225 EFI Over fueling? Smells like gas and down on power.

[44Mag]

2000 Mercury 225 EFI, serial number 0T121338 on a Triton TR21. I have just rebuilt this engine over the winter and I have been fighting through some issues with it. New pistons, rings, bearings, seals, reeds (cages were lapped) injectors tested and serviced, new thermostats, plug wires, pulse pump rebuilt, you get the idea. I tried my best to rebuild anything that that was questionable as I want this to last a long time. Engine has ran well for the most part through the breakin period, but all at once it really started to run poorly. The last issue turned out to be a failed CDM on cylinder #6, causing #2, #4, #6 to run poorly, foul plugs and the engine to have low power. Replaced coil, also added extra ground wires for ECMS and CDM s as I read that they can be an issue as well, back up and running fairly well, but I noticed it smelled like fuel and I still thought smoething just felt "off". Got home and checked for leaks and could not find anything. Next trip out it was back to being a pig, struggled to get on plane and would only run 64 MPH as opposed to the normal 68-70. It also idled a little rough with the occasional stutter or misfire. Changed and gapped spark plugs, this was no help. Still smelled like gas badly. Brought it home, trimmed engine down in the garage to drain and let it set a couple of days. When I went back to work on it I noticed an oily fuel/oil mixture that had drained onto the floor, appeared to have come from the intake area and ran down a wire harness for the trim motor. I suspected a possible reed issue, so I pulled the intake manifold loose to inspect the reeds. Reeds look great, no issues, but I did find what I thought was an usual amount of oil and gas pooled up in the intake, mainly around cylinders 3 and 4 reeds and in the bottom. I cleaned this out and reinstalled the intake. Put my pressure gauge on the fuel rail and turned the key to the on position. It was 40 PSI, so I let pump finish cylcling and turn off and watch the gauge to make sure it was holding pressure. It appears to be fine, no visual leaks looking through the butterlies and held pressure for roughly 5 minutes before slowly going down. After 10 minutes it was down to 34PSI. I am thinking this is not my issue, so I removed the thermostats and verified that they are working properly and not stuck, and hot water tested them. Check good, 143 degree stats. I have tested the stator, cylinder head temp sensor, IAT sensor, and MAP sensor with an OHM meter using the specs from the manual. Ran on the engine on the hose while in a tank and verified all of my cylinders are firing with the timing light. TPS is set to .98 volts. I am just not finding anything unusal that ican say is the issue. I have been running my stock pair of ignition and fuel ecm's as I am no longer running my shaved heads, and have went back to stock heads on this engine. Just for the hell of it I put my other pair of ECM's which are flashed to 300 PM spec and took it to the lake for a test run. It ran much better! Holeshot was back, it ran 67-68 on the GPS. I ran it around for about 15 minutes. When I shut it down to put it back on the trailer I noticed the gas smell is still very heavy, and it appears to be just dumping to much fuel. I think the "hotter" ignition from the 300 PM ECU just maksed my problem. So, I know I took the long road to get here, but my question is...what am I missing here? What could be causing this engine to over fuel like this? I am still running the oil injection on this engine as well. Any help would be appreciated, thank you in advance. It is also drinking gas like 900 HP Chevy big block! lol

[lpugh]

That motor will run pig rich at 5900 unless the rev limiter has been raised, I found on that motor a stock fuel module is the best as it runs to rich especially wound high, 250 does better for the ignition

Verify that is an accurate gauge

• On early-model (2001) EFI systems - 34-36 psi (234-248 kPa).
• On later-model (2002 and later) EFI systems - 41-45 psi (283-310 kPa).

Some one will confirm the correct pressure for your motor if 4 psi to high that would add to your problem
When testing the air and temps sensors be sure to check them at the higher temp ranges

[JOE54]

leaking fuel inside cowl , possible bleed hose leak or press side of pulse pump hose leaking fuel either being drawn into intake , run it up to max rpm set it back down look at plugs ( no idleing )

[44Mag]

My fuel gauge is accurate, and I also wondered if that 4 psi would cause it. But that is deadheaded, key on engine off. Isn't the regulator supposed to prevent it from exceeding the spec? Maybe I do have a bad regulator. I will also double check my temp sensors.

