1993 OMC 5.0L HO (Ford) will not start!

[Jono69]

Good afternoon everyone. After a nice long afternoon on the river, I got her back to the dock no problem. Went to start it to pull it around to the trailer and she would not start. Ran awesome all day, no issues at all. Now she just turns and turns, every once in a while it will start to fire up but as soon as I let the key go it is gone. Once again I am working with a 1993 OMC Cobra 5.0L HO Ford motor and Cobra outdrive. I got her home and have been tearing into it and still can't find my issue. Tried adjusting idle mixture, poured some gas into the carb, a little shot of starting fluid, double checked all connections at the battery and behind the key switch and kill switch, nothing is working. Anyone have any ideas? As always your input is greatly appreciated.
Thanks,
Jon

 

[Don S]

Re: 1993 OMC 5.0L HO (Ford) will not start!

Do you have spark?

 

[Jono69]

Re: 1993 OMC 5.0L HO (Ford) will not start!

Yes sir, I pulled the #1 spark plug and tested it against the exhaust manifold and spark was present.

 

[Jono69]

Re: 1993 OMC 5.0L HO (Ford) will not start!

Also, this is the carbureted engine.

 

[Don S]

Re: 1993 OMC 5.0L HO (Ford) will not start!

Pull the coil wire out of the distributor cap. Hold it about 1/2" away from a good clean ground (No paint) and see if you have a snapping blue spark, or a yellow spark. Makes a big difference under compression.

Also pull all the spark plugs and look for any signs of water. Rust, drops of water etc. What do the plugs look like?

 

[Jono69]

Re: 1993 OMC 5.0L HO (Ford) will not start!

I've pulled a couple plugs now. All spark against a ground. All are a little damp with fuel but otherwise are real clean. I will try the coil wire once my helper gets over here. Looking a little deeper at everything, I noticed my gauges are not coming alive when I click the key to the "on" position. But begin to show readings during cranking, which is odd. Wondering if that has something to do with it somehow. Going to throw the Fluke on there and see what happens. Results forthcoming in a few minutes.

 

[Jono69]

Re: 1993 OMC 5.0L HO (Ford) will not start!

Pull the coil wire out of the distributor cap. Hold it about 1/2" away from a good clean ground (No paint) and see if you have a snapping blue spark, or a yellow spark. Makes a big difference under compression.

Also pull all the spark plugs and look for any signs of water. Rust, drops of water etc. What do the plugs look like?

Don, yellow spark from the coil wire to ground.

 

[Don S]

Re: 1993 OMC 5.0L HO (Ford) will not start!

Wimpy spark, you aren't going to start an engine with that. Try this, use one of the other short plug wires as a coil wire and see if you get the same yellow spark.
What is the battery voltage (check on the battery posts with a volt meter, not the gauge at the helm)
What's the voltage going to the + terminal of the coil?

I assume you have the Prestolite BID distributor installed ?

 

[Jono69]

Re: 1993 OMC 5.0L HO (Ford) will not start!

Wimpy spark, you aren't going to start an engine with that. Try this, use one of the other short plug wires as a coil wire and see if you get the same yellow spark.
What is the battery voltage (check on the battery posts with a volt meter, not the gauge at the helm)
What's the voltage going to the + terminal of the coil?

I assume you have the Prestolite BID distributor installed ?

Battery Voltage at the terminals is at 12.45V
Testing from the + terminal of the coil to a clean ground: 9.2V
Testing from the + terminal to the negative terminal on the coil: 4.0V
Ohm reading between those two terminals 1.9ohms
Spark plug wire between the coil and a ground still showed a consistent yellow spark.
Once again, thank you for the assistance. I am still new to this motor.

 

[Jono69]

Re: 1993 OMC 5.0L HO (Ford) will not start!

And sorry, yes I have the Prestolite distributor.

 

[Jono69]

Re: 1993 OMC 5.0L HO (Ford) will not start!

Some more findings...
If I run a test light from the pos+ side of the coil to the neg- side of the coil, No light when the key is "ON", flashing light while cranking.
If I run a test light from the pos+ side of the coil to a engine ground, No light when the key is "ON", Solid light while cranking.
I am beginning to think there is something going on between my key switch-kill switch-up to the coil. Although different manufacturers, this is reminding me of when my key switch went bad in my old Mercury Sportjet 120. I created all kinds of havok on the motor's systems. I am going to start cheap with parts and go pick up a new ignition switch and kill switch tomorrow.
Please if you have any thoughts, I am all ears!

 

[Reinell-BRXL-191]

Re: 1993 OMC 5.0L HO (Ford) will not start!

mine did this exact same thing last week... ended up replacing the coil, and it fired right up... my coil seemed like it was working, but really wasn't... 15 dollars from autozone for a new 302 coil... ( I bought the 40 dollar MSD)

 

[Don S]

Re: 1993 OMC 5.0L HO (Ford) will not start!

