OX66 LP Fuel Pumps

[seasick]

Can someone else verify: my understanding is that the O2 sensor is useless at higher RPMs, it is only used for lower rpms. With the LP fuel pumps, take the hoses off and then try and suck and blow in each end you should be able to do one but not the other. I don't think that is the problem for you since you have greater fuel burn. I had one of the two on my HPDI go and the only symptom was that the motor felt like it was cutting out at higher rpms (a mechanic diagnosed it as "losing a coil when it heated up") Actually what was happening was that above 4000, the VST tank was getting sucked dry and the motor was starving for fuel. As soon as I brought the rpms below 4000, the remaining, good, lp pump was able to keep up with demand and refill the vst tank and the motor ran perfectly. The cut out and kick back in was so instantaneous it was like a cylinder (electrical) shut down. Like I said, probably not your problem but when I replaced both, the bad one would allow me to suck air back and the good one wouldn't.

That is a classic symptom. Usually though, a fuel pressure test on the fuel rail will show a drop in pressure as the high speed pumps starves. When surging at higher rpms or when the boat gets a little beaten up by the seas, 90% of the time, it is a VST issue and most often the VST screen is clogged. Is this the case here? I can't tell, there ave been so many parts changed and not enough diagnostics in my opinion

 

[fishinAK1]

...the only parts that have been changed, since symptoms occurred, have been plug boots, O2 sensor, and LP fuel pumps. And I feel like I’ve trying to diagnose the problem for the past 3 weeks

...the VST is completely 100% clean in this case.

 

[fishinAK1]

But I think your advice of trying to step back and diagnose 1 system at BBC a time is great. And that is what I am going to do. Starting with fresh gas from a kicker tank.

BUT, 1 more question thought first. I was thinking about what you said about the throttle not opening the valves all the way... looking at the throttle linkage rod, I’m not sure if I can adjust anything to make it open up anymore and still let it sit by the marked triangle in neutral position. The pic attached is at WOT. Is this where it should be

Also, I was again testing the TPS voltage while operating the throttle. I noticed that the same physical position on the throttle handle doesn’t always correspond to the same TPS voltage output. Is this normal?

...hard to explain...lemme try. If I start in Neutral, push the handle forward 3 inches the TPS says 1.0. V. Now if I push the throttle forward 4 more inches, and then pull back 4 inches, the TPS will say 1.5 (ish).

But again YES I will test new gas. But I am curious about throttle linkage adjustments and TPS voltage output.

 

[seasick]

But I think your advice of trying to step back and diagnose 1 system at BBC a time is great. And that is what I am going to do. Starting with fresh gas from a kicker tank.

BUT, 1 more question thought first. I was thinking about what you said about the throttle not opening the valves all the way... looking at the throttle linkage rod, I’m not sure if I can adjust anything to make it open up anymore and still let it sit by the marked triangle in neutral position. The pic attached is at WOT. Is this where it should be

Also, I was again testing the TPS voltage while operating the throttle. I noticed that the same physical position on the throttle handle doesn’t always correspond to the same TPS voltage output. Is this normal?

...hard to explain...lemme try. If I start in Neutral, push the handle forward 3 inches the TPS says 1.0. V. Now if I push the throttle forward 4 more inches, and then pull back 4 inches, the TPS will say 1.5 (ish).

But again YES I will test new gas. But I am curious about throttle linkage adjustments and TPS voltage output.

There is very little chance that testing the voltage by moving the throttle handle will give accurate results. Based on your other teasing the TPS is not the issue.
If the throttle cable is not opening the throttle plate all the way, wot could be affected. You could have a bad cable or a problem in the 704 control but don't run out and buy new ones. To check and adjust the throttle cable, I do it like this;
Disconnect the cable at the motor. With the shift override on the handle pushed in, push the handle all the way forward. Mark the spot where the center wire exits the sleeve at the motor end. Repeat but push the handle all the back and check that the cable end came out to the same mark or close to it.
Now push the handle into neutral position and go back and forth a little bit just to make sure it is in the neutral center position.
Make sure the idle screw is adjusted at the motor and connect the throttle control cable. If the clevis hole doesn't line up, you need to adjust the clevis end until it does.
Now move the throttle handle with the neutral override pressed fully forward and see if the throttle plate fully opened. It may not go all the way but should go pretty far open.
There is an adjustment in the 704 control to set the end limits I believe but it really should not have changed. If the cable sheath is broken however, it can stretch and that will limit the center wire range.
Do I think that is your issue? Not really but who knows.
I still think it is fuel so work on the portable tank, remembering to connect it in such a way to eliminate as many fuel components as possible including the hose from the primer to the on motor filter.

