Mecruiser 7.4LX MPI Ignition System Issues . . .

[tpenfield]

Hello Folks:

I've been having an intermittent problem starting up my Mercruiser 7.4LX MPI engines (see S/N's in my sig below). So, before I get going on diagnostics and possibly replacing 'stuff', I'd thought I'd post it here to see if anyone can provide some insight or experience with a similar problem.

First off, I have twin engines with the electronic fuel injection (multi-port).

Normally when I go to start them, I turn the ignition switch on . . . get a single 2 second beep from the 'warning' system . . . turn the ignition to 'start' . . . the engine starts and I get a second beep. Good to go.

Lately, when I go to start the engines, it seems like the ignition switch is becoming intermittent, as it does not seem to make the ignition system turn on . . . I do not get the first 'beep' and if I turn the key to the start position - Nada. The port engine began doing this a few weeks back, but now the starboard engine has joined the 'fun'.

So, far, if I try a few times, I will get the 'beep' and then the engine will start. Once they are running, it is fine.

Looking through the manuals that I have, it looks like I have the 'ignition switches', the 'kill switches' and also the possibility of a 20 amp fuse in-line with each ignition switch. Before I go throwing new parts at this issue, I thought that I would see if any of the Mercruiser Guru's on the forum can shed show light on the ignition systems for the EFI engines. In replacing the ignition switches, I'll want to get a matched 'set' so that the keys are the same for port/starboard

So, my questions:

- Since both switches are showing the same problem intermittently, would there be something else to consider? At this point, I am not sure if the ignition switches are acting up, or if it could be the kill switches . . . or even the fuses.

- Where can I find more information about the 'beeps' that you get from the starting/ignition system? My engine seems to be covered, in the Mercruiser manual #16, and it looks like I may be missing the second book. So, far I have not come across any information specific to the EFI/MPI engine ignition system.

- Anything else that I should consider? I figure if it were the ignition switches, I might have the engines shutting off while underway . . . :noidea: so far that has not happened, but I am wondering if the fact that they have not, if it is pointing to something else :noidea:

As always, TIA for ay help.

 

[achris]

First read was to think fuses... Those glass 3AG fuses have a habit of getting corrosion on the ends and making bad contact. And it would be worse as more current is drawn, like when cranking the engine. My first step (regardless of anything else) would be to replace the fuses and their holders with the water-proof automotive 'blade' style. I put them in all the boats I work on now after one off my friends got caught 25 miles out to sea with a dead system...They are not expensive and they work really well....

These ones....

 

[tpenfield]

Thanks, Chris. I'll start with the fuses and work my way from there. The thing that seems odd is that with the system being somewhat intermittent, it has not conked out once the engine is running. . . . But of course, now that I said that, I'm sure it will start doing that. We had in-law relatives down to the beach for the weekend, and the last time they were here, my F-242 met its demise when the engine hydro-locked. I was worried that bad luck would strike again with the 33 footer and we'd be stranded. We were out boating yesterday, and the starboard engine was acting up with these symptoms . . . Fortunately it started after the third try. Just thinking it is winter in your half of the world, while much of the membership here is enjoying summer. I hope all is well.

 

[achris]

Thanks Ted, It's winter in Australia, and I'm not in Australia... I'm on a boat (almost 600' long!!!) off the coast of Gabon... We're installing a couple of oil production jackets ready for topsides to be added... Even though I'm just about on the equator it's unusually cold, only about 80 degrees... I'm cold enough to be warming a jacket and long pants.

Anyway, let us know how you go with the fuse replacement, also have a close look at the ends of the glass fuses and the contacts in the fuse holder. I wouldn't mind betting you'll find good signs of corrosion.

Chris....

 

[tpenfield]

A Quick Update . . .

I checked the ignition system wiring up at the helm for inline fuses, but it looks like there are circuit breakers, no fuses. So, I exercised the CB's a bit, and the engines seemed to start OK with no fuss.

