Some fuel pump pictures for reference

[dingy]

Here is a bunch of pictures I took of a 1st gen Venture fuel pump a week ago just for S&G's. The VMax is very similar, but I don't know for sure. Just offering this as maybe some help in understanding the mysterious fuel pump. It is not a really technical description below, but the basic operation.

In a nutshell, the pump operates by energizing a coil and pulling the plunger towards the contact end. This pushes in the contact assembly on the other end, breaking the current path to the coil. The plunger returns to rest position, contact closes & cycle repeats.

When the plunger pulls towards the contact, it pulls gas in from the tank into the pump cavity via a one way valve. On the Return stroke the fuel is pushed out another valve towards the carbs.

This happens until 1 of 2 things occur, first is pump builds up pressure in line and and the plunger does not return forward to complete pump stroke. 2nd is the fuel pump circuit times out after 4 seconds of not sensing motor running and cuts off current to pump.

On pump end there are two diaphragm type valves, one allows fuel to be pulled in to pump cavity, but not pushed back out towards fuel tank. Other allows fuel to be pushed out towards carbs, but not flow back into pump.

Not my best tech write up.

Gary

 

[one2dmax]

The pump pressure and flow will work but the brackets aren't setup for the Vmax and the inlet and outlet lines are wrong. But, those parts could be moved over if needed.

Sean

 

[SpecOps13]

Pictures worth many thousand words Gary.... Thanx....

 

[06VMAXIMUS]

Thanks for the pics and operation description. Its always nice to look at a break down of something before diving into it!

 

[rebar]

Thanks! This thread will help when I tear into mine on the stock bike.

My question is if this after-market pump could replace the stock pump on my custom bike without compromising any performance. And would it operate the same?

http://www.summitracing.com/parts/CRT-P74029/?rtype=10

Copied from another post..


The pump is designed to run under a few conditions.

1. There must be power (duh). There is forced on power for 5 seconds when the key (or kill switch) is first turned on. This activates the timer/relay. If the bike is not running (with a signal from one of the cylinders) then the relay shuts off and shuts off power to the pump. This is one of those things to help prevent fuel from being pumped in a crash condition.

2. Once there is power it will only run until it reaches operating pressure. So, lets say you let the bike sit for an extended period (a few days is enough sometimes) or you just got done rebuilding the carbs. The pump will run fast for the entire 5 seconds as it's trying to fill the blows and reach pressure. In the case of a carb rebuild it will do this a number of cycles (turning the key off and on) until it fills and reaches pressure.

Once the bike has been started and or the bowls filled and line pressure achieved the pump will not run again until some fuel has been used or pressure relieved (by a possible leaking diaphragm). So, the next time you shut off the bike and or restart it within a short period of time the pump will maybe only click once, twice, or none at all.

If the pump continually runs all the time or never slows down and stops, then it's not building pressure. This could be an air leak at one of the hoses, filter, stuck float, stuck or bad needle, or simply a worn out pump. Sometimes the small diaphragms internal to the pump become displaced and then it can't hold pressure. Much like there are two valves to each half of your heart there are two for the pump.

We've seen pumps that appear to be fine but exhibit the symptoms you are describing. Sometimes they don't effect the performance and sometimes they do.

Hopefully this will clear things up a bit.
__________________
Later,
Sean Morley

 

[brownrxmd]

I have two fuel pumps, one that came with the bike when I bought it a couple of weeks ago and new (used) one to replace the old one with. I followed the service manual and tested both pumps by applying 12v to the leads, nothing but a spark. Maybe I read the directions wrong. I dissected the pumps and the small wire on the right you see in picture #8 is melted in both pumps. One the wire is completely gone and I can't seem to figure out to completely disassemble the pump and the other has a small amt of wire that I hopefully can solder a replacement wire too. I'll give it a whirl then it's off to ebay to order a third pump I will not be testing. Geeze I kill myself sometimes.