How do you diagnose non starting issues on Fuel injected motorcycles?

I'm a car mechanic so I thought I'd be able to figure this out.. usually when I test fuel injectors I start with fuses and a diagnostic test to see if there's any fault codes... if there's none I usually get the injectors out and crank the engine to see if they spray fuel onto some paper towels... then i check power wiring and what not but fair to say I've only ran into minor injection power probs... Well I've got a 125cc motorcycle and I can't figure out why it's not starting it's got good spark, no fault codes & the injector fires with a good pulse it just won't fire up and stay running??? Can the injectors be out of timing on these??? Should I look for a crankshaft position sensor etc??? How would I go about getting it to start Its a xgj125-28 125cc with delphi fuel injection

Answers

thebax2006

Take the air cleaner off and spray starting fluid directly into the throttle body and start it. What's the fuel pressure? A bad fuel pump may be the problem. Now tell us you're out of gas!

Exoplanet

Good post with actual information. Yuppers, could be the timing. Could be the ride-by-wire butterfly valve or stepper motor. Could be the throttle position sensor. Could be a busted / shorted wire somewhere. Could be no compression--a stuck exhaust valve. Compression's easy to check. Gotta be something to do with fuel, spark, or air, dude.

Barry

Compression test. Maybe a valve is stuck partly open. Or a cracked valve head or seat. Compression, fuel and timed spark it has to run!

Anonymous

You are overthinking. Check injector resistance. Check injector pulse with a noid light. Check injector voltage and current with a scope while cranking (disable spark). Or simply pull injector and check if it is spraying fuel. Injector could be bad. Injector checks ok, check fuel pressure with a gauge. The fuel pumps on these Chinese bikes fail often many mechanics do not even check. Pressure checks ok, check compression.

Firestormer

You are not a car mechanic by any means. You are a kid who bought a cheap chinese bike, pulled it to bits because you think you know something about engines and now it is dead. A car mechanic would not describe valve clearances as "advanced"

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