jcorenman

I had a meeting in Seattle late last week, about 80 miles from here, and took the S4-- an '88 5-speed, 82K miles and running very sweetly. So I am heading home, a block from the freeway (Mercer and 9th, heading for the express lanes at 3:55...) and the engine quits. Cranks but won't start, no tools except Sharktuner and it says there is no fuel-- AFR is infinity to one. Crap. So I call AAA and order a fuel pump via Fedex, just in case.

AAA sends a flatbed with a competent driver, got on the last ferry home and I dive into it the next morning. I jumped the fuel pump and had pressure for a while, then nothing-- no pressure, no noise, no nothing. So I swap the fuel pump, new filter and hardline between (make a note: Do not overtighten the fittings, and keep a spare hardline around along with a pump and filter). Fire it up and BWAHH, back in business.

And of course I take the pump apart, I m curious as hell to see why an original pump would fail after 82K miles.

Here's the parts, all looks OK at first glance... except the commutator...



The commutator is badly worn and discolored, and the brushes are worn to their limit:




The pump itself looked fine, and spun freely-- nothing binding it up. A few wear marks on the rollers but nothing to write home about. And no noise, this was a quiet pump.





For reference, here is the commutator from our GT pump, when it ingested a piece of crap and jammed with around 20-30K miles, bright and shiny with no wear at all. (And also a quiet pump... very quiet, at the end).



Sooo.... Any ideas on why the commutator on this pump is so worn and burned looking? One of the brushes was worn to the point of having no more travel, and that was the failure. So obviously there was rapid brush wear, but why? Is there anything in an original pump that would have trouble with ethanol?

The only warning was a hiccup on the way into town in the morning, complete loss of power for half a second and then back on, as if nothing had happened... No noise, no loss of power or wobbles in the AFR at WOT, nothing...

Cheers, Jim

GregBBRD

That seems like insane wear.

I've replaced probably a couple of hundred of these pumps, but only taken a couple apart.

Wish I had looked at more and could give you more information.

Nicole

Sorry to hear you got stranded with such a strange failure!

Is there an average lifespan for these? I believe I have only replaced the infamously famous in-tank pump, and have no idea, if this one is still working

Hilton

Hmm.. you've owned this car since new too IIRC, which rules out the pump having been replaced with a used one at some point.

Its possible its related to the 87/88 having a different part number to the 89-95 pumps - 87/88 were designed to generate pressure without the benefit of a lift pump in the tank. Although why a different design of pump would have different metallurgy for the commutator is beyond me.

Bill Ball

Wow! And to think mine is still going strong at 253K miles without a hiccup. Never carried a spare before, but maybe I will now.

When I rebuilt my alternator at about 180K miles due to a noisy bearing, the commutator had SOME wear but not enough to junk it. Jim Morton mounted it in his lathe and cleaned it up.

Not sure what to make out of this.

danglerb

I don't see how carbon brushes could wear copper faster than themselves, so my guess is that this pump uses a different style of commutator and the brushes wore out.

Open up the fuel filter is see if its full of copper or carbon dust?

ROG100

The pump casting says made in 1998 (verified the orientation with other date stamps) so could have been a replacement pump at some time and maybe a used one - hence the wear.

Glen McCartney

Rog, I think that is '86, '98 down under maybe.

That is unbelievable wear for the amount of miles. My '85 with 205K still going strong on original pump. Hope I didn't just curse myself.

ROG100

Glen that is what I thought but then I compared it to all the other date stamps on parts here in the office. If you line up the dots around the circles with other date stamps it reads 98.

jcorenman

There are two problems with that theory:

1) We've owned this car since new, and this is the original pump.

2) The "6" could be a "9" but then the "8" would be upside-down. The two loops of the "8" are not symmetric. Here's another view, cropped and rotated:



If you invert it, then the "8" doesn't look right.

jcorenman

Good idea, I will do that. But I am sure it is dirty, the fuel that drained out of the inlet side of the filter was pretty dark. The filter was last changed at 68K miles in 2008.

Tom. M

I don't think the commutator wore as much as folks think it did...there's a casting scallop on the one side that the brushes couldn't have created....

perhaps the wrong brushes were used and thus reached their full travel long before they should have?

the flyin' scotsman

Jim...........sorry to hear of your FP troubles.

My pump quit like a light switch on the S4 (1988) and it was replaced but I never opened it up. Perhaps I shall and report into this thread.

ROG100

Had I known that I would not have wasted my time trying to give you an answer to your question 8>)

86 it is

IcemanG17

Jim
When my 88 S4 fuel pump died it did something weird....when "hot" (think running) it would die and not fire again until it was fully cool....then it would run briefly then die and not restart....

I measured the resistance of the old-dying pump....it was high near 10 ohms......when it was cool....and the car ran it dropped to under 2 ohms.....the brand new pump was right at 1.5 ohms if I remember correctly......