Article [11] ST1100 - Fuel Pump Replacement

So I installed the Airtex today. Will update this thread with a few pics once I get them uploaded, but do have a question....there is one mention of the vent hose in one of the posts in this thread and in both pictures of the two forum members that took a shot of their pump placed in the bracket just before it was re-inserted into the tank, neither pic has the vent hose in it. The Airtex doesn't have anywhere to attach a vent hose, so I'm assuming it is just taken out completely?

It appears that the nipple just inside the lower part of the tank that you can see after you unbolt the plate that is attached to the pump...the one that the vent hose attached to...it appears it turns towards the front of the bike and stays inside the tank. Does it just go somewhere higher in the upper portion of the tank? Is that what you can see when you take the filler cap off and peer in?
 
smunderdog said:
It appears that the nipple just inside the lower part of the tank that you can see after you unbolt the plate that is attached to the pump...the one that the vent hose attached to...it appears it turns towards the front of the bike and stays inside the tank. Does it just go somewhere higher in the upper portion of the tank? Is that what you can see when you take the filler cap off and peer in?
Click to expand...

Yes

https://www.st-owners.com/forums/sh...-4-gal-down.&p=1318920&viewfull=1#post1318920
 
So it is a vent...do I need to do anything to it now tha I'm running the Airtex? Now that it isn't connected to anything in the lower tank, it will just fill with fuel when I fill up the tank. But since the other open end is inside the filler neck of the tank, this isn't any big deal, right? It's not like it vents outside the tank somewhere and I need to plug either end of that pipe...

I've left my fuel level low and below everything until I get confirmation...
 
I'm just now questioning the purpose of that hose and tube. My recent problem pump problem was exascerbated by the hose splitting and falling off when I installed the auxiliary pump. Bike ran crappy. After getting the stock pump to run, and replaceing that hose, she ran good. When the stock pump failed again and I re-hooked up the aux. pump, she ran fine too. So, that tube, with the stock pump in place but not running, still provides some kind of service.
 
George, are you running the Airtex pump that replaces the stock pump, or are you running the facet external pump and leaving the stock pump in place?

With the Airtex, there isn't anywhere to hook the vent tube...
 
I've got an aftermarket aux pump, just what the auto parts store had on hand. It's not an Airtex but it got me home. :D
 
No, the aux. pump is inline between the stock pump and the carbs.

Mine is a Facet-Purolator, like this: http://www.racerpartswholesale.com/product/1740/Facet_Fuel_Pumps

I'm pretty sure that's the one I got, it got me home. Hard to fit under the tupper ware but so what at this point.

I'm gonna order this one from E-Bay. It's the one Kreis Weigel sez is a direct replacement for the submerged pump. $80 with free shipping.

Looked for the stock Mitsubishi part (UC-T02H90801) with no luck.
 
That appears identical to the Airtex brand pump I put in this weekend and that is documented in this thread. It does not have anywhere for the vent tube to attach like the OEM does, so my question still remains...with this pump, do we just scrap the vent hose? Anything we need to do to the vent pipe inside the tank or just leave it open?
 
One of the reasons I'm going with a direct replacement is to avoid having to answer this question. :D
 
Mark, put a switch in line for the Facet power wire. Only run it if ya need it. It can lay dormant 'til needed.
 
I screwed up my order and now have THREE of these awaiting payment. Sent'em a note and gonna call in a few to get it straightened out. :D
 
George said:
Mark, put a switch in line for the Facet power wire. Only run it if ya need it. It can lay dormant 'til needed.
Click to expand...

I relie on the kindness of friends and straingers. D'oh! great idea George!
 
Dumb question... Having one of these aux fuel pumps just sitting connected up to fuel lines but not powered. Does that add any resistance to the fuel system possibly lowering fuel pressure since it isn't actively helping out? Just wondering about that. There have to bee some blades (impeller) in there to actually pump the gas when the aux pump is powered that would cause some resistance to the fuel being pumped by the OEM pump.

Just a thought.
 
I would think it's similar to a turbo when not on boost, basically spinning slowly under the influence of the passing gases but basically not doing much (or taking much energy). Mine ran okay for 400 miles last Friday with the unpowered aux. pump in line. I'll do a flow test this afternoon after replacing lipSTick's pump with that from ReSTored.
 
I would image that they use some form of magnetic impeller in a design like this. So resistance would likely be base on how strong the magnets are in the impeller and/or in the motor.

You have to loose something but it likely isn't much if the PSI boost that the pump provides is pretty small.

Like I said, just wondering. If you made it that far without issues it is likely nothing. It largely depends on how sensitive the carbs are to variations from OEM specs in terms of fuel pressure. Much like when you thought the PSI was way high causing flooding, if it is too low you may run into lean conditions.

I would imagine that you could blow through a pump to get an idea of how much resistance there is. This isn't scientific by any means but it would give you an idea.
 
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