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Megasquirted [Megasquirt 2 V3] crossflow suddenly running rich


GaryH
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1700cc with GSXR throttle bodies. Been running fine for ages - suddenly the day before MOT [i reckon they know...] it [definitely an it at the moment] began running ridiculously rich, lumpy, stalling on throttle press, sooty plugs and black smoke from the exhaust just like putting massive jets in a carb car. Cancelled MOT as wouldn't have passed even a visible smoke test!

 

Connection to Tuner Studio shows tps gauge "in the red" with needle doing full cycles i.e. car running at 100% throttle all the time. Wouldn't recalibrate as values just kept climbing always ending with no difference between open and closed throttle - hence 100% fueling all the time.

 

Waited a week for new GSXR tps from Suxuki dealer. "Passes" multimeter resistance test - shows gain/loss of resistance from closed to open position when turned with a screwdriver off the car, but exactly as paragraph above unable to calibrate new sensor when it's connected to the car.

 

Have renewed the relay board switched and non-switched power supplies, earth post and all ground connections to it so shouldn't be a power or earth issue.

 

Today, new problem, while double checking all the above the Tuner Studio temperature gauge climbed with a cold engine to fix at 80o C, even with the CLT wires disconnected it stays there. Wires to temperature sensor pass continuity test with multimeter, but again not able to get any calibration with Tuner Studio. Like my head tps gauge is still spinning full circles.

 

Any ideas? I'm beginning to think that the relay board, or worse still the ECU is in the way out.

 

Gary

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Sounds earthy, most weird electrical problems are, but are you able to check the voltages at the ECU end, just before they get into the ECU?

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An open circuit on the coolant sensor will give a high reading like that. Megasquirt uses a separate sensor earth for all the sensors, including tps and coolant. The megasquirt online manual for the version you have will tell you which pin from the ecu it is. The idea of this is to eliminate interference and weird different ground potential effects. This and the other earths for the injectors, coil pack, etc should be checked for a good connection to battery, or chassis. It is possible the tps and coolant sensors are earthed to the engine, which is bad practice, but check the engine earth too. If the coolant sensor is single pin, rather than two pin, then it will be earthed via the engine block and ground strap. Megasquirt installations are very dependent on the quality of the wiring loom and how earthing and shielding is handled. Also try removing and replacing the ecu plug and check the contacts each side for signs of corrosion.

Jen

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Hi all.

I agree that most electrical issues are earth related. The ground from the relay board is connected to a now new bolt, in turn I've put a new earth strap between it and the earthing bolt on the chassis cross rail on the engine bay side of the scuttle. Also replaced the engine earth strap that also bolts here. So far concentrated on chassis/relay board earthing. Will have another go when my patience is back!

Coolant sensor is two pin. Lots of previous soldering to check over, have already had to remake a few joins - can feel a heavy investment in heat shrink coming on.

Will have a look at the ecu as suggested by Jen, have got manual now so see what's next.

Thanks for help so far.

Gary

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If you continue having problems, try connecting the various megasquirt earths directly to the battery negative terminal, rather than an earth point on the chassis. Also, keep the sensor earth and other megasquirt earths apart right up to the battery -ve connection.

Jen

Edited to add:

I've been re-reading some of the megasquirt stuff.

The sensor earths, tps and coolant temperature included, all go to a specific sensor earth pin on the megasquirt connector, not to ground points elsewhere. As both your tps and CTS readings are playing up, I strongly suspect this is the area to look at first.

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Hi all, especially to Jen for manual reading, thank you for your advice. I have a happy son and daughter as our project Westfield is mended.

Went through the wiring and remade every earth point and every soldered joint that I could find, including some of the pcb connector fixing points.

Tps and temp gauage now fine, recalibrated and the engine is running smoothly again, "she" is better.

Thanks again.

Gary

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