New Here

[SMajor]

I'm hoping I can get some help here. I've already downloaded some manuals from this site which have been very useful.  I don't mind paying $12 for a year. It would be well worth it to me to get some help. 

Hope I'm in the right place to post this. 

A neighbor of mine moved away recently and left his 1983 Yamaha XVZ12 with me. Hasn't been started in several years. When I turn the key on the fuel pump works for just a split second. The red light on the dash is always flashing. I'm assuming that shows a problem with something the main computer controls. I have ordered several relays from Ebay and replaced some that I know were bad. I have 3 of the fuel pump control units and according to the test procedure in one of the manuals they all test bad. When I leave it out none of the relays work but with it in one relay comes on and stays on but the fuel pump relay just comes on for a split second. I know the fuel pump works well because when I remove it and hook it up to 12 volts it pumps very well. I know at some point as much as I hate it I'm going to have to pull the carburetors and clean them. I'll have to ask for help on that too later. I've already replaced the fuel pressure sensor it was bad. Any advice would be very helpful. 

Thanks. 

[Marcarl]

So your specific question is on the relays right now?

[saddlebum]

On 10/27/2024 at 9:02 AM, SMajor said:

I'm hoping I can get some help here. I've already downloaded some manuals from this site which have been very useful.  I don't mind paying $12 for a year. It would be well worth it to me to get some help. 

Hope I'm in the right place to post this. 

A neighbor of mine moved away recently and left his 1983 Yamaha XVZ12 with me. Hasn't been started in several years. When I turn the key on the fuel pump works for just a split second. The red light on the dash is always flashing. I'm assuming that shows a problem with something the main computer controls. I have ordered several relays from Ebay and replaced some that I know were bad. I have 3 of the fuel pump control units and according to the test procedure in one of the manuals they all test bad. When I leave it out none of the relays work but with it in one relay comes on and stays on but the fuel pump relay just comes on for a split second. I know the fuel pump works well because when I remove it and hook it up to 12 volts it pumps very well. I know at some point as much as I hate it I'm going to have to pull the carburetors and clean them. I'll have to ask for help on that too later. I've already replaced the fuel pressure sensor it was bad. Any advice would be very helpful. 

Thanks. 

1st of all the fuel pump runs on both a timer and a line pressure sensor so it is quite normal to turn the key on and off for several cycles to get fuel to the carbs if they are empty. When the carbs are full the pump will barely run but a click or two.

2nd  Check your screen to see what is displayed when the red light is on or flashing it could simply mean your getting low on fuel or your side stand is down while in gear. In the case of fuel level the light will flash when getting low. slow at 1st than faster as it gets lower and finally solid when your very low.

[SMajor]

Thanks. 1st I've been trying the fuel pump with both fuel lines disconnected and it only runs for a split second. I had to replace the fuel pressure sensor it was bad. I had found out on this site how to check it. 

2nd Thanks for the advice on the screen. I drained all of the stale gas out and have a 1/2 tank of good fuel. I'll check tomorrow to see what is showing on the screen. 

[SMajor]

I downloaded the manuals from this website and can't find the Fuel Pump Control Unit on the electrical schematic. The wires going to my unit are Black, Red with White, Blue with White and Brown or gray can't really tell. there is nothing on the schematic with these wires going to it. I have bought 3 of these on Ebay and none of them test out like it shows in the manual.