I just went through the whole trouble with replacing LP, IP (vp44) - decided on upgrading to a FASS lift pump and vulcun 1/2" diameter drawstraw. I'm not sure if the procedure to cut the drawstraw was done correctly by the shop, because I'm seeing the fuel pressure fluctuate and drop from a nominal reading of around 15 psi to 5 psi and even nil during stop and go or sloshing around - this is with a fuel tank reading of just under 1/4 tank? I had thought the drawstraw would eliminate this problem, and that I would at least be able to drive the fuel tank down to the 1/8 tank warning lite on dash? Albeit, the fuel pressure fluctuates, but I'm not hearing or feeling a loss of power. So with all that, I'm wondering if the drawstraw can be cut so that the tank can be suck down to at least 1/8 of a tank? The mechanic also replaced the fuel tank sending unit, because I ran out of diesel at 1/2 tank ... Is this something I should bring back to the mechanic - in that the shop said I should be able to suck the tank down dry with the drawstraw? thanks, DD

 

Did they drop the tank or remove the bed? If they dropped the tank and did not support it the same way that it hangs in the truck, i.e. let it sit on the ground while they installed it, then the draw straw will be too short.

 

They dropped the tank.. I'm wondering if the cut the drawstraw too short? Should the straw extend through a drilled hole in the bottom of the sump can in order to get max fuel availability sucked out of the tank? Does it matter? Thanks, DD

 

Fix it right, bottom feed, no more problems.

 

Did they put the DS in the canister?

No, you can leave the bottom screen in the canister, but if they had the tank on the ground when they tested it for fit, it's too short. When you put the tube in the canister with the tank on the ground, the canister is higher than with the tank in the truck... the canister adjusts, if you did not know that.

I don't know if I'm explaining the tank thing well enough... do you understand what I'm talking about?

 

The DrawStraw you have sounds like a DSII. This requires a hole in the tank NOT in the module. Almost always with pressure issues at 1/4 tank it's one of two things.

First, installation. Almost always, the tube has been cut too short AND a hard slash has been put on the tube. It will suck air at it's highest point remember. I am speaking from experience as you cannot believe the number of these I have fixed.

Second, bad fuel readings. This can be caused by a bad sender of most likely, the tube was placed where it contacts the sender at low tank levels.

Dave

 

I appreciate the replies - here's the history: After having IP and FASS installed, I ran out of fuel at 1/4 tank indicated on fuel gauge. So I had the mechanics install a drawstraw, and since I did not have the in tank LP, I ordered the 1/2" diameter type that fits through the canister, and a mechanical fuel pressure gauge - all seemed fine until I ran out of fuel at 1/2 tank indicated on fuel gauge. The mechanics then told me I had a defective fuel level sending unit - that was replaced last week. After that ordeal, I decided to drive truck until I was down to 1/8 tank where the low fuel warning indicator comes on - thinking this is my usual fill up point and an acceptable test that all is installed and working correctly.
The truck didn't make it to 1/8 tank - fuel pressures started dropping erratically at 1/4 tank so I filled up and that problem went away.
So I'm back to the original problem where I'll run out of fuel at 1/4 tank. What needs to be done to resolve this issue - do I need to order another drawstraw and have get the mechanics to understand the procedure of cutting length correctly? Thanks, DD

 

It's hard to say buy something without knowing exactly what's going on. Short of dropping the tank and inspecting the install, it's a tough call.

Dave

 

DD, in case you haven't done it yet, do a search using Draw Straw and you will find lots of info, especially in the older threads. I did that before I installed my DS. Mine is installed in the module and I removed both screens in the puck so that my DS actually extends below the bottom of the puck. I also replaced the sending unit at the same time. After almost a year it seems to be working fine although I rarely let my trucks' fuel tank get below a half a tank; especially during the summers around here. As a test, after my install, I did run it down to when the "low fuel" light came on. I then filled up and the truck had around 9 gallons in it which I believe is about right. Also I might add that since I had removed both screens in the puck, I installed a Fleetguard in-line filter screen just before the LP. I'm probably going to replace that with a Racor filter.

 

Thanks to all for your replies! After reviewing more than I'd ever want to know about drawstraws, fuel pumps, injector pumps, and procedures for installing a drawstraw to compensate for a higher performance fuel pump (as in FASS), I've come to the conclusion, and this is after confirming with the mechanic as well, that the tank measurement was skewed by the amount of fuel in the tank, and that the tank was removed and benched, so to speak, during the measure and cut lenth procedure. This most likely caused a measurement error - the tank being weighted by the remaining fuel in tank skewing the measurement about 1/8" too short. So I just ordered from Vulcan the straw portion only, and the mechanic has agreed to R&R with said consideration - to also crown the cut instead of slashing a diagonal. Hopefully, this will be the last time the tank will be dropped and fitted accordingly. Gad this has been a long haul - the truck not hauling anything for seemingly a whole Winter season what with all the fuel issues.
It would be great if Vulcan performance included some semblance of a procedure - especially with all the good information availed on the internet these days. Hope this helps another chap riding in the same kind of saddle.
Thanks, DD

 

I completely agree.

I have been lobbying to that end for some time. But there is a sound reason for NOT doing that. Liability. It seems that if you tell a guy to mount it in 'X' location and they have an issue, you now owe them something. Got a call today in fact to that effect.

But the bottom line is that we are going to rewrite the installation instructions that will be specific and generic enough to satisfy everyone's concerns. It is a priority for me, but I have several irons in the fire and just cannot get it done as quickly as I would like.

We are even kicking the idea of some short installation videos that can be hosted on our website. That way a guy can see moving pictures of what he has read and available at any hour, may make the installation process more painless.

You would think after the literally thousands of these units sold, we would have better directions by now. But he ball is rolling and we had a discussion about it yesterday in fact.

So please bear with us and I look forward to answering questions to the best of my ability in the meantime.

Dave

 

I strongly recommend taking the bed off with at least a half a tank of fuel in it... if you want to do this, let me know, and I'll give you some tips...

 

Yeah, probably easier if you don't have a good jack. I have helped buddies in their driveways with a simple floor jack and a piece of 2x8. Gotta get the balance right and support the rear on jack stands.

I prefer to do it in the shop with the modified trans jack!

Dave

 

madhat, I sure would be interested in the pop the bed procedure this time around in that when I bring the truck to the shop it will most likely still have 3/4 tank of fuel - curious to know which way is preferable: dropping the tank or popping the truck bed? Thanks, DD

 

One other thing to consider is that if the sending unit was a modified in-tank pump unit, these can cause more issues than solve due to the "Baskets" restriction to allow fuel to permeate into it.

The in-tank baskets have a ventui on the bottom that uses return fuel from the in-tank pump to suck fuel off the bottom. This keeps the basket full and keeps the pump happy. Well if the pump is removed from all of this, the wonderful venturi is disabled and becomes a restriction. Normally you will see half tank issues once the fuel level drops below the top of the basket. The FASS will empty the basket out, and pump sucks air. Fuel will then refresh and the whole process starts again.

How to fix you ask? Well simple really....if you have the sending unit out again, you might consider plumbing the FASS return into the basket. I would suggest using a tube to make sure the return fuel is sent to the bottom under fuel level to reduce splashing and foaming. When this is done, it has worked wonderfully.