starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

I have wiring diagrams ,from the mercruiser shop book. Tough following, reaching out too fellow boaters, that possibly had simuliar issues or a boater with knowledge in this area
I have a 1984 mercruiser 488 engine. ( ford engine )
4 cylinder

Living with an electrical starting issue for quite some time.
WHen boat was in for engine work shop saw what I was talking about. They think electrical harness has too be changed. But once they seperated the prongs in harness it worked fine.
Then it acted up again months later.
I did the same , connections are clean, no visual breaks, good firm connection.
Got it going. Woking fine, then a Month later won't start

Time as come too correct this issue.

A wire must be shorting out, some were in coil area or electrical harness

Most times difficult starting. Eventually I get it started and once started it starts first turn of key
Once cold, wont start
Seperate electrical harness from male and female ends, some times this gets it going, othertimes no.

Other day would not start at all.
Neighbor was helping he has more knowldege
He ran a hot wire from starter postive too positive on coil. Started right up. and started without jumper many times

Later that day I tried starting and no luck, had too run jumper was tough starting but eventually started. Once it started and ran a few minutes was able too shut off and restart with out jumper wire many times

There are two positive wires going too coil , I beleive one is the purple/ yellow other is purplish in color
I beleive purple/yellow goes from one of the two legs from starter senolid. Other wire not sure, ( does it go from coil too key?) The other yellow/ red off prong of starter senolid goes too safety switch off of throttle. WOrks as it should

Negative has a gray coming in from harness ( not sure from were ) but goes from harness too neg of coil pig tales with a black wire which goes under dist.cap.

If one of the two wires had a split some were it would not start after jumper wire was removed, but it starts first turn of key once its started from cold start.

During past few months, purchased, new key switch, coil, starter senolid, new points, new plugs,

SO put your thinking hats on
What wiring should I be searching for ?????
Going from harness too coil mercruiser book says its a resister wiring, not easily replaced.
If I run my own wiring what should I do ?

SIDE NOTE
Replaced unreliable stator regulator charging with a one wire marine alternator.
All old stator and regulator wiring was cut, some were removed others caped.
SIDE NOTE
4 barrel carb , ( not sure what part is called ) there are two wires one connection, used for cold starting.
Most of this wiring is under tape, not sure were they come from ,do they pig tale off positive of coil wiring?
When I was feeling around back of carb, I took wiring off, felt a little warm and once I removed battery needle on dash jumped to around 14 volts, when I re- attached , went down a lot, like there is a drain ???
Could be un related or the cause of my problems , All in same general area


thanks
al

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

I have a 1984 mercruiser 488 engine. ( ford engine )

Click to expand...

Just an FYI, it is not a Ford engine, only a Ford head. The block and manifolds are all Mercruiser.

Now, on to your problem. You say you have a starting problem. What kind of problem is it? Engine won't crank? Engine cranks and just won't run? Turn the key and nothing happens? Turn the key and something clicks?

You probably don't need a complete harness.

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

alan ber said:

I have wiring diagrams ,from the mercruiser shop book. Tough following, reaching out too fellow boaters, that possibly had simuliar issues or a boater with knowledge in this area
I have a 1984 mercruiser 488 engine. ( ford engine )
4 cylinder

Click to expand...

No it isn't. It's a Mercruiser engine that uses SOME Ford internal parts. Pistons, rods, a head.
Do you have an engine serial number (it will be a 7 digit number)?

alan ber said:

Living with an electrical starting issue for quite some time.

Click to expand...

Define 'starting issue'... Is it not cranking, cranking but not firing, cranking but only firing on some cylinders?

alan ber said:

WHen boat was in for engine work shop saw what I was talking about. They think electrical harness has too be changed. But once they seperated the prongs in harness it worked fine.

Click to expand...

Which pin was 'separated'?

alan ber said:

Then it acted up again months later.
I did the same , connections are clean, no visual breaks, good firm connection.
Got it going. Woking fine, then a Month later won't start

Time as come too correct this issue.

A wire must be shorting out, some were in coil area or electrical harness

Click to expand...

If a wire 'shorts out' it will get hot and burn. Is this what you are seeing?

alan ber said:

Most times difficult starting. Eventually I get it started and once started it starts first turn of key
Once cold, wont start
Seperate electrical harness from male and female ends, some times this gets it going, othertimes no.

