20 amp ign fuse blowing

[borz170]

2007 Larson 180 Sport Volvo Penta 3.0

The 20 amp fuse under the dash that controls the ign switch and everything connected to it is blowing. When the engine cools down to below ~100 degrees, it will start, but will blow the fuse once it heats up to operating temp. If you try to jump the circut---no spark until engine cools.
???

 

[Don S]

Re: 20 amp ign fuse blowing

First thing you need to do is isolate engine compartment from helm.

First, remove the R5 ignition relay from the relay fuse box on the engine. put a jumper wire between the red and purple wires of the relay as shown below. Then disconnect the Purple wire from the Alternator.

Start the engine and see if the fuse blows. If it does, you have a problem in the instrument panel wiring. If it doesn't blow, plug the alternator back in and try it again.
NOTE: to shut off the engine, you will have to remove the jumper wire.

Here is a link to the wiring diagrams for your engine you can download.
http://www.4shared.com/file/169768257/270fa078/7746659_Wiring_Diagrams.html

 

[Alpheus]

Re: 20 amp ign fuse blowing

The 20 amp fuse under the dash that controls the ign switch and everything connected to it

What all do you have connected to it? Did you add any aftermarket equipment to that fuse? (radio,amp,fishfinder,ETC) After you isolate if its under the dash or in the engine compartment, just start pulling one accessory at a time until you find the short...

 

[borz170]

Re: 20 amp ign fuse blowing

Thanks for your help. I know I wrote this question a long time ago, but yesterday was the first chance I was able to work on this. Again, the ign fuse blew when comming off plane after about 20 minutes of running. Could a pinched wire in the tilt/trim throtle switch harness be causing this short? I will perform the test that you recomended ASAP. The only problem is that I will have to be running the boat to see if it dies. Hopefully it does exactly what it has been doing, so I can perform some diagnostics. I hate intermitent electrical issues. Just a thought, could the ign coil be causing this issue?

 

[Don S]

Re: 20 amp ign fuse blowing

Have you done the test I mentioned above?

Could a pinched wire in the tilt/trim throtle switch harness be causing this short?

Nope, it's not connected to the ignition in any way. Did you download the wiring diagram I gave you a link to?

 

[borz170]

Re: 20 amp ign fuse blowing

I have the service manual and have been reading it the past few days. It is a selocs vp manual, but is very informative. I have not been able to perform the tests yet because I have been working in the fire station. I get out at 2 today and plan on working on her tonight. From reading, I think my pronlem rests in the tach terminal inside the ign coil. The tach has been intermittent lately. I will do your tests, then the tests for the ign coil/module. I'll get her!

 

[borz170]

Re: 20 amp ign fuse blowing

Well, I performed the test to isolate the helm, and the fuse was still blowing. It wouldn't even last long enough to start, it would blow within 2 seconds in the on position. I plugged everything back in and started pulling pigtail connectors under the helm in order to locate the short. Nothing was found...it continued to blow fuses. I thought it could be an ign switch because one of the terminals had come slightly loose. The next morning, I replaced the ign switch. Prior to replacement, I checked to see if it was blowing fuses...nothing happened. I replaced the ign switch anyways, and let her run for a few minutes. Meanwhile, I was puzzled beyond belief.

I decided to check some connections on the engine. I pulled the temp alarm sensor and it imediately blew the fuse. I replaced the fuse, plugged it back in and nothing. It worked fine. A friend decided to follow me in his boat so we could sea-trial. Ran fine for about 1/2 hr, where we pulled up to a beach. Shut off boat for about 1/2 hr. Started boat--- blew a fuse after about 30 seconds of running on plane. This time the engine hesitated a bit before quitting. I replaced the fuse,'pulled the temp alarm sensor wire from the sensor and fired her up with no
problem. We ran for another 15 minutes before beaching again for 30 minutes or so. Started her up and ran fine for 10 minutes when I shut her
down again. Stopped for a few hrs, drove the boat for about 45 minutes toward home with no trouble until right before we made it home. Engine started bogging, so I slowed her down to an idle---the engine died but the fuse didn't blow. I attpted to start her and the fuse blew. I replaced the fuse, plugged the temp sensor back in and the boat started right back up. I am so lost and confused. I am losing my mind with this problem. Does anyone have any suggestions? Thanks in advance.

 

[borz170]

Re: 20 amp ign fuse blowing

Today I am going to work on excorcising the demons from my boat. Yesterday, I was able to search through iboats forums regarding ign fuse shorts. Every one I found ended up being a dead short. Most were due to a pinched wire or a corrosion issue. At this point, I have only one decent consistancy---the harness connecting the temp sending unit and the temp alarm. I am going to expose those wires first. Hopefully I will find a broken or exposed wire, concluding my search. If not, I am going to expose all of the wires in the engine compartment in search of a bad wire. This boat is an
'07, but it has already had the engine pulled and replaced twice. I did it the second time. The dealer did it the first time. There is a good possibility that a wire was compromised during the double removal and installation. The problem first started after I reinstalled the engine, so I bet I messed something up. I do have one thing going for me---The engine is a 3.0 and there is enough room to sleep in the engine compartment. I should have no trouble searching all of the wires.

The only other place I disturbed any wires, is inside the gunnel where the shifter mounts. I had to replace the entire shift mechanism twice. Although I don't remember having any wires in my way, all of the wires run through that area. Also, if Don S is correct, the problem doesn't exist in the engine compartment. This is based on the test results that he advised me on.

We will see. Please, if anyone else has any comments or experience, feel free to chime in.

Don S, Thanks for your help!

 

[borz170]

Re: 20 amp ign fuse blowing

Well, I think I finally excorcised the demons from my boat! Yesterday, I searched the harness from the temp sensor back to the plug and guess what I found? A pinched purple wire that was going to the alternator. The wire was bare and a hole was found in the electrical tape in the same spot. It was grounding out on the valve cover! After cutting out the bad section and splicing it back together, I retaped everything and hooked it all back up. We put about 2 hrs on her during a sea trial with 0 issues. I really hope this was the problem. I know it seems obvious, but this was an intermittent problem that became more constant lately. The obvious conclusion is that I have indeed fixed the problem. All of the other wires seemed fine, so I am 90% sure that I found the issue.

Thanks to all who responded to this thread, and more importantly, thanks to those who created threads in the past regarding ign shorts. I must have read through a 1/2 dozen of them and they all seemed to be fixed the same way mine was. Iboats and its members rock!

 

[Bondo]

Re: 20 amp ign fuse blowing

Ayuh,... Considering the Purple wires are the Igntion circuit,...
I'd say you've probably found your Gremlin...