f150 misfiring. have tried everything i can think of. HELP!!!!

[Josephmast94]

I have twin Yamaha 04 F150s, the port side just started acting up (shaking and not preforming like the other engine). after a long series of test we determined cylinder 4 is not firing. replaced the spark plug, even though it seemed to be sparking just fine, didn't help, and compressions are all around 150. I switched two of the injectors and used a test light, there seems to be a pulsing ground going to the injector, just like the others. I even bought a YDS kit to run the codes, but it did not show any error codes or any problems. like I said there are problems, when the motor is running you can unhook the # 4 plug wire and it runs the exact same, no change in tone or RPM. when we tried that on the other motor it started running rough just like the port side does. so I am very confident there is a problem somewhere, just need help figuring it out. I will be online checking for updates tonight so I will be able to respond rather quickly to any questions. thanks in advance for any help.

 

[alldodge]

Re: f150 misfiring. have tried everything i can think of. HELP!!!!

:welcome: to iboats

No expert on your outboards but I'm thinking your not getting fuel to the injector. Your getting spark, replaced the injector with another and no part follows the problem. The problem stays on the cylinder and compression is good.

 

[Josephmast94]

Re: f150 misfiring. have tried everything i can think of. HELP!!!!

:welcome: to iboats

No expert on your outboards but I'm thinking your not getting fuel to the injector. Your getting spark, replaced the injector with another and no part follows the problem. The problem stays on the cylinder and compression is good.

that is correct, problem stays at #4. #4 is also the bottom cylinder is that could help anyone.

 

[99yam40]

Re: f150 misfiring. have tried everything i can think of. HELP!!!!

. after a long series of test we determined cylinder 4 is not firing. replaced the spark plug, even though it seemed to be sparking just fine

Did you test to see if spark would jump a 7/16" gap ?
Saying it seems to be sparking does not mean it is

Just for the info
Pulling plug wires off with out giving it a place to jump to ,can harm the coils and other electrical parts with high/spiking voltages

 

[Josephmast94]

Re: f150 misfiring. have tried everything i can think of. HELP!!!!

Did you test to see if spark would jump a 7/16" gap ?
Saying it seems to be sparking does not mean it is

Just for the info
Pulling plug wires off with out giving it a place to jump to ,can harm the coils and other electrical parts with high/spiking voltages

hen

no we did not see if it would jump a 7/16 gap. when I said it seems to be sparking I was going off of the fact I could see (and feel) it was getting juice, then replaced the plug , which apparently did not help. how should I do the 7/16 test? i am open for any suggestions at this point.

 

[99yam40]

Re: f150 misfiring. have tried everything i can think of. HELP!!!!

adjustable spark testers are sold at a lot of auto part stores and on line

good Compression, good spark at the correct time and the correct air to fuel ratio and the cylinder will fire

not sure if that motor has lift pumps run off of crankcase pluses, but if it does a leaking one could make a cylinder too rich to fire properly

 

[Josephmast94]

Re: f150 misfiring. have tried everything i can think of. HELP!!!!

adjustable spark testers are sold at a lot of auto part stores and on line

good Compression, good spark at the correct time and the correct air to fuel ratio and the cylinder will fire

not sure if that motor has lift pumps run off of crankcase pluses, but if it does a leaking one could make a cylinder too rich to fire properly

I does have two mechanical fuel pumps on the back side of the engine that are ran off the camshaft I believe. we have had a "oil making" problem with the motor, I attributed it to the fact the thermostat was corroded and stuck open. could one of the diaphragms be damaged and be causing both problems?

 

[99yam40]

Re: f150 misfiring. have tried everything i can think of. HELP!!!!

sorry I forgot it was a 4 stroke, have no idea if they would affect running as they run off of cam

 

[Capt Ken]

Re: f150 misfiring. have tried everything i can think of. HELP!!!!

Being it uses a common fuel rail and you swapped injectors, that is ruled out. Have you swapped coils yet to see if the problem stays or moves?

 

[alldodge]

Re: f150 misfiring. have tried everything i can think of. HELP!!!!

The no expert guy here again, been looking around and found another guy with problems back in 2010. His problem turned out to be the filter screens on the fuel rail. Might be worth a look

http://forums.iboats.com/yamaha-suzuki-outboards/yammi-f150-fuel-probs-198670.html

 

[Capt Ken]

Re: f150 misfiring. have tried everything i can think of. HELP!!!!

If that was the problem then the miss would have moved with the injector being the filters are pressed into the top of the injector, not the fuel rail.