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Fuel Pump Intermittently Priming (maybe solved)


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I have 2020 T-Boss that's been pretty rock solid up until now.   

I haven't driven it in a few weeks so I went out to start it and it wouldn't start initially.  After about the tenth try, it cranked and ran perfect. After shutting it down for a few minutes, it wouldn't start again.  I started thinking maybe it was the injector but that didn't make sense.  Then someone mentioned listening for the fuel pump to prime with the engine off but the key on.  After about the tenth try, the pump would prime and engine would start.

Sounds more like a bad connection somewhere than a bad pump right?  If the pump was bad, it wouldn't prime or run.  Problem is, I can't find where any of the wires coming from the tank, terminate.  They're all wrapped up and merge into a larger set of wrapped wires.

Also, under the hood I couldn't find a relay or fuse for the pump.  Are they somewhere else?

I'd hate to just throw a new pump at it and have the problem persist.

 

Thanks

 

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The fuel pumps on these vehicles are generally prettuy stupid devices, their only job is to keep fuel line pressure around 43.5 psi (3 bar¹). When powered up they just run 'til the line pressure is as desired then shut down until the pressure falls as the engine consumes fuel. They are not intelligently monitored or commanded. by the ECU--they just do their thing if there is sufficient pressure in the line when powered up  they will not run, I think this is what you are observing. To test it you'll need to monitor the fuel pressure and make sure the pump runs when the pressure is less than 30 psi or so. Or divert the fuel line to a container and make sure the pump runs continuously with the key on--be careful though, at 40 psi gasoline can spray everywhere.

How many cc is your t-boss? As a 2020 it is a LInhai under the Massimo badges--I do not have much info on the Linhai machines yet. However the fuel pump relay is likely a little black box in the fuse block.

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¹ - 3 bar (43.5 psi)  is the pressure standard for fuel injector capacity ratings--most vehicle makers supply them with that pressure.

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  • 2 weeks later...
9 hours ago, TapBoss said:

Hey Cliffy,  he's got a slightly different model 550  than mine so 493cc.

It is most definitely a Linhai-550 then...

I wish Massimo (and others) would stop doing that--493 cc is at best a "500", stretching it to 550 in the model designation is a bit much. Years go I has a BSA 441 Victor. guess how many cc displacement it was?

1969-bsa-441-victor-760x570.jpeg.4fd451e1e521ad66527d948fa6525b02.jpeg

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4 minutes ago, cliffyk said:

It is most definitely a Linhai-550 then...

I wish Massimo (and others) would stop doing that--493 cc is at best a "500", stretching it to 550 in the model designation is a bit much. Years go I has a BSA 441 Victor. guess how many cc displacement it was?

1969-bsa-441-victor-760x570.jpeg.4fd451e1e521ad66527d948fa6525b02.jpeg

The engine in my Mule is a FE290 though it's 286cc....

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  • 3 weeks later...

Finally got around to messing with it.

Pulled the hose and cranked it to see if fuel would spray out and it did not.  Assumed it was the pump so I replaced it and now the second pump isn't spraying either.  I could hear it priming when you turned on the key when I first got the machine, nothing out of either pump now.  Guess it's a power issue.  I've already looked at the fuses and the relays.

Any suggestions on where to look next?  I tried jumping the fuel pump ground to the frame with no luck.  I have a call in to Massimo tech support, he thinks it's a relay but unsure of which one so he's supposed to get back with me.  

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  • Rustynutzz changed the title to Fuel Pump Intermittently Priming (maybe solved)

Finally spoke to the rep and there is an relay for the fuel pump, it's just not under the hood with the rest.

It's sitting just above the fuel tank with an plug attached to it, all covered by a rubber housing.  I pulled the plug out and it was corroded.  New one is on the way, I'll update when it gets here.

IMG_20210503_184737.jpg

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