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Jaco

ECU and fuel cut relay

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The trouble is on a 2000 vfr 800 from Canada. I purchased this bike in June and when I turned the key I had to flip the kill switch 2 or 3 time for the pump to start priming, then the FI light came off and bike started fine. Now the pump prime rarely when I turn the key or flip the kill switch. I can always crank the bike. The engine stop relay clic when I turn the key but not the fuel cut relay, except rarely when the pump prime obviously. No HISS on the bike.

I tested the engine stop relay, the bank angle relay and the fuel cut relay. They all seem to work properly. The kill switch works fine. When the pump prime I got 12 volts at the fuel cut relay (Brown/Bl and Bl/white), and nothing when it doesn't. I checked the continuity between the ECU and the fuel cut relay (the Br/Bl wire) and it's ok. I also checked the continuity of the Black/white wire that goes from the engine stop relay to the fuel cut relay and it's ok. I have 12 volt between the black and white wires of the fuel cut relay and the ground.
It looks like the ecu fails to give its signal to the fuel cut relay when I turn the ignition on. I want to be sure that the trouble is with my ECU before purchasing another one. Is there anything else that can stop the ECU from giving it's signal to the fuel cut relay? Or Am I missing something?



Any help would be appreciate!

 

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You must get 12v on the Black/White wire at the Fuel Cut Relay EVERY time your ignition switch is turned ON. This appears to be your issue. The ECM is not an issue at this point, because the 12v to the relay is NOT there intermittently.

The ECM will supply the controlling Ground for the Fuel Cut Relay to energise, BUT you MUST see the 12v on the Black/White wire at ALL times when Ignition is ON.

With everything you've checked I would replace the Engine Stop Relay it may be intermittent as this feeds the 12v on the Black/White wire to both ECM and the Fuel Cut Relay. You could swap it with your Hi Beam relay and see how you go.

You should also check your 30amp main fuse next to your Starter Relay. Both fuse and wiring can suffer badly from heat stress and high resistance contact causing similar issues.

You could also have an intermittent Bank Angle Sensor. This can be by-passed for fault finding purposes by simply grounding the Red/Orange wire of the BAS.

The ECM is generally a very reliable device. Good Grounds and power supply need to be established before suspecting the ECM.

Let's know how you get on.

 

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Both my(2001 Fi-y)  fuel cut and engine stop relays have failed over years, they both had intermittent failures - sometimes when trying to start the bike and sometimes whilst riding(which really gets your attention!)

so I'd change both before looking for a new ECU.

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Thank you for the feedbacks!

 

The bike is a 5th gen (2000)

The 30 amp main fuse seems fine

I swap my high beam relays with the fuel cut relay and the engine stop relay, I bypass the bank angle sensor and the trouble stay the same.

I always have 12 volts between the ground and the bl/w wire when I turn the key on. Also the Bl/w wire that feeds the ECU show 12 volt each time I turn the key on

When I bypass the fuel cut relay the pump always prime and when I ground the energizing side (br/bl) of the fuel cut relay, the pump prime.

Every time the fuel cut relay click the pump prime and the bike start

When the fuel cut relay don't click, I have 12 volts between the br/bl wire and the ground. When it click the voltage drop to zero for 2 sec

 

So when the key is turned on, the engine stop relay always do its job and feeds the ECU and the fuel cut relay. If I understand correctly, the problem is the br/bl coming from the ECU not doing his job (this wire show good continuity from the ecu plug to the fuel cut relay). From there I only see 2 options: the ECU is failing or something forbids the ECU from activating the pump. Since the bank angle sensor is ok, what else could do that?

 

I have the honda service manual for the bike.  It says that "there should be no continuity only when the 12 volt battery is connected" All my relays show no continuity when they're not hooked to 12 volts... am I wrong or the manual is wrong there?

 

 

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On 23 August 2019 at 5:08 AM, Jaco said:

When the pump prime I got 12 volts at the fuel cut relay (Brown/Bl and Bl/white), and nothing when it doesn't

Your statement above made me think you had intermittent voltage at the Black/White wire!

 

You need to check the ECM Grounds are solidly grounded back to the battery Negative terminal, so continuity back to the battery NOT just the bike frame. To energise the Fuel Cut Relay the ECM relies on good grounds at the ECM.

There appears to be 3 Grounds for the ECM. (plus one Signal Ground at B2.)

B1 a Green wire, and on the A connector there are two Green/Pink wires A9 and A20, make sure you get good solid grounding on these wires A9, A20 and B1.

 

Check your bike and Wiring Diagram to verify the Grounds I've mentioned. The above Drawing I posted, VFR800 Engine Management System might not be exactly as per your bike.

 

Also, all the Relays (Headlight, Engine Stop, Hi Beam and Fuel Cut) are Normally Open so = No continuity between the contacts until energised.

 

WARNING - If you by-pass or link out the Fuel Cut Relay to check the Fuel Pump BE VERY CAREFUL. If you accidentally place +12v on the Brown/Black wire (ECM Fuel Cut Relay control Ground) you could destroy the ECM!