If I run a test light from the pos+ side of the coil to the neg- side of the coil, No light when the key is "ON", flashing light while cranking.

That's because you bypassed the coil. Don't do that.

Unplug the ESA module (5 wire plug) and see if you get good spark.

If not, leave it disconnected and put a jumper wire from the positive terminal of the battery to the + (positive) terminal on the coil. This completely bypasses the boats ignition system.

 

[Jono69]

Re: 1993 OMC 5.0L HO (Ford) will not start!

That's because you bypassed the coil. Don't do that.

Unplug the ESA module (5 wire plug) and see if you get good spark.

If not, leave it disconnected and put a jumper wire from the positive terminal of the battery to the + (positive) terminal on the coil. This completely bypasses the boats ignition system.

Where is the ESA module located? I don't see any 5 wire plugs.
Also, regarding the second part, once I run the jumper wire, do I try to start it?

 

[Jono69]

Re: 1993 OMC 5.0L HO (Ford) will not start!

Also, I replaced the ignition switch today because it was faulty. Also threw in a new kill switch because I was already in there. Replaced the coil as well. Still nothing. And now my new switch appears to not be working already as the gauges do not come alive when the key is switched on. It worked for a while. Great.

 

[Don S]

Re: 1993 OMC 5.0L HO (Ford) will not start!

I have no idea where it's at or even if you have a 93. Could you post the full model number of your engine?
Here is a parts breakdown for a 93, and there is 7 different models and I just picked one. It may not even be what you have.
Item 40 in this diagram is the ESA module.



You really need to stop throwing parts at it until you find out where the problem is.

 

[Jono69]

Re: 1993 OMC 5.0L HO (Ford) will not start!

1993 OMC Cobra 5.0L HO Carburated
Model# 502APRJVB
Serial# T01251205

Unplugged the ESA module, still looked to me like a weak spark, and was yellow in color. Ran the jumper between the coil+ and the bat+, spark looked about the same, maybe a little stronger.
And I know I jumped the gun a little bit with the parts, but I thought I had it pinned down, clearly I was wrong. Live and learn.

 

[Don S]

Re: 1993 OMC 5.0L HO (Ford) will not start!

You should have 2 purple wires on the + terminal of the coil. Remove the one from the ignition switch. Leave the one on the coil that goes to the distributor. Now with your jumper wire from the battery to the + terminal of the coil hooked up, check for spark again. What color.

If still yellow, hook the purple wire back up and do the following tests using a volt meter. Actually, an analog volt meter works better for these tests if you have one.

With the Key in the run position, engine not running (obviously). Leave the ESA module disconnected.

1. Voltage between + and - battery terminals, not touching the cables, the battery terminals only.

2. On the engine, between + terminal of the coil and a good clean engine ground (Not the battery or battery cable)

3. Same test as #2 above, only this time with the engine cranking over for a few seconds.

4. Same as test 3 above, only this time put the black test lead of your volt meter on the negative terminal of the battery. Not the cable, the battery terminal itself.

 

[Jono69]

Re: 1993 OMC 5.0L HO (Ford) will not start!

Ok Don. Finally back at it after a long Mother's Day weekend with family. Wanted to post earlier but internet at home is not cooperating today.
I did the first test on post exactly as written. Pulled the #1 plug out to check the spark. To my surprise, she fired up instantaneously. Boy did that catch me off guard! Loud without that plug in! Shut her down right away. Replaced the plug. Cranked her again and started up. Running like a dream. Hmmm. Waited for a bit tried again, same result. Started right up. Pulled the coil to dist. wire and the spark looked nice and strong. Bitter-sweet moment. I would love to get her out on the water ASAP (couldn't be any nicer today through the next 10 days, sunny, 80s), but I really Need to know what the deal was before I trust her to the seas again. I have a feeling it will creep up again mid-Mississippi River at dusk during my trip in a couple weeks.
I ended up running the tests at the bottom of your post anyway for good measure. Results:
Test #1 12.55v
Test #2 10.45v
Test #3 9.5v
Test #4 9.7v
Same results with the ESA unplugged and connected.
Any wisdom for me here guys?!

 

[Don S]

Re: 1993 OMC 5.0L HO (Ford) will not start!

Ok, you need to find those 2 lost volts between test 1 and 2. They should be almost identical.

I would start by cleaning and tightening all battery cables and making sure the crimped cable ends on the cables are good and there are no holes in the cable and swelled areas. Then tighten them with real nuts and a wrench (No Wingnuts).
Check your main harness connectors. Check for loose wires at the ignition switch.

You aren't going to get good spark with only 9.5 volts.

Since it starts with the jumper wire, you know it's just a voltage issue.