85 fuel pump issues

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heintz54449

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hello all,
first time posting here, iv had my 89 for 20 years now, bought with 4 miles on it. the reason i am writing is for a friend. he has a 85 that has some issues. from what i understand the fuel pump is thinking the system is pressurized all the time, thus never running except when the key is turned on and it does its original prime pump.:ummm: the only way he can run it down the road is turn the kill switch or key off and on every quarter mile. makes for not fun riding. any way if some one could get me pointed in the right direction i would greatly appreciate it. thanks for any info!

dean
 
Welcome, Dean. I'm surprised nobody has jumped in on this one yet. I don't have many ideas for you, other than 1) verifying power to the pump while the bike is running (wire a test light across the pump terminals to see if power goes off after the bike is started), or 2) pull the pump apart to check the diaphragms (usually this results in constant clicking, not lack of fuel, but it's something to look at).

Link to the pump diaphragm check:
http://vmaxforum.net/showthread.php?t=8775&highlight=fuel+pump+diaphragm
 
Sounds like a problem in your fuel sensor/relay circut. The fuel pump circuit consists of the fuel pump relay, fuel pump, and fuel reserve switch

The pump will try run for about 5 seconds when the main engine stop switch is turned to ON or when you switch the reserve switch to RES
When the engine is running the fuel pump will keep pumping fuel to the carbs as they need it - unless you're low on fuel then the pump will stop until you switch the reserve switch to RES

Ask your friend to try switching to Reserve instead of using the kill switch to see if the fuel pump will kick back in - if it runs continuously in that position then the problem is in the fuel sender circuit, if it only fills the carbs for 5 seconds then the problem is between the CDI and fuel pump relay (this is where I think the problem is)

The fuel pump relay is behind the left side cover - it is the box towards the front of the bike

PS: The fuel pump relay uses the pulse signal from the coils on cylinder #1 to tell if the engine is running (grey wire)
 
thanks all who responded. so if he had changed from the stock coils to 4 individual coils on top of the plugs would this may may have messed with the system? tanks again for your responses and knowledge.
 
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