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oh it's a sad morning! All 3 ecm grounds are good... There is aprox 0.9 ohms between them and the neg. terminal of the battery. Thanks for the insight Grum. If you have any other idea, i'll be glad to read them!

 

"When the pump prime I got 12 volts at the fuel cut relay (Brown/Bl and Bl/white), and nothing when it doesn't." What I meant there wasn't clear sorry (I'm a French Canadian...) Between the frame and the energizing side of the Fuel cut relay (Br/Bl or Bl/W) I read 12 volts when the relay doesn't click, and if per chance the relay click the voltage drop to 0, telling me that the ECU is grounding the relay via the BR/Bl wire, energizing it and making the pump goes purr...

 

When the bike is starting, it runs fine, never had any trouble. If the fuel cut relay serve any purpose while i'm riding why doesn't it fail then? I'm starting to think that my wife is praying some voodoo god to put a woe on me and the bike...

 

Anybody ever open an ECM? Maybe it's just a loose soldering point in it... This sounds desperate, doesn't it? 😛 

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9 hours ago, Jaco said:

When the pump prime I got 12 volts at the fuel cut relay (Brown/Bl and Bl/white), and nothing when it doesn't." What I meant there wasn't clear sorry (I'm a French Canadian...) Between the frame and the energizing side of the Fuel cut relay (Br/Bl or Bl/W) I read 12 volts when the relay doesn't click, and if per chance the relay click the voltage drop to 0, telling me that the ECU is grounding the relay via the BR/Bl wire, energizing it and making the pump goes purr...

 

Ok merci, I fully understand what you mean.

 

Just also want to be sure... You definitely do have a healthy battery? And terminals clean and tight? Sorry if I'm stating the obvious!

It really does sound like you have some faulty intermittent issue with the ECM Fuel Relay control output.

I wonder if it's worth checking if the ECM has any stored fault codes? Probably not applicable with this fault?

 

BEFORE Replacing the ECM I would try a few radical things!

- Do a good visual check on both ECM plug and sockets. Pay particular attention to Ground pins A9, A20 and B1 as well as the 12v power in at B8 and the Fuel Relay control output at A5. Are there any burnt pins or sockets or loose wire connections?

- With everything connected and power On and in the Fault State. Listen very carefully for the Fuel Cut Relay to energise or the Fuel Pump to prime for 2secs. Now starting at the ECM flex the cables working your way towards the Fuel Cut Relay, this might identify a poor connection.

- Identify the Ground stud on the bike frame that has the 2 Green/Pink wires and the Green wire (ECM Grounds). Have a good look at the lugs and wires being properly crimped or soldered. Clean the stud connection to frame, again, making sure it is electrically bonded to the battery Negative.

- At the Fuel Cut Relay make sure the Brown/Black ECM control ground wire is properly connected to the Relay base. Nothing loose or poorly crimped.

- Your issue could also be a thermal one within the ECM, possibly an internal cracked solder joint. Try unbolting the ECM from the bike leaving it fully connected and again, with power on in the Fault State try warming up the ECM with a hairdryer and listen for the Fuel Pump to prime.

- As far as I'm aware the ECM is potted to prevent moisture ingress and can't be worked on.

 

Just for Info - The Fuel Pump should prime for approximately 2 sec at switch On. Then when Cam or Crank pulses (not sure which one) are identified by the ECM it will run the fuel pump continuously, this also means while cranking during start.

 

Unless someone else has any ideas, and without physically working on your bike I can't think of anything else to mention. Failing anything discovered from above checks it's looking like a new ECM could be the go.

 

Good Luck and please keep us posted with how you get on, so we can ALL learn from your experience.

Au Revoir.

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Cut the earth block wires out of the harness & clean then solder them all together. I had weird electrical gremlins with mine until I did that. Much cheaper & the ECU is not the issue, as it would be permanent. If the earth block trick does not cure it check the wires connected to the ECU, they have been known to vibration split inside their insulation ! Very hard to find when unless you catch it in the disconnected position, slight movement reconnects it 😞 

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Ah yes that bloody earth block, good call Mowhawk. I'd been staring at the circuit diagram for too long looking at the direct ground points and other wiring for the ECM forgetting the dam circuit diagram doesn't show this common earthing block. 

Although Jaco has already checked the ECM grounds and power and found them to be OK, I would have thought this to be sufficient just to at least get the initial fuel prime to work constantly, however doing the earth block mod is a good idea before replacing the ECM.

I beg to differ with an intermittent fault within an ECM, this may be rare but can most certainly happen.

Cheers. 

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I checked all the grounds again. Battery and terminal are neat. My earth block looks shinny and show no visible imperfection. 

I heated the ECM with a hairdryer and the pump primed... but I wasn't able to repeat it...

The engine stop relay works every time (feeding the ECM and the fuel cut relay)

That rules out everything (is my logic too hasty here?) except the wire coming from the ECM grounding the fuel cut relay (B5)

If a ground problem at the ECM was the reason of my trouble, most of the time I shouldn't have continuity between B1, A9 or A20. But even by twisting the harness I never lost continuity between there and the neg. terminal.

