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In tank fuel pump

Posted: Wed Sep 30, 2015 8:43 am
by Stan
Research question ; if an in tank fuel pump goes bad is it possible to pull fuel thru the pump even though it's not operating?
I'm thinking of replacing the factory rear tank with a 23 gal "sump pump " tank . Installing a switched low pressure pump {5-7 psi} in the tank and also a low pressure frame mounted pump {also switched} as a backup in case the intank pump failed. The frame pump would be wired but not plumbed just mounted in a location where it would be relatively easy to reroute/connect the fuel line to.
Yes - no -Maybe ?

Posted: Tue Oct 06, 2015 11:34 pm
by DirtDonk
Are there many low pressure pumps out there that are meant to be tank mounted? Not sure I've seen one, but never looked either.

Some pumps are no problem to pull through, while others don't like it. Some of those that are not normally pulled through though, might still let fuel through even if they're not cooperating fully.
Not sure what that would do to performance however. Would it just mean less volume? More wear and tear on the puller pump? Inconsistent flow? Not sure...

So I'm in the "maybe" category. Definitely check the specs on the pumps you're looking at. Some may or may not say specifically whether they can be pulled through, but sometimes the type of pump is helpful. Some types are more pull-friendly than others.


Posted: Fri Dec 18, 2015 1:09 pm
by TonyNokes
I would recommend buying a good in-tank high pressure pump and keep it simple.... Cuz, I didn't!

Posted: Sat Dec 19, 2015 11:22 am
by DirtDonk
Sounds like he's running carbureted but wants the quiet reliability (relatively) of an in-tank pump. That right Stan?
If you don't find a low-pressure pump suitable for in-tank mounting, I'd just mount two pumps on the frame somewhere and utilize some sort of quick disconnect feature. Or if you really don't want to get dirty, you could switch the pump flow through a solenoid valve instead of manually changing the connections when the primary goes out.

But that's just from never having searched for a low pressure in-tank pump before. Maybe they exist.
I'm not sure you'd want to take a 90psi pump and regulate it down to 3-5psi or not. Maybe someone knows whether that's possible or recommended.


Posted: Sat Dec 19, 2015 12:09 pm
by Stan
One if the Bronco Vendors ( not on West Coast - LOL) used to list a low pressure in tank pump - I havent looked in last 6.months or so to see if they still do.
Basicly Paul I was thinking about an in tank pump for noise and longevity but having one of the low pressure frame mounted pumps that WHs sells as a backup in case the in tank pump went bad. Make it a quick trail fix untill i could get home and drop the tank.
The reason im thinking of going to an electric pump is I keep getting air in the fuel line just before the carb. ( yes ive checked for leaks - removed manual selector valve and that has helped) so if the Broncos been sitting for a while i have to crank the starter for a bit to get the motor started. The thought on the electric pump is i could just turn the ignition key on for a few seconds let the pump fill the line before trying to start it.
I had dual electric pumps on the '76 when i bought it ( one for each tank that switched with the "fuel gage switch" but had issues with burning out motors and pumps - but they weren't properly wired and it didnt help that we were running the tanks empty before switching over to the other tank.

Posted: Sat Dec 19, 2015 1:11 pm
by DirtDonk
You can't really run any pump dry when it's still fairly new. Mechanical pumps are a little more forgiving of that once they've worn in a bit. I used to run mine dry literally every tankful. Got real quick at flipping that floor switch!
But the pump already had close to 60k miles on it at the time. Lasted another 40k of that abuse, but when I put the new one on I didn't do that for a long time after.

Electric pumps absolutely cannot be run dry when they're even remotely new. I don't know the limit, but I'd sure wait for at least 10k before putting that kind of heat into one. Those little buggers can be spinning up pretty fast when working, and that builds a lot of heat. Quickly.
Best not to temp fate.

I remember the stories from back about '86 or '87 of people running their Grand Nationals out of gas when they were new. Two things were expensive to replace on one of those Buicks. The ignition control module, and the fuel pump. I think the fuel pumps were $400 at the time, and the ICM's were over $750!!!!
Definitely did not want to overheat either one. That's a lot of money now even, so you can imagine what that did you a heart rate 30 years ago!