By Rusty Beavers
I'm working on a Coleman UTV 400 that has a rough idle, owner has had it for about a year. When I say it has a rough idle, it doesn't have the continuous smooth running sound. At times you can hear it kinda skip, sputter, or like the RPM has fallen (RPM stay constant according to the gauge) It's not as bad as it was after I replaced the fuel filter and fuel injector (both are Chiki) not sure if that is a quality brand at this point. Checked the spark plug, it was a little foul, but not too bad. (Since the engine is still idling bad I'm going to replace that) Cleaned the throttle body making sure the carbon and soot has been removed, and the air-filter has been cleaned. New fuel is being used so it's not old or been standing. They did tell me that they were using non-ethanol fuel, not sure if that would be causing the issue. Next two things I can think of that maybe the issue is the O2 sensor or the valves need adjusting.
Thoughts and suggestions? Thanks in advance.
This post will explain how to hook up your PC to the ECU of a Hisun/Coleman/Etc UTV to be able to read error codes & engine parameters for troubleshooting purposes.
This is applicable to all small engines using the Delphi MT-05 ECU. This should cover all fuel injected Hisun models, as well as various other Chinese FI engines, as the Delphi MT-05 ECU seems to be the favored ECU solution.
Even though we get actual engine error codes to display on the dash, sometimes we have “pending codes” (not yet confirmed by the ECU) or other intermittent issues that are hard to diagnose, for example a poorly connected sensor that may give intermittent false readings, or a sensor that’s putting out bad date, but not bad enough for the ECU to realize.
The setup requires 2 cables, which are available for around $25 combined, a PC with a USB port, and some charityware software called “HUD ECU Hacker”. This gives the same functionality as the $300 dealer code scanner for a fraction of the price.
In searching I found info about HUD ECU Hacker, but I have yet to see info anywhere about how to hook it up to a Hisun, so I took the leap and bought some cables, and made it work. I will show a step by step of how to do so in post two.
I will be breaking this down into 2 posts:
Delphi ECU Info & Overview (This post) System setup & use Delphi ECU Info (Skip ahead to the next post if your eyes glaze over technical details)
The Delphi MT-05 ECU was developed to allow small engines to use fuel injection. A fuel injection system requires feedback from various sensors to operate efficiently. This feedback allows the adjustment of ignition timing, fuel injection volume, etc to efficiently and cleanly produce the most power possible from a given engine.
The MT-05 ECU has a number of sensors that are required for proper functioning including; Coolant temp, crankshaft position, intake temp, intake pressure, exhaust O2, throttle position, as well as some other optional sensors that are used on more complex vehicles.
From the sensors the ECU adjusts: Fuel injector timing/pulse, Idle air control valve, and ignition coil
The Delphi MT-05 puts out diagnostic data, however it is not ODB2 like a modern car, where is where it gets tricky reading it. There are three options, there is an old 16 bit piece of software Delphi has that is not able to run on a modern computer, there is the motorscanner tool for dealers ($300), or there is freeware HUD ECU Hacker with the proper cables.
I installed a new GY6 150cc engine in a Bull Dog Pup 200 and when I put it in drive, it grinds for a second and then runs fine. Works great when i place it in reverse. Could it be from it idling too high? Any help would be greatly appreciated.
I have a Mule 550 (FE290D engine) that sat for several years and would not start. A few years ago I replaced the fuel filter and carburetor, at which point it started right up and developed full power. More recently, I've changed the air filter, fuel pump, ignition coil (gapped to spec), and spark plug, and adjusted the valves. The engine still has a lope/surge at part throttle and at idle. Rather than idling at a stable speed, it speeds up and slows down until it quits. It snaps to life right away if I open the throttle, so I don't think it's starved of fuel. I can always get it to restart immediately if I choke it while cranking, then it will die after several seconds again. It takes some cranking to start hot when not choked. I've tried adjusting the idle mixture, but no setting seems to make it stable. It won't idle at all with the throttle fully closed; I have to turn the stop screw to hold it slightly open.
I suspect it's getting idle air, since the passages are open, but that the idle jet isn't providing adequate fuel, such that I am having to hold the throttle open and idle it off the main jet which isn't stable. This is just speculation. I've cleaned the idle jet and tried a larger size, but it made zero difference. The carburetor seems to be clean. It's been doing this since I installed the new carb. The gas tank seems to be clean, although it's hard to see inside.
I posted a video of what it's doing:
What's next? Try another carburetor?