How to test fuel pump output volume


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WingAdmin
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How to test fuel pump output volume

Post by WingAdmin » Thu Oct 30, 2014 11:41 am



When the engine uses up fuel from the gas tank, that fuel has to be replaced with air. The gas cap has a vent in it that lets a small amount of air in as required. Over time, this vent can get clogged, usually with fuel deposits.

When the tank is nearly empty, there is a large amount of air in the tank. Air is easily compressible, so the fuel pump doesn't have an overly difficult time pumping gas out and creating a slight vacuum in the tank as a result. The less fuel in the tank (i.e. the more air) the easier it is to pump fuel out, decompressing the remaining air (relative to outside atmospheric pressure).

However, you go to the gas station and fill up. Now there is very little air left in the tank. The pump tries to pump gas out of the tank, but there is almost no air volume in the tank to expand, and fuel sure doesn't expand under pressure. The end result is that the volume of fuel the pump is able to pump out is severely restricted. The engine starts running lean, so it bogs down.

You switch the choke on, which enrichens the mixture, so this helps, but eventually there just isn't enough fuel to run the engine properly.

If you let the bike sit for a while, eventually enough air leaks through the gas cap, and the bike will run again - until more gas is pumped out, and the problem occurs again.

This is easy to diagnose: Next time this happens, loosen the gas cap. If you get an inrush of air, and the bike suddenly comes to life, then you know that this is what is going on.

Sometimes this is a combination of several issues: clogged gas cap vent, clogged fuel filter and/or weakening/failing fuel pump. One on its own might not be enough to produce symptoms, but two or more at the same time can cause the bike to bog down or quit altogether. You might clean or replace the gas cap, only to find that a few months down the road, the fuel pump dies completely.

If removing your gas cap does bring your bike back to life, take it off and let it soak in a pan of Seafoam overnight. A lot of times this will fix the problem. You can also try boiling it in a pot of water for a while. Either way, you might want to do a fuel pump volume test to ensure it is operating correctly:

Fuel Pump Operation Test
Remove the right fairing inner cover.
Turn the ignition switch OFF.
Disconnect the engine control module connector.
Short the BLK/WHT and BLK/BLU wire connector terminals with a jumper wire.
Fuel Pump Test 1
Fuel Pump Test 1
Disconnect the fuel pump outlet line at the fuel filter. Hold a graduated beaker under the tube.
WARNING: Keep gasoline away from flames or sparks. Wipe up spilled gasoline at once.
Turn the ignition switch ON, let fuel flow into the beaker for 5 seconds, then turn the ignition switch off.
Multiply the amount in the beaker by 12 to determine the fuel pump flow capacity per minute.
Fuel Pump Minimum Flow: 640 cc (21.6 oz)/minute
Fuel Pump Test 2
Fuel Pump Test 2



donny475
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Re: How to test fuel pump output volume

Post by donny475 » Thu Apr 20, 2017 10:13 am

Are we to jumper the two wire on the plug or on the ECM? I tried the plug and turned the key on-nothing....should we be hitting starter too? Mine is a 1996 SE. Thanks in Advance..

edit to post.......must have kill switch in run position :lol:

bluthundr31
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Re: How to test fuel pump output volume

Post by bluthundr31 » Wed Jul 12, 2017 12:17 am

When I tried to disconnect the ECM cable, the black plastic "housing" came off but the connector stayed stuck to the ECM. Does the connector have "tabs" that hook onto the ECM? It doesn't come off easily and I fear that pulling on the wires will damage their connection.

Does the "jumper" go on the "harness" side or on the ECM itself?

The schematic in Clymers says that pins #4, and #21 are the blk/blu and blk/whi wires. I'll jump these two together, then put kill switch in "run" position and turn the key on. THAT should make the fuel pump work and flow gasoline?

bluthundr31
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Re: How to test fuel pump output volume

Post by bluthundr31 » Thu Jul 13, 2017 3:18 pm

I have the ECM connector freed.

