Fuel Pump

[Mustang505]

Hi Guys
somewhere on this site someone wrote some info about an alternative fuel pump to the standard intank pump. It was an external low pressure aftermarket pump you could use if the intank one failed. I cannot find this post with the details. does anyone else know?

[paso750]

say, you really used the search function ?
the main fuel pump threads
http://forums.ducatipaso.org/viewtopic.php?f=13&t=4179
http://forums.ducatipaso.org/viewtopic.php?f=13&t=3142
from here:
http://forums.ducatipaso.org/viewtopic.php?f=13&t=3035

I have thrown away they crappy fuel pump out of the tank and installed an external membrane fuel pump from a Yamaha (driven by vacuum from the intake line behind the carb).

Ducs like the Monster also use an underpressure fuel pump btw.

G.

[Mustang505]

Paso 750 mate - i really did use it and when you type in Fuel pump it comes up with a million finds - after an hour of reading every other post but the one i'm looking for..............i gave up. obviously your searh powers are better than mine!!!!!! But for this I thank you. Also I have another excuse, just been through a 7.1 earthquake and 2 weeks of after shocks - not good for the nerves - kinda f... up your head a bit.
Cheers

[paso750]

I`m sorry to hear that. Hope things are ok though. As far as that is possible after such an incident.
Regarding the search. I just looked for "external fuel pump" and restricted the search to the 750 Sport forum and the results are only 6.
Btw the guy with the external Yamaha fuel pump wrote it`s from a Yamaha TDM 850.

G.

some pumps may have 4 connections.

[paso750]

I knew I had seen this on a webpage somewhere.
This autrian guy (http://www.8ung.at/manxman/Opti/Sportopti.htm) swapped the fuel pump with an external one.
Short translation. Below the carb on the inlet manifold there`s the connection for the syncronisation tester. Swap the screw with a screwed nipple. The tube for the underpressure connection should not be a soft one. Then he removed the pump from the tank and replaced it with a tube that reached to the tanks bottom. At the end he fixed a mesh filter (with a cable tie).
He kept the Y connector before the carb (the return line).
He says this changed the behaviour of the engine/carb very positively, too (next to ca. 300ccm more fuel capacity in the tank)

G.
original

modified

[ducinthebay]

Nice pics, and a very nice graphic that shows why you can't simply yank the fuel pump in the Sport.

With the Monster vacuum pump, does that also work as a petcock also? As I remember, a diaphragm pump has a light spring so when the engine isn't running, it seals off the flow of gasoline. Or am I asking too much of it?

I replaced my fuel petcock with a banjo fitting, but I'm still running the fuel pump. Seems to work fine, but this option looks very interesting. I would have to assume that the vacuum pump doesn't put out much pressure.

Cheers,

[paso750]

I would have to assume that the vacuum pump doesn't put out much pressure

If also a 900SS/Monster uses it, that should be fine I`d think.

G.

[Mustang505]

So if you were to run a vacuum pump off Mikunis - you connect the vacuum line to one of the inlet mainfolds?

[paso750]

this is from a Monster parts catalogue
(Phil, number 4 is the fuel valve so it`s not integrated in the pump, but it`s also underpressure activated)



I guess fuel pumps with 4 connections may be the ones with an integrated valve.

G.

[ducinthebay]

Interesting. They used one of the vacuum lines to turn on the fuel, and another to pump the fuel. Since I have Dellortos on my Sport, I should probably use one for the fuel valve, and one to run to the Magnet Marelli ecu.

Cheers,

[angelix]

from the german post, i understand that the exit of the pump goes to a splitter (Yconnector) with a TUBE going to the carb(s) and another tube to the return.

why the second tube to the return?

looking at the Monster setup, there is NO return, so the pump is connected DIRECLY to the carbs, whiche makes sense as the pump works ONLY then the engine is running and delivery is proportional to the RPMs.

I have FCRS connected directly to the pum with no return and until now I have not had any signs of overflowing.

[higgy]

Having a return line allows for a more consistant fuel pressure and puts less strain on the shutoff for the float level.Generally it allows for a cooler operating fuel pump as well.
We use this setup where I work exclusively mainly because it allows us to use a coriolis type measuring system for more accurate fuel measurement.

[angelix]

Having a return line allows for a more consistant fuel pressure and puts less strain on the shutoff for the float level.Generally it allows for a cooler operating fuel pump as well.
We use this setup where I work exclusively mainly because it allows us to use a coriolis type measuring system for more accurate fuel measurement.

I understand that, but, as far as I know, "vaccum operated pumps" are not designed to work with a return.

I will ask the matter directly to the Mikuni dealership where I got my pump from and will post their reply.

[Mustang505]

Angelix
what vacuum pump have you fitted from Mikuni?

[ducinthebay]

In general, vacuum pumps are pretty low pressure and fairly low flow. Easily enough for a 750-1000cc twin. Most snowmobiles use them. A "T" in the line will just allow for a more constant pressure and delivery of the gasoline, which is always good.

If you are running a vacuum pump and the FCRs, the floats can probably deal with low pressure adequately, but a "T" will even out the pressure and it should run better. Even if you aren't experiencing any overflow, you may be running a higher float bowl level than anticipated, which will make the bike run richer across the range. The stock pump, on the other hand, will probably overwhelm most any carb with out a "T" in the line.

Cheers,