F100 Motor Problem Troubleshoot

[Summer Breeze]

Suddenly my motor (1999 F100) has started to run pretty ragged. Hard to fire up and maintain idle and seems to only be firing on two cylinders. Did some basic trouble shooting with my brother in law who is an auto mechanic and here is what we come up with:<br />Cylinders 1 and 4 not firing properly<br />All spark plugs burning clean; none fouled<br />All plug wires generating spark<br />Swapped the coils and removed individual plug wires with motor idling to see if one of the coils could be bad - negative<br />Doesn't seem like a fuel filter problem because motor will run at almost full power at higher RPM's 3000 to 5000<br />Checked the fuses they are OK<br /><br />The motor seems to have been running fine over the last couple years with the exception of occasional blue smoke on startup.<br />I am planning to have it serviced soon, but most places down here are booked for the next couple weeks. I'm wondering if you guys may be able to shed some insight into this , seen similar occurrences or can give me some idea of what to expect in terms of repair.<br />Thank you.<br />

 

[rodbolt]

Re: F100 Motor Problem Troubleshoot

hello<br /> take my advice. dont let a car mechanic monky with you high performace outboard, most just dont get it.<br />your describing a carb problem. you will need a manometer to check them and to set them after you rebuild them. you shoud do a spark test and a leakdown test before the carb job. the carb job on that engine is not for the faint hearted. its a long operation and its rather delicate. it either works as designed or its ragged. test the auto enrichment circuits for sticking or binding.<br /> the blue smoke at start up is operator error. re read your owners manual for the reason why.<br /> good luck and keep posting but test the engine mechanical first.

 

[Summer Breeze]

Re: F100 Motor Problem Troubleshoot

Thanks Rodbolt,<br />Sounds like I need to take it to a certified Yamaha tech. Is it normal to be in need of carb rebuild after only 4 years (I haven't really used it much during fall and winter months)? Could it just be in need of adjustment? Also, would it cause any damage to run it in its present state? We are approaching the peak of salmon fishing here in the NW and most shops are booked at least a week or two.<br />I hate to miss out on fishing right now, I could use my 6HP to fish but don't want to chance messing up the main any worse.<br />Thanks again for your time.

 

[rodbolt]

Re: F100 Motor Problem Troubleshoot

hello<br /> the hardly use it part is probably what got ya. if you do have a fuel restriction you may run the risk of a burned exhaust valve. Mechanics take bribes. trust me .cash gets workorders moved about. enogh cash and I show up at the boat.<br /> good luck and keep posting.<br /> PS you may try pulling the drains and flushing the carbs with carb cleaner then flush by pumping the primer bulb.

 

[fastcatch8]

Re: F100 Motor Problem Troubleshoot

I recently had the same problem and the mechanic found the filter screen on the fuel pump was clogged up. I have the f22 yamaha. I use shell gas exclusively and suspect this is the problem.

 

[Summer Breeze]

Re: F100 Motor Problem Troubleshoot

Fastcatch8,<br />Thanks, maybe thats why there seems to be link between cylinders 1 and 4. They are probably running on the same pump. I'll check this myself and take rodbolts suggestion of draining the carb bowls, etc.<br />I hate to have to fork out 400 buck for a carb rebuild if not necessary.This motor has about 450 hours on it.

 

[Summer Breeze]

Re: F100 Motor Problem Troubleshoot

Rodbolt,<br />Is the filter screen on the fuel pump that fastcatch8 refers to really the diaphram? I'm looking in the service manual exploded diagram and I am not seeing a screen per se in the fuel pump.<br /><br />Thanks again

 

[rodbolt]

Re: F100 Motor Problem Troubleshoot

I dont know of any fuel pump screens. there is a filter mounted before the pump . some carbs had a filter in the actual fuel inlet pipe at the carb that can clog. its time for a systematic troublshooting session. first eliminate mechanical sorces with a leakdown test. next test all the TPS and sensor values. next test that the spark can jump a 7/16th gap. then you will be onto the fuel system.<br /> good luck and keep posting

 

[Summer Breeze]

Re: F100 Motor Problem Troubleshoot

Rodbolt,<br />Earlier you mentioned the blue smoke at startup due to operator error. I checked my owner's manual, but could not find any mention as to the cause of this.<br />Since I can't get my rig into a shop yet, I ran some Yamaha Ring Free thru the motor and replaced the fuel filter last night. It seemed to start running a little better. Can idle now at 600 to 800 RPM, but was still cutting out at the shift position. One of the guys at a local dealership recommended using the ring free to clean the carbs out. I'm going to run the motor tomorrow seeing if maybe any difference made.<br /><br />Wish I could find an independent Yamaha tech in my area.<br />Thank for all your help; much appreciated.

