Generic Fuel Pump

[Guest Nocalnative89]

Earlier this week I diagnosed my faulty fuel pump (W/ everyone here's help) and ran for a bit on gravity feed. It was fine but running out of gas after something like 40 miles was not ideal for me (The reserve has never worked on my tank).

So since I am dead broke right now I ebayed a generic in line fuel pump that pumps about 3 PSI. Had to splice the wires with the original connector and get creative with placement and line length to get it together but it all fit.

So the pump works fine and the bike runs no problem. However, the pump doesnt seem to shut off like the original. I think my problem is I incorrectly assumed the fuel pump relay was in charge of shutting the pump off when the float bowls were full but in retrospect I believe it was the pump itself that senses the back pressure and shuts off. Am I correct in that thought?

Also, what problems can occur from the pump constantly running (Only while the bike is running of course). Will it flood at idle? Do the float bowls overflow and leak? Id rather not burn my bike to the ground. If these are things that can happen does anyone have an idea on how I could fab a solution? If its too troublesome or expensive Ill just go back to gravity feed but Id like to keep it pumped.

Thanks

[gll429]

the relay is supposed to shut the pump down.. so its possible the new pump may have a problem too.

well.

you said your reserve has never worked..

that may be due to a clogged fuel screen on the inside of the tank..

there are 2 was to deal with this.

drain all gas from tank.

#1.. remove the petcock from the tank.. remove the fuel level sensor from the bottom.

use an air compressor and blow though all 3 holes to make sure they are clear. make sure the reserve lube is at the bottom of tank..

or #2 bypass the petcock method

remove the petcock and the fuel level sensor from the tank

look inside the tank and verify the gas tube from the bottom of the tank to the petcock.

use a long screw driver and insert into the gas line at the bottom of the tank.

use a hammer to tap the driver THROUGH the line it will now work on gravity until you are at the bottom of your tank.

however... you no longer have a reserve on the flip side you no longer have to worry about your fuel pump.

[NakedViffer]

Its not the relay that shuts the pump off while the bike is still running, because there is no pressure sensing control circuitry anywhere on the bike.. Its the design of the pump. They used a real weak pump, that can't pump any real static pressure, so as soon as the pump gets a little resistance in its flow it stops because its not powerful enough to continue pumping. The pump you bought I'm sure is designed to actually hold 3psi of pressure constantly.

[YoshiHNS]

Its not the relay that shuts the pump off while the bike is still running, because there is no pressure sensing control circuitry anywhere on the bike.. Its the design of the pump. They used a real weak pump, that can't pump any real static pressure, so as soon as the pump gets a little resistance in its flow it stops because its not powerful enough to continue pumping. The pump you bought I'm sure is designed to actually hold 3psi of pressure constantly.

Yes. The pump is supposed to shut off on its own from the pressure build up. I think it's only 1 psi, maybe less. Just a hair above standard ATM. The relay just turns the power on or off.

[Guest]

So what problems is a constant 3 PSI pressure going to cause?

[gll429]

Its not the relay that shuts the pump off while the bike is still running, because there is no pressure sensing control circuitry anywhere on the bike.. Its the design of the pump. They used a real weak pump, that can't pump any real static pressure, so as soon as the pump gets a little resistance in its flow it stops because its not powerful enough to continue pumping. The pump you bought I'm sure is designed to actually hold 3psi of pressure constantly.

whoops your right.. the relay is to let the pump run while the motor is turning.

[greatwhite]

While I've never found the info anywhere nor taken a pump apart, I'm willing to bet the OEM pump is internally regulated for pressure. When my float needles wouldn't seat, you could feel the fuel pump ticking away and happily dumping fuel overboard. Once the carbs were cleaned and the needles seated, the pump ticks until pressure is reached and then stops. Once running, you can feel the occasional "tick" to top off the bowls. If it was jsut a weak pump, it would continue to tick even when it dead headed. The fuel pump serves another purpose besides feeding the carbs, it's the fuel shut off in a crash. Engine stops, pump stops, no more fuel leaking. At least that's the theory behind it....flawed as it may be (we are talking about early 80's tech here after all)

There's also the option of gravity feed, as you already know.

