fuel injected gas tank baffle

[dyeager535]

It does starve for fuel when the tank gets low.

Peoples heads should roll.

That sucks that those trays are that much of a problem. When I got my tank I wondered what exactly it was supposed to do, at least compared to the stock setup.

I guess most people don't use trucks as trucks, therefore they don't see any difference.

 

[4X4HIGH]

If there are no holes, how does the gas get into the tray?

I have the little steel dish thing in the bottom with one small hole on each side (aftermarket 31 gal TBI tank). It does starve for fuel when the tank gets low. I don't know what affect the higher pressure pump (TPI) has versus the TBI ones. It is fairly well documented in other threads that the plastic baffles work better, but break.

The newer setups with tank inside the tank work really well and you can usually drain the tank completely. My car has a check valve on the bottom of the plastic tank and the return line feeding into the plastic tank. I've taken the pump out before where that inner tank was over 1/2 full while the surrounding tank was almost empty. My only complaints are that it gives no warning and if it is run dry needs like 3-4 gallons before it will run again. I don't see why one of those plastic inner-units couldn't be retrofitted into some other tank/cell instead of fabbing some baffles. You just need the large style top opening.

Very easy question to answer. When you fill your tank there is gas in the tray and the fuel pick-up AND return are within that tray so now there is always fuel in the tray. Why do people have troubles then you might say, will that's an easy answer also. The tray wasn't designed large enough to hold fuel while in an off camber situation, it's not like GM expected people to drive at crazy angles and stuff. The baffle tray satisfied GM engineers for normal street driving habits that 99% of people do with these vehicles.

 

[79rustyk10]

I've replaced a pump in my FACTORY tank and the tray was just a plain simple squarish open tray, no "mazes" whatsoever.

When I did the TBI swap, I got a tank from a friend who parted out his 87 shortbox K10, and it was how Scott described it.

 

[dyeager535]

When I did the TBI swap, I got a tank from a friend who parted out his 87 shortbox K10, and it was how Scott described it.

Must have been two designs then, the photos I linked to earlier show what I had seen in a K5 tank. Odd that GM changed them...either that or there were two different manufacturers, since the pictured one is supposedly an '87 too, which means two different sump designs the same year, both in pickups!

 

[eagle mark]

There's no way a square box with no inlet/outlet is going to work properly! Depending on how high the box was you would run out of fuel at 2-6 gallons sitting still idling. Return is going to run out sooner or later?

All the ones I've seen look like the photo dygear535 posted:
http://67-72chevytrucks.com/vboard/showpost.php?p=4992939&postcount=10

Including metal and steel and other then GM vehicles back to 1972 IH Pickup that had a very shallow long tank. Strange how the design is used by many manufacturers for that many years? It works...

But newer cars GM and others use a complete drop in fuel pump, gauge, return tank and they are spring loaded to push the bottom mounts on tank while not crushing the sock.

Here's a write up of a very cheap highly effective fuel supply. If your building a fuel cell it's excellent but works in stock tanks too.
http://www.gearhead-efi.com/gm-ecm-pcm-conversion/in-tank-fuel-pump-conversion.html

Since your building it have you looked for the fuel cell foam that comes in built ones? Great for slosh in all directions.

Coating the inside of the steel tanks is really needed, even worse any ethonal fuel.

These baffles really only come into play when the tank is low. I've run no baffles to 1/4 tank and never had an issue? Not sure you could make one work at 1/4 tank in a rock crawler sitting almost on its side type stuff for to long that low?

HTH!

 

[blazinzuk]

Well however the stock baffle in a stock tank is it works very very well.

I sat at this angle for a solid 30 minutes while they were trying to get me winched back up.

I had probably half a tank in that photo maybe a little less. But still I was pretty much over on my side.

That write up that eagle mark posted is excellent and I will be doing it very nearly like that I think.

I will not use foam seen too many problems from it.

 

[blazinzuk]

And I don't think I need to worry about coating the tank it will be built out of stainless steel

 

[Blue85]

When you fill your tank there is gas in the tray and the fuel pick-up AND return are within that tray so now there is always fuel in the tray.

I'm still not following the logic. You have gas in the tray, but it is being consumed. So if the truck is on it's side for long enough, it will run the tray dry. How does more get in? Then with no angle - let's say the tray is 3" tall - how can you ever drain the last 3" of fuel from the tank?

When I say I have trouble with fuel starvation, that is with like 2 gallons or less left in the tank. I've never seen the problem off road.

 

[eagle mark]

Well however the stock baffle in a stock tank is it works very very well.

I sat at this angle for a solid 30 minutes while they were trying to get me winched back up.

I had probably half a tank in that photo maybe a little less. But still I was pretty much over on my side.

That write up that eagle mark posted is excellent and I will be doing it very nearly like that I think.

I will not use foam seen too many problems from it.

This is the situation I was talking about. No baffle is going to help when low on fuel. Well won't help for long...

I'd bet the only broken plastc baffle tanks seen were in off roaders without a skid plate and hit the gas tank, even a slide over something could break them.

