1997 454 xli MEFI-1 replaced, now 3000 max wot

First year of owning this boat and learning more and more about it every week it seems.

The ECM went out on port engine. I switch them and problem follows bad ECM.

So GM discontinued these, crusader has zero answer for this other than if I find one somehow, they will program it for me free. I found one on ebay and they programmed it. Got it back and engine fired right up, only when I try to get on plane, it's fine going up to 2900-3000 but then just boggs and surges, like either starved for fuel or ECM is limiting engine performance. Engine ran perfect before ECM failed.

Then I see a post on here from previous owner and it appears he has put automotive injectors from Napa on these engines. 1) is this what possibly caused my ECM to fail? These things are not suppose to go out. 2) What would put ECM into a certain mode to only allow 75% throttle?

It runs smooth as ever in neutral or just trolling around at 1500-1800 and will get up past 3500 with ease in neutral but loaded its like its overruling or something bc if I back off wot it's surges up for a second but then back below 3100

Been a month long battle just figuring out the ECM went south. Going down to change all fuel filters today, It's not acting like a fuel filter problem tho, that usually is hard start issue and dies with throttle increase, this thing sounds great and will hit limiter if I let it in neutral.

The fuel filter has 65 hrs on it since last change. I have added 330 racors sand bypassed the little 110. Is 60 hours a lot for a racor in E10 environment?

Did you try swapping ECMs again to see if the problem follows the newly programmed ECM?

Yes, I did this morning but it's raining so didn't get to go out.

Also changed Racor and pancake filter. Will know more tomorrow when I can get her out.

Take a fuel pressure gauge and use it on the next trip...not only at idle but under full load as well.

If the injectors are incompatible with the drivers in the ECU, they usually don't work....most injector families use a specific electrical connector and that eliminates many of those issues...being as you get up to 3000 rpm (under load), the basics of the ecu-injector connections are fine.

I don't think there is any "self protection" logic in an MEFI-1...being as there is NO monitoring of the fuel system by the ECU, fuel gauge is a good starting point... If my memory is failing and that logic is present, there should be a trouble code stored...

I agree that the early ECU's have no idea what is actually happening in the fuel system so the injectors would not cause the ECU to fail. I would be concerned that the replacement injectors were not sized correctly and could run too lean and engine damage has or could occur. If the plug colors look good maybe you should just leave as is. Or you could pull an injector and get the numbers. Some research on the internet will tell you what engine and model it is intended for. Then more research will let you find the rated flow. Then comes the hard part, finding the rated flow on the correct Crusader injectors. But I found it eventually for my engines (5.7s) so it can be done. Most of the flow information is on sites maintained by the hot rod community. Then you will know.

As for the ECU and/or whatever else is the current issue, you need a manual. A good start would be the Mercruiser Service Manual 23. Go on the net and Google MEFI 2 Diagnostics Manual. About the eighth hit down is an item called " [PDF] Service Manual ". That is the Mercruiser manual and the chapter on MEFI 1 and 2 is very good, likely lifted directly from the GM manual. The MEFI 1 and 2 are (I am told) interchangeable. Real MEFI 1 manuals are available for sale on the web as well if you want to go that route.

CaboJohn

[FONT=Tahoma, Calibri, Verdana, Geneva, sans-serif]Great info guys and thank you. I moved the ECM over to other engine and changed Racor. Took it out tonight and still doing same thing with old ECM on the engine that won't get up under load. Runs great 650-2900 and is strong and smooth to that point. When I go from 75% to 100% throttle at around 2900 it tries to get to 3100 but just starts backing down rpms and has a deep grrrrrrr like its laboring at full throttle, kinda sounds like a 4 barrel does when you get into it , then i will back it down to 75% and it tries to grab but just won't ......maybe not enough / maybe too much fuel?? Does this possibly sound like symptoms of a fuel pump going out? I'm getting gauges to test pressure ASAP, I know its hard to diagnose without it. Napa store I stopped at didn't have any today.

Would distributor cap and rotor change I did cause this? It runs so smooth at low-mid rpm I feel like she is firing on 8 . Maybe bad fuel but no real water came out of Racor bowl?

It's baffling how it was running fine when I slipped it two weekends ago. Took a 60 mile round trip up on plane a month ago and performed great.

