[Av8Duc]

I am aggravated beyond belief. My '94 consumes fuel pumps regularly. I have been using the O'Reilly's in house premium brand with the lifetime warranty and they're tired of me replacing them every couple of months. A hot rodder friend of mine said to chase all of the ground points to make sure that they are good. Great advice, but I'm thinking of foregoing all of that and simply converting to pure gravity feed. I think that I could put an elbow and barb fitting on the tank drain and go from there. I am using FCR carbs, but it will draw now through the dead fuel pump so shouldn't be an issue.

What do you all think? Crazy-talk?

 

[thrasher_s]

I am no expert, but I am also interested in a "pump-free" solution.

What I do know is that the Carby SS with racked FCR41s WILL gravity feed, but not the whole tank. I have heard of people modifying the internals so it will use more of the tank, but I don't know from experience.

 

[Dave G]

I am no expert, but I am also interested in a "pump-free" solution.

What I do know is that the Carby SS with racked FCR41s WILL gravity feed, but not the whole tank. I have heard of people modifying the internals so it will use more of the tank, but I don't know from experience.

You can change the pick up a bit but the problem is you need to get fuel bowls below the tank. No amount of modifying is going to get that unless you reduce the capacity or jack up the fuel tank.

 

[Dave G]

I am aggravated beyond belief. My '94 consumes fuel pumps regularly. I have been using the O'Reilly's in house premium brand with the lifetime warranty and they're tired of me replacing them every couple of months. A hot rodder friend of mine said to chase all of the ground points to make sure that they are good. Great advice, but I'm thinking of foregoing all of that and simply converting to pure gravity feed. I think that I could put an elbow and barb fitting on the tank drain and go from there. I am using FCR carbs, but it will draw now through the dead fuel pump so shouldn't be an issue.

What do you all think? Crazy-talk?

Make sure you include a cut off valve. Its a good idea anyway as FCR's love filling the sump with fuel.

 

[RockAZ]

So if you bench test one of the failed fuel pumps out of the tank - what?, motor burned out? Won't spin?

Hmmm,...

Maybe smaller hoses inside the tank and use only an external gas filter? Easily 80% of the fuel pump output is simply circulated back to the tank - blockage on the return? Or maybe the wrong type of hoses are immersed in the tank, not submersible so they are now pinched shut?

Something don't sound right here, sure - quality control has gone downhill on all reman/refurb stuff but this is beyond the expected and I think there may be another cause. Bad electrical? Should affect something else beside the fuel pump, imo,... but ground points are a serious known issue on the 900SS so don't overlook it.

So, back to the hose size inside the tank, is that trying to put through more gpm than the return line can handle? Still have two lines out, one back, right? I suppose a serious amount of schmegma floating inside the tank can wreck a pump, but it seems your carbs would be affected rather than the pump. What does the filter and the sock look like now? They have been replaced, right? That 10-15% Ethanol can eat those socks rotten fairly quickly and turn them into a sticky goo.

 

[Av8Duc]

Forgot about the bowl height. I'll have to look at that.

The lines don't appear to be blocked. When I replace the old with new, the return line has a strong stream of fuel coming back. I'll look at the initial screen for material clogging it.

I'm going to get out the trusty Fluke multimeter and shoot the ground side and look at some continuity values. That should indicate where the problem lies.

I did buy a Facet external pump, but it will be hard to locate it as it's relatively large.

Grrrr!

 

[jahjah]

I did buy a Facet external pump, but it will be hard to locate it as it's relatively large.

Grrrr!

If you are talking about the square Facet pump they have been making for 40+ years, they are reliable but very continuously noisy, IMO.

 

[ducvet]

Not normal to go through pumps, I do not even stock fuel pumps for carbys because I almost never change them. I would start by checking things over and if all is good with the bike I would buy a used oem pump not a aftermarket. I lost the fuel pump in my 851 and we used an aftermarket pump that one lasted 1/4 the life of oem. now if I have a bike that needs a pump my #1 choice is always oem just used so it is not as much money.

I have built gravity feed bikes but we have converted some of them back to fuel pumps because they can run into situations where you drain the bowls some times. This has been with FCR's with a rack (high mount) and split singles which are mounted lower, if you want dependable fuel use a pump. Do not discount using a vacuum operated pump like the monsters use either they work fine too and are external. If you do run Gravity feed you may want/need to change the float needle and seat to a larger size IIRC the FCRs have an option that is better suited for gravity feed.

 

[Av8Duc]

Thanks everyone. I'll get to it this weekend I hope and will let you know what I find. First thing is to shoot the wires from the pump to ground.

