PROBLEM SOLVED - OX66 - High Idle & intermittent no ignition

[IFish4Tuna]

Hello - I have 2 issues. I'm not sure if they are related could use some qualified help on next steps.

1999 GW Bimini 306
Twin 1999 Saltwater Series OX66 250HP
I do my own maintenance, and have the service manual

Problem Description :

1. High Idle - 1100+/- RPM. The first issue began about 5 trips ago. Occurs shortly after engine is warmed up as well as after driven and returned to idle. Upon start up will be about 700 RPM. If put into gear and immediately return to idle will begin. Will also begin if just let run for a bit at idle. I have also seen where it never comes down from 1100 after start up.
2. Intermittently Turn key - HP fuel pump runs, but not even a click from starter. This began yesterday at the mooring when I began to trouble shoot #1. I have noticed the HP fuel pump will run for quite a while where as the other engine is only runs for about 5-10 seconds. I did not time either the good or bad engine during this.

Diagnosis done so far on #1:

• Swapped a few parts from good (port) engine to bad (starboard)
  • Thermo Sensor
  • Both Thermo Switches
  • O2 sensor (see 9/25 update)
• Tested Throttle Position Sensor - (see 9/26 update)
• Checked thermostats for corrosion. Both look good and also put in new thermos just in case.
• Checked Poppet (see 9/26 update)
• Decarb can/hose method (see 9/26 update)

Diagnosis done on #2:

• Nothing really. I don't know where to begin. It's intermittent, Electrical is not my strongest area. Not sure if it is directly related to #1 or just a 2nd problem
• I read in post on the internet about a guy with intermittent starting issue (as well as stalling issue, which I do not have) that he replaced relay and it solved it. Not sure if they meant starter relay or if that makes sense.
• Sometimes I turn the key and nothing. If I let it sit, and listen for the HP pump, and then go back and turn it will start. Sometimes I turn key off and back on and it starts. Sometimes I try/off/try/off and nothing. Then wait and it starts.
• I do think it is strange that port engine's HP pump runs only briefly with key in on position and starboard runs for quite a while.

Parts replaced earlier in the summer (both engines):
This was done to address a dieseling situation after key shut off, and also house battery not charging.

• Lighting Coil
• Rectifier/Regulator
• Pulser Coil

Thanks in advance, Ed

 

[seasick]

Take cowling off and replicate high idle issue. Without touching the throttle control, check the linkage at the motor starting with the throttle plate linkage. See if the lower adjusting screw is hitting the stop. If not, press on it and see if the motor idle drops. If it does, you have a bad throttle cable or a loose cable ( at the motor) mount.
A clogged O2 sensor system can affect idle as well as other ranges but leave that alone for now.
I am not sure what the HS pump runs longer since I am not sure what turns it off. It is possible I guess that a problem with the VST tank filling could cause the HS pump to starve and keep trying to pump fuel.The vast tank not filling could be a few things, LP pumps or lift pump ( if equipped) could be a cause as could an air leak in the fuel side. Try pumping the primer bulb before turning on the ignition to see if the pump shuts off faster. Note that if the primer doesn't get firm, you will have to find and fix that issue first.
Your starter relay issue is probably a bad connection especially since it started after you futzed around.

 

[IFish4Tuna]

Thanks.

Off to look at linkage.

I do not think I had done anything that would have caused the starter issue. The only thing I had done prior to it beginning to occur was remove the thermo sensor for testing. I could swap relays also I guess. I'm not confident on testing it since its intermittent and I expect the test results could also be intermittent/not reliable.

I will also check to see if the pump ever/never turns off w/ the key on.

Always something w these engines.

 

[IFish4Tuna]

Pump is shutting off now (today so far) and have not had problem turning it over so focussing on high idle. Linkage looks ok. Pulled o2 and clewned w seafoam spray. Tube had some build up but not bad. Fired it up warmed up came down to 700 then up to 1100. Going to swap 02s instead of bringing home to test it.

fun…

 

[seasick]

You should clean the O2 sensor in a liquid like Ring Free or even Carb cleaner, The liquid should not go past the slots in the sensor tip or you can damage it.
On that engine there is a spool/thimble part that goes into a hole in the cylinder wall. It is accessible when you pull the O2 sensor housing. That spool can get gummed up and should be checked. That said, I don't think the O2 sensor is your issue. If the sensor is good but plugged, the motor will run rich. That is OK when cold since that is how chocking is accomplished but after warm up, a too rich mixture will cause excess blackish smoke and plug fouling.
The TPS on that motor does not control engine speed like some do in other brand motors. It acts as data for the computer to determine how much.
fuel to inject.
The throttle bodies linkages are all connected to a common linkage and only the lowest 'idle' screw should be adjusted. The other screws should not be touched. To adjust correctly is complicated.
It is possible that you have a sticky injector that is not shutting off correctly and injecting more gas than it should.

You could test for a cylinder issue by getting the engine into the mode where the idle is high and then unplug spark wires one at a time to see what the motor does, rev wise. If ine cylinder has a dramatic effect, that is the place to look first for a stick injector.

 

[IFish4Tuna]

I've been told/read that can't use carb cleaner on 02 sensor. So I used the seafoam spray on the original. Then, w/ no results, I swapped them from engine to engine and problem persists, and the engine w/ all the parts from the starbaord runs just fine.

The throttle screw is seated when I press so there's no movement there. I did not notice any slop in the throttle cable bracket.

I forgot to mention in original post that I also ran blinky test and it is not throwing any codes.