I found correct injecetors today and will be getting those. Please elaborate on how lean burn could cause engine damage? Im pretty green on fuel systems.

I've put 60 hrs on it since I bought the boat and has 500 on it now. Im probably going to have to hire a tech, I'm getting out of my comfort zone On some of this stuff and I can't check pressures alone anyway.

I didn't change the throttle body fuel filter bc the 110 micron pancake filter was spotless. maybe I should try that as well.

Thanks for the input. I will win eventually.
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Place your fuel sample in a clear container than add some fresh fuel to your sample. Allow it to sit overnight. If its bad you will see a clear line between the old and new fuel.

Lean burn will cause higher than normal temps in the combustion chamber and can lead to burned exhaust valves and loss of compression and power.

Having said that, a consistent, rapid falloff of power at 3000 rpm sounds more like fuel starvation due to lack of adequate flow. As you were advised by Mark, start with the pressure test. If flow limitation is the issue, you will see fuel pressure fall off when your engine starts to bog. Once you know that is the problem, then you can search for the cause. If fuel pressure is good, then a compression test would be a logical next step.

Post #6 says "throttle body" so you will have to buy or fabricate an adapter to connect a pressure gauge....

Update; I pulled fuel sample from Racor bowl and has zero water in it, bugs or anything. It is however very light yellow colored compared to a sample I pulled last year that is much darker but last years was pure gas and they have since switched to E10 on the water here, so this may be the reason for the color change? Also changed the short fuel filter on top of Throttle body. (makomark there is already a valve on my metal fuel line for pressure testing BTW) Put sta-bil in to treat tanks and let it sit for 4-5 hours, not really expecting anything but just in case. Took it out for a hour and still same issue. I have yet to get my hands on a pressure guage, My co worker keeps forgetting it, delaying my victory.

I am leaning towards a sensor being failed. With the ECM failure and dealing with that mess I completely forgot about seeing a DTC 14 when I hooked up a code-mate to the engine which was a stored fault as a Eengine coolant sensor value being high according to the diagnostic manual. I think my ECM is in a protective state of some sort b/c it runs so well up to 2800-2900 then literally will not go above 3100 under a load. I just purchased two ect's as well as a MAP sensor. Question I am asking myself even if I replace these, do I have to clear any DTC's to get the ECM out of this mode if it so happens this is the case? Or will it just be stored as a fault and recognize the signal when new one is replaced.

All sensors are original from what I can tell so its not far fetched to think after 16 years these are starting to go. The ECM going out is still a punch in the gut but instead of switching sensors from engine to engine I am going to start replacing them until I find the issue and add to my maintence log with hours etc.

I don't know about MEFI 1 but on later ECUs the "power reduction mode" will kick in for high temps or low oil pressure. It happens at 2500 rpm and works by shutting down one of the injector drivers, thereby killing four of the eight injectors (these are MPI engines). Power drops greatly and you cannot sustain the 2500 rpm. When you drop below 1200 rpm all injectors will again function. If you have a TBI engine (see post 6) then I am not sure if you have that feature or how it would work, but 3000 rpm sounds awfully high for an engine protection system. In any case, while the code for temp may be retained I believe the protection mode will not be triggered again once the sensor output is correct. So if your engine is seeing some sort of a power reduction mode response, the ECU thinks the problem is still there.

Until you verify good fuel pressure readings above 3000 rpm I believe a fuel delivery issue is still a prime suspect. But fixing these things often is more a process than a single "aha" moment. That is why you are usually wise to spend more time on tests and diagnosis rather than buying parts.

My data shows a 14 as ECT LOW = too cold...as a rule, that will increase the fuel delivered but depends upon the specific failure mechanism. I'd expect a bad ECT to kill your fuel economy vs limiting your upper RPM.

I can't find an reference to a power reduction mode in the MEFI-1 or -2 stuff I have.

You don't have to clear a DTC to regain normal operation of the ECU; the DTC's sole purpose is diagnostics...and I concur with CaboJohn's last paragraph...

Post #6 says "Would distributor cap and rotor change I did cause this?" When did you do it? Since trouble shooting your problem or before the problem started? Double and triple check that the firing order is correct. Follow each wire to make sure it goes to the proper plug, you may have some wires crossed.

