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RSRBOB
RSRBOB, Technician
Category: Motorcycle
Satisfied Customers: 1078
Experience:  Former Factory Service Rep, Dlr Line Tech, Service Manager, General Manager, Store Owner
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I have an 08 yamaha rhino 700. Installed new crank,

Customer Question

I have an 08 yamaha rhino 700. Installed new crank, piston,cylinder, timing chain. Started right up and ran well for several hours. Engine died and won't restart. Has compression, good spark, fuel pressure and injector pulses. Injector is spraying. Checked timing. Code 46 on dash display. Tried to run diagnostics and all sensors read out ok. It would not do coil test, injector test, or fuel pump relay test. Replaced ECU with new one (Procom) Still no start. Tried to run diagnostics with new ecu and would not respond. Installed old ecu and now it won't go into diagnostic mode at all. Dash still reads out otherwise (fuel gauge,clock,odometer,etc.) Code 46 still shows. Voltage at ecu orange wire is 12.7. Cranks normally.
Submitted: 1 year ago.
Category: Motorcycle
Expert:  RSRBOB replied 1 year ago.

Hi and thank you for your question.

I would like some additional details from you to help sort this problem out.

1.) What is the current (post failure, not post re-build) compression in psi?

2.) What is the current leak down?

Thanks,

RSRBOB

Customer: replied 1 year ago.
I have been trying to find a 10mm compression adaptor, but it will blow your finger off the plug hole while cranking. Wanting to check cylinder leak down, but need fitting. Any ideas why I can no longer access the ecu diagnostics.
Customer: replied 1 year ago.
I will have adaptor Thurs. I do have a leakdown tester and will get back to you after testing. Still would like to get into the diagnostics problem.
Expert:  RSRBOB replied 1 year ago.

That sounds like a communication issue. Not exactly unheard of. Going to look up the code 46 in a service manual. I will get back with you on that one. The other thought that comes to mind is if the flywheel spun or shifted on the crankshaft so that although you have spark, do you have it at the correct time. Perhaps it would be worth having a look at seeing if TDC on the flywheel still agrees with piston TDC.

RSRBOB

Customer: replied 1 year ago.
Checked tdc think it's good. Will recheck to verify. From what I found 46 referred to improper voltage to ecm. Orange wire at ecu read battery v 12.75. Will wait for adaptor to do leak down. Back to basics. Get back to u.
Expert:  RSRBOB replied 1 year ago.

Hi.

I checked the service manual and code 46 is charging system failure. The service manual references checking the AC output of the stator and the diodes in the rectifier. If both check out, then check the wiring between the stator and rectifier and rectifier and battery.

RSRBOB

PS, sitll interested in the leak down results too.

Customer: replied 1 year ago.
Thanks for the added info. Still waiting for 10mm adapter. Going to check some stuff out today. get back to u.
Al
Expert:  RSRBOB replied 1 year ago.

No problem. Just repost to this thread when you have new info. They are very good about e mailing me plus posting the message at the top of my feed on here so I can't really miss it.

RSRBOB

Customer: replied 1 year ago.
Hi. Rechecked TDC believe it to be correct. Compression reads 95psi. Leakdown is around 5%. Installed an engine to frame ground cable. Also put rectifier ground between rectifier and frame to insure good grounds. Can read diagnostic inputs air temp,water temp, tps, lean angle batt v, etc. ECU won't trigger coil or injector or fuel pump relay thru onboard test. Fuel pump comes on with key on. Fuel press was 47psi. Plug fires when cranking. Injector pulses noid light. Had injector out and connected to fuel line and sprays when cranking. Tried unplugging stator and rectifier seperately and cranking it. Zip. Plugged in new ECU (Procom).
Customer: replied 1 year ago.
Compression is actually 65psi with throttle wide open. Leakdown is around 5%. No start with new ECU. Book says OK for compression. Added a little oil to cyl. Raised compression to about 73psi.
Expert:  RSRBOB replied 1 year ago.

Thank you.

On the leak down test, did you have to hold the crank on the T mark while performing this test or once you had it set to the T did it stay on its own without the crankshaft being stopped from rotating?

