I just installed a vacuum fuel pump on my tecumseh yesterday, took it out today and found that after I accelerate from idle, I seem to lose fuel pressure for some reason. When I start it I can see fuel getting pumped through my clear fuel filter, but after I accelerate, its like I just ran out of gas and the engine will die. I crank it over and it will start after a few seconds and do the same thing again. I tapped the intake as a source for my vacuum. I'm wondering if I'm losing vacuum as I accelerate causing the diaphragm in the pump to stop pulsing? or maybe too much vacuum and its holding the diaphragm in one position? any info would be great.
Fuel Issue
- Thread starter cmorin543
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EagleTalons
Master JB Welder
Was the vacuum pump used or new?
its a new pump.... this is the one I got - http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=160428414509
Blazkowiez
Kart Aficionado
Where did you connect the vacuum on the engine? What size is the engine etc?
These are what I use when I actually need one... Mikuni FTW!
To be honest the part you got looks kinda Chinese, I have no idea how good it may or may not be my friend. I'm not trying to be negative, but when I go looking for parts I think of will this work before I think of price.
These are what I use when I actually need one... Mikuni FTW!
To be honest the part you got looks kinda Chinese, I have no idea how good it may or may not be my friend. I'm not trying to be negative, but when I go looking for parts I think of will this work before I think of price.
anderkart
Moderator
That cheapo pulse pump you got there looks like it would only have the capability of supplying enough fuel for a very small engine. Your results seem to be confirming this. I agree with Blazkowiez suggestion of replacing it with a Mikuni pulse pump. A company named Walbro also makes high quality pulse pumps.
EagleTalons
Master JB Welder
Here is an idea, could test the pump out, using a vacuum line on your car's engine and pump a small glass of water with it. Have the person rev the car up and down and note the flow of the gas.
anderkart
Moderator
A Pulse pump wouldn't work at all like that, they need an input signal that alternates/pulses between vacuum and a slight pressure to actuate their diaphragm back and forth. A constant vacuum signal off a car engine would just draw the pumps diaphragm in one time and then hold it there.
EagleTalons
Master JB Welder
Oh, hmm how could you test it then?
anderkart
Moderator
I'd test it right on the kart by ruling out any other potential problems. A few common problems to check are:
1 - Pulse pumps should be mounted on top of the engine and as close to the carb as possible because they have much more ability to draw fuel than push it.
2 - You also want to keep the Pulse line as short as possible because It'll be stretching and contracting the little rubber hose a little and this ends up causing a slightly weaker pulse signal to actually be reaching the pump, lowering its performance.
2 - The pulse line should also have some type of clamps at each end to eliminate any leakage at the fittings. (wire ties or small hose clamps are fine) All the lines should have clamps but both ends of the pumps input fuel line definitely needs clamps to help keep it from drawing in air instead of fuel.
3 - You'd also want to confirm that the fuel tank has some type of vent, otherwise the pump will create a vacuum in the tank and this will soon stop the pump from working at all.
1 - Pulse pumps should be mounted on top of the engine and as close to the carb as possible because they have much more ability to draw fuel than push it.
2 - You also want to keep the Pulse line as short as possible because It'll be stretching and contracting the little rubber hose a little and this ends up causing a slightly weaker pulse signal to actually be reaching the pump, lowering its performance.
2 - The pulse line should also have some type of clamps at each end to eliminate any leakage at the fittings. (wire ties or small hose clamps are fine) All the lines should have clamps but both ends of the pumps input fuel line definitely needs clamps to help keep it from drawing in air instead of fuel.
3 - You'd also want to confirm that the fuel tank has some type of vent, otherwise the pump will create a vacuum in the tank and this will soon stop the pump from working at all.
Thanks guys for all the advice. Found out the problem was a combination of gravity and too low of a pressure pump. I race the kart on a small oval track. 90% of the guys I race have left wheel drive and run clockwise around the track... In this direction, gravity was pulling the fuel away from my carburetor. I tried going the opposite way around the track and the engine runs perfectly.
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