DF225 Intermittent Dips in Power, fuel issue

[hanksboat]

2004 Johnson 225 (DF225) that has run smoothly except for having to change the IAC valve a few times. I've had since March. I'll be cruising at 4000 rpm and I'll feel a sudden dip in the power band. I'll push the throttle down and rev through it. It just started happening. It feel like it stops getting good fuel for moments. Sometime it will result in rough running - perhaps that's a lean condition, not sure. Some research has told me a fuel pressure regulator, a clogged high pressure pump strainer,, or fault HP pump. Any clarity from the board? It seems to have gotten a lot worse as I have approached the last quarter of my gas tank for the first time - makes me think possibly water in fuel - but that could just be the condition getting worse.

[hanksboat]

Update (still unsolved):

I took off the VST and opened it up. It's clean as a whistle. The float, needle, and HP strainer look brand new. I tested the Fuel Pressure Regulator and it opened up at 38PSI (Service manual calls for 34-38.5 PSI). The HP pump works but I have no idea if it's failing or not and being intermittent.

I traveled up to the Purge Valve. I've heard this can cause issues. The Resistance spec is 25-28 Ohms, mine measured between 30.5 and 33 ohms as I never could get the same reading, even with two difference ohm meters. So, it's out of spec. However, I did the shop test on it, placing 12V and applied 20 psi of air. It allows air through. What I noticed is that even when I removed the power, it still allowed SOME air through, just not the full amount. I don't want to just throw parts but all signs point to replace this Purge Valve, right? Perhaps it's stuck open at the wrong times, creating a vacuum leak. After this happens I do get some rough engine feels, reminiscent of a vacuum leak.

Other notes:
I thought the Vacuum Switching Valve was ohm testing out of range, but checked later and it was 42.5 (37-44ohm range), so acceptable. I was curious of this part since it is supposed to operate at 4200 RPM (close to my problem RPM) but adjusting the intake tract volume.

I tested the thermostats a while back and they were right around the edge of their tolerance. I'll probably just replace them.

I've seem reports to replace primer bulb - I really don't see how that's related here. TPS voltages at Closed thottle and WOT were almost ideal. White wire is clean and just fine.

I've got a new Mitsubishi IAC installed and working, but my motor has gone through a few recently. Has there been any discovery as to what causes their failure? Just having two separate issues may be a coincidence, but want to see if anyone has linked the two issues. When I am having my engine dipping in power @ 4000RPM, I can throttle down and power through it. It's like I'm forcing something open (or closed).

[hanksboat]

Still looking for help - the problem got worse and now comes often when I accelerate. I replaced the purge valve - didn't help. I replaced the anti-siphon valve, checked the tank vent, and double clamped all hoses - no improvement. I am now getting the 4-3 fuel injector code. I took all injectors out and bench cleaned and tested. They all functioned well and looked very clean to start with. I ohmed all the Fuel injector wired from the ECM plug back to the injector plug and they all seemed good. I'm not seeing a wire issue. Could a bad fuel pump be causing this injector code or is this specifically thrown when an injector is problematic? I can purchase a noid lite kit or other LED test kit if needed. I'm just at a loss and close to just buying another ECM to see if that's the issue.

[Moonlighter]

Check battery, clean connections, check white wire. If the ecu is not getting good power all sorts of strange problems happen, including loss of power.

So clean and check main battery cables, find the white wire connections, clean,inspect the wires Make sure no corrosion.

[redlowrey]

Still looking for help - the problem got worse and now comes often when I accelerate. I replaced the purge valve - didn't help. I replaced the anti-siphon valve, checked the tank vent, and double clamped all hoses - no improvement. I am now getting the 4-3 fuel injector code. I took all injectors out and bench cleaned and tested. They all functioned well and looked very clean to start with. I ohmed all the Fuel injector wired from the ECM plug back to the injector plug and they all seemed good. I'm not seeing a wire issue. Could a bad fuel pump be causing this injector code or is this specifically thrown when an injector is problematic? I can purchase a noid lite kit or other LED test kit if needed. I'm just at a loss and close to just buying another ECM to see if that's the issue.

To me it sounds like you have a cyl dropping out, did you individually check the resistance of each injector, and what resistance value did you get, when you say bench cleaned and tested, is that by you just supplying bat pos and a ground, or did you pulse them at high frequency and pulse width.

