mercrusier injectors shut down at higher rpms

[cabsales1]

1999 305 engine runs great until about 3500 rpms then the injectors quit getting voltage. If you just drive around at lower rpms it will run ok at first but will eventually start failing at lower rpms till you end up paddling home. I suspect the computer but would like to really diagnose it instead of just hanging parts on it at random. Does any body have any ideas or a flow chart on diagnosing my problem? It would be real nice if I could find a schematic on the ECM pinouts and voltage. Thanks in advance. Craig

 

[cabsales1]

Re: mercrusier injectors shut down at higher rpms

P.S. This is a 1999 Caravelle 20' 6" VIN# VCN11022G899 with a 5.0 Mercruiser Alpha 1. I have used noid lights and can see it go dead when it hits the higher rpm's (It has 2 injectors so I can run the boat on 1 and watch the light on the second one). I have also put a timing light on the spark wires and it still has spark when the injectors go dead. When the rpm goes down the injectors start firing again. I have also checked the OHMS on the injectors and they both check out OK. I would take it to the marina to have it hooked up to a diagnostic machine but I live in Iowa and there are 3 marinas within driving distance and they have a Month waiting list. Summer will be over before it gets fixed. Actually this is a friends boat and I'm trying to help him out. I have drag raced and worked on cars for over 30 years and very capable of fixing it if I can get a few schematics or a Service Manual in my hands. I'll either have to fix it old school and do voltage pinout on the ECM or find some way to get the codes off the computer (I'm sure it probably has some stored on it). But again the problem lies with not being able to get one of the marinas to find a time slot to fit it in. We are in dire need of more boat mechanics in this area but it is only a 6 month a year industry here with our weather in Iowa. I ussually fix quite a few of them in a summer for friends but need alittle help with this one. I really suspect the computer, but refuse to just hang parts on stuff. Any help is appreciated!!! Craig

 

[Reel Poor]

Re: mercrusier injectors shut down at higher rpms

You said the injectors are loosing fire. Have you actually checked for voltage at the injectors with a volt meter when the noid light quits flashing? The ECU does not supply voltage to the injectors, it controls the ground/pulsing side of the injectors. The voltage is supplied via the ignition relay then through the ignition fuse.

 

[cabsales1]

Re: mercrusier injectors shut down at higher rpms

Thanks REAL POOR for the help.
I haven't checked it with a volt meter yet. I have only had a noid light on it and observed it flashing properly and when the boat hits a certain RPM it shuts off. I'll check both injector wires today with a volt meter to see if it still has voltage or if the ground input wire from the ECM is the wire losing it's signal. Thanks alot for the tip on how the injectors get their signal from the ECM it's pointing me in the right direction. Craig.

 

[newport dave]

Re: mercrusier injectors shut down at higher rpms

You can check codes by using these instructions;


How to make a Marine EFI Code tool for under $1.00

Materials needed:

One 12volt resistor type LED light
One small paperclip cut in half


This home made code tool will work on most marine EFI systems with the ten pin DLC (Data Link Connector).

How to hook it up:

1) Ignition key ?OFF?
2) Remove the cap from the Data Link Connector (DLC)
3) Slide the LED into the female terminals of position E and F on the DLC, making sure that the positive side goes into terminal F and the negative side into terminal E
4) Turn the ignition key to the ?ON? position (LED should come on)
5) Insert the half paperclip into terminals A and B ? This puts the engine in ?Service Mode? - (you will hear fuel pump come on, and code will begin to flash on the LED)
6) Read codes by observing LED flashs. If the self diagnostic system is working it will flash code 12 ? one flash, pause, two flashes, long pause ? it will repeat three times. If other codes are present they will flash in order of lowest to highest.

For more details on how to read codes, clear codes, what ?Service Mode? is, how to set base timing, etc. refer to appropriate service manual.

I don?t recommend making and using this tool unless you are confident that you can do it correctly. Hooking it up incorrectly could damage the ECM.

Dave

 

[cabsales1]

Re: mercrusier injectors shut down at higher rpms

Looked at boat this afternoon and found that it had one code stored in the computer. It was code 14 Coolant Temperature Sensor (CTS) Low Temp. I have a couple of questions 1 how do I check it for voltage to see if it is good or not? All the wires are connected no corosion on it ect... I need the voltage or OHM reading information. I suspect I'm going to find it to be bad as the few times I've rode in the boat checking it out it has consumed large amounts of fuel. I'm suspecting that this could be caused by it still being in the rich mode that it would be running in until it tells the ECM it is warm and no longer needs choke mode. The Second question is could this be the cause of the injectors stopping firing at the higher RPM's. Perhaps the computer not being able to drive the injectors under such a load and shutting down? Begging for answers??? Craig

 

[Don S]

Re: mercrusier injectors shut down at higher rpms

Engine off, disconnect the ECT sensor. Turn ign. on, engine off. Check the voltage across the harness connector, should have above 4 volts.
If it does, you need to check the resistance of the sensor itself.
160? = 450 ohms
70? = 3,400 ohms
40? = 7,500 ohms
0? = 25.000 ohms

 

[DHPMARINE]

Re: mercrusier injectors shut down at higher rpms

Had something a bit similar a week or so ago. 4.3 V6. Sometimes would run sometimes would not.When it ran,the injectors would quit around 2500 RPM. We hooked up the computer,but also had few codes. But when I revved it up,and the injectors quit,I realized the whole engine had lost electricity. Dash gauges worked,so I figured the ignition switch was OK.Checked the engine circuit breaker,it was OK.

Next went to the fuses on the engine,and when I touched the housing holding them,I heard the fuel pump kick in.Had 2 'cracked' fuses that powered the ECU. Replaced them,ran great.

Probably not common,but it almost had me buffaloed.

