Old Style Fuel Pump Runs Too Much, Too Often

[SpecOps13]

I've been fighting this on my 89 for some time. When I turn the key on, sometimes the fuel pump runs for the given 5 seconds as the older model Max's will. Sometimes it will go click, click and be done.

Once the engine is at operating temp, I can turn the key on and off a dozen times and it will normally run the fuel pump for the 5 seconds each time. I've had the air box off and watched. It doesn't overflow. I reinstalled the valve cover plastic shield on the rear cylinders in an attempot to block some of the heat. Seems to be of no help...

I've been through the entire fuel system including opening the fuel pump to verify that everything is in place and in good shape. Everything in the fuel system has been cleaned or replaced.. The bike is finally running great but this and a few other minor things are driving me nuts.

Others have said their older Max's do or had done the exact same thing. CaptainKyle said one of his drove him crazy but he never found out what caused the pump to act this way..


Help!!!! Somebody's got to know more about this........

 

[jfeagins]

You say you inspected inside the pump diaphram end and that BOTH little black rubber valves are in place - and no minute bits of unwanted contaminates are stuck in there anywhere?

If so, and it's all good, then I'm stumped why your pump would re-run that long each time you turned the key on. Those fuel lines should stay pressurized for longer than that. Unless, maybe, you've got a needle/seat thing going on in at least one carb and just aren't able to see the gas when it flows over.

 

[SpecOps13]

Yes, everything in the pump was in place, good shape and clean. It normally works right except when the bike is warmed up. Even then sometimes it works as it's supposed to....:ummm::ummm::ummm:

 

[ninjaneer]

so i'm confused, is a normal pump suppose to run for 5 secs? i have no reference. it seems like my '04 does the same as yours some days it primes up for 5, other days (maybe time of days) i turn the key and vvVV done. i've never paid it no nevermind--thought the erratic behavior was "normal" so to speak? dunno.

 

[one2dmax]

The pump is designed to run under a few conditions.

1. There must be power (duh). There is forced on power for 5 seconds when the key (or kill switch) is first turned on. This activates the timer/relay. If the bike is not running (with a signal from one of the cylinders) then the relay shuts off and shuts off power to the pump. This is one of those things to help prevent fuel from being pumped in a crash condition.

2. Once there is power it will only run until it reaches operating pressure. So, lets say you let the bike sit for an extended period (a few days is enough sometimes) or you just got done rebuilding the carbs. The pump will run fast for the entire 5 seconds as it's trying to fill the blows and reach pressure. In the case of a carb rebuild it will do this a number of cycles (turning the key off and on) until it fills and reaches pressure.

Once the bike has been started and or the bowls filled and line pressure achieved the pump will not run again until some fuel has been used or pressure relieved (by a possible leaking diaphragm). So, the next time you shut off the bike and or restart it within a short period of time the pump will maybe only click once, twice, or none at all.

If the pump continually runs all the time or never slows down and stops, then it's not building pressure. This could be an air leak at one of the hoses, filter, stuck float, stuck or bad needle, or simply a worn out pump. Sometimes the small diaphragms internal to the pump become displaced and then it can't hold pressure. Much like there are two valves to each half of your heart there are two for the pump.

We've seen pumps that appear to be fine but exhibit the symptoms you are describing. Sometimes they don't effect the performance and sometimes they do.

Hopefully this will clear things up a bit.

 

[ninjaneer]

cool thanks sean. :thumbs up:

 

[SpecOps13]

Sean, that was a fantastic explanation, as always. Thanx.:biglaugh:
If this continues can you recommend a readily obtainable Automotive Fuel Pump that would work and could be used?


With this 89, I've been through almost every scenario of failures possible, even the leaky lines. I'm all but a thousand percent sure that all the peripheral stuff is good right now. This problem persists when the bike is warm or hot, the pump just doesn't want to quit. When I put my hand on the pump after the warm bike starts, I can feel that the pump is still running. If I turn the key off and back on, it runs for 5 seconds again and again with each cycle of the key. As I said, nothing overflows. Let the bike cool down and normally it will go Click, Click and stop...:confused2::ummm:

Thanx to everyone for inputs...

 

[Miles Long]

I've been fighting this on my 89 for some time. When I turn the key on, sometimes the fuel pump runs for the given 5 seconds as the older model Max's will. Sometimes it will go click, click and be done.

Once the engine is at operating temp, I can turn the key on and off a dozen times and it will normally run the fuel pump for the 5 seconds each time. I've had the air box off and watched. It doesn't overflow. I reinstalled the valve cover plastic shield on the rear cylinders in an attempot to block some of the heat. Seems to be of no help...

I've been through the entire fuel system including opening the fuel pump to verify that everything is in place and in good shape. Everything in the fuel system has been cleaned or replaced.. The bike is finally running great but this and a few other minor things are driving me nuts.

Others have said their older Max's do or had done the exact same thing. CaptainKyle said one of his drove him crazy but he never found out what caused the pump to act this way..


Help!!!! Somebody's got to know more about this........

Looking at the Clymer,manual, the difference in the fuel pump electrical circuit,'85-'92 models compared to '93 to present, is that the earlier models do not incorporate a "starting circuit cutoff relay". This must be the "relay/timer" dodad that Sean mentioned in his reply. In any case, your '89 doesn't have one. Maybe this explains the erratic behavior, corrected by Yamaha eventually?
Have you tried swapping out the pumps, using the '94 one in your older bike, providing they are interchangeable?(if not, another older style pump) If swapping doesn't cure the problem, it would have to be in the circuitry. Have you done the troubleshooting for the earlier fuel pump and circuits, as outlined by Clymer?(page 46 and 240-242)
Cheers, Miles

 

[SpecOps13]

Miles, I've decided that swapping from a good bike to one that's malfunctioning will give the result of 2 bikes with problems.:bang head::rofl_200:

Anyone have an aftermarket fuel pump suggestion????

 

[one2dmax]

I haven't tried an aftermarket pump yet. Looking at 3psi or so. All years have a timer in them which does the 5 second run if first turned on and no/low pressure is present.

 

[SpecOps13]

Thanks Sean...:biglaugh:

I was out riding tonight and after the bike was warmed up, it started to run on 3 cylinders.
Had some trash in carb 2, holding the inlet open and overflowing that carb. Cleared that, tested
the Plugs, Fired right up on 4 cylinders... Pump was then acting like it's supposed to, again... :ummm:

Devious POS Bike....:rofl_200::rofl_200::rofl_200: