Bad ECM

Joined
Aug 17, 2010
Messages
12
Location
Macedon NY
The problem: When the key is turned on the fuel pump doesn't run ( whirly sound) and the bike won't start. I've discovered the br/bl wire on the fuel cut out relay field coil leading to the ECM has 10.5 volts on it , as measured from relay terminal to ground .
When I ground this wire the fuel pump runs as long as the wire is grounded. I've swapped relays with known good ones it's definitely not the relay. There are no stored ECM faults, ignition and run switches are fine.
*I fear this suggests I have a bad ECU!
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Before I spend big bucks on one of these I could use some help with ruling out any other conditions that might cause this problem or prevent the ECM from pulling the br/bl wire low.
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I'd like to understand
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1) What shuts the pump of when the key is first turned on . ( ECM timing function I presume?)
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2) Does the pump run continuously when the engine is running? With the engine is running, on my bike if I remove unground the br/bl while hile idling the bike runs 10 seconds max and gradually dies from fuel starvation
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3) Could there be any other inputs to the ECM that prohibits the br/bl wire on the fuel cut out coil from being pulled low?
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4)There's another br/bl wire that runs from the fuel pump (black connector) to the instrument cluster. What does this do? I've read its used to drive the instrument cluster. If so what voltage might I expect to read on this wire?
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Any help would be greatly appreciated
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Regards
Joel Spano
Rochester NY
585-355-8366
 

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Blrfl

Natural Rider Enhancement
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Fast Blue One
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Start with the basics before trying to diagnose problems that probably aren't there.

What's the standing voltage of your battery and what does it sink to when you crank the starter?

--Mark
 

Dave.David

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SB California USA
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05,ST1300-04VTX1800R
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8938
Read about your FPR, Fuel Pressure Regulator. And check your power at the pump. Green wire needs ground , try using a jump wire from the plate atop the tank to a good ground. Good luck.

Sent from my SAMSUNG-SM-G935A using Tapatalk
 
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jspano01
Joined
Aug 17, 2010
Messages
12
Location
Macedon NY
Thanks David

The fuel top plate ground wire has three tenths of an ohm resistance. I consider this a "good" ground.

Battery voltage is 13.2 volts across the battery terminals key off no load.
Power never makes it to the pump unless I ground the control wire leading to the ECU. However when the ECU control wire is grounded to force the pump to start there's 12.1 VDC available at the relay contacts which drops to 11.5-ish once the pump is running and the ground is maintained.

To be certain I swapped the ST battery with my Gold wing battery ( known good unit).I'm moving past battery voltage and supply voltage at the pump for now. For record the current draw from the battery thru my amp meter is 5.6 amps when the key is turned on and about 9.6 amps when I force the fuel pump on this seems reasonable to me.

As far as the fuel pressure regulator is concerned this is a purely mechanical device using a spring pressure and diaphragm mounted to the fuel rail and which serves to bypass excess pressure created by the fuel pump back to the tank and maintain a relative constant pressure in the fuel rail for the injectors (in my case 55 psi) . However, before the system can build fuel pressure the fuel pump has to run which is my dilemma.

If I've misunderstood the Fuel pump regulator enlighten me.

Keep the suggestions coming they're a lot cheaper than a new ECU .

Thanks
Joel
 
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jspano01
Joined
Aug 17, 2010
Messages
12
Location
Macedon NY
Oh yes I forgot to mention the current readings were measured with the head light fuse removed.
Don't want to kill the battery during all the troubleshooting.
 
Joined
Feb 3, 2017
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Schroon Lake, NY
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2010 ST-1300
Just a long shot but the fuel pump wont run if the engine cut-off switch is off. Maybe check the contacts in the switch and the wires that effect the pump?
 
Joined
Mar 20, 2016
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Location
Auckland, New Zealand
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2005 ST1300
STOC #
8901
The second wire from the pump connector to the instrument console is used for a low fuel warning light, nothing to do with the pump aside from sharing the ground connection.

AFAIK the fuel pump relay is solely driven by the ECU, and it should be energised for a few seconds when you turn the key on, and then constantly when the engine is running.

I think Woodybelle is probably correct that the ECU needs an input from the bank angle sensor as well before allowing the pump to run. My understanding is the bank angle sensor is intended to stop the engine in a tip-over, and it would make sense to stop the fuel pump in that instance too. The BAS provides a ground path that allows the engine stop relay to energise.

So next step would be to locate and test the Engine Stop Relay.
 
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jspano01
Joined
Aug 17, 2010
Messages
12
Location
Macedon NY
Thanks Terry


You're the first guy to provide a definitive a statement on theory of operation. Thank you !

The confirmation of the wire leading from the pump to the instrument cluster for low fuel only is helpful.
I suspected the ECM timing for closing the fuel cut out relay at "key on" and during engine but having it verified is comforting. Now I can move forward with confidence.

The bank angle is providing power to the adjacent fuel cut out relay and the ECM on the black and white wires .
With the key on , engine run switch on, I measured 12.2 volts on the Grey 23 pin ECM connector (ECM removed ) the two black/ white wires provided this voltage from the bank angle sensor relay contacts.

The engine start stop switch provides power to the bank angle sensor and relay and since this relay energizes and remains energized I believe the start stop switch ,the bank angle relay ,fuel cut out relay , and ignition switch are all good.

Checking for proper ECU grounding:
Measured continuity on the black 23 pin ECM connector ( ECM removed ) good continuity on green /pink and green /blue wires leading to ground. (i.e. .3 ohms )

The ECM is for sure failing to drive the brown / black wire low on pin 4 leading from the fuel cut out relay to the ECM. The engine will start and run indefinitely ( ½ hour run time check so far ) as long as I ground this lead .

I'm running out of things to check.

Regards
Joel
 
Joined
Jan 8, 2011
Messages
7,062
Location
Arizona
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2007 Honda ST1300A
Here is just something to think about, if something on your bike caused damage to the ECM, would it not be possible that it may damage a borrowed ECM as well?
A burger and beer may not be enough to make someone happy if you toast their ECM by accident. Just putting this out there.
 
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jspano01
Joined
Aug 17, 2010
Messages
12
Location
Macedon NY
Igofar

I agree. I wouldn't feel comfortable using another members ECM. Would be happy to offer mine to test in another bike to confirm the same failure mode.

Some amusing history.
First failure on the bike was two weeks ago running at 60 mph the bike just quit as if the engine run switch was turned off. Can't remember what displays lights did or didn't come on but it just die. Pulled over and found the bike would crank but not start not even pop ,nothing except crank. Waited 1/2 hour and the bike would start again and run maybe another 30 miles. Of course I didn't have tools a meter or schematics at that time it's a Honda no need to right?

That night pulled a fault code that indicated the crank shaft position in sensor was bad , I recall a few days of stuttering during idle and rough running so I replaced it and on the next ride same thing, thirty miles into ride bike just quit. ( full tank of gas ) This time I was prepared discovered two ignition wires from the ECM to the coils had the insulation rubbed off. I found this by dumb luck. It appears the tool bag was the culprit. Couldn't find any metal to metal contact so taped the wires waited 1/2 hour drove the bike home and tore into the rear cowl the next morning. Checked all the ECM relays and wires for more damage corrosion found nothing , repaired the coil wires figured I got it licked this time!

