Q Fuel pump current

[Q45tech]

Did some testing today on a brand new fuel pump and controller:

Initial 5 seconds [cold start] 7.1 amperes, then immediately settled down to 3.2 amperes............4.0 at intermediate speed.

My recently noisey pump is up to 4.2 amperes at idle yet only 6 at cold start..............5.1 at intermediate.

Will try to measure more pumps so we can get an average ........it will take a while to get a 25-50 pump sample!

Unless members can do their cars for me, need an accurate ammeter and two spade lugs to substitute for the 15 amp fuse.

I will try to measure the melting point of the solder connection that normally fails in amperes..........function of inside heat in the FRCU...........heat in trunk.......... ambient outside.

[Q451990]

Unless members can do their cars for me, need an accurate ammeter and two spade lugs to substitute for the 15 amp fuse.

I assume most meters can handle the 15A DC load... We have a couple of Fluke meters, so they should be fairly accurate. I'll try to do that soon. I can give you measurements for a 48K pump and a 3K pump.

By the way, I found a vacuum gauge (for those plenum measurements you wanted) - now all I need to do is go by a parts place and get some hose and find a tee... I haven't forgotten, just short on time as usual!

Heath

[Q45tech]

Eventually we will get a set of NORMALIZED readings which can help even dealer technicans...........as they really don't take the time.

Have measured a few more plenum vacuums and 18" HG seems to be the normal warm idle vacuum.

Unfortunately that is a combo of the throttle plate and the IAC.

[Qdog]

Less than 1000 miles on new fuel pump. Measuring at fuel pump fuse terminals: 3.2 amps before cranking, 7.2 amps after start for about 10 seconds, settling quickly to 2.2 at fast idle. Remained between 2.15 and 2.6 amps while taking a 16 mile trip on city freeways. 2.2 at warm idle, not more than 2.5-2.6 at half throttle. Didn't have room in traffic for a full throttle test. Ambient 38 F, full tank, fuel filter has about 8K on it, the tank looked completely clean when I replaced the pump. Only the filter sock was dark gray. Not bad for 161K, original pump per service records. Replaced it to be safe.

[Q45tech]

Thanks a lot!.............2.2----3.2 [brand new] *>3.2>4.2 noisey at idle.

After we get 20 measurements we can find the mean brand new and the mean noisey............extrapolate the failure current.

Again my guess is 5.0 amps at idle.

Your 7.2 during first 10 seconds after crank is the killer [also WOT] with a 15 amp fuse one could assume this is normal.

Roughly what a non speed controlled pump draws all the time.http://www.delphi.com/pdf/e/fuel_pump_medhigh.pdf

From the above 8.0 amps max 6.5 amp typical at 13.5 volts see the chart on page 2.

"""The instrument is a personal computer-based system with menu-driven software and is housed in a rugged case that fits within the size restrictions of carry-on luggage. The unit is battery powered and can be used either in the hangar or on the flight line by maintenance personnel.

ORNL's current signature analysis works either remotely or locally by connecting probes to electrical lines carrying current to the fuel pump.

"Our system measures changes in the electric current drawn by a motor as an indicator of changes in the mechanical load that it is driving," said Howard Haynes, one of the pioneers of the technology. "In this case, the changes in current reflect wear in either the pump or motor assembly."

By using the instrument, mechanics can identify wear in the fuel pump that has exceeded allowable tolerances -– remotely and under harsh environments such as those with the C-141, where the pumps are submerged in the fuel. """"""""""

[Q45tech]

Probably a good idea to run a wire from + side of pump into cabin and meaure the voltage drop under WOT .........wire/connector/relay corrosion or FPCU.

Interesting that these turbine type pumps do degrade in flow with age............but as long a WOT fuel pressure measured after fuel filter is 43.4 psi or higher at WOT 6,900 rpm [460 squirts per second from 4 injectors-----55% duty cycle] everything is ok.

[aaronl]

I rode in the back seat of my Q this weekend and heard the dreaded fuel pump buzz. Now that I know that it is there I can hear it while driving. Sucker is a noisy as a stirred up hive of bees even with a full tank.

I read all the posts that turned up with "fuel pump" for search criteria, any way....

I measured the pump current and mine is in line with new pump measurements as posted in this thread.

3.12 amps at key on, 5.12 when starting then2. amps at idle with a little rise at moderate driving. Crusing at 65 about 2.4 amps. If I put my foot in it current will rise to about 6.6 at the shift point arround 6,600rpm. When coasting down from speed current drops to about 1.8 amps.

Measurements were made with a Fluke 87III. I have two of these and checked that they read the same values.

Q45A, 70K miles. So, based on what I have read here I think I can hold off on replacing the pump until after Christmas at the least.

I looked at the pump pictures posted by Texasoil in the rides section. I have searched, but not found any posts on the results of cleaning up the pump in the photos.

aaron

[Q451990]

I'd say that a good average change interval would be at 80K, but there are a lot of variables. Gas quality being the biggest one.

Without a lot more data sets, I think an amp test may not be well tested enough to know what amperage indicates impending doom.

Heath

[maxnix]

I replaced one of my (the Austin one) pumps at 62K just to be safe after I heard the buzz on while it primed. Have yet to tear the old one apart or measure the voltage as I don't have a meter.

Texasoil is in Houston, so maybe you could vist for more information on the disassembly process.

[Q45tech]

You must look at the current waveform with a current probe and oscilloscope to see the individual [8,12,16] current peaks as the commutator rotates.Meters just read the average current of all, not if you have 1 or 2 bad ones.Use goggle to search for fuel pump waveforms!

[aaronl]

Well.....I do just happen to have a scope and a current probe. I will check it out.

aaronl

[texasoil]

Just for the record, the fuel pump I disassembley runs whisper quiet with the corrosion on the rotor polished off. I suspect that at some time in its life it got a little water in the fuel and the fuel did not have adequate anti-corrosion additive in it. In th eyear before R&R I drove nearly 40K miles back and forth from Houston to Krotz Springs La (40 mi east of Baton Rogue on Hwy 190) Numerous fillups with fuel of uncertain pedigree. --2 fuel filters, 4 treatments with Techron.There's some lonespme stretches on the old routs I used (IH10 was always under construction with 30min to 2 hr delays all the time)