still messing with the looper - fuel pump?

[tal]

J120TLCOS - Recently found my WOT timing was off about 6 degrees. I set this up and did a test run about a month ago or so before it got too cold. That day I went out the engine seemed to run ok at WOT but slowing down then hitting the throttle again would cause an odd surge of power and cutting out for a few seconds then it would clear up. It sort of sounded like it was starving for fuel. In addition, I'm still having the high idle issues while not in gear. I'm wondering if the 438559 is running too lean at idle and WOT for my engine? I see the 140hp guys running this pump with no issues so I don't see why it wouldn't work for the 120hp.

I've been through this thing over and over. Carbs cleaned (3 times), timing set, new fuel lines, new filter, new fuel tanks and fittings, link and sync is 100% correct and not holding butterflies open, new cam roller 120 psi for all 4 cylinders...everything except fuel pump really. I did take it apart probably 2 months ago to inspect and everything looked good with no rips but perhaps it's just not adequate for my engine. I'm pretty much out of ideas. Short of throwing on a new fuel pump and messing with idle jets, I have no other choice but to haul it in to a mechanic, which is nonsense because I've done all this work myself already.

 

[CharlieB]

Re: still messing with the looper - fuel pump?

It is NOT the fuel pump unless there is a problem with the pulse limiter valve in the pressure/vacuum hose to the crankcase. That pump should be more than capable of supplying all the fuel your motor needs.

The 'surge' in power is an interesting condition, double check the fuel lines and filter/screen after the fuel pump to be sure there is no restriction, any flow restriction could reduce WOT power yet at any reduced throttle setting allow the carbs to refill, giving you that 'surge'' of full power until the fuel levels fall to the restricted flow level.


A fast idle can be caused by a number of things, advanced idle timing, intake leak, fat idle mixture, leaking enrichener valve, too high carb float level, all must be checked and ruled out one by one.

 

[Dhadley]

Re: still messing with the looper - fuel pump?

There's a chance the old style pump may not be supplying enough fuel. Just something you'll have to check by pressure & volume.

You said the timing was off by 6 degrees which is a ton for a looper. What is the wide open timing set at now? What was it set at?

 

[kenmyfam]

Re: still messing with the looper - fuel pump?

Check the fuel pump output. Mine is great as are others I have done....but that does not mean yours is putting enough out.

 

[tal]

Re: still messing with the looper - fuel pump?

I'll check the fuel pump output this weekend. I do have a small fram automotive filter inline instead of the plastic screen. I threw the plastic away because it was cracked and leaking. I wouldn't think this would be very restrictive but perhaps I should replace it with the factory plastic screen.

The WOT timing was at 21-22 before I set it at 28* where it's supposed to be. Now it seems like it might not be getting enough fuel or something with the WOT timing set where it should be. In an older post I talked about how the timing base was actually sticking and not hitting the WOT stop. After I unstuck it the engine ran better. Then I found I was not getting the right WOT timing so I adjusted that and I'm here now. As far as the fast idle goes, it only happens when I take it out of gear. In gear I have the rpms set at 750 like the book calls for, but when I take it out of gear it idles up to 1400 or so. If I leave it in gear and attempt to adjust the idle below 750 it starts to miss and eventually dies because the idle screw retards the timing too much.

There's no sticking of butterflies or cables and everything is returning back to correct link/sync position. It just wants to idle high with no load on it. Carbs, floats, etc are in perfect condition. I have fully disassembled them and cleaned them 3 times (after rebuild kits) since I bought this motor in early October. I am sure it is not carb passages.

 

[ezeke]

Re: still messing with the looper - fuel pump?

I'll check the fuel pump output this weekend. I do have a small fram automotive filter inline instead of the plastic screen. I threw the plastic away because it was cracked and leaking. I wouldn't think this would be very restrictive but perhaps I should replace it with the factory plastic screen..........

Neither. Get a full sized water-separating fuel filter mounted as close to the tank as possible. They work on gravity, so the more stable the location, the better.

 

[tal]

Re: still messing with the looper - fuel pump?

