Fuel Pump Trouble

Guys,

I had a problem with my Vmax (1990) and my mechanic said it could be the Fuel Pump and Fuel Pump Relay. And so we did order the parts abroad by giving the Year Model, Engine, and Chassis number of the bike. But when the parts came to my doorstep, the Fuel Pump Relay sent was different. The one from my bike has six (6) pins, yet the one sent to me has four (4).



I asked the vendor and showed them the same picture, and they said that the part from my bike is not a Fuel Pump Relay but a Control Unit Assy of 1997 model.

And so i thought yeah all right that's another problem. I am really confused. Please refer to pictures below and please please please help me!

Pic 1 and 2 shows what we think is the Fuel Pump Relay, with 6 pins




Pic 3 shows the wirings connected to it


th_help:

What problem were you having?

Vmax has a 6-pin fuel pump relay, the 4-pin relay is the sidestand/starting circuit cut-off relay

http://www.morleysmuscle.com/wp-content/uploads/2009/12/Vmax-Wiring_Diagrams1.pdf

^^ thanks very much! This solves it (i think). I will send the diagram to the vendor and have them review it. I might need your assistance again and for now, cheers!

davesax36 said:

What problem were you having?

Click to expand...

+1............

If your mechanic is guessing....instead of knowing.....You might not need either part (relay or pump)......what are the symptoms of what's wrong??

Now the vendor has sent me a picture of the what is think is the Fuel Pump Relay, but saying this is from the 1997 model. See pictures below.





I am also attaching here the picture of my own piece, the one that is not working on my bike. See below.



I know they pretty much look the same. But would this new piece from the vendor (1997) work on my bike (1990)?

Im confused.

:bang head:

We still don't know the symptoms your bike is experiencing. Search around on here and you'll find that a fuel pump relay is not too often the issue.

Describe what was happening that kept it from starting and the brain trust here will go to work helping you help yourself. For whatever reason, there just aren't that many mechanics that seem to be able to accurately diagnose Vmax issues.

Sent from my SM-N900V using Tapatalk

Thanks for the help! Here is the full story:

My VMax would start no issue and while in neutral would rev to max rpm without any issues. However, when there is any load i.e. 2nd gear and above 5,000rpm, then the bike does not perform. I bought it used and the tank was filthy/rusty, which I cleaned and zinc coated inside, cleaned the cooling system which was also a mess and checked the electrics/ignition system which seems to be fine, as is the compression and spark. However, when checking the fuel pump it would not spit out much fuel into the carbs (these have also been dismantled and cleaned too btw).

To check if it was the fuel pump I got a cheap (very) fuel pump that would fit and hooked it up and tested. The bike seemed to work fine and no issue with the 'non performance under load. However, the cheap fuel pump lasted about 2 hours and then died. This made me think it might have something to do with the relay.

I then ordered both these OEM parts - pump and relay. I now have the OEM fuel pump (1990) which is correct, but Yamaha only has the 1997 fuel pump relay - can anyone confirm that this will still work on the 1990 model? I have not tired the new fuel pump on the bike as yet for fear that I might damage it due to the relay being the root cause of the issue.

I have to add...I may be completely wrong in my diagnosis and would consider myself a mediocre mechanic.

I hope the above makes sense and I really appreciate any and all feedback!

Thanks in advance,

If you didn't tear down the carbs all way to the jet blocks and clean the pilot jets you're gonna have problems again fast. Lean and out of sync carbs can do crazy things like rev up to the sky and freak you out. I'd go on ronayers.com and check the part numbers, but I think the fuel pump relay has been the same at least since the wiring harness changed in 1990. You might check to see what voltage you're actually getting at the fuel pump if it killed another pump. We only need to make 3psi for our fuel system to work.

Did the cheap fuel pump just quit pumping fuel or just died and you don't hear no pumping action?
Are you able to blow air thru vent port and also fuel outlet port on the tank?
Did you check the tip over valve that's on the plastic line coming off the vent port of the tank? The tip over valve is on the vent line leading down to the bottom of the bike. You should be able to suck air from the top where it connects to the fuel tank.

Folks,

Thanks so much for the responses.

Davesax36, all the points that you mentioned have been done. Tearing down the carbs, resyncing them, which is not an easy job as it self but done thank you. You said you think the 1997 relay should work on the 1990 model...i have checked ronayers.com but dont seem to be able to get this question confirmed. Is there anybody else that could maybe help?

Alorio1, all the points you mentioned we also have previously done and double checked. In answer to the question regarding to the fuel pump functioning... it stopped working completely and no pumping noise could be heard. It was a very very cheap china fuel pump made no doubt for a local scooter. In my suspicion is that it is not a sound mechanical device in the first place.

Thanks again for your responses. And if anybody could ask around questions applicable to the 1990 model relay I would be grateful!

Hi guys,

Thanks very much for the help. I have replaced the fuel pump with a new one (took awhile because I had to order the part from another country) and I am now seeing white smoke coming out. Is this normal? What could be the problem now? [headscratch]

Can be remnants of water condensation on cans. Let it run for a while till it warms up and check again.

Just my 2 cents but through this thread I Haven't seen the words Fuel Filter??:ummm:

If you have a lot of fuel additives dumped into your fuel tank, it can cause smoke also.......

Water vapor is more clear than white. Antifreeze burns white...