In-the-tank fuel pumps cause death and destruction

this also means you should keep your tank level from getting too low.
Otherwise you can shorten the life of your pump.

 

The biggest problem with these things is changing them. I had to pull half
of my car apart to do it !!

 

About 6" above and rear of the pedals. Personally thought it was a
stupid design, but then again the Beetles were never the greatest for
heat I'd heard.

 

Another urban legend.

Matt

 

Not totally. Running the pump VERY low on fuel reduces cooling and
lubrication and CAN hasten the pump's demise.

 

I'm not sure what you saw, but that wasn't a gas heater. Gas heaters were
mounted inside and parallel to the left front quarter panel, under the front
deck lid. They were/are roughly the shape and size of an old Electolux
cannister vacuum.

Personally thought it was a

Actually the heaters were ok but the defrosters were horrible. Add a gas
heater and you could almost cook a roast in one.
Btw, I still have two, a '62 sunroof and a '69 vert.
H

 

Absolutely not on lubrication. It is impossible not to have gasoline in
the pump at the bearings if the vehicle is running off of fuel from the
pump since the bearings (more accurately, bushings in almost all
consumer vehicles)are within the internal pump volume (the shaft and
bearings are surrounded by the fuel as it flows thru the pump. If
there's no gasoline at the bearings, neither is there fuel getting to
the engine, i.e., the engine will not run, and most likely neither will
the pump for very long at all (and that's not "low" in fuel - that's
"out of" fuel). The bearings running dry or even slightly low is not a
credible situation at all - not even at the point that the engine cuts
off due to your "running out of gas" (at which time the pump still is
full of fuel).

As far as the cooling aspect, yeah - you might have that on a
technicality, but you do have a steady cool volume of the fuel running
thru the complete internals of the pump/motor assy. So, probably the
outside surface of the pump (case and magnets, which are on the inside
surface of the case) will rise a few degrees, but the insides (armature,
brushes, bearings/bushings) would rise *very* little (due to the volume
flow rate of ambient temperature fluid that bathes those components. I
doubt that those thermal effects are at all significant in pump life.

IMO...

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

 

It is amazing how these myths get started whenever there is a change in
technology and just refuse to die. I wonder how the old style pumps
that were connected to the engine block ever managed to stay cool!

People don't understand that electric motors can be designed to run at
fairly high temps. If the above assertion were true their would be a
lot more electric fuel pump failures as I know a lot of people who run
low on gas, and even out of gas, fairly frequently. It is almost the
same things as the exploding gas tank myth. Even people who won't
accept a logical technical argument have to admit that is just isn't
happening in the real world. There is a reason for that!


Matt

 

I'll have to take your word on that, despite how worked & was used as.

 

You are forgetting when the tank is very low the pump can "suck air" on
corners, hills, stop and go...and that is very hard on a vane type pump. It
seems to kill GM pumps alot more than Fords. I just helped a friend change
one on his blazer-he said- I thought I was just out of gas, the tank was low
and I was trying to make it to the next gas station. I guess it could have
been coincidence, but I really doubt it IMO.

 

The vane pumps are worst for failure contributed to by low fuel - and
the old in-tank pumps on carbureted engines DID have this problem. In
the early eighties? there was a buletin from Toyota IIRC. Although the
"low fuel warning" light came on with about 30 miles worth of fuel
left in the tank, the factory recommended you treat it as short term
emergency reserve only.

I replaced a few pumps in those days.

 

Join the club, pal. Done it TWICE.

 

Why is it very hard on vane type pumps?

Matt

 

When you say "vane" type pump, is that roller vane, or some other type
of vane?

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

 

I dont really think it would matter. Even if it was some type of turbin or
what I think they call a slide? I believe there are 3 problems in the case
I mentioned above. One is cooling by the fuel, another is lubrication by the
fuel, and the worst one of all I think is the fatigue from a gas to a liquid
instantly. Think of your boat prop. If it catches air, the force when it
hits water again is sometimes enough to break the shear pin in the prop,
almost like hitting a log in the water at full throttle. I would say the
problem is the higher the speed the pump turns, the more the problems with
all the above. Does that make since or do you all think I'm caaaraaazy?

 

It's called cavitation. Yes - that may be a problem.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

 

I don't think you are crazy, I just don't think the problems you
mentioned are significant. If they were, you'd see cars littering the
road side with failed fuel pumps, and that just isn't happening. I've
owned several cars over the last 20 years that had electric fuel pumps
and I've yet to have a single failure.


Matt

 

No, cavitation occurs when the inertial forces are so high that pockets
of vapor from the liquid form. This isn't the same as liquid
starvation, which is what I believe he's referring to here, at least
judging by the boat prop example. A prop that "catches air" usually
means it came out of the water. A prop cavitates while completely
submerged in the water.


Matt

 

I've got access to an '88 K2500, '90 C2500, '93 C1500, '98 C2500,
and a '01 K1500.... so far the '01 hasn't had the fuel pump fail on
it.. yet. both the '88 and the '90 on their third pumps.

-Bret

 

My 94 K1500 is doing fine at 86,000 on its original pump. You must just
be hard on equipment!


Matt