 

[dyeager535]

I'd bet the only broken plastc baffle tanks seen were in off roaders without a skid plate and hit the gas tank, even a slide over something could break them.

The one broken one I saw was from an accident. Sudden stop with sloshing fuel is apparently enough to break them.

 

[eagle mark]

Well that's not good and explains why so many guys have seen them broken if that will do it, I've never seen one broke? Haven't looked much either except when replacing a pump...

The baffle is just a short term cure when fuel is low, for sudden acceleration, deceleration and turning forcing fuel to outside of tank. If tank is really low it will only help for short time. Covers street driving well till empty...

 

[dyeager535]

Climbing passes even on the freeway I can "lose" more than an 1/8 of a tank of gas based on fuel movement of course, at 1/4 tank of gas a K5 should have ~8 gallons left, the aftermarket design is inherently far inferior compared to the "box" GM used I was talking about...I see that being a HUGE problem, at least potentially. A smaller tank would have an even more pronounced problem.

I have yet (in about 10 years) had the truck stall based on fuel level, but due to knowing the poorly designed sump in the aftermarket tank, I take pains not to let it get below 1/4 tank if I'm going to be anywhere with long hills or on logging roads in general. I really don't like having to worry about that, and having to leave 8 gallons of fuel in the tank costs me about 128 miles in range on the freeway, about 80 miles off-road. Living 20 minutes (one way) to the nearest gas station also factors in.

If I were making the tank myself, I'd use the "maze type" sump I referenced to, I'd make it fairly large, and I'd probably make it at least half as tall as the tank itself, if not almost to the top of the tank for a dedicated off-road rig. If it went to the top of the tank, there would be little need for baffles.

 

[4X4HIGH]

I'm still not following the logic. You have gas in the tray, but it is being consumed. So if the truck is on it's side for long enough, it will run the tray dry. How does more get in? Then with no angle - let's say the tray is 3" tall - how can you ever drain the last 3" of fuel from the tank?

When I say I have trouble with fuel starvation, that is with like 2 gallons or less left in the tank. I've never seen the problem off road.

I don't know how to say it much clearer but i'll try this. There is a tray in the tank in which the fuel pump pick-up is located, also with the tray is the fuel return line. The amount of fuel consumed is ALOT less than the fuel returned back to the tank (inside the tray) so until the fuel level in the tank becomes shallower than the tray itself there will always be fuel in the tray.

Did that explain it any better for you?

 

[Blue85]

...so until the fuel level in the tank becomes shallower than the tray itself...

Isn't this really the level we are most concerned with? Let me give you a hint about how more fuel gets into the tray when the tank level is lower than the tray - there are holes.

The whole reason the baffles/maze/box works better is that it acts more like a one-way path for fuel. The tray can dump it's fuel right over the edge when you put the rig on angles.

 

[4X4HIGH]

Isn't this really the level we are most concerned with? Let me give you a hint about how more fuel gets into the tray when the tank level is lower than the tray - there are holes.

The whole reason the baffles/maze/box works better is that it acts more like a one-way path for fuel. The tray can dump it's fuel right over the edge when you put the rig on angles.

The tray in my factory 89 blazer tank DOES NOT have any holes in it (other than for the pins that stick through for the clips that hold it down) nor does it have a maze or secondary tray. Mine is simply a plastic square tray about 2" tall.

 

[dyeager535]

Here is a good picture of what the aftermarket thinks a sump should look like: http://ls1tech.com/forums/attachmen...tra-efi-gas-tank-yay-nay-fuel-sump-baffle.jpg The one in my truck is even worse, and it's a Spectra as well. Kind of defeats the whole purpose of the sump to have drain holes in it.

 

[eagle mark]

Now if you used a sump like that one which is about 4 inches high? You would have no fuel in it until tank is 4 inches high, about 8 gallons? So if you install the tank and put 5 gallons in? It won't get any fuel to run...

So what some fuel is returned, some fuel is being used and without a new supply it will be a dry hole in a wet tank...

The whole purpose for the baffle/sump is to keep some fuel near pickup of fuel pump when tank is low and G force pushs fuel to outside of tank, away from pump. So you can use all fuel in tank.

How does having one with no inlet/outlet help? OK it will help till tank is low but could run out if you let the vehicle idle sitting still, like warming up? Or when tank is really low not splash enough fuel into tray? Cruise a smooth highway and run out of fuel with a few gallons left?

 

[dyeager535]

That is typical aftermarket. It will fill up with fuel fine, that's what the two small holes in the bottom are! I guess someone forgot that the holes will also drain fuel...

 

[eagle mark]

I didn't see any holes...EDIT: now I do, I thought they were for mounting...) but at least if there are holes it will fill. Yes holes will let fuel out too! But slow, just need fuel there for keeping fuel supply at low tank when slosh will move all fuel away... it's not rocket science...

I've done a lot of conversions with no sump/baffles and never had an issue! But never went below 1/4 tank. This entire subject is for less then 1/4 tank... less depending on shape of tank...