 

[fishinAK1]

Thank you all. I’m going to try to find a Winky Blinky. I see Sims has them in stock. I was just hoping to save a few bucks and find a used one. ...$50 shipping, to AK, from Sims.
I’m also gonna try to run fresh gas today.
My throttle box is a 703. But I assume a similar process as Seasick described for 704.

 

[seasick]

One is single handle, the other dual handle. Internally they are the same for the most part

 

[fishinAK1]

I just ran around on the kicker tank for 1/2 hour. Trying all RPM ranges. Guess what? NO SURGING!
Only a couple little hiccups near the end, which I’m attributing to grabbing air near the bottom of small gas tank.
Holy cripes! Could this surging issue really be due to bad gas!?
Early on I ruled out bad gas because it didn’t seem to surge at higher rpms. I thought it’d be consistently surging throughout throttle if gas was the culprit.
i did try a new fuel line between the racor s as d outboard, early on. same problem. So I feel confident ruling out plumbing downstream of Racor

However, unfortunately i can’t get past 4900 rpms at WOT. But this is likely an unrelated issue. Maybe I just need to adjust the throttle cable.

WELL now what to do w 1/2 tank (45 gal) of potentially bad gas?

Thank you all. I’ll report back when I’m 100% the gas was the cause. And I have WOT issue figured out.

 

[DennisG01]

I just ran around on the kicker tank for 1/2 hour. Trying all RPM ranges. Guess what? NO SURGING!

Good!

I feel like we had this conversation (and that recommendation) a while back, but I couldn't find that thread - maybe it was with someone else. Regardless, the second suggestion I would have had was to run the regular cap, but with the fuel cap off. That will also tell us good info. Try that.

How does the gas smell? What additives do you use? Did you drain some gas, from the VST tank, into a clear gas jar (spaghetti)? Do that, too - and post a pic.

 

[fishinAK1]

Dennis-
Do you mean run off the regular TANK either the cap off? The regular tank is a 5 yr old 86 gal aluminum tank with an always open vent hose. Curious whst would running wo the cap tell us?

Yes, I have drained, smelled, observed the VST has multiple times. NEVER a drop of water. Looks clear, and smells like gasoline. Pic attached.

also haven’t had a drop of water in the Racor either. Or the onboard filter....

Can gas be “bad” without water or particulates?

 

[fishinAK1]

I usually add a can of Seafoam to about every 80 gal or so. And I likely (can’t remember for 100% sure) added Stabil this past fall.
For 10 years I have only used Yamalube 2 stroke oil. However, once this is remedied I’m converting to Pennzoil Xtended life.

 

[DennisG01]

Yes, run off the 86 gallon tank with the fuel fill cap off. This is the easiest way to see if the vent line/fitting is clogged... which would restrict fuel to the engine.

-- If the problem goes away, you found the culprit - either an internally failing vent line, a low spot in the vent line where fuel has accumulated (clog) or the vent fitting is clogged.

-- If you still have the problem, then the issue is... the fuel pickup tube is clogged or cracked, the AS valve (if you have one) is clogged (cleanable) or the main fuel line is clogged/failed internally.

It's all about narrowing down the possibilities/variables!

If the fuel looks good and smells good... it's good.

 

[fishinAK1]

Old vs new.
New gas slightly clearer. And slightly more “gas” smell...

 

[DennisG01]

The color of that old gas is perfectly fine. It's when it start's looking brown and smelling like varnish that it's a problem.

 

[fishinAK1]

Well I took boat out again this evening. Trying to narrow down further. First ran from kicker tank to Racor with existing lines to outboard. This resulted in surging again.
Then ran straight from kicker tank to outboard (same as earlier this morning). This time the surge was back. Albeit, seems less frequent and less dramatic than when running through the Racor

Also interesting, this evening during both trials there was a surge that started around 3000 surged up to 3600 and stayed there. Typically, these surges only surge up 400 rpms, then promptly drop right back down.

SO what did I accomplish today... Eliminated “bad gas”, and perhaps plumbing between the tank and outboard as the culprit. Although it is interesting that it did seem to run noticeably better with kicker strait to OB.

Also, in general, I feel like each time we take it out during these “tests”the surges seem to be a fit less frequent? Coincidence? Idk.