Neither. Get a full sized water-separating fuel filter mounted as close to the tank as possible. They work on gravity, so the more stable the location, the better.

got a link to a good reasonably priced one?

Thanks

 

[ezeke]

Re: still messing with the looper - fuel pump?

http://www.iboats.com/Fuel-Water-Se...9514236--**********.804943853--view_id.187573

 

[tal]

Re: still messing with the looper - fuel pump?

Cool. Thanks. Now I need to find a place to mount it in between my 2 little plastic 6 gallon tanks.

 

[Dhadley]

Re: still messing with the looper - fuel pump?

No stock 120 is supposed to be anywhere near 28* timing. If that's where you have it I'm shocked it's still running. Recheck the spec in your OE service manual. Quick.

And if your 2 6 gal tanks have 5/16" lines your motor won't like that either.

 

[tal]

Re: still messing with the looper - fuel pump?

Stock timing for my engine is 22* according to manual and the sticker which is still on the carb silencer, I think I made a typo above because it is not at 28*. Sorry for confusion. Fuel line is 3/8 from tanks.

I'm beginning to steer myself away from a fuel issue though. Last night I had it running on muffs, of course, idling high. I began by lowering my idle down with the idle screw by screwing it in. Once I hit a certain rpm range it started doing its patented rough idle miss - the reason why I couldn't idle it down on the lake because it would die at trolling speed with this miss. It seems to be one cylinder or one bank.

I began messing around with the wires and I found if I pulled the starboard bottom plug the engine would idle flawlessly and not miss a beat. Plug it back in and it started missing right away. I swapped coils on the starboard side engine bank and it still did the same. So basically, as I'm trying to idle down my engine, I hit a certain RPM and start getting missfires on the bottom starboard cylinder. If I idle the engine around 1400-1600rpms the miss goes away. I'm leaning towards an electrical issue that surfaces around a low rpm and goes away at higher rpms. Does this make any sense? BTW thanks for the suggestions so far. I'm determined to get this figured out.

 

[nymack66]

Re: still messing with the looper - fuel pump?

I'll check the fuel pump output this weekend. I do have a small fram automotive filter inline instead of the plastic screen. I threw the plastic away because it was cracked and leaking. I wouldn't think this would be very restrictive but perhaps I should replace it with the factory plastic screen.

The WOT timing was at 21-22 before I set it at 28* where it's supposed to be. Now it seems like it might not be getting enough fuel or something with the WOT timing set where it should be. In an older post I talked about how the timing base was actually sticking and not hitting the WOT stop. After I unstuck it the engine ran better. Then I found I was not getting the right WOT timing so I adjusted that and I'm here now. As far as the fast idle goes, it only happens when I take it out of gear. In gear I have the rpms set at 750 like the book calls for, but when I take it out of gear it idles up to 1400 or so. If I leave it in gear and attempt to adjust the idle below 750 it starts to miss and eventually dies because the idle screw retards the timing too much.

There's no sticking of butterflies or cables and everything is returning back to correct link/sync position. It just wants to idle high with no load on it. Carbs, floats, etc are in perfect condition. I have fully disassembled them and cleaned them 3 times (after rebuild kits) since I bought this motor in early October. I am sure it is not carb passages.

NEVER install a automotive filter on 2 stroke engine, If you are pre-mixing this type of filter will never pass 2 stroke oil, it will clog and destroy your engine..

 

[tal]

Re: still messing with the looper - fuel pump?

The small inline filter has been on for about 3 months but I'm getting a fuel/water separator. Interesting though as it seems to be getting plenty of oil.

 

[nymack66]

Re: still messing with the looper - fuel pump?

Please verify the replacement fuel/water separator you are buying has the correct filter for a 2 stroke (pre-mix) and not a 4 stroke..
I have a fuel/water separator installed however the filter on it indicates something to this effect "will not separate 2 stroke oil" or safe for pre-mix ..Just FYI ..

 

[CharlieB]

Re: still messing with the looper - fuel pump?

... rough idle miss - the reason why I couldn't idle it down on the lake because it would die at trolling speed with this miss. It seems to be one cylinder or one bank.