[lpugh]

My fuel gauge is accurate, and I also wondered if that 4 psi would cause it. But that is deadheaded, key on engine off. Isn't the regulator supposed to prevent it from exceeding the spec? Maybe I do have a bad regulator. I will also double check my temp sensors.

Dead head would be high, test regulated pressure

[44Mag]

Holds steady at 36 psi.

[44Mag]

Joe54, I have inspected all of the bleed lines and fuel lines as they have all recently been replaced and I am not finding any issues. However, I do feel like the gas smell is much worse after a run and then setting down to an idle, especially if I trim the engine up. My intentions on swapping the ecms was only to prove to myself that this is probably not a faulty ECM issue, as it is running very rich with both sets of ecms, the 300's just handled it better. So it's just something else.

[JOE54]

Holds steady at 36 psi.

indicates no leak in inj housing

[EuropeanAM]

36 psi probably isn't going to cause the problems you are indicating. I would however remove the pressure regulator and inspect/clean the FINAL screen that is hidden in the brass flange. If it's restricted it can cause HIGH pressure (sometimes after running for a bit it can climb as well).

[44Mag]

I think I may have found the issue, and JOE54 nailed it. I went into my garge last night to look over the things that everyone has suggested, and proceeded to check the fuel pressure regulator final screen and further inspect for leaks. Upon entering the garage I could smell gas as soon as I got near the boat, which had now been sitting for over a day. I reinstalled my gauge on the schrader and continued to run the pump to and pump the fuel bulb to get the pressure as high as I could. After messing around for a while and removing checking several things over I happened to notice that the grey main fuel ine running to the pulse pump turned while I was moving things around. Upon further inspection I found gas running down the back side of the line and out the engine and onto my splash well, which is always getting washed out when in the water. The cheap clamp I used had failed! Am I thinking correctly that this would not show up during a pressure test on the EFI side, as the system probably has a check valve? I also found the bolts holding the pump to the engine to be not loose, but not nearly as tight as they should have been and possibly enough to casue a vacuum leak inside the pump. I have a new pulse pump rebuild kit on order along with new temp sensors just because they are 20 years old. I will report back if this takes care of my issues once everythig arrives. Thank you to everyone for the help!

[JOE54]

dont gimme credit on it just yet suction side may not have leak when mtr is running but could have air leak there would thnk it would be lean , you get a OEM pump kit ,and you did check full range of TPS OPERATION , installed seperate grnds on ecu s , you may eliminate fuel smell and leak but not fix problem

[44Mag]

Like I said, we will see what happens and at least iam fixing something that needs to be fixed. I really hate just throwing parts at problems. When I posted this, I was out of ideas and hopefully this at least got me head into the right direction. But that is why I am going to rebuild the pulse pump again. I am wondering if maybe the fuel is coming more from the pump than the line, which could be casuing a vacuum leak. I am pretty sure that if the vaccum drops, the MAP sensor would see that and instruct the ECM to supply more fuel ( increase injector pulse width). Or if it was leaning out due to a leaking supply hose, The ECM would still see this and command more fuel. This could make it dump more fuel, no matter how much it was actually getting. Just my theory, and worth a shot. Maybe I am wrong and I got this theory backwards, but it should be done anyhow. I installed the extra ground wires a while back when this started and I have checked the TPS at least 15 times. I even bought the harness to do it correctly. It sweeps from .98 - 4.02 volts very consistantly and I have verified that I am getting full throttle with my hotfoot.

[NoSloProcraft]

The Fuel injection is closed loop and cannot detect rich or lean exhaust. It only compensates for fuel based on MAP, Engine temp and IAT. Also overspeed will cause a fuel dump.