Right! You'd be stunned at how well a MARINE engine will idle and run with two wires crossed. My boat planned off slightly harder than normal with one motor on 6 cylinders. It popped through the carb when it topped 2,500 rpms, which clued me in.

Jeff

I dug thru the Mercruiser manuals and guess what...they have a "power reduction mode" in their early ECU's that starts at 2800 rpms.

that said, it is somewhat ambiguous as to whether it was implemented in the TBI's as well as the MPI systems. Unlike the newer versions, this mode is activated by discrete switches, just like the "standard" warning horn systems...their troubleshooting section also states a bad ECT sensor will limit rpms as well as produce several other symptoms...just food for thought

Can't you put one of those hand held computers on that and see what's wrong?

Jeff

If its not fuel related, that's the way I'd approach it...on the early MEFI stuff, there is literally no monitoring of the fuel system by the ECU...

Damn! Have to keep experimenting 'til you figure it out.

Jeff

[FONT=Tahoma, Calibri, Verdana, Geneva, sans-serif]Update 2. I purchased a EcT and MAP sensor. Replaced them before I left the slip. Still doing same thing but did see 3200-3300. I also finally got a fuel pressure gauge. My engines have the rubber housed fuel pump and I can't find psi specs On this pump? It's not the same return style pump in the parts book.

Key on 2 second fuel pressure was about 6 psi. Book says this is low.

Port - idles at 12 and wot is 12.5

Starboard - idles at 16 and wot is 10. Trouble engine.

This confused the hell out of me me. But then thought higher pressure at idle means possibly fuel is restriced before the injectors and thought about the fuel pressure regulator on the TBI housing. There is a spring and diaphragm in there that could be restricting fuel delivery, gave some love taps while engine was off around this area and underneath etc, went back out and damn boat came right up on plane and got up to 4200 before i brought it down to cruise range. Stayed up for 3 miles and ran perfect.. My wot is still low at 4200 and I think it's the automotive injectors run more lean from what I'm being told. New ones on the way. Fuel pumps may be weak as well but need to confirm this some how. Really don't want to buy new ones. . I will rebuild the pressure regulator when I replace injectors.

I need to see 19-20 psi from my fuel pumps from everything I read in both my manuals. However the regulator is set at 13psi for the injectors. This pump I have is used on the 5.7 as well and I think the pressures may be lower. My engines seem to be early builds going by serial number so looks like they changed fuel pumps at some point.

I don't think I'm out of the woods just yet but I think I'm on right track at least. Oh and old ECT or MAP sensor replaced may have done something as well. It after all. had thrown a fault and yes there is a ECM rpm reduction mode. It may have cleared this after I shut it down while switching gauge over to the other engine.
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Anyone have anything on these regulators? I'm sure they are discontinued like everything else on this fuel system.

Progress...yes, most every part is NLA...that said, many independent injector shops can get high quality replacements if they want to...many don't want to mess with them because there isn't enough demand to warrant the expense.

The GM data I have says the BBC TBI stuff prefers 28 PSI and the SBC TBI prefers the lower pressure you cited...If you have the factory values, go with them.

Fuel pressure dropping with the throttle opening isn't a good sign...i'd investigate that one further...

That's the problem. When the pressure drops the motor leans out--not good.

Jeff

McCoy38, I have the same 1997 454xli's as you, where did you find the original tbi fuel injectors that you purchased? Also, do you have the original part number and the numbers for the ones you ordered? Thanks

bertram30 said:

McCoy38, I have the same 1997 454xli's as you, where did you find the original tbi fuel injectors that you purchased? Also, do you have the original part number and the numbers for the ones you ordered? Thanks

Click to expand...

No I got them from a guy on ebay. Have not installed them yet. Seemed to know his stuff but we will see.
fuelinjector.citymaker.com/contact.html

I have a 1998 Carver with Crusader 454 xLi’s
Pressure should be around what you mentioned19 -20, mine ran at 21.
Couple of manuals I use are Crusader Tecm600 and Tecm620
If a sensor is out of spec, the “Check Engine” light should come on.
Then checking ECM code should help.

Bertram30 FYI those injectors did not work, Engines would run normal under no load but die as soon as placed in gear.