1990 Johnson 150 won't start but will when plug is out

[Odawg753]

Hey guys trying to start the boat for the season and it won't start. I just replaced all 6 coil packs just because they looked completely shot. So it wasn't starting and then I pulled plug out to test for spark and it started right up with the plug out. Put it back in and it won't start. What could this be?

 

[racerone]

Take the starter motor apart for an inspection.

 

[Odawg753]

Take the starter motor apart for an inspection.

It still cranks either way just won't fire up with all plugs in

 

[racerone]

I forgot to add that you could load test the battery and inspect battery cables.

 

[oldboat1]

Been working on my old inboard -- ordered an onboard charger, and noticed there are load testers available for $20 or so.

Removing a plug reduces compression -- sounds like it's just enough to get it spinning fast enough. Battery fully charged?

 

[Odawg753]

Been working on my old inboard -- ordered an onboard charger, and noticed there are load testers available for $20 or so.

Removing a plug reduces compression -- sounds like it's just enough to get it spinning fast enough. Battery fully charged?

The motor cranks great, that's not the issue. It just doesn't start. I'm thinking maybe a power pack issue?

 

[Odawg753]

Guys the motor cranks perfectly fine. Actually have 2 new batteries. The problem is that it won't start with plug in.

 

[racerone]

I do not believe your motor is cranking " just fine "----Take starter apart for inspection and cleaning.-----That would cost you nothing.

 

[sutor623]

The motor cranks great, that's not the issue. It just doesn't start. I'm thinking maybe a power pack issue?

No, this doesn't point to a powerpack issue. You say that you are reaching cranking speed (250rpms) with starter motor, but removing that one plug gives is that little budge just enough to get the motor to turn over. Starter motor spins faster with each plug removed, that's why we pull all plugs when doing a compression test.

Just curious, do you have spark on all 6?

These guys have been working on engines a long time.

 

[Odawg753]

No, this doesn't point to a powerpack issue. You say that you are reaching cranking speed (250rpms) with starter motor, but removing that one plug gives is that little budge just enough to get the motor to turn over. Starter motor spins faster with each plug removed, that's why we pull all plugs when doing a compression test.

Just curious, do you have spark on all 6?

These guys have been working on engines a long time.

There spark on all but only starts when either cylinder 4 and 5 are out. I will crank it today and see how fast it's cranking.

 

[emdsapmgr]

You may have an ignition problem, such as a weak stator. It may make enough juice to fire the plugs when out, but not when cranking under compression with all 6 plugs in the powerhead.

 

[Odawg753]

Alright guys, I took your input. I took apart starter cleaned it all out. Tried again and still same thing. Then I connected 200 amp jump and got some coughs out of it which is a great sign. I'm stumped though the old batteries were a 500mca and 625mca. Now I put brand new ones in yesterday both 825mca. Where are common grounds that get corroded. The battery terminals are clean. Thanks again guys for any more help.

 

[sutor623]

Go to the link in my sig, CDI Troubleshooting. Start checking components as EMD has suggested. If you dont have a DVA meter, buy one.

 

[emdsapmgr]

You could have some current loss on some wiring when cranking. For instance the short red wire from the solenoid to the starter. After cranking, feel that wire and see if it is hot. Same with other wiring. Hot wires indicate they are not transferring current properly. That can include internal wiring damage, poor connections at the wire end connector, or frayed wires.

 

[w2much]

As emdsapmgr says. Also you might jumper cable your starter to the batteries. Be care with your + and - . I had a bad battery cable give me a bad day or two . Checked fine on resistance but would not carry full current, salt had worked its way up beyond where I could see the damage.

 

[ondarvr]

Are the two plug wires switched, what happens if you leave the plugs in and just pull the plug wires off?

 

[sutor623]

Are the two plug wires switched, what happens if you leave the plugs in and just pull the plug wires off?

I have heard of people mixing up the power pack wires on this engine also.

 

[Odawg753]

Are the two plug wires switched, what happens if you leave the plugs in and just pull the plug wires off?

Na they haven't been changed. On separate sides of motor in seperate looms anyway

 

[ondarvr]

But what happens when you just pull the plug wires off?