Does it make a difference with temp when it starts to miss, because these engine run in open loop, the computer has know idea what is happening inside the combustion chamber. The computer will be monitoring each injector through a current limiting resister and each time the driver grounds the signal it will sense current.

Battery voltage plays a very important role on these engines, these engines do not have software inside to account for voltage drop, and the first sign is usually problems with the stepper motor, easy to check first at the battery at rest, then cranking, then at the main relay, then on the gray wires at the iac valve cranking. If you have less than 10. volts when cranking idle problems will start happening.

If you could get it to play up on the muffs you could just connect up a digital multimeter on volts, oscilloscope would be better, and check each injector ground while it is running at the computer, if the driver did not go to ground, the meter will read battery voltage.

If you have an engine miss and you are starting to get an injector code you would think that they would be related.

[hanksboat]

Thanks for the detailed replies.

I have recently gone through battery connections and Perko connection of white wire. All have been cleaned and applied dielectric.

I checked each injectors resistance - all measured 12.4 to 12.6 Ohms, which is in spec. By bench testing, I attached a tube to the injector inlet with about 15" of carb cleaner. With 40psi of pressure, I tapped (manually pulsed) the 12V battery to spray out the cleaner. I did each twice.

It seems like it starts to miss once the temp rises to 140F or so but that may just be the randomness of it. This is pretty quick. However, after it's completely warmed up it comes and goes. I can cruise for 15 minutes and feel nothing then it returns. It's very prevalent though - will usually have spells every few minutes that last for a few minutes.

I noticed the voltage at the motor terminals was 12.36V (12.54V at battery). The voltage at the injector was 10.89V, so about 1.5V drop. I assume that once the motor is running, the alternator keeps the voltage higher, no? Batteries are 1 year old and I keep them on a drip charger a few days after every trip.

One weird thing was I opened the bullet connector of the white wire and took the "dead" side and did a continuity test to the ground terminal on the engine. It buzzed - but then later didn't. And then buzzed another time. Is the white wire EVER supposed to have continuity to the engine negative?

[redlowrey]

Did you know that there is a very fine small filter at the injector inlet, if you don't remove it you won't clean them properly, if you blow air from the other end after you clean the tip, then start pulsing you will blow the rubbish out of the filter. I would be checking the battery voltage while the engine is running and hot at each of your injectors, your battery supply goes to a couple plug connectors before it reaches the injectors, if you could check these while it is missing it should point you in the right direction.
You need a wiring schematic so you know where to test the injector grounds at the ecu when you go from supply to ground.

The secret off success here is to catch it when it is missing and try to pin point it to your problem if you can catch it missing pull a connector of each coil and at least find which cyl it is.

[hanksboat]

Did you know that there is a very fine small filter at the injector inlet, if you don't remove it you won't clean them properly, if you blow air from the other end after you clean the tip, then start pulsing you will blow the rubbish out of the filter. I would be checking the battery voltage while the engine is running and hot at each of your injectors, your battery supply goes to a couple plug connectors before it reaches the injectors, if you could check these while it is missing it should point you in the right direction.
You need a wiring schematic so you know where to test the injector grounds at the ecu when you go from supply to ground.

The secret off success here is to catch it when it is missing and try to pin point it to your problem if you can catch it missing pull a connector of each coil and at least find which cyl it is.

I didn't know that. I may end up redoing the injector cleaning if I fail at finding a wiring issue. They just seemed really clean and operated all very consistently - maybe though.

To check the voltage AT the injectors while the engine is running - that's going to be difficult. I do have a wiring diagram and it looks like the IAC valve has a gray wire I can check. I did the noid light test today. It's the LED that plugs into the injector plug - as I turned over the engine all led's flashed. I figured they would since it's an intermittent issue.

Here's the point I should bring up some history. I bought the boat not running in March because it threw a flywheel magnet and destroyed the stator. I replaced the stator, regulator/rectifiers. It also killed the ECM, so I replaced that too. Then everything worked fine for a few months until this issue slowly, but surely crept in. I'm thinking if I have a short, it could be related to that path of damage, crossing over to a injector wire - not sure if gray wire or ground wire though. I think I'll take the boat back out and wait for it to act up - then pull off an ignition coil 1 by one. I assume it may shut off or at least bog down unless I pull the bad cylinder. If I find it - I can jump out that switch/ground injector wire back to the ECM. If it works then I know it's that wire. If not, then I guess I can jump out the gray wire. Or just replace the whole damn wiring harness...

