdaleyj/2010-10-30131147.jpg

 

[bgott]

Neither link works.

 

[rdaleyj]

Here's the van two frames later
HTTP://i1126.photobucket.com/albums/1610/rdaleyj/2010-10-30131147.jpg

Here's the van a couple of frames earlier has lower amperage but readable
HTTP://1126.photobucket.com/albums1610/rdaleyj/2010-10-30131128.jpg

 

[rdaleyj]

Sorry bout that bgott im working off a cell phone, don't have a pc anymore.

 

[Bran Diezel]

is it low on fuel?

 

[rdaleyj]

It is kinda low not completely out. Did you see the pics on photobucket? Looks maybe like intermittent spurts of fuel getting to the pump,

 

[Bran Diezel]

i had an astro van last week that was above empty that you would drive down the road and it was like the computer would cut out above 2500 rpm. it was like everything would shut down and after the revs dropped it would come back on for a sec and then cut off again. i had a dodge do that and it was the cmp. the crank controls the timing 0-2500 and the cam 2500+ on that car so i figured maybe the same thing here. well that didn't fix this problem. i noticed the fuel pump was absolutely screaming too. after troubleshooting for a few hours, a few test drives and a couple crank relearns i took it to my buddys garage to see what he thought. i ran out of gas on the way there. put 5 gallons in it, the fuel pump was quiet and the problem was gone. lol

 

[Stick]

At this point, it sounds like you are playing with a toy and trying to find your problem (which is cool), but you haven't covered the basics. Dump a couple of gallons of fuel in the thing, check the fuel pressure, do a flow test, and if it fails the flow test or the pressure test, replace the pump with an OE one.

As it stands right now, it sounds like you have low pressure (gauge won't move), and low rotational speed (4100rpm). I'd probably drop the tank, jumper power and ground to the pump, and check the pump output directly from the pump. Then if it needs to be replaced, you are halfway there. If the pump checks fine, the problem is further down the line.

 

[rdaleyj]

Last week i unplugged the harness to the external high pressure pump started it and the rotational speed of the pump didn't change any ruling out anymore voltage drops and since no pressure at the rail I'll next add another can of gas and check fuel flow, hoping its the high pressure pump and not the in tank pump i bought from the Ford dealer last year for over $300 dollars. And thnx again for all your good input.

 

[rdaleyj]

Okay fellows here's an update on the ford vans fps. With the pressure gauge it seems a bad connection hooked it up again and pressure is normal.
I also realized that both intank and main pump are 6 bar commutator pumps. Intank 11ms main pump 10.80ms

 

[rdaleyj]

Here's the link in case i can't upload it right
HTTP://www.Facebook.com/album/ PHP?...and how the h*** do you do this the easy way?

 

[rdaleyj]

Sorry guys the quick link doesn't work, it will work
if you type it all in, i tested it .:-( but does anybody know how to underscore the entire link? Now my greatest mystery.

 

[hvychve]

pressure will determine current ramp peak, low pressure pumps will run in range of 2-7 amps (9-13 psi) 50-60psi = around 12 amps, if your inductive low amp probe has an arrow , should be pointed towards flow of current and zero'd before clamping low amp reading would indicate worn commutator in pump, if you say you have unusually low amp reading and a new pump, might be set up wrong, try scaling your meter down on the amplitude to engage pattern for viewing and if you have cursors , hit the pause and use cursors to messure you peak (high point of pattern) you should not see much more than ten percent difference between the highest point of the highest ramp, to the highest point of the lowest ramp, how are you messureing frequency, its more of an rpm, 6000 rpm set up on a 20mili second scale