Other day would not start at all.
Neighbor was helping he has more knowldege
He ran a hot wire from starter postive too positive on coil. Started right up. and started without jumper many times

Later that day I tried starting and no luck, had too run jumper was tough starting but eventually started. Once it started and ran a few minutes was able too shut off and restart with out jumper wire many times

There are two positive wires going too coil , I beleive one is the purple/ yellow other is purplish in color
I beleive purple/yellow goes from one of the two legs from starter senolid. Other wire not sure, ( does it go from coil too key?) The other yellow/ red off prong of starter senolid goes too safety switch off of throttle. WOrks as it should

Click to expand...

2 wires go to the coil positive. One is the resistive wire that keeps the ignition system working when the key is in the RUN position. It's resistance is such that the coil is fed with about 7 volts. The other wire is from the 'I' terminal on the starter and feeds the coil with full 12volts during cranking, 'START' position on the key.

alan ber said:

Negative has a gray coming in from harness ( not sure from were ) but goes from harness too neg of coil pig tales with a black wire which goes under dist.cap.

Click to expand...

3 wires should be coming from the negative side of the coil. The gray is the tacho feed, one of the blacks is to the points in the distributor, the other black goes to the shift interrupt switch (NOT safety switch).

alan ber said:

If one of the two wires had a split some were it would not start after jumper wire was removed, but it starts first turn of key once its started from cold start.

During past few months, purchased, new key switch, coil, starter senolid, new points, new plugs,

Click to expand...

We call this 'shotgun troubleshooting'. Just throw as many parts as possible at it until it's fixed. It is NOT a proper diagnostic troubleshooting technique. Get yourself a multimeter or test light and start diagnosing the problem logically and methodically.

alan ber said:

SO put your thinking hats on
What wiring should I be searching for ?????
Going from harness too coil mercruiser book says its a resister wiring, not easily replaced.
If I run my own wiring what should I do ?

Click to expand...

Merc sell a resistive wire kit to replace the current wire. But you should make absolutely sure that's what the problem is before you go tearing into the wiring harness.

alan ber said:

SIDE NOTE
Replaced unreliable stator regulator charging with a one wire marine alternator.
All old stator and regulator wiring was cut, some were removed others caped.
SIDE NOTE
4 barrel carb , ( not sure what part is called ) there are two wires one connection, used for cold starting.
Most of this wiring is under tape, not sure were they come from ,do they pig tale off positive of coil wiring?
When I was feeling around back of carb, I took wiring off, felt a little warm and once I removed battery needle on dash jumped to around 14 volts, when I re- attached , went down a lot, like there is a drain ???
Could be un related or the cause of my problems , All in same general area


thanks
al

Click to expand...

Chris...........

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

Morning Don
Cranks great, has new starter senolid,new key switch, coil
at times starts as it should
other times wont
Told there is a bad wire somewere, causing weak spark, yesterday ran jumper wire from starter too hot leg of coil, fired up, removing hot wire started first turn of key many times. Later in day when cold same issue, cranking away, once i jumped off starter fired up and once warmed was able too start first turn of key without jumper cable.
not sure what wiring I should be looking for
thanks
al

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

Does your starter have a solenoid on it or do you have one without the solenoid?

Also, do you have a purple/yellow wire running from the + terminal of the coil to either the start solenoid on the starter or the slave solenoid?

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

One other note, does your starter slave solenoid (the one not mounted on the starter) have the small terminals marked S and I ?

Make sure you have this purple yellow wire on your solenoid on the I terminal. That is what puts full power to your coil when starting. If you had a faulty resistor wire, it wouldn't run at all.

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

Saga continues
I have a solenoid on starter, plus slave solenoid
purple/ yellow wire is correct, the other wire yellow/red goes too trottle
At times it wont start.
I crank away, over and over, it sounds like it wants too start but does not
While I am cranking I have my battery charger on too make sure I have enough power

Eventually I put a jumper wire from starter positive ( big bolt ) and run it too positive of coil turn key it starts right away.
I remove jumper wiring. After few minutes I shut it down, able too start over and over with key no problem

this sounds crazy
wont start , put a jumper wire on, starts, then able too start over and over first turn of key?????????

could the solenoid in starter be bad and jumping gets it going and works until it gets too a dead spot?