So, I'll see how things go and if the problem comes back. Since the boat is 18 years old, the circuit breakers may be getting a bit crusty inside. I think they are "ETA" brand CB's

It is a good thing that I did not run out and buy new ignition switches, as it seems that they are fine.

 

[alldodge]

Howdy Ted, is your boat setup with separate batteries for each engine, or one bank used to start both?

 

[tpenfield]

Howdy Ted, is your boat setup with separate batteries for each engine, or one bank used to start both?

One bank of batteries that start both engines (Perko Switch to select the battery/batteries)

 

[alldodge]

One bank of batteries that start both engines (Perko Switch to select the battery/batteries)

That being the case I would trace back how power comes to the keys, may be something in common their.

 

[tpenfield]

That being the case I would trace back how power comes to the keys, may be something in common there.

yup, power comes from the circuit breakers, which gets its power from the main power bus that goes forward to the helm CB panel If the system behaves itself for a while, then it is probably the CB's getting corrosion on the inside. If not, then I'll have to keep looking.

 

[tpenfield]

The starboard engine ignition did not 'fire up' once today . . . I immediately tried again and it 'activated'. So, I guess I will continue to monitor things and perhaps test out the circuit breakers.

 

[muc]

You can find information about your warning buzzers in the owners manual.

 

[tpenfield]

You can find information about your warning buzzers in the owners manual.

Yea, it looks like the manual for my engines (Manual #16) is in 2 books . . . I have 'Book 1' and I did not see anything specific about the warning buzzer (beeps) so I am searching for 'Book 2' . . .

 

[muc]

Not sure if it's covered in the service manual, but it is covered in the owners manual ---- the one that comes with the boat.

 

[mr300z87]

Hi Ted, I have been quietly following along your progress on the Formula and have been impressed with all your work. Interment electrical problems are never always tough to fix. Have you tried the site boatinfo.com to look for book 2 of manual 16? I notice the site does not like the iPad though. If that does not work for you pm me an email address and I can share my PDF copy which includes all the sections. Btw I just watched the video you posted on your other tread looked like a great day to be on the bay. Wish Barnagat bay would flatten out like that when I am going out. Have a great Sunday.

 

[tpenfield]

Not sure if it's covered in the service manual, but it is covered in the owners manual ---- the one that comes with the boat.

Yup, Page 29-31 of the operation manual talks about the warning system . . . Looks like the 2 second 'beep' is just a test of the buzzer when the ignition is turned on. Nothing else really to it, other than the standard temp/oil/outdrive warnings. I thought that maybe with the EFI there would be some other warning beeps.



The Mercruiser manual also talks about an inline fuse, but I have yet to find it. The Formula schematic does not detail the fuse, only the CB's.

Perhaps I'll take a closer look today.

 

[alldodge]

Top of the morning to you. Below is a link which has the entire manual 16 for download.
http://www.maxumownersclub.com/foru...8-454-502-Gen-V-VI-(1993-1997)-Service-Manual

Also here are the things which can cause the alarms and beeps. Keep in mind some of these will not happen with our year engines but it not a bad resource.
Warning system Faults, SC1000 Yes/No, Audio Alarm, Available Power %, Description.