Furthermore, if I had a failing wire going to the fuel cut relay, the bike wouldn't be running fine once it starts. Apart from the pump not priming when i turn the key, the bike never failed in any aspect. So the fuel cut relay isn't acting up while I'm riding the bike, telling me that the link between it and the ECM (Br/Bl wire) is fine.

If my logic is correct, that leaves only the ECM or some maleficent woe.

With that in mind I order an ECM from ebay today, hoping that it wouldn't be in vain.

I'll keep you informed

 

Someone know if my Canadian ECM (38770-MBG-A01) can be replaced with one from England (38770-MBG-D01) without to much trouble?

 

Thank again!

 

 

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1 hour ago, Jaco said:

I checked all the grounds again. Battery and terminal are neat. My earth block looks shinny and show no visible imperfection. 

I heated the ECM with a hairdryer and the pump primed... but I wasn't able to repeat it...

The engine stop relay works every time (feeding the ECM and the fuel cut relay)

That rules out everything (is my logic too hasty here?) except the wire coming from the ECM grounding the fuel cut relay (B5)

If a ground problem at the ECM was the reason of my trouble, most of the time I shouldn't have continuity between B1, A9 or A20. But even by twisting the harness I never lost continuity between there and the neg. terminal.

Furthermore, if I had a failing wire going to the fuel cut relay, the bike wouldn't be running fine once it starts. Apart from the pump not priming when i turn the key, the bike never failed in any aspect. So the fuel cut relay isn't acting up while I'm riding the bike, telling me that the link between it and the ECM (Br/Bl wire) is fine.

If my logic is correct, that leaves only the ECM or some maleficent woe.

With that in mind I order an ECM from ebay today, hoping that it wouldn't be in vain.

I'll keep you informed

 

Someone know if my Canadian ECM (38770-MBG-A01) can be replaced with one from England (38770-MBG-D01) without to much trouble?

 

Thank again!

 

 

Hi Jaco.

You've done a great job in diagnosing and trouble shooting your issue, and a good write up on what you've done. Good luck with the ECM replacement and keep us posted. You may well have detected a thermal fault within the ECM using the hairdryer trick.

Can only assume the difference in Canadian and England ECM would be the HISS version(England) and non HISS. Be worth just sticking with the exact part number of your original, might save some heartache! Is there a label or Part Number stamped on your ECM?

If all else fails, make sure you throw away your wife's Voodoo Doll ! :ohmy:

Cheers.:beer:

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Hi!

The pump wasn't priming because a little pink wire linking the ignition switch and the ECM was bad. I should have thought of that before suspecting my ECM...

 

Thank again for all the advices!

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6 hours ago, Jaco said:

Hi!

The pump wasn't priming because a little pink wire linking the ignition switch and the ECM was bad. I should have thought of that before suspecting my ECM...

 

Thank again for all the advices!

Hi Jaco.

It's surprising that the pink wire is only on the after 99 drawing and its connection to the Ignition Switch VC is not shown on the ignition switch link connections at the bottom of the drawing.

 

Also the service manual regarding the Ignition Switch does not mention this connection, nor is the pink wire mentioned for any of the ECM Power and Ground checks!. It's not connected or used on 6gens either.

 

Ignition Switch pink wire called VC!! Can't find any info that would tie this wire to Fuel Pump ops. It's obviously not the main power for the ECM, that comes from the Engine Stop Relay.

 

If you have any info regarding this mystery pink wire could you please share it with us. Do you remember what the Pin number is for it on the B connector?

 

Glad it's all sorted hopefully there's  nothing still intermittent lurking!

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On 30 August 2019 at 11:31 AM, Grum said:

Hi Jaco.

It's surprising that the pink wire is only on the after 99 drawing and its connection to the Ignition Switch VC is not shown on the ignition switch link connections at the bottom of the drawing.

 

Also the service manual regarding the Ignition Switch does not mention this connection, nor is the pink wire mentioned for any of the ECM Power and Ground checks!. It's not connected or used on 6gens either.

 

Ignition Switch pink wire called VC!! Can't find any info that would tie this wire to Fuel Pump ops. It's obviously not the main power for the ECM, that comes from the Engine Stop Relay.

 

If you have any info regarding this mystery pink wire could you please share it with us. Do you remember what the Pin number is for it on the B connector?

 

Glad it's all sorted hopefully there's  nothing still intermittent lurking!

Well, did some research and answered my own question!

 

The mystery Pink Wire from the Ignition Switch to the ECM is possibly some form of anti theft hotwire security!

 

Underneath the ignition switch is a Zener Diode that drops 12v down to 9v and sends this to the ECM via the Pink Wire. If the ECM sees 0v or 12v on this wire the ECM will NOT fire up completely, it must see 9v. Effects are Fi light ON and NO Fuel Pump prime.

 

Definelty one to remember for anyone who has a four wire ignition switch having the Pink Wire.

Cheers.:beer:

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