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Fuel issue


Go to solution Solved by Dsluder,

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Posted

I am having an issue with a hs500. I bought it broken and have been trying to get it running. It seems to be starving for fuel. If I put my hand over the intake it will crank but will not run for very long because I'm not able to get the correct airflow with my hand. The things I have done so far are. Replaced the fuel pump, fuel filter, mass airflow sensor, idle air adjuster, fuel injector, cleaned the throttle body, replaced the ecu, and still the same issue. I notice the injector does not spray when removed from the head. I dont know if that is common. 

 

I am out of ideas on what to do next. I have removed the fuel line from the injector and it is getting plenty of fuel. If anyone has an idea on what could possibly be the issue I would be happy to try anything at this point.

Posted

Is this HS500  an atv or utv ? Does it have any other designations.. such as HS500atv-2, HS500atv-Bruger..  There are quite a few options in atv and utv.. all called HS500***

Posted

This is a utv. I need to look up the vin again to see exactly what model. It is an older machine.

The pump runs when the key is turned on. I haven't checked the pressure but did replace the pump. I wanted to eliminate that issue first. If I put 12 volts to the injector it sprays fine. The injector is also new. I don't have a service manual. I see there is one for download on this site so I will get that downloaded. The last possible issue I can fathom is a faulty harness. 

 

Posted

Ok. If any of the wiring is broken it should set a trouble code in the computer and flash a light at you... I should think. The exceptions are if the power supply or the earth to the ECU (computer) fail, then the ECU can't record a code because the power's off.. So the manual will say to check the earths and the power supplies, and it could have several of each going to the ECU.

Then, we generally look at the mechanical side of things, so a stuck injector, faulty pump or regulator, in some vehicles something like a broken key on the crank so there is no signal coming out of the crank angle sensor.. stuff like that.

I'll have a look at the manual later..

Posted

Actually..  Just reread and realised it ran when you put your hand over the inlet..  You should check for air leaks into the inlet manifold, and possibly leaks in the inlet hose between the air-filter and the throttle body(depending on sort of sensor it has)..

I'll get onto the manual later.. when the day's too hot for work.

Some idea of the year would be good too because I see there are HS500utv, and HS500utv-5..  And possibly 2,3,4 models as well..

Posted

Well I didn't get far reading up on the manuals I had, they were mostly carb models. I did find an owners manual though for a HS500 that was fuel injected and it had a trouble code for something called FPR.. which I'd guess could be fuel pressure regulator.. I'm guessing your bike isn't flashing it's dash at you and so it's not likely that a fuel pressure injector would have an electrical problem, but the regulator might be seized up.  I'm not sure that FPR does mean fuel pressure regulator, but every other code and it's abbreviated name  I recognised.

Also not sure a fuel pressure regulator problem would respond to your hand being over the inlet like that either. If the regulator is adjusted and sensitive to vacuum, it should work the opposite way. Generally when there's a load on the engine, and we open the throttle causing the vacuum to drop, the fuel pressure needs to go up.  When the manifold gets more vacuum(your hand over it), it should lower the pressure..  All just assumption that it is a pressure regulator, that it is controlled by vacuum, but the only lead I found..

We really need a manual...

Posted

I looked up the vin and it is a 2012 hisun 500. Didn't get any more info from it than that. I included it below. Not sure it will help. 

A manual would be great! I could check grounds and see if that may be the issue. At this point I think I'm going to get a new harness and see if it is a wire issue. My only hesitation with that is the harness only plugs in and if it is a ground issue it will not help. 

20250205_171418.jpg

Posted

The easiest test is to leave it plugged in and check from all  the positive power wires going in to all the earths coming out. You do it with the key off and then with it on to test all the power wires. The trouble is, without a wiring diagram we wouldn't be sure we'd actually identified all the power wires just by colour.. The plug may be water proof too and need a bit of tweaking to allow access to the terminals to check the power etc.

I don't really think the power or earths are going to be it though if it ran briefly when you had your hand over the inlet.

I wonder if the brief run was brief because the fuel pump had only run to prime the system when you'd turned the key on, then switched itself off, as it's meant to do, but then didn't turn on like it's meant to when it got the  crankshaft rotation signal that is meant to keep the pump running when the engine is running. 