DHP

 

[87 bayliner]

Re: mercrusier injectors shut down at higher rpms

does this motor use a crank position sensor? had a similar prob with my chev truck a year ago. replaced the sensor and the problem was solved.

 

[Don S]

Re: mercrusier injectors shut down at higher rpms

Nope.

 

[cabsales1]

Re: mercrusier injectors shut down at higher rpms

Thanks alot for the info Guys and the Help!!! Don is correct it doesn't have a crank sensor on this boat. By the way Don thanks for the voltages on the ECT sensor it checks out bad and will replace it tomarrow when the marina is open to get one. I have already checked out all the fuses, ground wires ect. to the ECM and they are all OK!!! When the injectors stop firing the computer still has power to it and the plug wires are still firing. It just quits sending the pulse to the injector wires and they quit firing. This is a fairly simple ECM unit compared to ZR1 Vettes and the such. There really isn't very many sensors on it and they all are quite simple circuits to check with a volt meter. I wish I had all the info like Don S just sent me on the ECT sensor, volt ranges on each sensor, pinout voltages and ranges on the ECM, ect... With the right information in hand I'm sure I'll get it running but scouring the internet for such info for free is to time consuming and I'm doing this fix for a friend and won't be charging him much if anything for doing it. My friend is convinced that if he is going to own this boat that about the first purchase that he needs to make is the Dealer Service Manual (not the aftermarket ones although some of them are pretty good also). All the info I need should be in a "Good" Service Manual. I prefer to purchase the most current and up to date ones I can get my hands on and have convinced him to make this purchase ASAP. Does anybody know off hand the most current and accurate PN# for this boats manual??? Again I Thank all you guys for any info you have I really do appreciate it. I'm a newbie on this site but I belong to several other forums for car racing ect... and I'm quite aware that it takes valuable time to correspond with people and that none of you are being paid for your time or expertise. I believe the term KUDOS is appropriate to all out there helping their fellow boaters!!!!!! Craig

 

[Reel Poor]

Re: mercrusier injectors shut down at higher rpms

Like you said it's pretty simple system. If the injectors are loosing their ground signal it's either wiring, distributor reference signal, or ECU problems.

Can you post the engine serial number. Need that to really know what your working on and to get the right repair manual.

 

[cabsales1]

Re: mercrusier injectors shut down at higher rpms

Thanks Real Poor for the reply the engine Serial# is OLO94169 and the Drive Serial# is OL195479. I'm not sure if the O's are zero's or O's they have a slash threw them. Hope this helps? Craig

 

[Don S]

Re: mercrusier injectors shut down at higher rpms

0L094169 Everything in your SN is actually a number except for the L which is a Letter in all the SN's.
Anyway, you do have a 98 engine, and service manual #24 is the one you want, it's PN is 90-861327--1, you want to make sure you get the --1, which is revision 1. The original didn't have any EFI information in it.

 

[cabsales1]

Re: mercrusier injectors shut down at higher rpms

Thanks alot Don for the part# for the service manual. This is what I needed to keep going in the right direction. My friend went to the marina today and purchased the sensor for the water temp guage by accident instead of the one with 2 wires ECT that runs the computer temperature. He told the marina he had a code 14, you would think they would be able to give him the right one but it was a younger gal behind the counter and she probably didn't realize that there are 2 coolant temperature sensors. Anyway he drove 45 miles to the boat to put it on and realized he had the wrong one. He put it on anyway just for good measure and decided to clean the other one up a little more and now the boat seems to be running OK. I told him to still purchase the other correct ECT sensor and replace it anyway as it may be working now but could be intermitent. We will replace it and take the boat on a good ride in the next day or so just to make sure it is indead fixed. Again I Thank All of you for your help and will let you know the outcome. It kind of surprises me that just a bad Coolant sensor is capable of overloading the computers injector circuit. I don't really understand how it is capable of doing so, therefore I'm still a bit sceptical that I have this thing all fixed or if something is still wrong and intermitent and just working for the time being.
I told my friend that if he takes it for a good trial run and I'm not with him to do the smart thing and go up river not down (way easier floating home rather than paddling you butt off upstream). Anyway we got the Shop Manual now and will let you all know if this takes care of the problem. Thanks Again Craig

 

[Don S]

Re: mercrusier injectors shut down at higher rpms

The PN for the ECT Sensor is 805218T, might want to give a call and make sure they have the right one before he makes the trip again.
THe fact that the ECT can cause the problem doesn't surprise me, the ECM is probably seeing a VERY cold engine and is limiting the rpm till it warms up. I suspected it, only couldn't find anything about it doing that in the manual.

 

[mrosales]

Re: mercrusier injectors shut down at higher rpms

I have a fairly new 4.3L 220hp MPI Mercruiser (year 2006) engine on a 2006 Triton 201F deck boat. The engine will get up to 4500-5500 rpms and then slowly start slowing down to about 2500-3000rpms. The engine doesn't shut off completely and will continue to run. The engine is still under warranty. I took it to one Mercury shop in the New Orleans area and they checked obvious items, belts, water/fuel filter, etc., and after running it on the water were able to reproduce the problem. The shop owner said he didn't have a Mercruiser engine expert in-house to take the engine apart and recommended I tow it back to the Triton dealer which is in another city which I plan to do.

Is this a symptom of the fuel injectors shutting down? I've also read about Mercruiser V6 engine blocks having salt water leakeage through the valves and rusting internal engine parts (cylinders,vavles, etc..).

I am not an expert mechanic but I would appreciate if somebody could tell me if they had similiar experiences and how Mercury handled them.

Email: mrosales@charter.net

 

[Don S]

Re: mercrusier injectors shut down at higher rpms

Start a new thread with your question, this thread is for cabsales problem.