Ok suggestions for next steps? I’d like to check the fuel pressure while running and during surges. Just hate running wo cowl and hanging of the back of the boat.
I’m going to mention one more thing. That I hate to bring up because of the fact it likely has nothing to do with this. But maybe...
On 3 occasions in the past 3 years (once during same trip that these current symptoms began occurring). The little linkage with the white roller has bent inward causing poor contact with that cam that the throttle link rod attaches to. What this ends up resulting in is a very sticky throttle progression. Then it Bends to the point it will barely throttle up. After slightly bending back towards cam. Alls good. Never could figure out what actually causes this or how it binds enough to bend. Anyone ever have a similar issue w this part I’ll attach pic)bending?
Again I doubt this has anything to do with current issues. But maybe... is it possible the throttle cable is binding and/or relaxing causing the surge?

I know this makes my outboard sound old junky. But honestly it’s not. It’s been well cared for and only has 750 hrs.

Thank you!

 

[Sparkdog118]

Maybe hook up the test tank hose to the feed hose where it comes out of the main tank. This will test all the plumbing in the boat. If it surges, Then most likely you have a collapsed fuel feed hose. If not, you either have bad gas or a blockage in the fuel pickup.

 

[Sparkdog118]

Oh. Didn’t see your last post. I have had some problems with the Yamaha grey hose turning to jelly and collapsing when suction is applied and when you pump the ball, it blows it back up and feeds just fine. Then the fuel pump sucks it down again real soon. Also if the racor is sucking air at the o ring just above the clear glass it will surge.

 

[DennisG01]

Well, it kinda feels like we're jumping all over here - I'm sure it's quite frustrating for you. Since it is now surging on the portable tank, even directly to the OB, you can forget about everything upstream of the engine... unless you didn't open the kicker tank's vent?

Can you better explain the surging? How long it takes to surge ("promptly" can be subjective)... does it recover by itself and how long does it take?

I wouldn't worry about running without the hood - just rinse it off after you're done and spray some Boeshield T9 on it. Definitely get a fuel pressure gauge on there at this point. Let's see what's going on. With the hood off, you can have someone physically watch the linkages, too.

 

[Sparkdog118]

I have had the best luck with oem OMC fuel hose. It is about 8 bucks a foot, I have been putting it in customers boats for years without 1 complaint. I’ve had the same fuel hose in my boat for over 10 years and it is still in excellent shape. I usually install 5/16 inch to a Yamaha like yours.

 

[fishinAK1]

Can you better explain the surging? How long it takes to surge ("promptly" can be subjective)... does it recover by itself and how long does it take

You bet I can explain. The surging most commonly occurs between 2500 and 4000. It hasn’t surged at all above 4100 rpms and or under 1000rpms. Seems more prevalent when throttling down rather than throttling up.
Each surge quickly increases the rpms by 400 then falls back to normal, by itself, within 2 seconds. Maybe ”surge” isn’t a good description, more like rpm “jolt”)
EXCEPT the 2x this evening, that I mentioned in lost post, where it surged about 600 rpms and never when back down. Until I handled the throttle of corse.

...mentioning 5/16” fuel line, the line that I was running off the portable tank today came w my 9.9 kicker. Likely not 5/16”. But fit the nipple on the onboard fuel filter. So I assumed it was fine....

Thank you all so very much. I do sincerely appreciate it! I am at an all time mechanical frustrations high!!

 

[DennisG01]

I am at an all time mechanical frustrations high!!

I don't doubt it!

OK... just to double check... you had the vent open on the porta tank? Double check that hose - squeeze every inch of it making sure there are no soft spots.

Assuming that's OK, go ahead with the plan to monitor fuel rail pressure and observe the linkages. I'm trying to stick with no cost things to begin with. But after that, the Winky "might" be of help - worst case, you bought another tool... which is never a bad thing!

I don't like "throwing parts" at a problem - it's not the proper way to do it. BUT, have you ever had the injectors rebuilt? It's about $20/injector and if you don't know when it was done, if ever, this can be chalked up to a maintenance item - and could be a cause for the issue. No guarantees, of course, but it's not a bad idea to have them done, anyways.

EDIT: I wanted to add something, but take this with a grain of salt as it's really just WAG. I'm also wondering if excessive heat (build up inside the cooling passageways) could be an issue - affecting either the fuel or a sensor. There's a bunch of "if's" coming up, but it's another free check... IF heat is the problem and IF it's minor enough then taking the cowl off MIGHT (kinda like an "if") provide enough cooling to correct them problem... which would then lead towards cleaning the passageways.