Engine/Transmission (1998.5 - 2002) Draw Straw II

[MKreiberg]

So I finally got the tank out





I was going to do the Draw Straw II so that I could maintain the OEM pickup for a backup system... but it seems the boys at chrysler put a lot of thought into keeping that pump fed at lower fuel levels.



My question is this: How low of a fuel level is anyone comfortable with when running the separate draw straw? - seems to me like less than a quarter tank or so and you are in jeopardy of slosh exposing the pickup - I sure would be more comfortable with some sort of baffle system.



Any experiences?

 

[jeepit]

I usually fill at 1/4 tank but I have run it down to 1/8 tank already. I had it just under 1/8 last week and saw the fuel pressure guage fluctuate on the way to the fuel depot. .

 

[ERuhl]

I had the drawstraw, same experience as jeepit, swapped it out for a new stock module again.

 

[EOwen]

ERuhl,

With the exception of gauges, exhuast, and Amsoil, my 02 is pretty much stock.

I have the warranty in the tank pusher pump, and have just now started having fuel pressure issues fluctuating up and down. Tell me what you would recommend. Sounds like your profile may no longer be up to date. What is the stock module you swapped back to?

Thanks

 

[ERuhl]

ERuhl,
With the exception of gauges, exhuast, and Amsoil, my 02 is pretty much stock.
I have the warranty in the tank pusher pump, and have just now started having fuel pressure issues fluctuating up and down. Tell me what you would recommend. Sounds like your profile may no longer be up to date. What is the stock module you swapped back to?
Thanks

Good catch, I deleted the drawstraw from my profile. I missed the fact that you're looking at the drawstraw2, I don't have any experience with that version and the in-tank pump. If it ditches the return fuel bowl, then I'd expect similar results though.

I avoided the in-tank replacement and kept the external carter (went through 4 of them) up until I recently replaced it with the walbro. So by "stock module" I mean the original module designed for an external pump. I'm not a fan of the in-tank replacement, but for an effectively stock truck it should be fine. At a minimum I'd suggest replacing all of the banjo fittings with AN fittings. Is the pump still covered by warranty?

 

[EOwen]

yes, but wont they just put another in tank pump?

not planning to stay stock forever, just until transmission building becomes a priority.

 

[ERuhl]

If you're planning to step it up from stock, then what path you take depends on the extent of your plans. The Walbro pump is fine for my needs, but might not be sufficient for whatever you have planned. What is your HP goal?

 

[rweis]

I have a DrawStraw and totally gutted the OEM cannister. All the cannister does is a physical holder for the DrawStraw. My DrawStraw pickup sits on the bottom of the tank.



I was doing a project about the fuel level sender when I did the DrawStraw and had determined that for my '02 1 inch of tank depth = 3 gallons of fuel. When the "low fuel" light comes on in my truck the tank has approximately 10 gallons of fuel remaining which translates into about 3 inches of fuel. I live in Florida and as long as it is flat I'm ok with that.



When I went to the mountains this summer then I fed the bed aux tank to keep the OEM tank full and stopped for fuel at 1/2 OEM tank (the aux tank empty). I am in effect using the OEM tank as the sump and the aux tank as the primary fuel source.



There is a thread about adding a sump to the OEM tank which I do not think ever went into an experimental testing phase. A second concept was to have the OEM tank feeding a fuel cell (5 gallons) as a sump and feeding out of the fuel cell to the engine. A pump would keep the 5 gallon sump full regardless until the OEM tank was empty or the "low fuel" light comes on. The excess fuel into the sump would return to the tank.



If you look at the cannister, the hot return fuel is dumped into the top of the cannister and the upper portion of the cannister acts as a fuel sump feeding the lower mesh filter portion. The only problem I see is not cooling the fuel on the way back to the tank.



Just some thoughts,



Bob Weis

 

[jeepit]

I had the drawstraw, same experience as jeepit, swapped it out for a new stock module again.

I have the DrawStraw with a gutted stock fuel module.

 

[ERuhl]

I have the DrawStraw with a gutted stock fuel module.

Yup, that's what I had. I gutted the stock module completely and ran the tube to the bottom of the tank like Bob described. The first time I saw the fuel pressure drop with ~1/8 tank I regretted the mod. This was on flat land, just using the brakes and it'd start sucking air. Removed the modified module, installed a spiffy new stock module, all is well again. Idle psi is unchanged, WOT dropped ~1psi.