Tomorrow barring any rain preventing me from working on it, I am going to remove intake cover and spray the throttle bodies to see if there any air leaks and confirm the intakes all seat well. I am suspicious that maybe because the engine heats up something shrinks and air getting in. I'm running out of ideas. I am not sure If I can pull the plug wires while it's running to determine if one injector vs another don't want to get shocked.

 

[glacierbaze]

You can buy what is basically a pair of plastic pliers in any auto parts store, to pull and replace plug wires.

 

[IFish4Tuna]

Thanks Glacierbaze - also - I realized I did not do the TPS test properly. So I will do that again tomorrow w/ linkage disconnected and throttle body closed.

 

[ttles714]

I believe 2 different issues and not related .... I would post this on the Boats.net Yamaha Forum ... There are a couple guys there that are pretty sharp .. one is a little nicer than the other !! LOL .... for my 2 cents , I will weigh in on the starter issue... The "click" is the solenoid getting power from the key switch.... Check that it is actually "transferring " the high amp voltage to the starter itself. If it is, This may indicate that the heavy battery cables my be corroded and unable to carry the proper amperage from the battery to the starter. (even though they may read proper voltage... A bad ground will do the same ... You may actually have to do a physical check of the wires from the battery thru the rigging tube. It is not uncommon for the copper inside the sheath to be so corroded that it cannot carry proper amperage, yet still read proper voltage,... Another thought here is to swap starters and solenoids ...

As far as the high idle goes, I think you covered most of the bases... Is it possible that it is actually a throttle linkage or cable issue ????

I would like to know how you make out .... good luck ,., tony

 

[seasick]

I forgot to ask this question. When starting with a cold motor is the idle high and lowers as the motor warms up? It should.

Also back to the throttle cable; The lower screw as mentioned is the idle speed adjustment. When the helm control is in the neutral position, that screw should hit the stop. Check when cold and after the idle problem. If the screw does not touch the stop, he throttle cable needs adjustment.
One other thing that might keep the throttle open is not likely but still possible and that is a problem with the oil pump linkage. That too should be checked for a loose or broken clamp, or misadjustment. That linkage is activated by the throttle mechanism and if stuck or binding can keep the throttle from fully closing.

 

[IFish4Tuna]

Yes on cold start idles high and comes down to 700 other times it says high

Also throttle acrew is touching plate at cold. Oil lonkage looks good.

going to run a decarb today and seen that has any effect. I’d be surprised but cant hurt.

The sun is out so easy work conditions today

 

[IFish4Tuna]

Well here's the day's report.... Thought I was on to something early on...

As noted above I intended to check the TPS again because I did not test it properly earlier. What I discovered is the engine w the trouble had a bad TPS reading. It was reading .21 vs .50 +/- .02

But no matter how I tried to adjust it, I could not get it to read .50. The highest reading was in the .30's. After about 45 mins crouched behind the engines I finally pulled it all the way off to have a close look. Well what I found out is that the little "T" on the back I could easily get to read. 50 but it would not align with the screw holes. So I decided to swap it with the port engine. That one read .50. FWIW I have adjusted these in the past on a different engine so know how sensitive they can be.

Before I put the "bad" one back on the port I twisted the "T" several times back and forth thinking maybe there is some corrosion on the inside. Then I put it back on the Port engine, and tested it and easily got it to read .50 before tightening the screws.

Then I moved on to a complete decarb of both engines.

Marine Engine Care | Sea Foam

Asked if he’s ever run into engine trouble out on the water, pro bass angler Chad Morgenthaler pauses and laughs before responding.

seafoamworks.com

During the starboard engine it ran at 700 the whole time during first cycle and did not creep up until the 2nd cycling of the engine (see instructions in link). During 2nd cycle it revved up and came back down on it's own 6 times in the course of about 7 mins.

Needless to say my harbor was thick grey smoke from all this.

i was feeling a bit confident that the problem would be gone due to the TPS setting and then good decarb with seafoam,

So I went for a 7 mile ride to gas up at the next harbor and blow out any remaining carbon.

As I was pulling up to the gas dock I put the boat in neutral and the rpms rose. After the gas up and starting up, the RPMs came down and went back up. Then after about 2 mins of drifting they came back down.

When I got back to my mooring, I pulled the poppet valve and inspected it. It was very clean. No buildup, not stuck open.

I ran out of time on pulling spark plugs but i did get a fuse puller from my hardware store that should do the trick. I guess that's my next option is to pull spark caps and see if one of the injectors is sticking open.

Running out of ideas now for sure....

 

[IFish4Tuna]

Problems solved. Thanks for the tips & recommendations. Much appreciated.

1. Idle speed. I made a minor adjustment to the remote control cables at the engine end for both gear shift and idle. That seem to have remedied the problem. Ran it for an hour or so in and out of gear as well as WOT and have not had it occur. I also sprayed / lubricated the cables at the engine end with silicon spray.

2. Intermittent starter not starting. As mentioned in my original post, I had replaced some electrical components a few weeks earlier. One of them was the regulator / rectifier. In order to replace that I had to remove all ground wires. And on re-assembly, one of the wires was the ground wire to the relay. Today when I was getting ready to replace the relay w/ a new one I was disconnecting wires, and when I pulled on the black ground it came out with the broken end of wire. No terminal ring. See photo. So it must have been just barely touching ground in order me to start the boat. Wow!

3. I have not noticed the fuel pump running excessively past the original day. Will keep an eye on that over time.