In-tank or external fuel pump

[slck57]

Hey guys, I am getting ready to buy a under bed mount fuel tank and was wondering what some experiences were with in tank fuel pumps or external? I will be going with fuel injection set up. Thanks!

[Speedbumpauto]

Not even a question for debate. NEVER use an external pump if you have a choice.

[mongocanfly]

and yet I used a external pump on my truck...lots of miles and no issues

[Indian113]

So did I and I've put over 30,000 miles on it only downfall I have is a small whine when it's running.

[Fred n' Ethel]

Originally Posted by Speedbumpauto

Not even a question for debate. NEVER use an external pump if you have a choice.

Just curious .... on what conditions do you base such a firm conviction on ?

Thanks.

[Indian113]

While your expounding on the virtues of a in tank pump tell him how much easier it is to change a external pump than a internal pump if they go bad.

[e015475]

I suppose if you have designed your tank installation such that it isn't three or four hours of labor to get the pump out of the tank when it fails, then an in-tank pump is incrementally better than an external pump.

Personally, I'm kind of put off by the cost of the tanks that will take an in-tank pump, unless you can somehow re-purpose a factory tank that already had one in it. The in-tank pumps ain't cheap either.

I use a stock first gen Camaro tank in my truck with a swirl pot and a boost pump. Works just as well as the expensive custom tanks and pumps at a lot less money. Replacing either pump is a ten minute job.

Yes it is a little more noisy, but jeez, it is a hot rod isn't it?

[joedoh]

external is fine if you follow the mounting instructions for drop and distance, and some guys do. it has to do with an external pump sucking fuel from a long straw, and an in tank pushing fuel out of the straw.


I prefer in tank like speedbump because the fuel surrounding it is a great heat sink to keep it cool. back in the day the hot ticket for a universal EFI pressure capable external pump was a bosch unit from an f150 with the efi 5.0

[Speedbumpauto]

What Joedoh said+! I've replaced the ext. pump in my 27 T already once at 20K miles AND it's a cell with a bottom fuel outlet so no siphon problems. I've replaced the ext. pump in my Samurai EFI conversion twice in 30K miles but continue to use it BECAUSE the design is such that a conversion would be horrible. I have a Corvette LS with the pump in the tank approaching 100K miles. Guess how many times that pump has been changed. So, yea, ext. is easier to change but, personally, I would sooner just not change them. When I did the 55, I knew the tank was leaving the cab. I also knew I would use an electric pump(kinda like the guy who asked the question) so the slight extra cost was nothing. Most all early EFI's from the factory were external. Now they're ALL internal. What does that tell you? Maybe my times around the block are different than your times around the block.

[e015475]

Maybe your times around the block are different than mine.

I've spent a few hot afternoons in parking lots in Phoenix pulling the pump out of the tank and replacing itwhen the car wouldn't start. (The cars where you can get to the pump from the passenger compartment are not too bad but my pickup had to be towed to a shop to have the tank dropped to replace the tank pump when it failed.)

The only external pump I ever replaced in almost 40 years of owning some sort of hot-rod is on a car I'd fab'd an aluminum tank for and didn't put a pre-filter and trashed the pump with aluminum shavings. Joe Doh's comment on having no or very low head pressure on the external pump is right-on and I always make sure I'm not asking too much of the pump on the suction side.

There's no doubt than an in-tank turbine style pump has superior reliability to a positive displacement external pump and with cars going 200K miles plus these days having an in tank pump is great for reliability. But the extra cost to put a pump in the tank in my old truck is out of proportion to the reliability benefit for a vehicle that'll be lucky to see 30K miles in its lifetime ( IMO). I didn't find the cost difference to be 'slight' - a custom tank with a filler neck where I wanted it was pretty spendy.

But YMMV and that's the fun of building them - its always interesting to see how other folks solved their build challenges.