You could experiment with that idea in mind. Keep trying to start it and see if it always starts then runs out of fuel pressure  and dies no matter what the revs or hand position, after some small time.. And you can generally feel the pressure they run at by holding the fuel hose somewhere that's going to be pressurised, and then turning the key on. You'll hear the pump and feel the hose stiffen. After a second or so the pump will go off and the hose should probably stay pressurised for some short time.. ten seconds say.. maybe less.

Test it, see if you think it's firing up with a bit of restricted air and the fading pressure from the prime.   Or.. Find the fuel pump relay and hot wire it so the pump runs all the time, except for when you switch it off of course as soon as you stop the engine.

Posted

I did order the wiring harness. Found it on ebay. I will definitely give the fuel system a good once over also in the meantime. I changed the fuel pump in hopes to solve any of these issues. It wouldn't be the first time I have received a bad parth though. I have a fuel pressure gauge I can insert at the injector to see what kind of pressure is making it to the injector. 

I did take the plug aprt for the injector in order to test the amount of voltage at the plug. I wasn't able to get a 12V reading. Best I was able to get was 10V without a manual I'm not sure if this is an acceptable reading. I did test the injector with 12V and it worked properly. This is what led me to change the ECU. Unfortunately after changing it I am having the same issue.

Are there any procedures for resetting the ECU?

 

 

Posted

I don't know much about Hisun.. Most ecu go through a self diagnosis and reset when the key's turned on. Ecu do learn and adapt to changing compression, dirty air filters etc, and that learnt modification of the tune is sometimes set back to original base line settings if you disconnect the battery for some time. I doubt that's what's needed though.

The 10v is not sounding right. Most injectors get supplied with 12v and then they get earhed in the ecu when they want it to inject. Injectors are sensitive to voltage to the extent that they adjust the injection timing and duration to compensate for the normal range of voltages between about twelve and fourteen point seven. Without the compensation the injector would inject more fuel at high voltages. That said though.. they do inject right down to slow cranking volts, which can be as low as nine volts. It should squirt at ten volts I would think. I'd look why that voltage is so low though. Some injectors have a relay to supply the voltage, and others they just feed the ignition/key power to the injector, and others again get sent their power from the ecu. And it's possible some injectors have a permanent earth and get power from the ecu when it's time to inject.

The fuel hose should have about 50Lb in. I'd test the pressure, check all the power supplies and earths to the ecu,  and check why the injector is only getting the ten volts. .Once you've found one earth it's a good chance any other wires of the same colour will also be earths, and the same will probably be true for the power.

Posted

Thanks! I'm going to get back into it this weekend. I will update once I've gotten these checked. Maybe I can find a solution so the next person with this issue will not need to beat their head against the work bench for as long as I have. Lol

Posted

I was looking for a atv manual for the same engine, and fuel injected, in the hope the wiring etc might be the same or very similar, but i could only find carb models.

A manual is what you need. All my suggestions are just based on some of the common efi systems and principles we find in the rest of the auto world..

Does this utv use Bosch components by any chance ?

Posted

I haven't seen any Bosch components. I looked for any earth's today and only found 1 main ground to the motor. I did disconnect and clean. 

Still same issue. Fires right up with intake blocked. Won't start otherwise. 

Posted

And does it start repeatedly ? And can you get it to run any longer by carefully managing your hand ?

Have you held the fuel hose and checked it has pressure ? Does the pressure drop while it's running, or does the hose stay stiff right till the engine has stopped running ?

  • Solution
Posted

It is finally running. 

I replaced the wiring harness and now it fires right up. In the end I replaced pretty much the entire fuel system. I replaced the harness yesterday and was having the same issue. Tonight I replaced the fuel lines and fuel filter ( filter was new) and while trying to prime the lines I found out the new harness had the fuel pump wired backwards. Once I swapped the wires and primed the system it fires right up. I increased the idle a little and it runs pretty well for sitting up for a few years. It has about 1600 miles on it so hopefully it will keep going for a while. 

I'll change the oil and get it put back together to see how well it runs under a load. 

I appreciate all your help and I hope anyone else having this issue finds this post helpful. 

Harness was 80 dollars on ebay. Took about 30 min to swap out. Hind sight I wish I would have tried that a while ago. 

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