Made the mistake of driving to a local water hole famous for hosting those guys that look like pirates on big loud V twins. Had my beer told some motorcycle lies and as luck would have it when I went to start the bike …..nothing but cranking noise followed by the obligatory explosion of laughter from the peanut gallery observing my misfortune.
Fifteen minutes later with the fuel cut out relay jumped the bike was running. Tail between my legs I drove home…………….. or attempted to! I got ten miles on a twenty mile return trip and the bike quit again. This time the fuel pump refused to run. Wife picked me up with the trailer I left connected to my car just in case I break down.
All the way home she gave me that “you dumb ****†smirk …it was not a good day for me or the Honda. Next morning removed the pump put 12 volts across the +/- terminals and it won't budge not even with a dental pick prying the rotor . One warranty fuel pump later I figured it's got be the pump right? I mean its prime riding season and I paid my dues in front of those Harley guys the world can't be this cruel.

This leads me to where I am today .
Fourth pin in on Black ECM connector the brown and black wire from the fuel cut out relay coil to the ECM does not ground. I figure the coil wire thing probably damaged the ECM
As far as the fuel pump failing well it's a Quantum high flow that replaced last year at this time and since it was replaced under warranty I won't complain about it being fabricated from chi-nee zium …..an inexpensive metal with a half- life inversely proportional to the criticality of the component it's used on.

As luck would have it the Quantum customer service group folks double shipped ….. I got two pumps for free. Thanks guys  What are the odds Partzilla will follow suite and double ship an ECM order?

For the record I have 62K flaw free miles on this awesome bike it's about due for some parts
 
Joined
Feb 3, 2017
Messages
833
Location
Schroon Lake, NY
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2010 ST-1300
Last year the crank shaft position in sensor went bad on my BMW r1100rt. I was driving home on the highway in a down pour and it just died. I coasted down an exit ramp. I waited 5 minutes and it started back up. Drove 10 miles died again so on until I got home. Next day it ran fine (no rain). Ended up finding the insulation on the wires to the sensor got crispy and fell off.
 
Joined
Jan 8, 2011
Messages
7,062
Location
Arizona
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2007 Honda ST1300A
Maybe they sent you two quantum high flow pumps because they know they fail and they sent you a spare just in case? I have no experience with aftermarket pumps, as I recommend OEM parts for stuff like that.
I would start looking around the fuel pump and or under the fuel tank to see if you pinched a line, disturbed a ground wire, or blocked a vent line or hose first.
I would also go to the front of the bike and check the crankshaft position sensor switch. These wires will be routed back on the left side of the engine (as seated on bike) and run right next to the exhaust system.
Its possible you have a cooked or damaged wire to this switch.
I would then check some or all of the following: pinched or clogged fuel hose, faulty fuel pump, clogged fuel filter, clogged fuel injector filter, sticking fuel injector needle, faulty or disconnected camshaft position (CMP) sensor, the crankshaft position (CKP) Sensor as stated above, and really look at a faulty fuel pump even though you replaced it (since its not a honda part).
When was the last time you did a TB sync? Your starter valve synchronization may be misadjusted, or the lines/5 way tee may be clogged.
 
Joined
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Medina, Tennessee
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2021 Tracer 9GT
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375
What year ST? Some 2003s had grounding and wiring harness issues and were recalled. Mine was one of them.
The first thing I would check after a load test on the battery is that all connections and grounds are clean and tight, then move on to all fuses, plugs, then relays.
 

dduelin

Tune my heart to sing Thy grace
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With the key ON do all of the lights in the front half of the bike operate normally including headlights, position lights, turn signals, horn, and instrument panel backlighting?

The ST is prone to ground circuit problems that can cause the fuel pump not to run, it's not an uncommon problem that manifests itself in various ways usually through some strange behavior in these circuits but not always. All the grounds (green wires on your Honda) in the front half of the bike including the fuel pump run through a small yellow bus bar behind the RH headlight and then through a white plastic 24 pin connector outboard of the left side frame above the left valve cover. Uncover the 24 pin connector and fashion a jumper wire to provide an alternate ground from the forward side of this connector's green wire directly to the frame. If the fuel pump spins up you are good to fashion a permanent ground repair.

My bike had lighting clues that came and went without engine run issues but eventually the fuel pump cut out and the bike would not start until the ground issue was resolved.
 
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