The only issue you could run into with you non OEM pump is the pressure forcing the needle off the seat against the pressure of the float when the level is full.

If it's not doing it now, you're probably fine.

I extended the fuel overflow line from where it stopped above the air box (!) to the tail and gave it a little down turn. Or you could do something similar by extending the drain line down under the bike where the battery drain is.

With the lines extended top the tail, any over fuel will dump on the ground and you can turn the bike off if it happens rather than pour fuel all over the bikes internal bits or tires.

Only problem with under the engine is you might end up puking fuel on the rear tire and then maybe a nasty surprise when you lean it over.....

Lines are only going to cost a few bucks.

I extend all the drain lines on all my bikes to a place where it won't do any harm if they puke.....unless you're the poor sucker staring at my bike's tail light that day.

;)

[NakedViffer]

I wish I hadn't have thrown my stock pump away or I could've opened it and showed you pictures.. Your theory makes sense, and something like that would work great, but you need to look at the whole picture. This is a carbureted motorcycle made in the 90's, it was even affordable. Which gives reason that it wouldn't be anything complicated like that, if it was, it would have been pretty advanced for its time and every magazine would have written about it.

You may even be right about it stopping at a given psi, but its only because the pump stalls from lack of strength at a certain point. And like I said before, I believe this pump is more flow only, and not very capable of pumping static pressure. I played around with mine for quite a bit while it was working intermittently. I had leads from it going straight to 12v and it was easy to see how it operated when going from empty bowls. It would power on and operate at a good pace, then after a few seconds as the bowls filled and it saw resistance it bogged down until it chugged to a stop. And you are right, you will notice it tick 'on' here and there while the bike is running, buts only because fuel is drawn from the bowl thus relieving some of the pressure its fighting and allowing the pump to top up the float bowl a little till the needle closes the feed again.

[greatwhite]

Entirely possible, like I said I've never taken one apart.

It's completely beliveable that it's simply a deadheaded electromagnetic diaphram style pump.

Pretty sure it's not a rotor pump.

At any rate, the OP should be fine if the replacement pump doesn't have enough pressure capacity to force the float needles off thier seat.

I'd still make sure the overflow lines were out from under the seat though...cheap insurance.

[YoshiHNS]

Using the higher pressure fuel pump you're going to force too much fuel in the carbs. If all goes well, it should pour out the overflow tube, but the engine will still be running rich. Maybe enough to foul the plug. Safe to say it will run below optimal.

If you don't want to swallow the bill for an OEM pump, might have to start looking aftermarket. Not going to be an easy search though. Suggest you go back on gravity feed if you want to be 100% safe.

[Guest]

Today it finally ran too rich and killed itself. Let it crank for a bit with the pump unplugged to clear out everything then it lasted long enough for me to get home. Serves me right for tryin to go cheap with the pump lol. Ill be on the lookout for a pump and run gravity in the mean time I guess. I found an oem on EBAY for 150. Should I jump or can it be had for cheaper if Im patient?

You guys have been very helpful as always

[DaveM]

If it's made like the old Hurricane/CBR pumps there is a pressure switch built into the end of the pump housing. If you still had the old pump you could probably bring it back to life by pulling the cover and lightly filing the points. If gravity is not doing it for you, the F/2/3/4 pumps are interchangeable. I bet it will interchange with a VFR too (though I've never seen the early VFR pump). CBR pumps are abundant on eBay - $50 - $100 bucks.

[Guest]

So looking at CBR pumps, the only difference seems to be a hose coming out of the top (Vac?). Searches have yeilded many people who think the CBR pumps might work but nothing sure enough for me to blindly buy another pump.

VFR Pump:http://www.ebay.com/itm/320980606108?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

CBR Pump: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&vxp=mtr&item=160886448483

Any insight on that? The CBR pump would save me like 50 bucks.