The other question is have you run down the code 46 for a charging system problem?

I am not clear on your answer to this question, so yes or no, after you have cranked the engine trying to start it and giving it sufficient time to start if it were going to, does the spark plug come out of the cylinder wet?

Thanks

RSRBOB

Customer: replied 1 year ago.
Rechecked leakdown with piston up. Had to put a strong arm on the socket for the crank nut and tie it down as it would be very difficult to hold it. Leakdown very minimal. 2 to 3 % if that. Spark plug was wet after cranking to start. The code 46 is now gone with every thing connected and with original ECU. Don't know why, it was there from the moment it died.
Expert:  RSRBOB replied 1 year ago.

Thank you for the additional information.

I find it very unusual that you would have to hold the crank still, which is why I asked the question. Just wondering if the flywheel is not keyed properly to the crank and therefore the T mark is off, which would make the cam timing off. Can you put a straw or something down the spark plug hole to see if it changes direction of travel as the T mark passes the reference mark on the crank case?

RSRBOB

Customer: replied 1 year ago.
Hi, The T mark you refer to is an I for TDC. See no T mark. See the H mark for the firing range. If air pressure is applied above the piston it's going to push it down to the bottom, why wouldn't it? I indexed the TDC several times before contacting you. The crank I mark aligns with the groove in the sight hole while the cam gear mark is aligned with the pointer on the head on the compression stroke. Everything moves as it should.
Expert:  RSRBOB replied 1 year ago.

Correct, the "I" mark for TDC is on the cam gear. What we need to determine is not where the cam is, but the piston position. I am trying to confirm that when the cam is in the TDCC position the piston is actually at the top of its travel. Hence, the straw down the spark plug hole and watching for it to change direction as the I ***** *****nes up. There is a small plug on the crank case cover that should have a mark for TDC as well.

As far as your question as to why the crank should not have to be held, think about the piston.rod at TDC. The wrist pin, crank pin and main bearing pivots are in perfect alignment at TDC and the air pressure is pushing straight down on the rod. Since there is no angle involved, the crank will stay at the TDC position without being held "IF" everything is correct. If it has to be held at TDC, it could very well be our problem. The procedure I am asking you to perform is confirming where the piston is. What you have done previously is confirm the orientation between the crank mark (flywheel) and the cam mark are correct. It does not guarantee the flywheel has not slipped or turned on the crankshaft.

So if the spark plug is coming out wet, with gas I assume, then it cannot be getting spark, as long as our flywheel hasn't slipped. Spark at the incorrect time will also prevent an engine from running, so we are back to confirming where the piston is when the spark occurs.

The way the picture is being painted, everything is perfect, but it doesn't run. Something is being overlooked, we just have to find it.

RSRBOB

Customer: replied 1 year ago.
Hi, as I said I indexed the piston TDC with a feeler in spark plug hole. With piston at TDC, the I mark on the crank lines up with the groove in the view hole as it should. I only referenced the cam to let you know everything lines up and that the piston is in fact at the top of it's travel and was not using the cam mark to determine the piston position.
Customer: replied 1 year ago.
I put a paint dot on the flywheel H mark and used a timing light while cranking to check the firing. It does fire as the mark aligns with the groove in the crankcase view hole. Using the timing light on the cam mark shows it firing around 5 or so before TDC.
Customer: replied 1 year ago.
I was finally able to apply the air at TDC without holdig the crank by very slowly increasing the pressure. All timing marks were aligned and stayed in correct position. That said and nothing changed, I'm still where I was when I started. The H that I referred to earlier was shown in the book as the firing range and it looks like that is where it's firing.
Expert:  RSRBOB replied 1 year ago.

I am going to opt out of this. Something is being overlooked but this has the feeling that you are more interested in proving you are right than you are in looking for a problem.

Customer: replied 1 year ago.
Sorry you feel that way. I was only looking for an answer. I was only trying to show you that all of my findings were valid and knew something odd was going on. Thanks for all the wasted time and bailing out on me.