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Old 01-03-2011, 03:29 AM   #1
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Default 5.0L wont start

Hi All

Last had the boat out 3 weeks ago and ran like a dream. Has been raining since then and havent been able to get out. boat is outside but covered.

Yesterday, drove 60 miles to put it in the water, and couldnt get it started. Thought it might have been just flooded, but an hour later, and I was loading it back on the trailer with no luck. Also tried again this morning and no go.

Boat turns over, but doesnt seem to fire. occasionally fires as though it is going to start, but then nothing. When ignition is let off, it also has some blow back through the carby, which I thought may be something to do with the timing?

I also went and had a better look this morning, had key on while looking at the plugs, and all of a sudden alarm started going, and would not stop. When cranked over alarm stops, and then starts again afterwards. Motor Oil is constantly checked, and is just below full.


Had the boat fully serviced and checked over a month ago, everything looks healthy, plugs are clean.

I have just finished reading this post
http://www.maxumownersclub.com/forum...ght=boat+start

Towards the bottom of the post, someone mentions could be oil sender or kill switch. I would be leaning towards one of these being the problems, but does anyone else have any ideas, or can help diagnose and fix the problem before I take it to a mechanic?

Boat is a 1999, 1900SR, 5.0L carby.


Thanks
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Old 01-03-2011, 02:41 PM   #2
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Ya need 3 basic things for the engine to start: fuel, compression, and ignition. Fuel; remove air cleaner/spark arrestor from top of carb, look into the top of the carb while opening the throttle (an assistant, or really long arms, helps). If you see gas being squirted into the carb you can check "fuel" off your list. Compression; barring a catastrophic failure compression does not just go away so check that off your list too. Ignition; pull the spark plug wire from any one of the plugs, pull the boot back until the metal connector is close the boot opening, position the metal connecter close to a grounded metal part of the engine - about 1/8 to 1/4 of an inch (needed to suggest holding the plug wire boot with something insulated), and have someone try to start the engine. No spark = no start.

Yes, the engine probably has a safety circuit that disables the ignition if it senses a lack of oil pressure. The oil pressure sender is the device, and is inexpensive to replace. I believe you can validate it by jumping the two wires that connect to the sender. If place a jumper (like a paper clip) across the wires and the engine then starts - well, there ya go. If not, you'll have to dig in deeper.

Dan
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Old 01-04-2011, 07:03 AM   #3
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Thanks Dan

More than enough fuel floating around the other day, so dont think that was a problem (also forgot to mention I tried using some 'Start ya Bastard', or Ether the other day, didnt help), which leaves the spark. Will check the Plug lead as you mentioned, then oil pressure sender also as you have mentioned and let you know how it goes.

Thanks again
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Old 01-04-2011, 03:05 PM   #4
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No problem John.

If you have a product available that is actually called "Start ya Bastard" I'm moving to Australia because, apparently, you blokes have a sense of humor.

At this point you'll also have to keep in mind that, if you've been cranking and cranking the engine - thereby dumping lots of fuel into the cylinders, the spark plugs might now be fouled beyond use. Might be a good idea to remove at least one to have a look. If it looks wet and icky - consider replacing 'em all.

Dan
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Old 01-04-2011, 09:54 PM   #5
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SS, you're always a wealth of knowledge. I always thought the 3-part equation was Fuel, Air, Ignition . Obviously that would apply to any combustion. Certainly an engine will need compression too, but wouldn't that make it a 4-part equation?

On a side note: Would the engine still turn-over when the kill switch is engaged? I thought it would just 'click'. IF so, couldn't we rule out the kill switch from the equation?
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Old 01-04-2011, 11:23 PM   #6
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the engine will turn over fully if the kill switch is engaged...(don't ask how I know.)...but it just wont fire....

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Old 01-05-2011, 02:23 PM   #7
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Shrew,

My dear wife once said to me, in her sweet, loving way; "...there's more than a passing possibility that you're wrong.....". Her timing and delivery were perfect, I laughed for an hour.

I consider "fuel" to be the combination of air and gasoline, since a gasoline engine won't run without both present. (insert wife's comment here).

The kill switch is certainly a possibility, and would easily explain why it was running fine and now it isn't. All the rain/moisture might also explain it - perhaps enough moisture collected under the dist cap to kill it.

Dan
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Old 01-05-2011, 05:16 PM   #8
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LMAO!!!!! Very good.
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Old 01-21-2011, 10:51 AM   #9
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Ok, replaced both switches and sender, just to cover all bases, and I am about to go on a bit of a rant here.

