F90 Does Not Start???

[rougeaut]

Figured it Out, Motor Running Just Fine

Hey just an update to let you know that this new motor to me is now running!
The trouble shooting process went through, commpresion testing, spark to plugs, correct wiring of coils to cylinders, complete fuel pressure testing and injector cleaning and replacement of one injector, fly wheel removed and checked for stripped woodriff key, timing was checked and reset.
I recently went through my SELOC manual and reviewed all of the sensors and how to test them. Even though the motor was starting and quickly stalling the timing was right on and when the Throttle Position Sensor(TPS) was tested it was not working so I replaced the TPS and now it fires right up and sounds great and runs smooth(although I have not put it in the water yet) as I am just finishing off a new floor installation so very soon. The total time that was spent on the motor was about 8-10 hrs and many beers thinking about the process but all in all having a Yamaha diagnostic software and connector could have saved some time but would not have helped me out with the clogged fuel injector. Anyway another Yamaha motor mystery figured out.

Thanks for your insight and or advice I believe it is good to have a sounding board to bounce off ideas and I hope to be able to help others I have helped many in the past and will try to continue to do so.

I went out and bought a gift card for a local beer and wine store for the mechanic at the Yamaha dealership that not only offered me advice but was willing to give me a complete VST tank and high pressure pump to take home to test on my motor for free.

PS a friend of mine once rebuilt a 250hp 2 strk motor completly and had the same problem as he started out with loss of power on WOT, took it to a few shops spent the money but no one could figure it out and after all of that he was sitting at the dock with the motor running without the cowling on and he was smoking a cig and noticed as he reved the motor up and it was losing power that the cig smoke was being sucked into the intake for the carbs but when being reved up one carb did not draw in the smoke. I turned out that the butterfly valve was loose/stripped on the shaft and when opened up to higher RPM the butterfly valve was closing starving the air to the cylinder, so you just never know.

Cheers and tight Lines!

[rougeaut]

Start n Stall Out

recheck your compression AFTER making sure the TDC is correct AND the cam marks line up correctly.
the F90 is an interfernce motor and WILL bend valves if cam timing s off.
it also doesnt like to start if the throttle is advanced.
check rail pressure wen it dies.

Hi I was sure to turn the motor over by hand 10-12 times to check and see and listen that nothing was interfering. I will recheck the compression tomorrow as you mentioned.

I rechecked the fuel pressure on the rail today and it was at 43 PSI with the key on and around 40 when it turned over and starts and runs for a few seconds, after it dies the pressure stays solid at 40-42 PSI for a few more seconds then slowly runs down. So it appears that the fuel pressure is not the problem.

I took a video of the motor starting and the fuel pressure gauge as it start and dies and holds the pressure would it be helpfull to post a link to a youtube link?
or is that done on this forum?
Cheers and happy 4th from Canada!

[ausnoelm]

*** I don't know why you even bother to repond to my post as you are not any help at all more of a tiny pest!
FYI It is a new engine to me, I bought a Yamaha manual the $171.00 yam manual was not in stock so for $30.00 I started to trouble shoot the engine. Now I have rebuilt a number of engines car/motor cycle/boat carbs etc even clasic Jaguar motors and transmissions, rear ends etc HAVE YOU done that much??
The motor did not start so I started with a compression test using my manual, then checked for spark, then cleaned my VST tank, filter, inlines filters all using my manual that showed these and bought a fuel pressure gauge to verify the fuel pressure was to spec. I found one sized injector and had the others cleaned with some help and good advice from others on this forum I moved forward to isolate the problem, it would seem to be a very systematic approach and now that I have validated all of the other aspects of the motor it is narrowed down to a specific issue.
This is what this forum is about or should be everyone else trying to help out either by suggesting some approach based on experience or helpfull idea not some Ya Who like you whining about buying real manual. I am somewhat enjoying working through the motor and learning about all of the components and specs. The timing I changed was only a few degrees and easy to get back to where I was. Perhaps timing scares you or removing 5 bolts to take off an intake manifold also scares you?

Stop whining to me about how you feel someone should work on a motor.

To everyone else thanks agian for your insight I am getting close to solving this issue and hope it is just a minor fix as the mian engine components seem to be all in good shape.
Cheers

not trying to insult you in anyway, or doubt your mechanical prowess, just pointing out that stabbing at "maybe" will usually get you nowhere, as mentioned, that engine is going to cause damage if the timing is not right.

[rodbolt17]

recheck your compression AFTER making sure the TDC is correct AND the cam marks line up correctly.
the F90 is an interfernce motor and WILL bend valves if cam timing s off.
it also doesnt like to start if the throttle is advanced.
check rail pressure wen it dies.

[rougeaut]

Assuming the black marks on the flywheel and bracket are your timing marks, you look to be 3 teeth off on your timing.

Close is not good enough, they must be spot on. Loosen the belt tensioner to get some slack in the belt, leave the cams where they are, turn the crank to line up the marks.

When getting the belt back in place, keep the slack on the tensioner side, no slack on the opposite side, or when tension is applied it will move your marks.

Hope this helps!