Note: I installed the drawstraw and set the tube length per the supplied directions with the tank sitting on the floor. In retrospect, I believe the tank should have been suspended just like it is under the truck. Since I didn't do that, I'm certain that I ended up with more clearance between the end of the tube and the bottom of the tank than I intended. I have no idea how much of a difference this really makes, maybe negligible, but reducing this clearance would have let me go a smidge lower on fuel before sucking air under braking. In the end it needs some form of bowl / baffle to keep the pickup submerged under braking / cornering / inclines / etc. and a pure drawstraw approach just doesn't cut it for me. And as noted, I'm not flowing enough fuel to really benefit from it anyway.

 

[rweis]

What I found the DrawStraw did for me was during towing. Before the DrawStraw I would start losing psi as even my little DD2's were demanding more fuel than the stock system could provide. After the DrawStraw I never had that problem again.



However, I can appreciate the comments about no sump and any incline or drawing the tank too low will draw air.



There is always a trade off as soon as you do the first modification.



Someone needs to come up with a sump, day tank, or some way that we know without a doubt there is a volume of fuel available. Replumb the orgional cannister with larger hoses?



My solution is to use the OEM tank as a sump and work off my bed tank, but that does not work for everyone. As mentioned above, to only draw down to x/x but that severly limits your range.



Ideas?



Bob Weis

 

[MKreiberg]

I went ahead and did the straw, and put the stock pickup back in like I intended - we'll see if I like it or not.



If it gets to be a pain, I'm thinking I'll either make a replacement pickup assy. similar to the stock one or get a stocker and modify it.

 

[isb360]

I posted the attached in another thread, but it applies here too:



I haven't had any trouble with the tank going (dangerously!) low, although I am a bit nervous about it, having modified the system. The only tricky thing about the Draw Straw is correctly measuring the length of the main fuel pickup tube in the module. I forget the numbers, but I believe you want it 1/4" off the bottom of the module and cut at an angle instead of parallel with the bottom of the module. This maximizes the amount of fuel you can use in your tank -- this should be nearly all of the available fuel -- and also allows easy suction without restriction. What makes it tricky is that the pickup tube delivered by Vulcan is very stiff and obviously comes off of a large roll, so it is bent into a gentle arc shape. You really won't be able to "straighten" it out after install, so doing a fit-up with the slightly arc'd tube and estimating the cut location that way is the way to go. If you straighten it out for purposes of cutting, it will relax into its arc'd shape and be too far up off of the floor, thus rendering the last bit of fuel (1/8 tank??) unrecoverable for use in the engine.

Just go slow and careful and you'll be fine.



Tim

 

[jkalchik]

I put a Draw Straw in my 99 24v a year ago. I've put 32 gallons of fuel into a 34 gallon tank, and the fuel pressure gauge was still steady at 14 psi.

As a side note, I *DO* have a cleanable filter in front of the relo'ed Carter pump.

 

[ERuhl]

The problem is that the tank is very long, very flat, and has no integrated baffles or a sump as Bob mentioned. The fuel naturally sloshes between the front and back of the tank as you brake, accelerate, and climb/descend hills which exposes a pure drawstraw setup (ie. completely gutted module) in "low" fuel conditions. Getting the pickup point close to the bottom only accomplishes so much, you need to keep the fuel at/above the pickup. In offroad fuel tanks the pickup is either on a flexible hose with a weight so it can "follow" the fuel, there are multiple pickup points in the tank, there is a baffle/trap built around the pickup, or a combination of these. Something as simple as two interlocking "U" shaped walls can be a pretty effective baffle / trap. This is something that takes up a bit of room and really needs to be part of the tank, not the module. The stock setup is convenient in the sense that it's part of the module (makes the tank fab inexpensive), however it's pretty elaborate in order to be effective with so little volume.

A compromise might be to design the baffle/trap such that you assemble it inside the tank, and then it is held in place by the gutted module. Frankly I like the coiled "spring loaded" hose of the stock module over the straight and rigid hose of the drawstraw, as it ensures that your pickup point is always at the bottom of the tank while accommodating reasonable motion of the tank floor. If there's a way to keep the fuel around the drawstraw, this may prove to be a non-issue.