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Jared k

1987 Honda 350d spark-no spark

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Hello I’m praying someone out there can help as I’m at my wits end. I recently bought a 1987 Honda 350d 4x4  and got blindsided. Ran for about 10 minutes then died. After series of trials come to find that it will start and run great until it gets warm and then dies with zero spark. I have found someone hot wired if you will a constant power wire to fan so it ran constantly. That led me to fan control unit, oil temp sensor, ignition coil, cdi box and fuel cut relay. I used manual and tested all the above and replaced each one out of desperation. No matter what I do- it will cold start beautifully and run for about 10 minutes then dies and zero spark situation. After about 20 mins it starts right back up with perfect spark. I have also “undone” the constant power to fan and even went as far as doing a ground out test to blue wire at oil temp sensor - the light for oil comes on and fan comes on in doing so. Still- no change and I’m frustrated. Please help!!!!

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You replaced the FCU, CDI too? Where did you get these components? Are the OEM used or new? 

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Yes sir, fcu is oem used from dealer with warranty- obviously because from what I’ve learned - not available new after market. Cdi I had went through the manuals test and it passed but I replaced anyway- it was an eBay job

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I can have it down to a science- starts cold and runs great- then after about 10-15 mins it shuts down- pull plug and no spark, wait 20 mins- perfect spark- like clock work and very consistent in that. 

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I appreciate it, why would the cdi allow perfect start and run then shut down and restart consistently? My thought if it was faulty is it would be inconsistent happenings, not so constant pattern but I don’t know 

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2 hours ago, Jared k said:

I appreciate it, why would the cdi allow perfect start and run then shut down and restart consistently? My thought if it was faulty is it would be inconsistent happenings, not so constant pattern but I don’t know 

 

That I can't say.  @retro @AKATV and @Melatv are the resident electrical gurus.

 

I've just seen examples over the years of people having similar problems that were resolved with a new CDI.  That said, I'd try to eliminate other possibilities first as I don't think there is a way to test the CDI's.

 

Have you measured voltage on your battery with the machine running?  The voltage regulators can go bad as well, and will kill spark sometimes.

 

And while we're discussing the CDI, you did make sure it was the right part, right?  There is the 86-87 TRX350A Fourtrax, which uses one CDI, the 87 350D Foreman, which is a one-year only oddball CDI, and then the 88-89 350D Foreman which uses a 3rd distinct CDI.

 

Three different CDI's on what more or less boils down to the same machine, and the CDI's are not interchangeable.  For yours you must have the 87 350D CDI. 

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I have not measured voltage while running- no, I will try that... and as far as the cdi- yes or at least I ordered it for the correct model and it stated it was for correct model, not to say they didn’t goof though. Would there be any other symptoms that might help me know wether or not I can rule it out?

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There are a few other things you can check, like the fuel relay. pulse generator. These are both lectronic modules 


 

How’s your fuel pump sound?

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I have checked and replaced the fuel “ cut” relay ( if that’s the same item?) and replaced that with an oem used warranties part. The fuel pump while running clicks periodically as I believe it’s supposed to and occasionally when I turn the key and try to start it does a series of clicks- assuming after pressure build up has depleted. Pulse generator test shows about 330 olms

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And now after installing new fan control unit - several go around later... when I turn the key on oil light doesn’t come on and fan is on whole time. If I lightly bang the fcu on tire the fan kicks back off- something is definitely strange. It just seems wierd that I’m having same issue with a different fcu

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Good job. How does your oil temp sensor check out?

 

it sounds like a bad fan control unit except —your other does the same thing, right? Can you tap on it and get the same response?

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@Goober can you bake these FCU's like you can the 400/450 Foremans?

 

I just had a dead 450 Foreman FCU that Fishfiles sent me and the "bake at 450 degrees for 8 mins" fixed it. 

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What’s the best way to check that sensor without having to submerge it in heated oil? And now I’m about 3 starts and stops into playing with it and was doing the battery charge voltage test( showed great) and now it is back to normal- turn key- oil light comes on - no fan on, starts up...

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Posted (edited)

I would try baking one of the FCU in an oven to see if you can revive it. 
i would try 200F for at least 3 hours. Let cool completely before you reinstall. See if that improves.

as last resort, bake in 450F oven for 5 minutes. This may cause smoking or burning electrical smell 

Edited by Goober

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Yes tapping either one on tire decently causes oil light flicks, fan on and off- back and forth... so this concluded two faulty fcus?

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I’ll try baking my old one as the other one was 127 bucks and they accept returns- if I melt something I may have a problem returning LOL 

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Posted (edited)

Test the oil sensor with ohmmeter —at 77F you should get between 9.5-10.5 KOhm

 

you can also poke an instant read thermometer into your dipstick hole to read oil temp. Not when running!
 

you fan should come on at 0.95 to 1.05 KOhm

Edited by Goober

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That was one thing I forgot to mention in my original post… I had suspected the oil temp sensor earlier so I ordered a aftermarket one and the only ones I could find came with one wire plug and my model requires two… I could not for the life of me find a replacement for it that matches up with the two plugs…

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So my oil is at almost exactly 100degrees and it reads5.49 olms I’ll wait until it cools to 77 and try again 

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Ok so was able to come across one oem used one on eBay and it’s 86 bucks!! However if I don’t need and can return this $127fcu, I’d feel better about that LOL. This thing has been just eating parts!!

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5.8

23 minutes ago, Jared k said:

So my oil is at almost exactly 100degrees and it reads5.49 olms I’ll wait until it cools to 77 and try again 

that sounds pretty good to me sofar.

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