HI Well I reread your comment and retried the static timing not as easy as it sounds and after a couple trys I got the motor started!!! it was so close that it was actualy almost starting when you turned it over it started turning over faster and faster but wouldn't quite get there then after readujsting it and it being so close I just let it sit for a bit and then tried it with no choke or fast idle and now it does the same thing consistantly: It turns over for about 3 seconds, starts runs for about 3 seconds then dies? The fuel bulb is full and tight and I can restart it time after time but with the same results.
Very Happy sound to hear it start for the first time and number of beers were sacraficed. Now I just need to figure out why it is dying.
FYI I popped off the flywheel cover I made a tool that my manual sugested to hold it and retorqued it to 137 lbs. The woodroof key was in great shape so that was another possible cuase eliminated at no cost.
The manual states do not try the timing light on it unless it is under load so I guess that is something I can not do at this point?
Anyway I just want to say THANKS for your comment it lead me to redoing the static alignment with the tension as you mentioned tension on the intake side of the belt.
Cheers n Beers

[99yam40]

A lot of 4 stroke motors will bend valves if the cam timing is off.

I have no idea if your is one of those or not, but a good manual should give the proper procedure for checking.

So good luck, I hope someone with a manual for your motor will look in and have answers for you

[rougeaut]

so lets just recap, so far you have.... messed with the timing, pulled the manifold off, cleaned the injectors, generally fiddled around with stuff without a genuine manual to know whether what you are looking at is what you are supposed to see, I said this way back, buy a GENUINE manual, and follow the trouble shooting steps, but only after you have rectified anything you may have already messed up. Stabbing at possible faults, and playing around with the timing is a sure way to empty your wallet.

*** I don't know why you even bother to repond to my post as you are not any help at all more of a tiny pest!
FYI It is a new engine to me, I bought a Yamaha manual the $171.00 yam manual was not in stock so for $30.00 I started to trouble shoot the engine. Now I have rebuilt a number of engines car/motor cycle/boat carbs etc even clasic Jaguar motors and transmissions, rear ends etc HAVE YOU done that much??
The motor did not start so I started with a compression test using my manual, then checked for spark, then cleaned my VST tank, filter, inlines filters all using my manual that showed these and bought a fuel pressure gauge to verify the fuel pressure was to spec. I found one sized injector and had the others cleaned with some help and good advice from others on this forum I moved forward to isolate the problem, it would seem to be a very systematic approach and now that I have validated all of the other aspects of the motor it is narrowed down to a specific issue.
This is what this forum is about or should be everyone else trying to help out either by suggesting some approach based on experience or helpfull idea not some Ya Who like you whining about buying real manual. I am somewhat enjoying working through the motor and learning about all of the components and specs. The timing I changed was only a few degrees and easy to get back to where I was. Perhaps timing scares you or removing 5 bolts to take off an intake manifold also scares you?

Stop whining to me about how you feel someone should work on a motor.

To everyone else thanks agian for your insight I am getting close to solving this issue and hope it is just a minor fix as the mian engine components seem to be all in good shape.
Cheers

[ausnoelm]

so lets just recap, so far you have.... messed with the timing, pulled the manifold off, cleaned the injectors, generally fiddled around with stuff without a genuine manual to know whether what you are looking at is what you are supposed to see, I said this way back, buy a GENUINE manual, and follow the trouble shooting steps, but only after you have rectified anything you may have already messed up. Stabbing at possible faults, and playing around with the timing is a sure way to empty your wallet.

[rougeaut]

Plug wire n Such

By any chance, you didn't cross your plug wires to the wrong plug? Just a thought.

Hi ya as this problem becomes more defined to the gas not getting into the cylinders I had the same thought about the plug wire not firing on the correct cylinder and it is also a new engine to me I checked the plug wiring and believe it is correct as show on the electrical schematic. The 07 F90 has 2 pulser coils the top is divied to 1 and 4 and the bottom to 2 and 3so it is wired as shown.
Not sure as to how move forward except rotate the engine over by hand and watch the valves open and close in the correct firing order?
Cheers

[rougeaut]

Hi thanks for the reply and I did try the realignment yesterday before you replied and I am not sure that I did it correctly but I losened the tensioner with the mark on the crankshaft set to TDC and then moved the cams so everything aligned I am not sure as to weather it make a diff or as you mentioned to align the cams first and keep them set and spin the crank? But it did not fire and agian no gas to the plugs??
Do you know if the intake cam can be out by 1 or more revolutions or is it set to the mark and that is that?
Cheers

[casey1240]

By any chance, you didn't cross your plug wires to the wrong plug? Just a thought.

[cvslawrence]

Assuming the black marks on the flywheel and bracket are your timing marks, you look to be 3 teeth off on your timing.

Close is not good enough, they must be spot on. Loosen the belt tensioner to get some slack in the belt, leave the cams where they are, turn the crank to line up the marks.

When getting the belt back in place, keep the slack on the tensioner side, no slack on the opposite side, or when tension is applied it will move your marks.

Hope this helps!

[ausnoelm]

I suggest you buy a GENUINE manual for your model, continuing to do what you are doing is going to get you deeper and deeper in poo, do NOT start by pulling things to bits and assuming anything, buy a manual and do the trouble shooting step by step.

[rougeaut]

The manual I have "Seloc" shows larger motors have a camshaft position sensor(CPS) but the F90 does not have any or list any CPS in the electrical schematics. As I have checked the static timing where the two marks on the cams align at the TDC for the comp stroke for #1.

Q) Is it possible that the intake cam is out by 360' or by a revelution? IE is there a way to see the the mark is aligned and that say the intake valve on the #1cylinder just opening or otherwise?
Cheers

[rougeaut]

Hi I checked the static timing marks and was told the timing belt almost never jumps and the belt is in great shape, I am not sure as to how to check the cam shaft timing but have a manual and will read up on it today, if not is there are there any other references as to how to do this online?
Cheerss and Thanks.