(1) Cam Sensor Yes 2 Bp/min 90% Open or short, engine must be cranking to set this fault code.
(2) ECT CKT HI Yes 2 Bp/min 90% Open
(3) ECT CKT LO Yes 2 Bp/min 90% Short
(4) ECT Coolant Overheat Yes Constant 6-100 % Engine guardian overheat condition
(5) EST 1-8 Open Yes 2 Bp/min NA Coil harness wire open
(6) EST 1-8 Short Yes 2 Bp/min NA Coil harness wire short
(7) Fuel Injector 1-8 Open Yes 2 Bp/min NA Fuel injector wire open.
(8) Fuel Injector 1-8 Short Yes 2 Bp/min NA Fuel injector wire short
(9) IAC Output Yes 2 Bp/min 90% Only with rpm
(10) Knock Sensor 1 Yes 2 Bp/min 90% Alarm sounds for 20 seconds in NEUTRAL and indefinitely in gear.
(11) Knock Sensor 2 Yes 2 Bp/min 90% Alarm sounds for 20 seconds in NEUTRAL and indefinitely in gear.
(12) Low Drive Lube Strategy Yes Steady Bp 0-100% Low oil in sterndrive.
(13) Low Oil Pressure Strategy Yes Constant 0-100% Low oil pressure strategy.
(14) MAP Sensor 1 Input High No 2 Bp/min 90% Short, no visual on SC1000.
(15) MAP Sensor 1 Input Low No 2 Bp/min 90% Open, no visual on SC1000.
(16) MAT Sensor Yes 2 Bp/min 90% Open or short in MAT circuit.
(17) Oil PSI CKT Hi Yes 2 Bp/min 90% Short, defaults to 51.7 psi.
(18) Oil PSI CKT Lo Yes 2 Bp/min 90% Open, zero oil pressure.
(19) Overspeed Yes Constant RPM Limit Engine over rpm limit
(20) Port EMCT CKT Hi Yes 2 Bp/min 90% Open, defaults to 32 degrees F.
(21) Port EMCT CKT Lo Yes 2 Bp/min 90% Short, defaults to 32 degrees F.
(22) Port EMCT CKT Overheat Yes Constant 6-100% Overheat condition, 212
degreesF(100 degrees C) limit.
(23) Sea Pump PSI Lo Yes Constant 6-100% Low water pressure strategy, defaults to 43.4 psi.
(24) Sea Pump CKT Hi Yes 2 Bp/min 90% Open.
(25)Sea Pump CKT Lo Yes 2 Bp/min 90% Short.
(26) STB EMCT CKT Hi Yes 2 Bp/min 90% Open, defaults to 32 degrees F.
(27) STB EMCT CKT Lo Yes 2 Bp/min 90% Short, defaults to 32 degrees F.
(28) STB EMCT CKT Overheat Yes Constant 6-100% Overheat condition, 212 degrees (100 degrees C) limit.
(29) Steer CKT Hi Yes No No Open and short.
(30) TPS1 CKT Hi Yes 2 Bp/min 90% Short, signal to 5v+, engine will not start. Refer to data monitor screen.
(31) TPS1 CKT Lo Yes 2 Bp/min 90% Open.
(32) TPS 1 Range Hi Yes 2 Bp/min 90% Above 4.8v, 994 counts.
(33) TPS 1 Range Lo Yes 2 Bp/min 90% Below 0.5v, 35 counts.
(34) Trim CKT Hi Yes No No Short, high range, visual warning on SC1000 only.
(35) Trim CKT Lo Yes No No Open, low range, visual warning on SC1000 only.
(36) 5 VDC PWR Low Yes 2 Bp/min varies Short any 5v+ to ground.

 

[mr300z87]

sorry posted the wrong link http://boatinfo.no/lib/library.html

 

[Merc4ever]

The fact it started in one engine then moved to the other makes me think ground problem. I think most of the "hot" stuff is independant of each other and would be odd to move to the other engine where a ground problem in boats can be corosion from moisture that is spreading like cancer.

 

[tpenfield]

Looks like I have the entire book . . . 930 pages . . . so that is "Book 1" and "Book 2" combined :noidea: I was just thinking it may have been in 2 PDF files. . . . .

Anyway, today is cloudy and might rain a bit, not a real boating day, so I will be checking the wiring, cleaning contacts, etc.

Thanks for all the help folks. :thumb: I'll post some updates

 

[Merc4ever]

Good luck, and don't forget to clean and tighten all grounds and battery terminals because I have seen many problems result from that in the automotive field that I worked in for several years. Not that I'm certain it is your problem but I have been a mechanic / electrician all my life and always spray WD 40 on the most critical connections to prevent future corrosion in the damp enviroment that they live in. Even in home electric service you have to apply grease to the aluminum wires that contact the copper or they eventually corode. Just don't ever use grease that insulates from making a connection (like anti-seaze) on battery terminal posts, Keep them dry then cover with grease only after tightening the clean connection.