The dam terminals are so small I can't get my jumper wire to make a good connection. How did your jumper fit, and can you describe? I've tried jamming multi-strand wires in the correct pins, jammed small solid wire, and sharp point probes but none make the fuel pump flow fuel when the key is on and the kill switch in "run" position.

bluthundr31
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Re: How to test fuel pump output volume

Post by bluthundr31 » Fri Jul 14, 2017 2:48 am

I saw that the manual says that the "stop" switch and the Bank-Angle sensor are linked in with the fuel pump.
I tested the "stop/run" switch and it is operating correctly.
When I tested the Bank-Angle sensor I got unexpected results. The manual says to put the voltmeters black probe (-) on the grn wire and the voltmeter red probe (+) on the red/whi wire to get 0-1 volt. I get 11.5 volts, repeated numerous times to verify I was on the right wire and the voltage reading. When I checked the (-) probe on the grn wire, and the (+) probe in the whi wire, I get 11.5 volts. The manual says I SHOULD get 10-14 volts from grn (-) and whi(+).
Getting 11.5 volts instead of 0-1 volt at the red/whi wire makes me think the Bank-Angle sensor is shot.
NOW I need to figure a way to by-pass the sensor so I can "trick" the system into thinking its fine, and then get the ECM connector problem verified. Anyone have an idea/tip/or suggestion?

bluthundr31
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Re: How to test fuel pump output volume

Post by bluthundr31 » Fri Jul 14, 2017 4:26 pm

I figured out the "jumper" problem. I had two "fork" connectors for 22AWG wire, I cut off one of the forks down to the base on both of them, then i used a short 22 AWG wire between them and crimped the connectors on tight. Its a good connection now and I'm confident I'll get true results from the test.

Still NO JOY on figuring out how to by-pass the Bank-Angle sensor though. I'm stumped trying to figure a way from the schematics, , , , Anyone have a suggestion/tip/trick, , , don't be shy, lemme know. Since the red/whi wire should only have 0-1 volt, I'm thinking i can cut it (to remove that "input") and do the fuel pump flow test to see if the pump works. If the pump doesn't work, that should indicate that the pump is bad, and maybe the bank-angle sensor too. If the pump works I can be sure the bank-angle sensor needs to be replaced.

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Re: How to test fuel pump output volume

Post by WingAdmin » Fri Jul 14, 2017 7:25 pm

bluthundr31 wrote:
Fri Jul 14, 2017 4:26 pm
I figured out the "jumper" problem. I had two "fork" connectors for 22AWG wire, I cut off one of the forks down to the base on both of them, then i used a short 22 AWG wire between them and crimped the connectors on tight. Its a good connection now and I'm confident I'll get true results from the test.

Still NO JOY on figuring out how to by-pass the Bank-Angle sensor though. I'm stumped trying to figure a way from the schematics, , , , Anyone have a suggestion/tip/trick, , , don't be shy, lemme know. Since the red/whi wire should only have 0-1 volt, I'm thinking i can cut it (to remove that "input") and do the fuel pump flow test to see if the pump works. If the pump doesn't work, that should indicate that the pump is bad, and maybe the bank-angle sensor too. If the pump works I can be sure the bank-angle sensor needs to be replaced.
Here's how to bypass the bank angle sensor:

viewtopic.php?f=6&t=28365&p=162699#p162699

bluthundr31
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Re: How to test fuel pump output volume

Post by bluthundr31 » Fri Jul 14, 2017 7:59 pm

Thanks for the info in the BAS by-pass. It'll help alot. GREAT SITE
Just in case I find a decent replacement sensor, I put my jumper after the green connector but before the body of the sensor. That way, a replacement sensor will plug-and-play with no modification necessary. eBay has a few used ones under $20 and new ones $65-130. Safety equipment is great, , ,but only when it works without making matters worse.

bluthundr31
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Re: How to test fuel pump output volume

Post by bluthundr31 » Sat Jul 15, 2017 10:11 pm

Can I bypass the ECM to power the fuel pump directly from the battery by jumping the + side of the battery to the "B" terminal and the - side to the "G" terminal on the disc atop the fuel pump?

bluthundr31
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Re: How to test fuel pump output volume

Post by bluthundr31 » Sun Jul 16, 2017 11:40 pm

I put a jumper from (+) side of battery to the ( B) connector terminal then a jumper from (-) side of battery to ground but no response/sound from fuel pump, AND no gas flow.

I'm going to remove/replace fuel pump ASAP.

bluthundr31
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Re: How to test fuel pump output volume

Post by bluthundr31 » Fri Jul 28, 2017 1:45 am

What circuit/relay activates the brief (2 sec.) fuel pump prime function which should occur as soon as the key is turned on? My pump has no response when the key turns on, and I don't get a brief (2 sec.) voltage spike on the "B" terminal as the key turns on. Is a bad relay the culprit?



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