Why is the factory fuel pump so finicky? when I first got my 350 it had the stock fuel pump, in the first thread I posted u can see all the bad stuff going on but it was not pumping nearly enough fuel even when first got it, second pump was one I got from eBay, cheapo Chinese pump that never even worked, third was from chucklenuts at aftershot motorspurts and it worked... for about 6 run hours? 7? Now it’s dead again, pulling 1.5 ounces per 10 secs. I’ve got good Engine compression 146psi, just did a top end rebuild everything is in top shape... I just did a leakdown test twice again it’s good, all my fuel lines are new, fuel filter is new and I put compressed air down all the lines to confirm there are no blockages. Why did the pump stop working? Maybe somebody can help me understand that....

But I was thinking why not go to electric. So I did some playing around...

A buddy had this pump and regulator layin around and donated it for my experiment.
The pump by itself puts out way too much fuel, almost as good pressure as my garden hose... but using the regulator I hooked up all the lines and set it to pump 5 ounces per 10 seconds, as close as I can get to the speed the vacuume pump should run, it seems the T relief valve can handle the extra flow fine. Plugged the line to the vacuum going to the case and started her up, I didn’t run it around as it’s pouring the rain today but it seemed to idle fine.

Does anybody use electric pumps on their setups? Anything I should know about doing it this way?

Seems to be an enixpencive way to improve reliability... especially if something like the fuel filter were to get gummed up... I can increase flow easily to help in a bind on the trails

That electric pump is not gona work in my opinion. Its just gona over power the system and flood the carb.
From what I read here you now have a good Engine that passes the leak down test, has 146psi, and your fuel lines are new with a new filter.
I re-read your post when you first got it. You said the tank was rusty but you cleaned it. You also say you blew air down the lines and apparently they are clear in the tank. You have gone through several fuel pumps now. I find it hard to believe they were all bad. In fact the one from chucklenuts actually worked and then stopped suddenly.
Something smells here. 1) Where is you fuel filter located ?? Is it before the pump OR after the pump going to the carb ??
2) Is your vacuum line from the Engine clear ?? You do have it hooked up correctly right ?? I say this because when I read your original post you guys didn't know which nipple on the pump to hook it too.
3) Did you ever buy a Polaris pump like I posted a pic of in the original thread ??
4) When you do the flow test do you remove the line at the carb and measure from there or do you take the line off some other place for this test ??
5) If it fails the test at the carb line then hook it up again and take a flow test from the return line right at the tank. If it passes there then that means the check valve is no good.

Edit: This is a very simple and a very good system. It works well. It can only be four things. 1) your pick up lines in the tank are crap (that's what my money is on) 2) you don't have it hooked up correctly 3) your check valve is toast 4) all three pumps are junk -- find it hard to believe but it is a possibility.

1: filter is before pump as manual diagram says... im pretty sure I got everything connected properly.
2: vacuume line from Engine is crystal clear
3: I have not tried the Polaris pump... I will though if somehow all 3pumps I have are shot... wudnt be surprised if I messed something up along the way though lol... how the one pump worked for a while and then won’t now is beyond my feeble mind.
4-5: I do the flow test at the check valve... question on this... should fuel always be flowing out the carb line and the overflow line, even when there is no back pressure from the carb? Cuz come to think of it’s always spraying out both ends...

Pickup lines in the tank did cause some resistance even with the electric pump... BUT when I did the vacuume pump test i tried it with putting the pickup lines on the tank aaand just dipping it in a 2 gallon gas can and it wouldn’t pick up from either.

I am kind of confuse about what you are saying here. You say "I do the flow test at the check valve". Not really sure what you are doing there. I leave everything alone and just remove the line at the carb. If that fails then put the line back on the carb and pull the return line at the tank. Measure again.
If it failed at the carb BUT passed at the tank then your check valve is shot. If it fails both then the pump, vacuum line, compression or pick up lines are the problem.
To answer that second part should fuel always be flowing to the carb and overflow line -- yes.
When carb is full the excess runs back to tank so that it does not flood the carb. The check valve is there to hold a couple of psi back pressure so that the carb gets the fuel first before it starts to run back to the tank. You need this slight back pressure. It is so low you can't measure it so forget it. Just do the tests. Anything more than a couple of psi back pressure will over come the floats and carb fuel valve.



Then based on this test I would say pump shot.
Pumps are designed to push liquid. They have a hard time creating vacuum to PULL liquid.

The problem with an electric pump is the volume of fuel flow and the extreme pressure it is putting out.
You will not be able to control either successfully with those small lines the oddy has. It's a delicate system. If the carb could block the fuel flow without flooding then that would be ideal. But that's not what we got.