 

[rodbolt]

Re: F100 Motor Problem Troubleshoot

the error I was talking about is shutting the motor off and leaving it at full trim down. the cylinders are actually sloping down towards the spark plugs and as it sits the oil runs past the rings and gets burned on start up. tilt the motor up 10* or after shut down so and see if that problem wont dissapear.<br /> if your auto tech friend has a Kv tester ask him to test the plug firing KiloVolts and post the results back.<br /> good luck and keep posting

 

[Summer Breeze]

Re: F100 Motor Problem Troubleshoot

Thanks Rodbolt,<br />I'll check with him on the Kv tester. Took the boat out today and it seems to be running even worse. I will not idle at all at the shift position and is missing very noticably. Also seems to have lost power at higher RPM's. I'm almost afraid to even run it. Very dishearting for a motor that is only four years old.

 

[diveextreme]

Re: F100 Motor Problem Troubleshoot

Jay T.<br /><br />I have the exact same problem with my 1999 F100. Its at the mechanics right now. What did you find out or did you just have a professional check it out as well? Let me know.

 

[jhnboat]

Re: F100 Motor Problem Troubleshoot

diveextreme,<br /><br />I had similar problems but more with hard starting and running rough for a minute or so. Turned out to be dirty carbs. Read my posts to see what worked for my problems. Good luck.

 

[Summer Breeze]

Re: F100 Motor Problem Troubleshoot

Originally posted by diveextreme:<br /> Jay T.<br /><br />I have the exact same problem with my 1999 F100. Its at the mechanics right now. What did you find out or did you just have a professional check it out as well? Let me know.

Diveextreeme,<br />I have not yet put it in the shop(will be on Monday) What was the verdict on yours? Mine wouldn't even fire up the last time out.<br />Thanks

 

[diveextreme]

Re: F100 Motor Problem Troubleshoot

I have taken it back three times to the dealer. Before I did so, I put in a Racor fuel/water separator, fuel filter, spark plugs, and some high octane fuel. Didn't help.<br /><br />Took it to the dealer and they rebuilt the carbs. $800.00 later, same problem, it would not go above 3400 rpms. <br /><br />Took it back. They said it was the filters going into each carborator. Each was replaced for only $46.00 total - obviously just the parts cost and no labor.<br /><br />Tested the day I got it back. Same problem! It is still in the shop now.

 

[Summer Breeze]

Re: F100 Motor Problem Troubleshoot

Well, looks like Rodbolt was correct with his first observation. The carbs needed to be rebuilt. There was water and bad gas in them. Only because I neglected to change my fuel/water seperator. I was thinking that I only needed to drain the bowl on the bottom of it. NOT! Looks like these need to be changed every season. I guess I learned a $450. lesson. Oh well, I'm just glad it was not something more serious. <br />Rodbolt, do you think there could be any other damage to the engine resulting from this? <br />I also asked my shop about a valve adjustment one of the mechanics was saying that it wasn't necessary on these motors. But the owners manual calls for an inspection on these yearly I beleive.

 

[rodbolt]

Re: F100 Motor Problem Troubleshoot

hello<br /> glad your immediate problem was solved. checking the valves on you engine is monkey work. its very easy and really requires no special tools. <br /> it does require you to learn what the valve train does and why it works. its simple to check and not that hard to adjust IF nessasary.<br />the normal specification will allow .oo2" from minimum to maximum with the piston at TDC on compression stroke.<br />in 10 minutes I could teach you if I could show you.<br /> I doubt you hurt anything. theses motors forgive a lot<br /> good luck and keep posting

 

[Summer Breeze]

Re: F100 Motor Problem Troubleshoot

Rodbolt,<br />I have my 6hp kicker running off the same fuel line. Is there a likelihood that its carbs may become fouled also? I plan on throwing a new seperator filter on the boat right away. I also recently added some Yamaha Ring Free into the gas. Not sure if this will be beneficial at all.<br /><br />Thanks

 

[rodbolt]

Re: F100 Motor Problem Troubleshoot

hello<br /> ringfree is good but wont help for trash or water. if you had water in the main and are running the kicker from the same tank there is a good chance its fouled as well. here in my area kickers dont get used enough and most have the carb cleaned every spring. install the filter and run it and see. the 6 hp carb is easy to clean.<br /> good luck and keep posting

 

[Summer Breeze]

Re: F100 Motor Problem Troubleshoot

Rodbolt,<br />You mentioned the 6hp easy to clean, can you elaborate? <br />It too is fouled and will not stay running at low RPM unless the choke is out.<br /><br />Thanks