Electric Fuel Pumps....

[BOBISTHEOILGUY]

At one time during discussions about fuel additives it was brought up as how many different fuel additives might affect a fuel pump... Well, I went and did a little research discussing with some top mechanics some of the problems they have seen.

Most have stated they have not seen the problem with the sock, now that isn't to say it doesn't happen just not been a problem down here.

What they did state was how if they do a fuel treatment that is extremely hard on the system which if they fail to cut off the return flow and this stuff gets back into the tank they see a fuel pump failure following within 2 wks of this. The problem some come up with is that the windings are shorting out due to the insulation being ate away by the additives which is like a very thin laqure insulating the wire where it is wrapped around the armature. Since I had no idea how this system actually worked, I got an old pump from one of the guys and did what I do best... Tore it apart!

Here is the guts of a basic electric fuel tank fuel pump. I also noticed that the fuel does in fact flow through the windings around the brushes and so forth which I would have thought it would have been isolated from that with a direct line through the unit which appeared not to be the case.

 

[matt cook]

Hmmm...I had a dealer fuel system clean about 2 months ago...and my pump went out last week...Hmmm?

I learned something today.

 

[MolaKule]

You would think that with all the fuel cleaners being bought and used more fuel pumps
would see failure.

I think if the fuel system were really laquered up and some strong cleaner was used to shock
the system, then yes, crud might get back into the pump; but then again, these pumps have
built-in tolerances as well.

 

[MolaKule]

Bob,

What about the so-called solid-state diaphram pumps? Anyone speak about
those?

Thanks

 

[BOBISTHEOILGUY]

No, haven't seen nor heard of them mola.

I can see where a highly sovent based additive could cause problems with the windings... The other mention is that many fail to do as suggested and over dose with pure fuel treatment and little gas which would cause more concentration.

Currently I have 5 or 6 different fuel additives I'm experimenting with myself. I have cut a sock apart, and stuck them in each additive. Also, I took some winding wire used for transformers / coils and such and have that sitting in them as well. I will be examining them to see how they are affected if any. more to come later.

 

[VaderSS]

quote:

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I also noticed that the fuel does in fact flow through the windings around the brushes and so forth

---

This makes me wonder... Many people say that letting the tank get below 1/2-1/4 shortens the life of the pump do to overheating. This would seem to contradict that.

I've only owned 2 cars with electric fuel pumps, the first one, a '93 Olds Ciera, had it's pump last 120k, I ran it to near empty every time.

The second one, my 96 Impala, had it's pump changed at 50k, and it had only had the level below 1/4 once or twice. It actually did not eat it's pump, but melted the pumps wiring harness, which is a notorious problem in these cars. The entire sending unit/fuel pump assembly was revised and so is changed as a unit.

 

[Patman]

The fuel pump that goes in the LS1 F-bodies seems very prone to failure when the tank is run low. There have been a ton of posts on the message boards from LS1 owners who ran out of gas, and then cooked their pumps. It doesn't seem to happen on the LT1 f-bodies though, so that pump must use a different design.

 

[MolaKule]

FWIW,

Replaced the '92 Burbs fuel pump last year. It had 253,000 miles on it; of course, its a 45 gallon
tank as well. When gas prices are high, I have to bring part of Fort Knox with me to the gas pump.

 

[tweeker43]

there are a couple different ways of mounting the pump in the tank. one is in a resevoir or module, the other is referred to pump-on-a-stick.

that would appear to be a walbro mss (modular single stage) pump. i believe these were the pump-on-a-stick variety. these rely on fuel tank geometry to keep fuel in the vicinity of the inlet.

a pump in a resevoir or module will have a check valve in the inlet of the module, so the inlet of the fuel pump is always in fuel.

i don't know about the LS-1 and LT-1 mounting methods. those are delco / delphi fuel pumps if i recall. they were a roller vane style pump, which had more moving parts.

if the fuel system treatment has high alcohol content it can degrade some of the components in the fuel system, particularly if it is added when the fuel is low.

bob, next time you cut a pump, cut around the pump. the can will slide off each end.

from the bottom of the picture to the top:
inlet assembly:
inlet puck, camring, wear plate, gerotor, seal support, seal

motor assembly:
armature, flux tube, magnets

outlet assembly:
outlet cover, armature brushes, check valve