Fuel issue

[goneriding]

Hey guys I need some direction, I have a 1988 Vmax that I am working on for my friend, he asked me to help get it running and what I found was a tank with a lot of water in it, a fuel filter that was clogged a fuel pump that didn't work and ungodly dirty carbs. So long story short I have cleaning the tank, replaced the filter and pump and cleaned the carbs (along with a lot of replacement parts in the carbs) but here is the problem, the bike will now start but will only run for a minute or so (it seems to run out of fuel). When I turn on the key I hear the clicking of the pump and it will restart again but then die. Is there something that may be keeping the fuel pump from filling the carbs as needed?

Thanks in advance!

 

[Redbone]

Have you checked the "reserve" switch on the handlebar, throttle side? Try moving the switch to the reserve position to see if it stays running.

 

[goneriding]

Have you checked the "reserve" switch on the handlebar, throttle side? Try moving the switch to the reserve position to see if it stays running.

Yes sir, I tried that same problem in either postiion (tank is full also).

 

[AMechEng]

Issues with the fuel pump are common. Especially old original pumps. I would replace it.
https://www.ebay.com/itm/NEW-Fuel-Pump-For-1985-2007-Yamaha-V-MAX-VMAX-V-MAX-1200-VMX12-VMX1200/262898406702?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

Edit: I see you already replaced the pump. I would disconnect the fuel line from the carbs and put into a bucket and make sure there is good flow and no obstruction. My goal would be to determine if it is a control issue, fuel supply issue, or carb issue.

 

[D-Max2012]

Hook a hose up to the breather line on the top of the tank and see if you can blow air into it.. If it is blocked from gunk, it will cause vacuum tank pressure which will cause the carbs to starve for fuel.. You can also test this by simply taking off the gas cap, start the bike, then see if it shuts down at the same interval.

 

[dannymax]

Floats & needles working as they should? Did you wet level check the float settings?

 

[goneriding]

First of all thanks for all of the responses so far, so here is the status update, I finally got a chance to put my hands on the bike again & I hooked up a separate gravity feed gas tank and disconnected the fuel pump. It seems to run fine like that, this is not a solution but helps eliminate some things like a carb or engine issue (I think). It seems to be down to a fuel delivery issue, correct? If that is the case, I did check the tank vent tube and it was open, the fuel pump does click on and pump fuel when I turn the key on (but not every time I turn on the key). Is there something that controls the fuel pump (tells it when to pump or not to pump?) Feel free to chime in, please!

 

[D-Max2012]

Since you hooked up an external gravity feed, and its working, you might want to examine that pump. If the little black diaphragms have shifted or are damaged inside the pump, you will have little or no fuel pressure. The pump's solenoid seems to be working (that's the click you hear).

 

[goneriding]

D-Max2012, I have taken the hose off and turned on the key with the pump connected and it shot fuel out at a pretty good rate but I am not sure if it is doing it consistently. thx

 

[D-Max2012]

D-Max2012, I have taken the hose off and turned on the key with the pump connected and it shot fuel out at a pretty good rate but I am not sure if it is doing it consistently. thx

I thought the same thing when I initially tested my pump.
I used some clear hose as a feed / return line, being fed from a glass pickle jar.
I wanted to see the flow when I connected 12v to the pump.
What I didn't know was, it can act very differently under pressure.

Out of curiosity, I opened up the pump, I found one of my diaphragms was shifted out of place.

When I put it all back together and ran the test again, the flow was twice as strong (shooting gas up and out of the jar..) Thank goodness I tested this outside and there were no sparks.. :eusa_dance: This was 5 years ago, and its been solid ever since.

 

[goneriding]

Good news, it is fixed, it seems the fuel pump I first purchased was the problem (it was an aftermarket new off brand), when I hooked up an oem used unit it worked fine. Thanks for the input, the bike is rolling again and out of my garage!

 

[MaxMidnight]

Would it be possible to check the supply voltage at the pump when the motor is running and see if it is interrupted and then the motor stalls?

If so it could indicate an issue with the fuel pump relay/ electrical supply.

And yes, I appreciate that with the switch on reserve it should bypass the cut out but as they say 'any port in a storm'.

 

[goneriding]

Success finally, I have failed to mention that the new fuel pump I bought was as aftermarket off brand (it was only about 10% of the cost of a new OEM pump), it seemed to pump strong when I straight wired it but would not work right on the bike. When I tossed that in favor of a used OEM pump everything worked perfectly. Should have known, if it looks too good to be true, it probably is. Thanks for everyone's help, I now know more than I intened about a Vmax fuel system.

 

[rdvmax]

Double check the vent for the gas tank.