Before I go further, I should mention that at no point while working on the motor recently, have I heard the Fuel pump running while the ignition is in 'ON" position. Should it be running when ignition is turned to 'ON'?

The reason I ask this, is because after replacing the switches and reconnecting, the fuel pump was still silent. After replacing each switch, I turned the engine (briefly) with a timing light connected, to see if it would flash when turning motor over, showing I was getting spark. NOt sure if I didnt have things connected well enough, but I decided to look further into it.

In the end, I took the purple and purple/yellow wires off switch on lower back of motor, port side (is listed as one of the starting and charging components in Mercruiser manual), and joined them together. Immediately fuel pump started running. First attempt at starting the motor, and hey presto! Started!!

I immediately assumed there is some problem with the switch, however I have since pulled apart the old one, and figured out exactly how it works (oil pressure pushes the 'gate' which completes the circuit).

SO after all that, and now I am home and have had time to think about it, a couple of questions:

1. is there a problem with the new switch, should fuel pump be running when ignition turned to 'ON'?

2. If not, have I just assumed that there is something wrong with switch when it is ok (I will actually try to start it when all connected next time!), or is there something else that I am overlooking?


And, for all those disbelievers, I have attached a photo of 'Start ya Bastard' ether.
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photo.jpg  
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Old 01-21-2011, 01:10 PM   #10
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john,

if you think the fuel pump is the problem take the hose of the fuelpump that connects it to the carburator......turn the key on like you are starting the motor, fuel will come out of the hose or it wont......you also can install a little fuel can on the hose that leads to the carborator and try to start the motor (bypass) dont forget to temporary disconnect the fuel pump.

just a simple option to get to know if the problem is befor or after the fuel pump.....but every time i turn my key one click to the right i hear the sound of the fuel pump that tells me its coming on pressure to transport the fuel....if you dont hear that anymore........??????

succes, and greatz, ed
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Old 01-21-2011, 08:44 PM   #11
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Quote:
Originally Posted by johno270583 View Post
And, for all those disbelievers, I have attached a photo of 'Start ya Bastard' ether.
THAT is hilarious, John, and strikes a particular funny bone in me because I can vividly recall several times, when I was young and broke, leaning over the fender of my '62 Chevy in the depth of winter administering shots of ether, then jumping into the drivers seat and twisting the key - all while muttering between clenched teeth; "Come on, start - ya bastard".

Anyway, the wiring diagram should show you what system the oil pressure switch disrupts. I know that fuel injected engines won't even think about starting unless the fuel lines are pressurized so I would think the pump would come on the moment you turn the key - but I can't swear to it. But on a carb engine there should be enough gas still in the float bowl to let the engine start, and run for a short time, even if the pump is disabled (assuming the engine was recently run).

When engine is off - no oil pressure so the switch is open. Start cranking the engine and oil pressure starts to build, and eventually builds enough to close the switch and complete the circuit. When the circuit is completed either A) the fuel pump is energized or B) the ignition system is energized.

If it's not apparent, I'm really just guessing. I would also guess that if the switch completes a pump circuit that there's also a relay in that circuit because I doubt that the switch could carry the amps necessary to run a pump.

So, in the final analysis, all my blathering above is useless drivel. Either trace the wiring by hand or by using the wiring diagram. You know all the major bits work. But, at least you have it narrowed down to 2 possibilities so you have a 50/50 chance of fixing it the first time. Helpful, no?

BTW, gald you made it through all the flooding in Brisbane, was quite a mess from what I've read/seen.

Dan
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Old 01-24-2011, 09:51 AM   #12
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Haha. Thanks Dan, you have pretty much did what I did while typing, thought out loud!

I have pretty much come to the same conclusions as you in the above, that even though fuel pump is not running when key turned to 'ON', once engine is turned over, oil pressure will build, causing pressure switch to close, in turn starting the fuel pump.

Unfortunately I took it for granted when the boat was running well, and didnt take any notice if the fuel pump was always running or not.

Anyway, I will have it out on Wednesday for Australia Day, so will play around with it then. Hopefully all my questions will be answered then.

Flood waters have receded, but has left quite a mess, was absolutely amazing the amount of water that built up after such a short period of rainfall, and extremely destructive. Just hopeful that it doesn't happen again soon. Sunny here at the moment, but there is a cyclone (hurricane) formed off the coast at the moment, which if moves closer, has the potential to dump a lot more rain here.
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Old 01-24-2011, 04:35 PM   #13
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Quote:
Originally Posted by johno270583 View Post
Unfortunately I took it for granted when the boat was running well, and didnt take any notice if the fuel pump was always running or not.
I'm guilty of that too, John, even though I'm normally pretty tuned into that sort of thing. I'll definately pay attention to it when the boat is pulled from hibernation.

