Testing GL1500 Spark Plug Wires


Information and questions on GL1500 Goldwings (1988-2000)
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SchueGeorge59
Posts: 9
Joined: Sun Apr 14, 2013 5:59 pm
Location: Stevensville, Michigan
Motorcycle: 1990 GL1500 Goldwing

Testing GL1500 Spark Plug Wires

Postby SchueGeorge59 » Mon Apr 22, 2013 6:42 pm



Hello All,
Brand New to this sight and excited to read the info posted already so bear with me if this is an old topic. I have a 1990 GL1500 that has been acting up since late last summer. Actually since before that but not seriously. Lost fire in two cylinders during a trip. Didn't bother things too bad while cruising down the road but was a real bear to take off loaded with gear and the wife. The problem got real bad one cool, damp morning till things dried out. Got home, tested the coils and had one that tested weaker than the other two so I replaced all three. (What a joy that was to do!) I cleaned the carbs while I had the area opened up. They really weren't bad at all since I had gone through them a couple of years earlier. Put it back together and some things were better but still not firing as needed. Took the plugs out and inspected them. #'s 2,3,4, and 5 were all perfect as far as burning pattern. #1 was not burning as hot but not wet either. #6 looked terrible. This verified readings that I took with an IR gun on the exhaust with both of those cylinders running cooler. What is the proper way to test the plug wires? Every test I have tried I find no difference between wires. Would you replace them anyway?



SchueGeorge59
Posts: 9
Joined: Sun Apr 14, 2013 5:59 pm
Location: Stevensville, Michigan
Motorcycle: 1990 GL1500 Goldwing

Re: Testing GL1500 Spark Plug Wires

Postby SchueGeorge59 » Mon Apr 22, 2013 7:49 pm

Forgot to add that I have also done a compression test and all cylinders were between 182 and 190 psi.

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WingAdmin
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Re: Testing GL1500 Spark Plug Wires

Postby WingAdmin » Mon Apr 22, 2013 9:51 pm

Try removing the wires and swapping them (those that can reach) and see if the problem follows the wire. If so, then you can pretty much guarantee the wire is at fault. If not, you need to look elsewhere.

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ct1500
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Re: Testing GL1500 Spark Plug Wires

Postby ct1500 » Mon Apr 22, 2013 10:49 pm

SchueGeorge59 wrote:Hello All,
Brand New to this sight and excited to read the info posted already so bear with me if this is an old topic. I have a 1990 GL1500 that has been acting up since late last summer. Actually since before that but not seriously. Lost fire in two cylinders during a trip. Didn't bother things too bad while cruising down the road but was a real bear to take off loaded with gear and the wife. The problem got real bad one cool, damp morning till things dried out. Got home, tested the coils and had one that tested weaker than the other two so I replaced all three. (What a joy that was to do!) I cleaned the carbs while I had the area opened up. They really weren't bad at all since I had gone through them a couple of years earlier. Put it back together and some things were better but still not firing as needed. Took the plugs out and inspected them. #'s 2,3,4, and 5 were all perfect as far as burning pattern. #1 was not burning as hot but not wet either. #6 looked terrible. This verified readings that I took with an IR gun on the exhaust with both of those cylinders running cooler. What is the proper way to test the plug wires? Every test I have tried I find no difference between wires. Would you replace them anyway?


You can test resistance of wires and coils easily. Front pair, middle pair and rear pair, one test lead on one side other lead on the other. Post back the results.

What is a terrible looking plug? One carb per side on the 1500 and all things equal plugs should have same characteristics per side. A problem or terrible looking plug would be lean looking from a vacuum leak if anything so long as other two plugs looked good. No way could the one plug look rich if the other two were fine unless there is something going on in the engine or had massive vacuum leaks between carb and the heads which would be in the intake runners for two. Follow along? While idling pinch off the vacuum hoses on the intake runners. Different years had them in different intakes. Note any change in running. What RPM does it idle at and is it smooth. Pictures of the plugs would be good.

Start off with this on the center stand:

The shade tree mechanics way to engine diagnosis:

Will start off on the premise of an otherwise well running and properly maintained engine and has developed a driveability concern. Filters and plugs have been changed at regular intervals. This is a first check of basic systems that anyone can do.

First off is to check the ignition system. With the bike warmed up and idling remove and replace one plug wire at a time from the spark plugs. What we want to observe here is a uniform idle RPM drop when the wire is removed providing no ignition to that cylinder. At this same time we are also testing the plug wires. While slowly removing the wire from plug you will hear a distinct snapping noise of the spark jumping to the plug. It should jump from 1/2-1 inch, this tells us the wires are good with no excess resistance. In rare cases the plug will only fire with the wire partly disconnected adding RPM and is likely due to a fouled plug.

Next up is to remove the spark plugs noting their condition and location within the engine. Note the condition of the plugs below which were taken from my 1500 when acquired with no driveability concerns except a release start type of turning over. Plug gaps were on the wide side. These could have been original twenty two year old plugs as the bike had only thirty thousand on the odometer and I was still going through it with frequent starts and idling. Note the two inner plugs (cyls.3&4) look like they have been running slightly hotter or leaner than the others. This is due in part because inner cylinders on an engine will typically run hotter than the ones on the corners. Note these same cylinders are the ones the vacuum hoses are attached to in the runners which could also contribute to the slight difference. All white or all black plugs on one side usually indicate carburetor problems. If you suspect a bad plug you can swap it with another and repeat to see if the problem follows the plug.

When pulling plug wires and none to little RPM drop we must then find if it is lean, rich or compression related. The second photo is replacement plug condition currently with 22k miles. Perfectly normal.
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SchueGeorge59
Posts: 9
Joined: Sun Apr 14, 2013 5:59 pm
Location: Stevensville, Michigan
Motorcycle: 1990 GL1500 Goldwing

Re: Testing GL1500 Spark Plug Wires

Postby SchueGeorge59 » Tue Apr 23, 2013 12:50 pm

Thanks for the help so far Wing A and ct1500.
ct, I have already done most of what you have posted. All good advice. The bike has been meticulously maintained due to being a motorhead from way back. I checked the resistance with both a hand held electrical meter as well as digging out my old engine analyzer. Both read the same as each other but had a slightly different resistance for coil wire 6 as apposed to CW5. All others pretty well matched. Readings are in the barn and as it's raining like crazy at the moment, that's where they will stay. All vacuum line were also gone over top to bottom last fall and are in good shape. I did take a couple of pictures of the spark plugs last night as well. Unfortunately I had already sprayed the #6 plug with cleaner so most of the hydrocarbon on the insulator was washed off. If I am successful at posting this pic, the only difference that can be seen is the color of the ground bar. Plugs 1 thru 5 have a nice consistent hot burn color whereas plug to #6 was brown.
I did a little phone networking to some riding buddies last night and was able to come up with a couple of plug wires to 'borrow' from a Wing that is in a shop for what he called a long-term repair. I will be picking those up tonight. Luckily the fairing has already been removed. My plan is to replace two of the wires I suspect to be weak and start it up to see if the problem goes away.
1000 miles. One Hot, one Cold
1000 miles. One Hot, one Cold




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