1984 venture fuel pressure switch

The fuel pressure switch sends constant voltage to the fuel pump relay on my bike. I can see this when the pressure is low but when pressure is achived I stll get 10.2 volts up to the relay ?????? is this normal ????? The relay will close when it gets 10.9 volts or higher. I guess I am just wondering if I need to change it or not. Or just let the pump run full time LOL....

Any help would be appreicated...

I don't believe there is a fuel pressure switch.

The fuel pressure is managed by the pump.

It is a piston type pump. A spring behind the piston pushes the piston into the chamber forcing fuel through the outlet. When the piston travels far enough it closes a set of contact points.

The points energize a solenoid pulling the piston back against the spring, drawing fuel through the inlet.

The cycle repeats until the fuel pressure is high enough to overcome the spring at which point the pump stops cycling.

As fuel travels into the carburetors the piston will begin to move, again closing the points when the pump chamber is empty.

This is why when you first turn the key (and kill switch) on the pump clicks rapidly, then slows as pressure builds.

The pump on mine is a rotary vane pump with a fuel pump relay and what the drawings show is a pressure switch. I have never pulled the air box out but its located under the air box as the print shows it .

Can you post the breakdown you are looking at? Something is not right here. The pump on an '84 is mounted behind the support bracket for the rear foot peg on the left side of the bike.

There is a kill switch (tip over protection) on the bike.

Mike

I checked two service manuals (1983 and a 1983 - 1985). There is a pressure sensor used to control timing advance. There is a fuel pump relay. There is a tip-over switch. I could not find a fuel pressure switch.

As has already been said, the fuel pump self-limits. It will run until fuel pressure exceeds a set level and then shut off. Most, if not all, fuel pumps are this way.

The pump on mine is a rotary vane pump with a fuel pump relay and what the drawings show is a pressure switch. I have never pulled the air box out but its located under the air box as the print shows it .

Under the air box are the carburtors... Never heard of a fuel pump in that area. Does it have a V-Max engine??? Maybe a previous owner jury rigged something in there?? We need to see what you're looking at....

The pump has been changed its not the factory pump. It is located behind the support bracket on the left side just above the ele regulator. The issue Im having with it is the fuel pump relay shuts it off after 5 minuets of riding and after the bike sets for 5 to 10 min it starts back up and goes again. If I put power on the pump after the relay drops out the pump will run with no issues and the engine will run all day. So if the pressure switch I see in the line side of the print is not controlling the fuel pump relay then I guess i need to know what is LOL.....

Attached is a picture of what a fuel pump looks like on an 83, yours would have been almost the same.

There is a pressure switch built into the fuel pump. It is referred to as a cutoff switch in the service manual.

Service manual pages attached for the fuel pump, this is from 86-93 manual, same as the 84.

Gary

Attached is a picture of what a fuel pump looks like on an 83, yours would have been almost the same.

 

There is a pressure switch built into the fuel pump. It is referred to as a cutoff switch in the service manual.

 

Service manual pages attached for the fuel pump, this is from 86-93 manual, same as the 84.

 

Gary

Did you know that someone appears to have stolen your fuel tank?

The typical electric fuel pump set-up has an electric pump connected to power through a relay, and some kind of safety device that will shut off the fuel pump in case of an accident. For example, a Chevrolet fuel pump will run only 2 seconds when the ignition key is turned to "on". This is long enough to pressurize the fuel rails for the injectors to be able to spray fuel. After the engine starts an oil pressure sensor tells the fuel pump relay to stay engaged. If an accident occurs and the engine dies, the oil pressure drops, the oil pressure sensor switch opens, and the fuel pump relay stops the pump.

It appears that the 1983 - 85 VR has a relay and an emergency shut-off switch. The pump will run when the key is turned on (stopping when it reaches max pressure). If the motorcycle falls over, the emergency shut-off switch cuts power to the fuel pump relay and the pump stops.

Thats where my pump is located but that is not the same pump. LOL Mine has bee modified. Any how I have gone back and looked at the prints to refresh my mind and found my print reading error. The fuel pump relay in energized when the ignigition is turned on period end of sentence. LOL That being said after running for 5 min I am losing voltage which is either being shorted out or the voltage regulator or something with the alternator

Thats where my pump is located but that is not the same pump. LOL Mine has bee modified. Any how I have gone back and looked at the prints to refresh my mind and found my print reading error. The fuel pump relay in energized when the ignigition is turned on period end of sentence. LOL That being said after running for 5 min I am losing voltage which is either being shorted out or the voltage regulator or something with the alternator

"Shorting out" would likely blow a fuse. A poor contact will drop available voltage.

Relays can have bad internal contacts. Have you replace the fuel pump relay?

Just about any 12V relay rated at the same current will work . . .

Connectors to the relay can get corroded. Have you cleaned the connectors?

Does your battery measure 13.5 - 14.5V when the engine is running?

Have you replace the fuel pump relay?

Just about any 12V relay rated at the same current will work . . .

The fuel pump relay on these bikes is special.

Few pictures below of the insides. 1st is of an 84-93 bike, second one is from an 83.

Most of circuitry is to get it to drop out 5 seconds after power is removed I think.

Gary

Yea It looks as if im going to have to go thru the wires and the relays LOL...... It only gets a max of 11.1 to the fuel pump relay and as it warms up the voltage drops to 10.2 It looks as if I have a bad conection or perhaps just an old piece of wire. The contacts are clean and the battery is reading 12.2 when running its reading 13.1

The fuel pump relay on these bikes is special.

 

Few pictures below of the insides. 1st is of an 84-93 bike, second one is from an 83.

 

Most of circuitry is to get it to drop out 5 seconds after power is removed I think.

 

Gary

That's interesting . . . I wonder if the 5 second delay is absolutely needed?

There is a similar looking device on my Ninja. When I got the bike the fuel pump would not run. Pump tested OK. I replaced this funny looking relay ($40) and still no pump. I finally figured out how to engage the relay with a jumper wire and it has been working fine for three years.

Actually, that 5 second dropout is for when you first turn the key on. After 5 seconds voltage is removed to the fuel pump until a timing pulse (bike running) is received from the TCI,m at which time the relay restores 12 volts to the fuel pump. I believe the issue is to prevent fuel from contrinuously being supplied to the carbs in case of a stuck float or something. Actuyally I'm really not sure of the why, just know about the what...

Actually, that 5 second dropout is for when you first turn the key on. After 5 seconds voltage is removed to the fuel pump until a timing pulse (bike running) is received from the TCI,m at which time the relay restores 12 volts to the fuel pump. I believe the issue is to prevent fuel from contrinuously being supplied to the carbs in case of a stuck float or something. Actuyally I'm really not sure of the why, just know about the what...

Well it is something like that. I was close.

I am on Percocets for a blown out disc in my back. Hard to type and stay in chair. Let alone be right. !!

Gary

Actually, that 5 second dropout is for when you first turn the key on. After 5 seconds voltage is removed to the fuel pump until a timing pulse (bike running) is received from the TCI,m at which time the relay restores 12 volts to the fuel pump. I believe the issue is to prevent fuel from contrinuously being supplied to the carbs in case of a stuck float or something. Actuyally I'm really not sure of the why, just know about the what...

Yes, makes sense. This follows the electric fuel pump safety shut-off concept that I described on a previous comment. If an accident occurs and the engine is no longer running, the safety-squad wants the fuel pump shut off to prevent a great big ball of fire.