Did you check you IAT sensor submerged in ice water, what was the OHM reading?

Have you replaced your fuel lines? I’ve been going through some of the same issue and found the 5/16” line from bulb to pulse pump had a collapsed liner. This was the blue Mercury hose that I replaced once already.

2AFC4F20-4EAC-472E-9603-F29BBC234BC6.jpeg

[44Mag]

NoSloProcraft, I was actually just reading through your post about what you have found with yours and then seen your comment. Thank you for the suggestion. I have tested my IAT, but not in an ice bath. I never would have thought to do this, as I have never heard of testing it that way. I do have a new one coming, but I will do this just because I want to know what exacly has been going on with this thing. And will check out that fuel line as well. That is the line that I found leaking at the pulse pump. I did replace all of the lines from the tank to the pump about five years ago, and all of the lines on the engine were replaced this spring when I rebuilt the engine. My grey line is the same one you have pictured......I think I will just replace it as well to be safe. I also ordered an OEM rebuild kit for the pulse pump. I suspect this may also have been comprimised as I did find the two bolts that hold it together to be "not as tight as they should have been", I actually wonder if some of my fuel leak was coming from here or possibly letting it suck air, which could cause low vaccum and possibly a rich condition if the Map sensor picked that up. At least that was my theory, but I have chased my tail with this thing. I tried my best to go through everything as I was putting it back together. It ran very good for the first couple of hours of use, and then these demons arrived, I may even be chasing two different problems here. Either way, I will still have way less money into it than if I would have just bought a new engine! lol I will let you know what I find once my parts arrive and I get back to working on it. Thank you for your help.

[EuropeanAM]

Speed/Density system, so technically it's always OPEN LOOP.

IAT's on these will often be so far off when they fail that it's painfully obvious. With Diagnostic Tools, you often see a temperature that's 7 or more digits long (leading to a chuckle and a "yeah-right"). Ice-bath idea is ok, as long as you check the actual temp of the water with a thermometer, for comparison.

[lpugh]

Yep, can not achieve closed loop without a O2 or air fuel ratio sensor

[44Mag]

I understand that this is an open-loop system and that the igniton and fuel curve are pre-mapped. But it still uses a MAP sensor, a TPS, and temp sensors to determine engine speed and load and make minor adjustments. They maybe preset, but they are still watching. So what does it do if it is seeing something that does not make sense to it? Please see the attached PDF from the manual and think about this, if the engine is at idle the MAP sensor should be seeing engine vacuum on the sensor (closed throttle genreally has the highest vacuum), and at WOT it probably does not have much vacuum but requires the most fuel. So a vaccum leak that is causing low vaccum at an idle could make a fuel system deliver a rich mixture at an idle don't you think?

[EuropeanAM]

Of course that would make the engine rich. As would a cold running engine, and in many cases any sensor that falls outside of it's pre-programmed limits.

Almost without exception: The default for "does not compute" is to dump more fuel.

One example we see a lot recently would be the IAT. Normally the IAT can result in up to a 10% variance in the MAP tables (depending on the temp it's signalling). However: I've seen 5 or 6 engines where the IAT value was reporting in the millions of degrees. You could barely get the engine to run at all (because the poor ECM had no clue what to do with that figure).

[44Mag]

UPDATE- I have rebuilt my vacuum operated fuel pump with an OEM kit (previously used a aftermarket) due to it leaking and replaced the fuel primer bulb and line to the pump just for the sake of doing so. I then tested my IAT sensor and temp sensor, and tested them in an ice bath. I did not find anything wrong with the old ones, and even compared the readings to my new sensors that I ordered and did not see any significant difference. Test ran the engine on the lake for a day and probably put rougly 20 miles and an hour on it on it. Fuel smell is gone and engine is back to performing normally. I believe 99% of my issue was coming from this leaking fuel pump. I will continue to test run and make sure the issues do not return this time. Thank you all very much for the help!

[JOE54]

YAAAAAY