Fuel Pump

[BWC54]

Is anyone succesfully using an external fuel pump on a Fit installation without an in tank pump? If so, what pump?

Thanks.

[problemchild]

http://www.apexspeed.com/forums/show...827#post351827

Kaitlin, Ray, and I all have external fuel pumps on our pre-99 VDs.

My issues have only triggered low pressure alarms and not affected performance. I did replace my fuel pump with the exact same model. I have a test day and double event since without seeing alarms.

[BWC54]

http://www.apexspeed.com/forums/show...827#post351827

Kaitlin, Ray, and I all have external fuel pumps on our pre-99 VDs.

My issues have only triggered low pressure alarms and not affected performance. I did replace my fuel pump with the exact same model. I have a test day and double event since without seeing alarms.

I saw that but you seemed to be having problems. What WOT fuel pressure are you maintaining now? Do you have the auxillary fuel pressure sensor on your car?

[problemchild]

I saw that but you seemed to be having problems. What WOT fuel pressure are you maintaining now? Do you have the auxillary fuel pressure sensor on your car?

48-52 psi measured with HPD supplied aux sensor.

[BWC54]

48-52 psi measured with HPD supplied aux sensor.

That's right where it needs to be. Are you running any filter on the pump inlet either external or internal to the cell? What's missing from all the Walbro performance curves is the NPSHR.

[problemchild]

That's right where it needs to be. Are you running any filter on the pump inlet either external or internal to the cell? What's missing from all the Walbro performance curves is the NPSHR.

No, I have the 10 micron filter after the pump and regulator. In the process of getting the car done, I have no filter from the cell before the pump, regulator, etc. I expect that may be my issue, and was surprised when the line from the cell appeared debri-free. Hopefully, one day I will add another filter earlier in the system to prevent fuel cell foam, etc from advancing.

[racinray]

Fyi, I did run into a fuel pick up issue at Summit due to the use of an external fuel pump. When I got down to about 1.5 gallons of fuel the pump started sucking air under hard braking and sustained lateral Gs. The regulator is pumping fuel back down the filler neck but it looks like it is taking too long to get to the pickup. I talked to ATL about this and they said that the VD fuel cells (at least 98 and earlier) were designed for carburated engines with low pressure fuel pumps. Our external pumps are running at around 100 psi so they are sucking the fuel out very quickly. The easy fix is to top up the cell and to not let it get that low on fuel. The better fix is to install a surge tank and have the excess fuel from the regulator enter the cell at a lower spot or even directly into the surge tank. Or you could obviously install an internal fuel pump and regulator. Neither option is that easy with my fuel cell but I like being able to get to the fuel pump and regulator pretty easily so I'm probably going to have a surge tank installed over the winter -- roughly $500.

Ray

[BWC54]

If you are using the Walbro GSL392 like Greg you're using much more pump than you really need. So you're just recycling more fuel through your regulator back into the tank making your pickup problem worse. If you used a lower capacity pump you would be decreasing your withdrawal rate at the pump inlet. This might reduce your pickup problem.

[racinray]

If you are using the Walbro GSL392 like Greg you're using much more pump than you really need. So you're just recycling more fuel through your regulator back into the tank making your pickup problem worse. If you used a lower capacity pump you would be decreasing your withdrawal rate at the pump inlet. This might reduce your pickup problem.

Yes, I'm sure your right that it will help it but even a 65psi pump is pumping much more fuel than a low pressure pump. Also, the 65 psi pumps seem to be a lot more expensive than the 120 psi pump. Not sure why.

Ray

[GP15]

Something else to watch out for as I ran into a similar problem on my H-prod car...
I have a small surge tank installed in my fuel cell and I use the return line from the regulator to help keep the surge tank full.

First time I ran with the set up I just stuck the return line hose in the surge tank.
Problem I ran into was the fuel returning can get aerated by the regulator, and the problem got worse when the ambient temps increased. The fuel pickup was too close to the return line so it would pull in aerated fuel. This compounded the problem as once the pump sucks in aerated fuel, it made the fuel even more aerated.

I was able to duplicate the problem at idle and identified the aeration problem by peering into the cell while the car was running. I could literally see the aerated fuel stream come out of the return line and imediately get pulled into the suction line. I reached in with a long screw driver to push the return line over by a few inches and saw immediate improvement.

Solution was to make sure I had a few inches of separation between the return line and the inlet line, and to add a small piece of fuel cell foam to act like a baffle to help break up any air bubbles before they got to the inlet line.

Location and orientation of the surge tank also made a difference. I have my tank located in the center laterally, approx. 2/3 back with the inlet facing forward so the the 3 trap door baffles were facing the sides and rear. I can run my 8-gallon cell down to about 1/2 gallon without any problems with this set up.

[BWC54]

Yes, I'm sure your right that it will help it but even a 65psi pump is pumping much more fuel than a low pressure pump. Also, the 65 psi pumps seem to be a lot more expensive than the 120 psi pump. Not sure why.

Ray

You could try a GSL391. It has a similar curve to the GSS250 in tank pump Honda has in their kits. I think it's about 45 GPH at 50 psi vs. 65 GPH at 50 psi for the GSL392.

[problemchild]

Much like Ray, my focus was on just getting my car done. I'm running ballast, 5 lbs with one driver and 75 with the other, so this is not an issue that is pressing. Using 2 galls per session from a 6 gallon cell, means I can ignore it for the time being. At some time, I will try and add an extension to my return inside the cell.

The pump I chose has fitting ends, and fit very nicely from a packaging perspective. My main concern is that it seemed to go soft.

Please keep up the info coming. It can only help future conversions.

[RussMcB]

I've always liked the idea of a small external tank fed by a low pressure pump. It has a lot of advantages, but, admittedly, can be a challenge in our tight cars. I made one for my FB and it would use almost every drop of fuel in the cell, and air would never get to the high pressure pump (or engine) until the system was completely dry.

[Neil_Roberts]

I've always liked the idea of a small external tank fed by a low pressure pump.

I like that idea too, but a tall one inside the cell with an open top. It doesn't take up any external room, there are no venting or overflow concerns, and there is no extra fuel source to feed a fire. It does take a pickup pump or two to feed the makeup tank, though.