With regards, e015475

[joedoh]

Originally Posted by e015475

The cars where you can get to the pump from the passenger compartment are not too bad

ha! I have a worthless relative (WR) whos parents bend heaven for her. WR fuel pump went bad and they begged me to fix it because I knew a lot about that make of car.

I was at the house, pulled the seat, no tools for the fuel lines, big plastic ring for the pump, in and out about 6 minutes. I was driving home and the parents called me complaining that if I didnt want to do it why did I even come by, I could hear WR raising 6 shades of hell in the background, "he was in my car and then he LEFT!". I let them exhaust themselves complaining and in a pause said "Its already done" and hung up. I havent lifted a finger for WR since.

[mr48chev]

The in tank is most likely the best way to go in the long run but one has to look at the practical side of things too. One of those is the "how much trouble is it going to be to change the pump no matter where you put it.

A tank that sits on top of the frame or on top of it's special made frame and has to come out the top means you have to remove the bed to access an in tank pump. That pretty well means that you have to figure out how to haul it home or at least get it to a shop where the bed can be removed if the pump fails.

In tank with a tank that can be dropped out the bottom with some but not a great effort is doable in a parking lot as was said above. A pain but it can be done by one guy with a jack most of the time.

External for it's faults or alleged faults can be swapped in short order as long as you can get one without a hassle. As long as it isn't some rare part that can only be had from the outfit that makes it or though their limited vendors you should be good outside of sometimes having to wait for it to come with a parts shipment or on the brown truck with a lot of red label shipping costs.

On parts that can fail on the road but can be replaced and go again like charging units, starters, water pumps, fuel pumps I'd prefer to go with something that was pretty well readily available. Engine, trans or rear end failure means that you either haul the rig home from no matter where you are or you haul it to a shop where it can be repaired if that works better.
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[slck57]

Thanks guys, great stuff! All be it I highly doubt this truck will be high mile driven but more like a few times a week. If I were to go with an external pump, what brand/pump would be good? Motor is a 383/430 hp crate engine and will have the Inglese Fast EFI 8 stack induction.

[mongocanfly]

I like the walbro pumps...

[e015475]

The 255 LPH Walbro is my choice.

[1project2many]

I would like to add that comparing in-tank and external as categories is somewhat unfair. GM in-tanks generally don't last anywhere nearly as long as other OEM pumps. I have installed Ford replacement pumps in my Suburban and in my Sunbird turbo because they are likely to run much longer than a stock replacement.

The Ford inline pump mentioned above will work but it was originally paired up with a low pressure, in-tank lift pump.

[Erics51chevy]

I bought a plastic under the bed tank. Had to tighten the bulkhead fitting because it was dripping. I have a 340lp walbro. There is a slight whine/ sucking noise but it doesnt bother me. Especially when you have an exhaust on it you wont hear it. I have a pre and post filter for it.

[slck57]

Thanks everyone for the advice. I ended up going with a Boyd's tank with in tank fuel pump.

[Speedbumpauto]

Especially for your EFI app., you won't regret it. Good choice.

[evilokc]

I had throttle body on mine with an external pump. the pump would get hot and when it did the motor didnt run right. it was easy to change when I burned it up though. the point of an in tank pump is to help keep it cool. I suppose if you can find a spot where the inline pump can stay cool it will work fine. if I were pressed I would say go in tank. they are a pain to change but require it a lot less often than an external. if you go external pay for a good one. don't skimp.---edit just saw he has already picked one when I posted this.

[_Ogre]

make sure you install the tank to where is is easy (relative) to drop
i've had to drop my tank 4 times for incompatibility of the inside fuel hose with methanol fuel
when i'd call nolimit they'd feign no problems in our product, finally talked to rob, he sent me the correct line
with a compatible hose (5 yrs) i like the internal pump and am pretty good at dropping the tank


i ran twin steel lines to the tank with short flex hose at the tank and motor
tank bolts under the frame, i've seen a couple builds here that slide into the frame
they'd have to pull the bed to pull the tank