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Louie
Louie, Technician
Category: Motorcycle
Satisfied Customers: 12675
Experience:  25+ yrs. experience
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Rmz 250 fuel injector not get signal to inject gas. Bench

Customer Question

Rmz 250 fuel injector not get signal to inject gas. Bench tested fuel injector with battery and works fine.
JA: Has the vehicle turned into a gas hog? And how does it start -- same as usual?
Customer: Died on track and will not push or kick. Spark yes. Fuel pressure yes but injector will not inject. Checked continuity back to ecm. So no broken wire back to ecm.
JA: What is the model/year of your motorcycle?
Customer: 2010. Stock ecm
JA: Are you fixing your bike yourself? What have you tried so far?
Customer: Checked fuel pressure. Spark. Fuel injector. Tested capacitor.
JA: Anything else you want the mechanic to know before I connect you?
Customer: I suspect the ecm.
Submitted: 1 year ago.
Category: Motorcycle
Customer: replied 1 year ago.
Tip over sensor seems fine. Checked for broken wires. There is no signal telling fuel injector to open. Will open and spray testing with 40 psi on bench. Will not open when kicking or pushing bike. Also tested capacitor assume it works because getting fuel pressure and also assume stator and voltage regulator
Good because spark and fuel pump pressure from kick start good.
Expert:  Louie replied 1 year ago.

Hi, I’m Louie. Sorry you had to wait awhile but I’ll do my best to help.

Initially, it would appear to be an ECM issue; "...Spark yes...Fuel pressure yes but injector will not inject..."

Still, proposed preliminary checks (if have not been done) on suspects:

  • • temporarily disconnect the black/yellow kill wire to the ECM;
  • • +V on the injector's red wire when attempting to start;
  • • pulsating 0V on the injector's green/white wire from ECM likewise when attempting to start.
Customer: replied 1 year ago.
I will try this when I get back home. Would the bike start with the black/yellow temp disconnected. I am curious about this because didn't know about kill wire to ECM
Expert:  Louie replied 1 year ago.

Based on the wiring diagram, yes. In the OFF position, the Engine Stop Switch switches the ECM's black/yellow wire to the black/white wire which is tied to the ground.

Customer: replied 1 year ago.
I got a new ecu but the bike would not fire. It appears not ecu. Really stumped. Can a secondary grounding in the master wire harness be causing some kind of kill
Customer: replied 1 year ago.
Tried several of the different injection map plugs. Just in case one was faulty.
Expert:  Louie replied 1 year ago.

Appreciate the post back.

And considering all of the above, then the triggers to the ECM would be highly suspect.

Part of the ECM is a CDI circuit that fires the ignition coil and a processor that pulses the injectors. The trigger would be from the pulser coil co-located with the magneto circuit.

Test the Ω / resistance between the pickup coil's red and green wires. Then check for its output' low pulsating voltage when attempting to start.

Might as well do the exciter coil and stator coil too.

Customer: replied 1 year ago.
Ok I am away till Saturday. But I will keep you posted on status. Thanks.
Expert:  Louie replied 1 year ago.

I understand,

And yes please; an update when able.

Customer: replied 1 year ago.
Appreciate the post back.And considering all of the above, then the triggers to the ECM would be highly suspect.Part of the ECM is a CDI circuit that fires the ignition coil and a processor that pulses the injectors. The trigger would be from the pulser coil co-located with the magneto circuit.Test the Ω / resistance between the pickup coil's red and green wires.
I got numbers and good continuity when testing.
Then check for its output' low pulsating voltage when attempting to start.
I had to set volt meter at 200M. Definitely got big reading change even with minor kick movement.Might as well do the exciter coil and stator coil too.
Went back and let pulled plug. Definite big spark even if 1/4 inch from frame.
Went back and tested fuel injector wire plug. Got no change in voltage after many kicks. I will check continuity back to ecm tomorrow. Previously checked this I was sure I had continuity and voltage up into 10 plus from kicks.
last time plug was position where wires had continuity but when plugged in maybe not. Now get no reading of voltage sent to fuel injector.
Expert:  Louie replied 1 year ago.

Hi again,

I recall that this particular model has a tip-over (TO) sensor that auto cutoff fuel flow. Please check this also.

Customer: replied 1 year ago.
I know where this module is. Can I disconnect to get bypass. I know on some like Yamaha voltage changes Depending on angle of bike.
Expert:  Louie replied 1 year ago.

Agree; yes. The purpose is to cut off fuel flow if the bike is leaned too much or dropped.

Perhaps the article HERE can shed further insight.

Customer: replied 1 year ago.
Ok here where I at.I bypassed the TO sensor and went back to fuel injector plug.• temporarily disconnect the black/yellow kill wire to the ECM;
• +V on the injector's red wire when attempting to start;
• pulsating 0V on the injector's green/white wire from ECM likewise when attempting to start.During kicks got following.
I got a instant ramp up on red wire with other terminal to ground.
I got ramp up to 12 volt with capacitor bleed out reading if one lead red and other green/white.
I got nothing if one lead on green/white and other on ground. Not sure if I'm doing pulsating test right.
Fuel injector not opening. I rigged pressurized line to elimate any fuel pressure issues.
I bench tested fuel injector previously by making 9 and 12 volt switch with and opened perfectly with even 20 psi fuel pressure.
Expert:  Louie replied 1 year ago.

Hi again,

Appreciate the update.

And based on all of the above, either an ECM or an injector issue.

A final test; temporarily disconnect the injector's green/white wire from the harness (to the ECM). Instead, connect a length of wire to the injector's green/white wire. While attempting to start, quickly/repeatedly scrape the other end of this wire against engine ground. The idea is to simulate a pulsating grounding of the green/white wire.

The expected result would be clicking/opening of the injector.

  • By process of elimination, IF the injector still fails to click/open, THEN the injector is faulty.
  • ...on the otherhand, IF the injector works, THEN the ECM would be suspect.
Customer: replied 1 year ago.
Here is where I am at now.
I was cleaning lots of connection plugs and looking for moisture and wire rub. I didn't find any but after doing TO sensor and fuel injector wires I got voltage readings for injector that looked good. Also tested injector installed on bike system and got it to spray. With old ecm and new ecm. I feel like I been chasing around in circles. Getting 12.5 to 13 peak volts at injector plug.
It's like the bike wants to start tried 200 kicks it goes through cycle of almost with small initial firing and then never kicks into running. Like its being grounded holding a kill button. I tried with kill switch connected and disconnected. Seemed same both ways.
Expert:  Louie replied 1 year ago.

Interesting.

Is the spark consistent when kick starting?

In some instances, I use alligator clips with wires to test wire multiple ground connections or even wire end to end particularly with intermittent problems. Click HERE.