04 40tlrc cylinder #1 not firing.

[Hd232smoke]

New here but have been lurking for awhile. The problem at hand has been going on for a year or two now and I have finally had enough. I have searched and have found some helpful posts and done a few test which I will explain.

Below 900-1000 rpm cylinder #1 stops firing and it will only idle on two cylinders. Once throttle is applied and it gets close to 1000 rpm you can clearly hear cylinder 1 start to fire and it runs great all the way to WOT at 5500 rpm. Come back down to idle and hit below 900 rpm I am right back down to two cylinders.

So as far as where I am at I’m trying to resolve this is:
-new plugs
-carbs meticulously cleaned
-tested for spark with an inline light (seems I have spark even when cylinder 1 isn’t firing)
- ohm’d out the coil packs
- swapped out working coil 2 for 1 and same problem
- new fuel line from tank to carbs (noticing bubbles in my fuel lines via clear)
- ohm’d out stator and pulses coils all seem to be within spec
- timing at idle looks ok at 7 deg retard and advances throughout the rpms

i am stumped and have just ordered a dva tester so I can start checking actual voltage on ignition system

I noticed my fuel pump when I unbolted it leaked when I primed the bulb so I am on my way to buy a new one now. Might not be delivering fuel to top carb? Idk. Getting pretty frustrating because it runs so well otherwise. Any help is appreciated.

compression- 110 on all cylinders

[panasonic]

So if the plug is firing and the cylinder is dead below 1000rpm it would seem you have a fuel problem.

Have you tried to pump the primer bulb when the problem is happening and see if it makes the any difference.?

It wouldn't hurt to rebuild or replace the fuel pump on a 16 year old engine anyway and it is not that expensive either. At least that will rule out that part of the fuel equation.

[99yam40]

sounds like the pilot jet or passages are plugged up.
once you get to the other passages the fuel flows as it should

edit: might be the top crank seal leaking sucking air affecting only #1 at low RPM

[Hd232smoke]

As far as the fuel pump I just replaced it but it has just started to piss rain so I have not been able to rule that out yet.

Also as for the jets or carbs i have a very hard time thinking there is a clog as I have cleaned the hell out of them. Every passage I could get to I have blown it out and have had carb cleaner coming out of every opening with what seems like zero flow restrictions.

Is the only way to test the seals with a leakdown test? And if it were a seal would that just be causing air to get in and make it lean out?

[99yam40]

the cylinder leak down test will not show it, the crank seal is on the crankcase not the cylinder.
there is no test I have heard of for the top crank seal.
maybe someone else has a way

[boscoe99]

Mist a little gasoline into the intake for the number one cylinder. If it starts to run it is clearly a fuel issue. Which it seems to be if you have spark on the number one plug.

If the carburetors were not ultrasonically cleaned you might have been spinning your wheels. It is hard to verify as being clean that which one cannot see. Or get to.

Would not hurt to put a manometer on the carb intakes to verify that are all pulling the same.

[99yam40]

Mist a little gasoline into the intake for the number one cylinder. If it starts to run it is clearly a fuel issue. Which it seems to be if you have spark on the number one plug.

If the carburetors were not ultrasonically cleaned you might have been spinning your wheels. It is hard to verify as being clean that which one cannot see. Or get to.

Would not hurt to put a manometer on the carb intakes to verify that are all pulling the same.

I had not thought about the OP not properly syncing the carbs after putting back on, but that is a possibility.

I am not sure if misting fuel into the intake to #1 would tell if top crank seal was sucking air, but with would tell is carb pilot jet or passages are a problem

[zenoahphobic]

Not mentioned, you need to check the physical synching of the carbies.
At idle the throttle plates are almost closed, your No1 may very well be closed and begins to fire when it opens a bit more, then allowing fuel to be sucked.
Vacuum balancing may not also work as wear maybe evident allowing small amount of air to enter where it shouldn’t, and then the reduced vacuum is not at the fuel jet/oriface outlet.

[zenoahphobic]

Simultaneous posting, Yam 40 you beat me to it!

[99yam40]

Simultaneous posting, Yam 40 you beat me to it!

yep, Boscoe got there 1st
my bet is he does not have a service manual with the procedures for working on his motor,
including the link and sync

[panasonic]

As far as the fuel pump I just replaced it but it has just started to piss rain so I have not been able to rule that out yet.

Also as for the jets or carbs i have a very hard time thinking there is a clog as I have cleaned the hell out of them. Every passage I could get to I have blown it out and have had carb cleaner coming out of every opening with what seems like zero flow restrictions.

Is the only way to test the seals with a leakdown test? And if it were a seal would that just be causing air to get in and make it lean out?

I just went through this with a friends engine. He had the carbs off at least three times for cleaning in the last few years and still it would not idle properly, but would run very well at every other throttle position.

I took carbs off and they looked spotless. Put them in my ultrasonic cleaner for extra long time. Put them back together, linked and sync them...the engine idles perfectly now.

Not saying your carbs are still dirty but it is a possibility.

[panasonic]

The ultrasonic cleaner I have will do one carb at a time. 20200929_231657.jpg

[Hd232smoke]

I have linked and sync according to the sm. I have also tried spraying some cleaner into carb 1 to see if it would pick up and it just bogs down. With an inline spark tester it seems to have steady spark when not firing as well as when firing. What I did notice though while checking timing was that the light seems to steady flash with no skips or hesitations that I can visibly see but the timing light will bounce between 7-9 atc and then all of the sudden that will disappear and TDC 2 appears when cylinder 1 stops firing. All while the timing light is still flashing. Sorry I tried to explain it my best.

Also I might need to invest in a cleaner as well for peace of mind.

[99yam40]

well that is interesting.
did you hook the timing light up to #2 plug wire to see what it is doing while #1 was missing also?

I would think this motor has 3 pulser coils telling the CDI when to fire each cylinder like my C40 does, So I am not sure how this CDI could get the firing mixed up.
maybe a short or some kind or cross connection between the pulser coils wiring to the CDI or inside the CDI

[Hd232smoke]

well that is interesting.
did you hook the timing light up to #2 plug wire to see what it is doing while #1 was missing also?

I would think this motor has 3 pulser coils telling the CDI when to fire each cylinder like my C40 does, So I am not sure how this CDI could get the firing mixed up.
maybe a short or some kind or cross connection between the pulser coils wiring to the CDI or inside the CDI

Yes I did hook the light up to #2 and it there is no "jumping around" going on even when #1 is not firing. Yes my model does have three pulser coils one for each cylinder and maybe I have a bad pulser but cannot properly test until my DVA tester arrives. So I have also noticed that i do not have to advance the timing at all to get #1 to fire I can simply move my throttle linkage to open the butterflies just enough to pick up some rpm and it will start to idle on all 3 again. Rpm of the flywheel/crank seems to be the deciding factor of what is causing this. Maybe a pulser is not picking up the signal below a certain flywheel speed and timing doesn't seem to be an issue because I don't have to advance the timing for cylinder 1 to fire? Wondering what else to test while I wait for the DVA. I understand I am just spitballing without proper testing but its bugging me..tetser should be here friday and hopefully that will help.