Ive also found a similar type pump for a suzuki without the hose and same hose configuration: http://www.ebay.com/itm/160885020002?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

[DaveM]

I think the hose on the back of the F4 pump is a breather tube for the pressure switch mechanisim. Did you happen to see these on ebay?

http://www.ebay.com/itm/FUEL-PUMP-Honda-CBR600-CBR900-893-GAS-UNIT-ELECTRIC-ASSEMBLY-/180852305263?pt=Motorcycles_Parts_Accessories&hash=item2a1ba32d6f&vxp=mtr

Brand new for $60

[gll429]

if you look at the vfr pump it has that short rectangle plastic bit at the bottom of it.. its a VENT.. ditto for the long tube on the cbr..

i have swapped them out before and they will work just fine,

[JZH]

The FACET solid state pump I have on my FP comes in several pressure ratings. I used a low-pressure one, but there may also be an even lower pressure version. The engine shouldn't need much pressure, considering that it (almost) runs perfectly on gravity...

Ciao,

[greatwhite]

I would think pressure is not your problem while the levels are down, but a problem when the floats shut off the needles. Without a pump shutoff, that 1-2 psi is most likely enough to overcome seat pressure....running rich and dying seems to support this.

Just kicking ideas around....

[Guest]

Good find DaveM, I ordered that so my problems should be over in a week or two.

And yeah, I actually ran out to dinner the other night by switching the tank petcock to off every so often to keep the bowls from over filling. So lesson learned and hopefully others find this thread before buying the wrong pump lol.

[Guest]

I could really use some help and this appears to be a similar topic. My bike stalled out on the freeway and sputtered to a stop after I installed a new fuel pump two months prior. I removed the rear plastic hoping to find a loose hose but didn't find much apart from a very hot pump. Naturally, I thought it was the pump and ordered another under warranty. Installed it and rode about 15 mins and it died again as if it were slowly running out of fuel. After reading your comments and testing both new pumps by running the bike and hearing the clicking noise I'm thinking it's the relay.

Is the best method to bypass the relay by bridging the black/black & blue wires and then riding for 15-20 mins to see if it dies? I don't mind this as a permanent fix as long as the bike stops dying on me.

Few things:
Fuel light turns on when I turn the ignition key.
If I let the bike sit for 20-30 mins it'll fire up again no problem for <15 mins.
Bike is a stock '94.
I bought an aftermarket pump from ebay so I'm not sure if it's pumping too much and flooding the float bowls or if that's even possible. I find it very unlikely that two pumps failed within 2 months of each other.
Last thing: the bike started acting up about a week and half prior to it dying. It took a little more throttle to not stall at a stop light after ~ 25 mins of riding, and the fuel delivery felt just a bit lean.

Thanks!

[YoshiHNS]

Jump the relay right out. Leave everything plugged in though. One of those wires affects your #4 coil IIRC.

[PFox]

So, if I understand the above posts correctly, a contemporary CBR pump will work on a 700?

I'm having a surging/stuttering issue at anything above 4500 RPM, or high loads in general. Cracking the choke a little smoothes it out, but won't completely get rid of it. I'm thinking fuel pump is going out on me?

[gll429]

it could be the pump.

or it may be the carbs..

pull the top of the airbox and the filter and run the bike. look at the slides and see if all are moving.

its also possible that one or more of the choke (enricher really) plungers are stuck. check them all and lube them with a DROP or 2 of oil.

and NO it's not from the carbs being out of sync. that only helps down near idle.

its also possible the fuel line is PINCHED so check that and fuel filters too.

[PFox]

Thanks. I checked the valve adjustment not more than 500 miles ago, did filters and oil then too. I'll run it to check the slides, they "felt" fine when I was in there.

I know they're enrichment valves, but it's so much easier to say "choke" that I forget. Standard engine oil or something lighter like air tool oil? I have both.

I really don't want it to be the stupid carbs. I know it's not bad, I just hate working on carbs.

[gll429]

tool oil would be best.

one of the slides may not be installed perfectly thats why you need to run it and check .

[PFox]

tool oil would be best.

one of the slides may not be installed perfectly thats why you need to run it and check .

Wouldn't an improperly installed slide show up well before now? The stumble started two days ago when I filled up the tank. My initial thought had been bad gas, I'm going to top it off from my good source tomorrow, and I have a bottle of cleaner in there as a "shock" treatment.