[mykwalkr]

Have you replaced the spark plugs? I had something similar happen to my DF140 that I thought was gas/filter/air/vst issue….changed the plugs and all is good.

[redlowrey]

How is it hard checking everything with the engine running, you should have over 13 volts on every thing that has battery voltage supplied to it, and zero volt on the grounds, injector ground will fluctuate because it will be going from supply to ground rapidly depending on frequency. Checking the injector ground at the computer would be better.

When I first read your post it sounded to me like a cyl was dropping out, spark or fuel, and then when you said you had an injector code I am assuming that the two are related. If you can't get it to play up and pin point the problem there is going to some expensive guessing. I have a lot of expensive equipment and forty years of accumulated knowledge to help me, so I feel your pain.

I am assuming when this problem started that you changed your spark plugs like the other post asked, I think the cheapest thing for you do with out spending a lot of money, if you can't locate where the miss is, buy one coil and spend a day on the water changing them one at a time and borrow a computer.

[hanksboat]

Thank you for your help - I can't really check any of the injector wires with the engine running since I'd have to be on the water. Removing injector plugs one by one with the air collector on is not too easy for me. It sounds like I would need the testing harness adapter with the 34 and 26 pin connectors. I would buy that, but I can also just buy a used wiring harness for about the same money! I did the noid light injector test with turning over the engine - they all flashed but that doesn't tell any more than they have power at least sometime. I tore into the harness as much as I could but don't see any signs of shorting - but there is a LOT I can't see.

I did not change the plugs but only removed and inspected them all. They are all so clean and well gapped, I hadn't thought of replacing. I may just replace.

I am planning on taking it back onto the water and seeing if it continues to act up (I have little faith the injector cleaning resolved it, but maybe!). Then I will remove 1 by 1 the ignition coils to see which cylinder is the issue.

I looked back through my old messages when I bought the boat. The mechanic that looked over it reported of the flywheel/stator damage but also had to replace two ignition coils. I still have them and they are cracked and bulged out pretty good. Could it be that I have another bad ignition coil or that one of those bad coils had some wire damage back towards the ECM? During my test, I'll do the coil swap to see if it's a bad coil.

[hanksboat]

I took it for a good 30 minute ride in all RPM ranges, including WOT. Ran great. I had cleaned the injectors, charged both batteries full, and cleaned the white wire connections and fuse holder this time. Maybe that did it. I'm keeping my fingers crossed though.....time will tell!

[Moonlighter]

It never, ever hurts to make sure that electrical system is in top order. May not be the problem but at least you can say its not the problem if issues recur.

Fingers crossed its sorted. There are some branches/joins in the harness part way along, may be worth pulling it all the way out and giving it a thorough check over sometime, especially if issues come back.

BtW I assume you have a water separating fuel filter in the line between tank and engine? Something like a Racor? Good insurance against crap and water in the fuel.

[hanksboat]

It never, ever hurts to make sure that electrical system is in top order. May not be the problem but at least you can say its not the problem if issues recur.

Fingers crossed its sorted. There are some branches/joins in the harness part way along, may be worth pulling it all the way out and giving it a thorough check over sometime, especially if issues come back.

BtW I assume you have a water separating fuel filter in the line between tank and engine? Something like a Racor? Good insurance against crap and water in the fuel.

Yep - I appreciate all the battery/connections preaching to guide people in that direction first. Our local Suzuki mechanic (Doss Marine, SC) mentions the same thing. And good advise about the harness. I will do that if it comes back, if it's not coil/plug related.

I do have a Racor directly after tank. I've gone through it and the filter/seperator has always looked spotless. Which also makes be suspect that my injector cleaning worked. HOWEVER, the fact that I could throttle down and "drive" through the problem does make it feel like I was pushing fuel through. If it was a short or bad coil, I don't see how that would change things. But maybe you can throttle through a down cylinder? Not sure.

[redlowrey]

Read your third post, problem is getting worse, missing while accelerating, now have 4.3 injector code, when accelerating, your ignition system is under max load and each injector driver in the computer is on for longer, I hope your problem does not come back, but I am not convinced.

When you say you can push through it, at a certain boat speed and engine load, the ignition system at times may need more secondary voltage than it does when the boat is going faster through the water less effort on the engine less secondary voltage.