225 EFI fouls spark plugs

[BW23]

97 Merc 225 EFI w/ 193 hours.<br /><br />During the past 20 hours the motor has been fouling plugs. I was using West Marine oil and I know that was a mistake. When I add new QL77C plugs and run the motor at 3500-3800 RPM for 30 min then check the plugs , they are very tan and not oily at all. (running lean) If I run the motor longer, in due time they foul. How?? Who knows?<br /><br />I have since change to MERC oil ( 3 hours ago) and added oil to my fuel tank (safety) for a ratio of at least 25 to 1. Motor seems to run better but now fouls the plugs at slower speeds (expected) and not higher speeds.<br /><br />FWIW, I replaced 1 CDM coil module 15 hours ago. Compression is within 5 psi between cylinders.<br /><br />Any thoughts on why to VRO systems would operate correctly at slow speed and not at high speed ? Boat is 3 hours away so repair ideas will have to wait til this weekend.<br /><br />Regards,<br />Dave

 

[jdkzrt]

Re: 225 EFI fouls spark plugs

Are you describing the plug color after idling up to the dock, or after switching the key off at 3800 rpm. This makes a big diffence, and you might be surprised at what you find (black, and oily).

 

[BW23]

Re: 225 EFI fouls spark plugs

The dry/tan occurs after 30 min. of running 3800 and 3 min. of slow no wake to the dock. Do the 3.0 liters have a history of VRO problems??<br /><br />Thanks in advance.

 

[clanton]

Re: 225 EFI fouls spark plugs

 

[clanton]

Re: 225 EFI fouls spark plugs

What is the correct sparkplug? Did you check pump adjustment, check valves?

 

[BW23]

Re: 225 EFI fouls spark plugs

Correct plug is Champ QL77 C gapped to .035.<br /><br /> To the best of my knowledge the oil pump has no adjustment. <br /><br />The reed valves??

 

[clanton]

Re: 225 EFI fouls spark plugs

I should have ask before , what is the engine serial number and cubic inch of engine? I may be looking in wrong manual.

 

[BW23]

Re: 225 EFI fouls spark plugs

0G570413 3.0 liter 1997<br /><br />Thanks

 

[BW23]

Re: 225 EFI fouls spark plugs

^

 

[marinegrh]

Re: 225 EFI fouls spark plugs

whats you engine temperatures, <br />if your running cold, no burn, to hot and to much burn, just a thought, efi's especially merc are prone to fouling the plugs when trolling your oil system is gear driven, if its slipping at high speed, you may not be getting enough oil to the engine, might want to take a look down the hole, also fuel pressure, what is it<br /><br />keep us infoed

 

[snapperbait]

Re: 225 EFI fouls spark plugs

Those oil tanks are pressurized by the engine... If the caps on the oil tank are not tight, or if a hose is loose, you could be leaking pressure and that could cause the oiling problem...

 

[The Marine Doctor]

Re: 225 EFI fouls spark plugs

As Marinegrh has said...check the fuel rail for adequate pressure.<br />If the pressure is low the engine will run lean.<br /><br />The EFI does not know how much fuel the engine is getting. It reads the TPI and MAP and various other sensors and calculates the time the injector needs to be open.<br /><br />So if the fuel rail pressure is low...there is not enough fuel being delivered to the cyl.<br /><br />TMD

 

[clanton]

Re: 225 EFI fouls spark plugs

The manual I have for this engine is a 2002 manual. The 2002 engine has an electrical oil pump controled by the ECM from 120-1 at idle to 50-1 at full throttle. The oil is pumped into vapor separator tank and mixed with the fuel before it goes to the injectors. If your engine is realy over oiling, problem is pump or ECM. I suggest you call Merc give the serial number of engine and they will ship you a manual that matches your engine, about 37.00 US. If you play with the control handle with key on engine off, the pump will go thru a prime cyle and pump extry oil.

 

[jdkzrt]

Re: 225 EFI fouls spark plugs

1) If your plugs are a tan (paper bag brown) color, they are not burning "lean". This is the color they should be.<br />2) If you are checking plugs after running no wake speed for 3 minutes, all you are reading is the idle speed condition of the plugs. The only way to see what is happening at 3800 rpm is to turn the key off at 3800 rpm (this is the ONLY way).<br />3) Plug color is not the way determine if your oil injection is working properly. At the very least, fill your oil tank and your fuel tank and go for a half hour run at high speed. Then figure out the ratio by compring fuel used versus oil used.

 

[jdkzrt]

Re: 225 EFI fouls spark plugs

1) If your plugs are a tan (paper bag brown) color, they are not burning "lean". This is the color they should be.<br />2) If you are checking plugs after running no wake speed for 3 minutes, all you are reading is the idle speed condition of the plugs. The only way to see what is happening at 3800 rpm is to turn the key off at 3800 rpm (this is the ONLY way).<br />3) Plug color is not the way determine if your oil injection is working properly. At the very least, fill your oil tank and your fuel tank and go for a half hour run at high speed. Then figure out the ratio by comparing fuel used versus oil used.

 

[greasemonkeyozi]

Re: 225 EFI fouls spark plugs

more advise, might help. Run your fuel ratio 50-1.

 

[BW23]

Re: 225 EFI fouls spark plugs

Thanks for the input guys. Here is the latest. <br /><br />While trouble shooting on Saturday, I found a small fuel hose leak which might change the overall fuel pressure. Replaced black tie wrap with proper hose clamp. This repair did not fix my problem so I began to look else where.<br /><br />I did some fuel/oil monitoring and it appears to be quite close. ( fuel flow meter, visual on oil tank).<br /><br />I'm now convinced it is another 1-2 CDM's (tested w/ timing light)causing an intermittent miss and fouling the plugs with un-burned. Worse when the engine is warm. Plan to purchase 2 more and test in 2 weeks.<br /><br />I'm getting closer thanks to all of your input.<br /><br />Regards,<br />Dave

 

[BW23]

Re: 225 EFI fouls spark plugs

^

 

[cvstucco]

Re: 225 EFI fouls spark plugs

I am having the same problem with my 225. I dropped it off friday after having this issue ruining my plans for the M-day weekend. My 225 kept fouling plugs, I took them out and cleaned them it would run fine and with plenty of power, after stopping and anchoring down for a while i restart and here we go again. smoke and sputter and the whole procedure restarts. The last time the plugs fouled I took them out and the motor would not restart. I have talked to mechanics and made phone calls and noone has a answer. Everyone has a diiferent opinion. this motor has only 22 hours on it and has had diagnostics performed and no prolems shown. Anyway, let me know what you find out about yours and I will let you know when I get mine back as well. Your problems seem exactly like mine.

 

[Faztbullet]

Re: 225 EFI fouls spark plugs

I would just about bet that you have a malfunctioning engine temp sensor. This sensor reads engine temp and sends signal to ECU. The ECU uses this signal to activate the fuel enrichment valve for cold starts and reduces timing in case of overheat. I suspect that yours is reading cold from time to time and engine is running a tad rich which will foul plugs. Also a non-firing plug will show as a miss with a timing light so double check before you buy CDM modules.Also a misadjusted TPI will change timing. A 0.05 volt change will result in a 1 degree change of ignition timing...so a lower voltage =retard and higher =advance. Hope I didnt ramble and get to technical