Let us know whatcha find out.

Dan
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Old 01-27-2011, 09:38 AM   #14
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So my findings from yesterday are:

Boat started a the start of the day with the Oil pressure switch bypassed, just to make sure it was going to run.
Then connected the switch. Did not hear fuel pump run (not to say it doesnt at all, I just couldnt hear it), but boat started immediately.

Guessing there is enough fuel in the carby bowl to get it running without the fuel pump, or if there isnt much, maybe the pump runs after turning the motor for a while and oil pressure builds? Either way, its running with the switch connected, which was my main priority.

Great day on the water, few unrelated issues but all good.

Now just need to find some more free weekends to get out before the end of summer (not that we really have a winter here in Brisbane!)

Thanks for your help Dan, Shrew, Seapuppy and Ed and Inge.
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Old 01-27-2011, 10:04 AM   #15
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your welcome....and hope you can spend some time at your boat coming weeks, but not to much.........then we have to wait such a long time on our summer

greatz, ed
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Old 01-27-2011, 03:50 PM   #16
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your welcome...now take some pics of your boat and post them here...we wanna see what we're helping with...


SP
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Old 02-02-2011, 07:51 AM   #17
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One last thing (for now at least), I am replacing a cracked coil. Do I need a resisted, or non-resisted Coil?

Guy at the store has sold me a non resisted, as the spark plugs are resisted, is this right?

I have been looking at the Mercruiser manual, and it seems to say there should be primary and secondary resistance?

Coil
Description GM EST Mercury
Coil Part Number 392-7803A4 392-7803A4
Primary Resistance .60-.80 Ohms .60-.80 Ohms
Secondary Resistance 9,400-11,700 Ohms 9,400-11,700 Ohms
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Old 02-02-2011, 02:31 PM   #18
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Nooooo idea, John, but since you have the coil specifications from the manual it seems you can just compare those to the specs of the new coil.

The purpose of "resistor" spark plugs, as well as "resistor" plug wires, is only to suppress ignition system interference into the vehicles' audio system. Not sure if I have ever heard of a coil designed for that purpose.

Wait - wait, where's SeaPuppy (Steve)? He's our resident electronics guru....

Dan
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Old 02-02-2011, 06:56 PM   #19
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Hey down under friend,
It looks like you are in good company here with the suggestions. Some other ideas from past experience with my T350MAG MPI's;
1. Fuel water separator filter, Have you changed that every 6 months or 100 hrs?
2. All Late model MerCruiser engines feature pointless "thunderbolt ignition” that is usually very trouble free with the exception of the Ignition modulator. It is the sensor that is located under the distributor cap that is a u shaped channel that is activated by a cup shaped wheel with notches in it that rotates thru the ignition modulator with an air gap that allows it to rotate freely. Each time a tooth rotates thru the sensor, it triggers the ignition spark. The trouble is that moisture will build up causing rust and corrosion to form on the sensor causing the sensor not to trigger. It is easy enough to see the corrosion by removing the dizzy cap.
I had this happen to both mills so I change or clean the sensor each time I change the dizzy rotor and cap. Getting the rotor off to change the /clean the sensor is a bit of a pain because the damn thing is only held on my slight interference fit, you simply push it on (or pull it off). I've had to use two mini pry bars to get the sucker off sometimes because they can be a bugger to get back off.
I carry onboard a vast assortment of the spare parts (in twos like Noah’s Arc cuz I have twins) which include the above too cuz there are two kinds of boaters; Those who have broke down,…….and those who will! ;-)
3. Shrew’s idea of the Kill lanyard switch could also cause this problem intermittently too. I had this happen to mine so I replaced them both. Problem solved.
Take care and hope it helps
Bella Sera 3300SCR
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Old 02-02-2011, 09:13 PM   #20
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someone call????....I hear...and obey!!..ok...no I don't ...but I did read it!!...


well...according to my owners man...the 350mag mpi engine fuel water seps on the seacore system gets replaced every 300 hrs....

as for a resistive/non-resisitive coil...you should have both plugs and coil resistive .....otherwise your going to get noise in the am/fm/vhf radio bands....
the wires should also be Resistive wires ..but I don't think i've seen non-res. in yrs....

SP
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