Verify your vacuum hooked up is correct at the pump.
Verify your IN line on the pump is hooked up correct.
Verify your OUT line on the pump is hooked up correct.
Verify your check valve is hooked up correct.

http://www.mikuni.com/c-fuel_pumps.html
DF44-211
Outlets: 1
Flow: 14 Liters/Hour

Be careful as there are Chinese copies ((( cheap ))) Nasty

Buy genuine. spend the $$$$

Dump the electric pump
verify the pulse line is connected and working.

Fuel filter as per pic
Fuel Filter Walbro style - 1/4" OD

Buy good quality fuel line

wyeeoddy

Read this it explains what I went thru after others including Honda shops mechanucs in USA that never checked the aftermarket E Pump output.
You see...vaccuum pumps are in sync with throttle carb demands relative to RPMs.The higher the RPMs the more fuel needed to satisfy the demands via the higher vaccuum.
Stick to the vaccuum pumps and check your vaccuum pulse port for avtuall readings to verify vacuum and any blockages.

viewtopic.php?f=1&t=11938&hilit=Ac550+fuel+pump&start=125

Ok i followed yalls directions, took all lines apart and tried again, best i could. Everything is hooked up properly:
All lines are clear
Vacuume line is clear and when i turn the Engine over without the vacuume line connected to pump i can feel the the air pulsing.
Pump is clean, all lines hooked up correctly, valve on correctly

I tried it with and without the fuel filter just to be sure it wasn't causing resistance
Still it wouldn't pump.

The only way i could get the pump to flow fuel at all is if i Submerged the pickup port on fuel, even then it only pumped fuel at less than 1oz per10sec. And only pushed it out of the tank return line of the valve...

So by what your saying this should mean the check valve and the pump should be dead correct? If the check valve is shot could that cause the pump not to pickup?

F.Y.I. pump im using is the exact one shown by wyeeoddy mikuni markings included... that's the one i got from chucklenuts at aftershot motorspurts.

1) pump is ded
2) NO

I have the Polaris pump on all 3 of my machines. No issues.

Man. Hard to believe all 3 of my pumps are bad. :/
Ill put in an order for a polaris pump asap.

The Check valve is on the output to the carby I hope

see pic

PS u got service manual

Yeah i have the manual, check valve on after pump going to carb as manual diagram says
After determinine the pump wouldn't pull i unplugged the check valve and blew air through it as the manual tells you to, it was leaking air in almost every direction its not supposed to so im probably gonna pick a new valve up too.

Meanwhile iv got some kreem working on the fuel tank rust, that should eliminate any resistance i was getting from the pickup lines.

Any more suggestions while im waiting on parts?

Won't that kreem plug up your pick up lines ??

Im not using the sealant,just the acid, in addition im gonna take some wire and try to push it through the pickup lines to be sure. Figure as long as i don't use the sealer it cudnt hurt

That's good because I seen a pic of an oddy tank someone was trying to sell on craiglist.
It had the kreem in it and in my opinion he destroyed it. It looked like someone put sprayfoam insulation in it. You can always tap your drain plug and pull fuel from there if you have to.

Lol yeah that sealer ‘works’ a little too well. IMO if you don't have leaks all throughout your tank then don't use it.
Yeah i hope i don't have to make a new pickup but, we shall see, pump arrives friday so the wait is on.

On a side note i got my fox air shocks in finally... mounted them up with curtis’ kit and its beautiful. Low psi setting factory so i took it to a local shop to nitrogen fill it... oh boy.
I told them to set it at 250psi took em all day to get it done, spring time must be busy for them. I get it home and put it on and the buggy is practically bottomed out on right side but left is fine... i put my guage on and they filled one to 250 psi. Other to 150 lmao. U gotta be kidding me

Heres a thought, if my carb wasn't working properly would that change the fact that the pump isnt working? A couple times i did the test i had the carb off the buggy just letting it breathe through the reeds, that shouldn't have screwed up my results would it?

Nope. Wouldn't matter.

New polaris pump is on, pulling from a gas can (tank is still being worked on) its pulling 4-4.5 oz per 10sec. Its barely pulling the requirement, but atleast its pulling now. Incredible that all 3 punps were bad. But since its barely pulling what it needs too... wat now, roll with it?

4.5 oz in ten sec is NOT "barely pulling the requirement". That's what it is suppose to put out. It's good to go.

Ok, just making sure i do everything right.
Thanks for the help, im sure ill have more questions to things i don't understand later lol

A real stupid ??

Has every it been running not in the shed. I mean driving and running tanks of fuel

Have you pressure tested the Engine

Have you done a compression test low compression would affect the pulse

Has the cylinder ever been taken off. If so was the Base gasket replaced with the metal
or paper gasket and the big one any silicon Gasket goo used.

Too much goo could of blocked the pulse hole

Could there be a bad seal as it seems strange the 3 pumps aren't
pumping and this new fancy polaris is not pumping as it should

I would put it together all STOCK no fancy bits and start from scratch

wyeeoddy