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

Just try putting a test lead from the two terminals the purple/yellow wire is hooked to and see if it starts cold. Could be nothing more than a bad wire.

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

You could also try putting a wire from the starters inboard small terminal (D in the image below) to the coil. That is how all the Chevy engines pick up extra power. It's just harder to get too on the 470 engines, probably why they go to the slave solenoid.

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

Hello Don
Can't hurt will add it tomorrow, should I leave current wiring and just add additional wiring from terminal D too positive on coil?
I have tightened down all wiring,found purple wiring off slave solenoid a little loose, not very but was able turn screw by hand, tightened everything down, ran test light. cranked boat, power correct. Has been starting easily all afternoon.??? Tomorrow another story ( lets hope what ever I did corrected the issue.
Thanks for all your help
Al in Orlando

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

If it was loose and you now have CLEAN (no corrosion, rust, crap or other gunk) on the original terminals, try that first tomorrow when it's cold. If it doesn't start, then take it off and hook up the wire from the starter to the coil and see if it starts.

A lot of this might be obvious if we could see it, but we can only go by what you type. So who knows what it all looks like (except you).

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

Want too make sure I understand you
If it does not start in morning, remove purple from slave solenoid, do I leave purple on other end at coil , . then add new wire from D terminal too positive terminal?

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

If it don't start in the morning, remove the old purple/yellow wire. Put it in your pocket. It may be bad.

Put a new wire with new terminal ends of the correct size, from the D terminal on the starter to the + terminal on the coil and see if it will start.

Then you will know if it was a loose connection, or a faulty wire causing the problem.

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

Follow up
Had same starting issues following morning
As I stated earlier once it finally started would start first turn of key.
Took your advice Don and used terminal D off starter solenoid, disconnected purple from slave solenoid and coil leaving low resistance which is purplish in color , still would not start.
I think I may have found the issue , put my thinking cap on, trying too trace wiring and thinking what does what I took key switch out
Switch is new.
remember I have had on and off electrical issues quite some time. Marine guy I use felt my issues stem from key switch. He did not have extra switch, he said go too Napa , pick up a 3 prong marine switch which I did. He said save some money , do it yourself, I did and worked fine for quite some time,But there must be a loose wire behind circuit board cause out of the blue it acts up .

This is what I discovered. with test light had continuious power on red, power on yellow/ red when cranking ,
jumped yellow/ red & low voltage wire had key on position and engine started right up. Once running put test light on,
red, lit
low voltage lit, but same lite power as red, did not seem like it was a dimmer light ( is it supposed too be dimmer or test light is low voltage and does not effect ?)
yellow not lit
so some were in key switch or general area something is not right ? but think I narrowed it down.
will let you know what i find

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

When the engine is cranking over, the yellow red wire does nothing but crank the starter.
The power to the coil comes for the purple yellow wire from the starter or slave solenoid (where every you have it hooked)
Power to the coil does not come from the resistor wire (While the engine is cranking)
The only time the resistor wire would lower the voltage to the coil is AFTER the engine is running.

Here is the wiring diagram with the helm brought down to basic ignition and starting. Slave solenoid may look different from the one you have, but it works internally the same.

Don S said:

Re: starting electrical issue on 1984 mercruiser 488 , 4 cylinder ?

When the engine is cranking over, the yellow red wire does nothing but crank the starter.
The power to the coil comes for the purple yellow wire from the starter or slave solenoid (where every you have it hooked)
Power to the coil does not come from the resistor wire (While the engine is cranking)
The only time the resistor wire would lower the voltage to the coil is AFTER the engine is running.

Here is the wiring diagram with the helm brought down to basic ignition and starting. Slave solenoid may look different from the one you have, but it works internally the same.

Click to expand...

hate to restart thread but this is way to misleading if he is having issues figuring out what wire does what. while your wirring diagram will run engine to wire it like this would be way away from original wirring. unless someone is going about compleatly rewiring out the whole wirring harness do not presume this wiring diagram is of use.


and for his issue test volts at + on coil with ignition on but not running. should be 5-10 volts. if not resistance wire or conection bad. then test voltage on + coil while starting voltage should be 10-13 if not solenoid or wiring from solenoid to coil bad. if both are withen these specs, i would replace the coil!