 

[EIGHTfortyEIGHT]

On the FCRs are 3 different needle and seat combos available depending on the set-up. With a low pressure fuel pump use the smallest, I use the medium with gravity feed. Its a problem and will starve the bike if you do not use at least the medium size if using gravity flow.

 

[Av8Duc]

Any idea of the needle designation/part number. I have other needles of different taper and diameter and may already have the ones you are referencing. With the bike on my table lift, I can see that the float bowls are quite a bit lower than the low part of the tank so gravity feed should work pretty well. To avoid gas sloshing around the tank I was thinking of adding some of the open cell foam that dirt bikers use to keep fuel from sloshing around the big desert tanks. All that I really need beyond that is a petcock.

 

[duczilla]

I have a 92 900ss that has had split 41 FCR's on it since 94. 80k miles of which 20k were track. Haven't had a fuel pump on it since 96. still running the original size float needles/seats. (not to be confused with the slide needle and emulsion tube). Never have I had a fuel starvation issue. Do use the shutoff at the base of the tank or put something more convenient in line. This is a non-issue.

 

[Av8Duc]

Thanks. Glad to know that someone has solved this.

 

[Av8Duc]

Duczilla, what did you do for the conversion, just remove the pump and draw through the existing plumbing? Or, did you remove the petcock and draw from there, or the tank drain? I have a Motion Pro in-line fuel shutoff and filter that I can use should I remove the pump/filter and draw through the existing plumbing.

 

[MrAlien]

I have converted quite a few bikes to gravity feed lately (not just Ducatis), my theory is the ethanol and other additives in modern pump gas damages the pump when the bike sits for a period of time. I have seen pump gas go bad after just a few weeks in my dirt bikes, now a days I just go down to the bike shop and jug of VP gas and thats what I keep in all my bikes (except my harley)

 

[ducvet]

Mr alien
If you are running race gas be sure to fog the motor after use as the race gas burns so clean there will be rust forming on any valve seat that is exposed shortly after. It is great stuff for storage as it will last a year plus without causing problems but running it on race gas and then just letting it sit is going to cause long term valve sealing issues.

 

[crashtest22]

I am very surprised to hear about you having that many problems with the fuel pumps.
My old 92 900 that I sold with 96k miles on it was still on the original pump.

If it were me I would be on the search for a oem pump and see what happens.
Though having less weight is never a bad thing even if its just a pesky pump

 

[Av8Duc]

Now for the rest of the story as they say. After having the fuel pump quit the last time I got out the multimeter and starting looking at continuity to ground. Good news is that the fuel pump negative had a very good ground <.2 Ohms. So, thinking that the ground is good I started fiddling with the electrical connector and making sure that it isn't being pinched by the tank and cleaning the contacts. I then reconnected the last "bad" fuel pump and it worked. Hooray!

Now, I feel silly that I didn't do a better job the first couple of times sorting out the connector.

 

[crashtest22]

Now for the rest of the story as they say. After having the fuel pump quit the last time I got out the multimeter and starting looking at continuity to ground. Good news is that the fuel pump negative had a very good ground <.2 Ohms. So, thinking that the ground is good I started fiddling with the electrical connector and making sure that it isn't being pinched by the tank and cleaning the contacts. I then reconnected the last "bad" fuel pump and it worked. Hooray!

Now, I feel silly that I didn't do a better job the first couple of times sorting out the connector.

but now you know what the problem was and remember knowing is half the battle lol....

Glad you got it sorted out

 

[steveb64]

Now for the rest of the story as they say. After having the fuel pump quit the last time I got out the multimeter and starting looking at continuity to ground. Good news is that the fuel pump negative had a very good ground <.2 Ohms. So, thinking that the ground is good I started fiddling with the electrical connector and making sure that it isn't being pinched by the tank and cleaning the contacts. I then reconnected the last "bad" fuel pump and it worked. Hooray!

Now, I feel silly that I didn't do a better job the first couple of times sorting out the connector.

Yup. Connectors (actually, pretty much all the electrics) can be a bit of a problem with these bikes. Have you done all your earth strap points? That'll help with starting/cranking speed. The headlight H4 plug/socket is also worth checking, and any signs of burning/brown marks - chuck it, and fit an aftermarket H4 one. Some use ceramic units - I have one, but fitted a regular car plastic one first, and it's been fine since - even with a 90/100W bulb, so never bothered with the ceramic. Heavy wiring direct from the battery via relays (one for high beam, one for low) is worth it while you're in there - and makes a massive improvement to the light output (my voltage at the headlight bulb went from 11.2v to 14v).

So - I guess you have a few spare fuel pumps?