I began messing around with the wires and I found if I pulled the starboard bottom plug the engine would idle flawlessly and not miss a beat. Plug it back in and it started missing right away. I swapped coils on the starboard side engine bank and it still did the same. So basically, as I'm trying to idle down my engine, I hit a certain RPM and start getting missfires on the bottom starboard cylinder. If I idle the engine around 1400-1600rpms the miss goes away. I'm leaning towards an electrical issue that surfaces around a low rpm and goes away at higher rpms. ....

Rig your timing light on that cyl and watch the timing for any change as you slow the idle into that range.

Just for drill, swap the packs to see if the problem swaps sides on the motor.

If the timing changes with NO change in the timing lever, no change other than RPM, you may have found your problem, also if it changes sides with swapping the packs it should be quite clear.

 

[Dhadley]

Re: still messing with the looper - fuel pump?

The idle is not adjusted on a V4 looper with the screw in the throttle arm. Reset all the sync & link by the book and run it again. It will idle high on the hose (no exhaust backpressure) so you have to set the idle rpm in the water.

 

[Dhadley]

Re: still messing with the looper - fuel pump?

CharlieB - just an FYI, that motor only has 1 power pack.

 

[ezeke]

Re: still messing with the looper - fuel pump?

.....I began messing around with the wires and I found if I pulled the starboard bottom plug the engine would idle flawlessly and not miss a beat. Plug it back in and it started missing right away. I swapped coils on the starboard side engine bank and it still did the same. ........

You might want to check your wires from the stator to the spark plugs in case something is switched.

 

[tal]

Re: still messing with the looper - fuel pump?

The idle is not adjusted on a V4 looper with the screw in the throttle arm. Reset all the sync & link by the book and run it again. It will idle high on the hose (no exhaust backpressure) so you have to set the idle rpm in the water.

I have adjusted the idle and done sync & link per manual instructions. I understand it will idle high on the hose but shouldn't be idling at 2500rpms. The last time I had it in the water it was set to idle ~800rpms in gear, anything lower would cause a miss and kill the motor. Naturally, when I took it out of gear it would idle up to 1400-1600rpms. The butterflies are completely closed. So now at home, idling the engine down and listening on muffs, it seems quite clear one of the pistons is missfiring. When I'm able to unplug that sparkplug, the engine smooths out perfectly. Now I'm down to carbs or electronics. Since I've rebuilt the carbs once and cleaned them twice (shining led flashlight through all passages to ensure they're clear) I'm leaning more towards an electrical issue. Especially since it seems like my WOT rpms aren't what they're supposed to be with a 21 pitch prop on a 15.5 bass boat ~ 5300rpms trimmed with engine on highest notch. This doesn't sound like the normal pack issues, however, so I'm trying to gather more info and diagnose more.

I will check my pack wires to ensure they're not swapped or anything. I'll also check for rubbed wires to ensure they're not grounding out anywhere. Although I don't know why it would only do it at low rpms if one of these is the issue.

I'll try the timing light thing tonight if it's not raining when I get home. It seems someone suggested that in the past and it completely slipped my mind. I guess that's what happens when you work on something on and off every 3 weeks.

Thanks

 

[tal]

Making progress?

Making progress?

I hooked up the timing light to the cylinder that seems to be missing. I discovered a definite unsteady fire pattern by observing the timing light strobe. I swapped coils with the cylinder right above it and no change. I swapped wires with the cylinder above it and the erratic strobe followed the wire. I went to nearby omc parts store, built the wire and installed it on the problematic cylinder. All 4 pistons appear to be getting the same consistent fire pattern now but there is still a definite miss or "huff" sound coming from the exhaust at low rpms, occasionally causing the engine to die. Once again I was able to trace the problem back to that same cylinder that had the bad wire. Yet the wire is no longer bad and I'm getting consistent spark.

So what does this mean? By unplugging lower starboard the engine will run fine on the remaining cylinders without missing a beat. By sticking that boot back on the plug the engine begins huffing or displaying a miss fire symptom which can cause it to die.