Small engine Pulse Fuel Pump

John T · Jul 10, 2013

I'm in the market for opinions (lay, professional, heck even Billy Bobs) as to other possible causes BESIDES the fuel pump itself??? being the culprit. I dont want to run out and buy a new pump if thats NOT the problem grrrrrrrr

My Yamaha G14 Gas Golf Cart uses one of those 3 port (Pulse, In, Out) fuel pumps similar to those many small gas engines use that have the Pulse line to the engine crankcase so differing pressure operates the pump and its fairly new.......The suction line to the gas tank is new as well as the drop down line in the tank, i.e. no restrictions and no visible pin holes or other air/vacuum leaks........My new small in line filter is between pumps output and carb input NOT in suction line to tank.

EVERY NOW N THEN SHE STARVES OUT OF GAS (YES tanks full) and the small in line filter between pump and carb is bone dry and regardless of cranking and choking she fails to prime up n pump. HOWEVER if you remove the line from pumps output (to carb) and crank her over she eventually primes up n starts pumping gas out the pump, hook the line back up and the carb fills n youre off to the races. Still it kinda "spurts" the gas out, sure not any what Id call any steady "flow". The engine is low on compression and has some blow by if that matters all that much to those type of pumps???

Sooooooooo Ima thinkin hop on Flea Bay and just order a new pump unless someone has a better idea of another cause besides the pump??? NO IM NOT installing an elec pump. I may go out and pull the Pulse line to the crankcase to insure its okay but I doubt thats the problem.

problems problems lol when the grandkids come if that carts not up n running they may pop a cork !!!!!

Ol John T and all

Billy Shafer · Jul 10, 2013

Onan has used that same type of pump for years. Biggest problem I have found outside of the pump. Is the vacuum line from the engine. Cracks or gets a little leak in it. I have also seen the pump housing crack,but that is rare.

Wayne in MN · Jul 10, 2013

Is the pump repairable? The pumping diaphragm flaps curl up with use. New part should be less $$ than a pump.

Bob Bancroft · Jul 10, 2013

I see you got your first reply from a Billy.
Since I'm Robert William I don't quite fit the "Billy Bob", but I'm close, just backwards.
If as Billy points out, the pulse line is OK, I think your low compression/ blow by is the main culprit. They aren't much of a pump to begin with, and have to count on definite pressure changes to do their thing.
Would hooking up a little electric pump just to trouble shoot it be out of the question?

sotxbill · Jul 10, 2013

(quoted from post at 07:40:22 07/10/13) I'm in the market for opinions (lay, professional, heck even Billy Bobs) as to other possible causes BESIDES the fuel pump itself??? being the culprit. I dont want to run out and buy a new pump if thats NOT the problem grrrrrrrr

My Yamaha G14 Gas Golf Cart uses one of those 3 port (Pulse, In, Out) fuel pumps similar to those many small gas engines use that have the Pulse line to the engine crankcase so differing pressure operates the pump and its fairly new.......The suction line to the gas tank is new as well as the drop down line in the tank, i.e. no restrictions and no visible pin holes or other air/vacuum leaks........My new small in line filter is between pumps output and carb input NOT in suction line to tank.

EVERY NOW N THEN SHE STARVES OUT OF GAS (YES tanks full) and the small in line filter between pump and carb is bone dry and regardless of cranking and choking she fails to prime up n pump. HOWEVER if you remove the line from pumps output (to carb) and crank her over she eventually primes up n starts pumping gas out the pump, hook the line back up and the carb fills n youre off to the races. Still it kinda "spurts" the gas out, sure not any what Id call any steady "flow". The engine is low on compression and has some blow by if that matters all that much to those type of pumps???

Sooooooooo Ima thinkin hop on Flea Bay and just order a new pump unless someone has a better idea of another cause besides the pump??? NO IM NOT installing an elec pump. I may go out and pull the Pulse line to the crankcase to insure its okay but I doubt thats the problem.

problems problems lol when the grandkids come if that carts not up n running they may pop a cork !!!!!

Ol John T and all

if still squirting,, look for a sticking float or problem in carb.. new gas will make needle valve stick badly. check float for adjustment.

buickanddeere · Jul 10, 2013

Low crankcase vacuum due to worn crankshaft seals or a crankcase leak

John T · Jul 10, 2013

Yep they sell replacement diaphram kits about 1/2 the price of a pump......

Thanks,

John T

notjustair · Jul 10, 2013

I just went through this with a mower. The little vent in the gas gap was plugged. Are you sure there isn't a vacuum in the tank? Next time it does it crack the lid and see if there's a whoosh.

John T · Jul 10, 2013

I have plenty of elec pumps laying around I could mess with if I have to, but some have too much pressure and can over ride the carbs needle n seat grrrrrrrrr

Theres a chance I may just overhaul the engine to stop oil use and blow by and Ima thinkin that will improve pump performance

John T

John T · Jul 10, 2013

Good suggestion, I will definitely look into that. It gets tough to pump gas out if air isnt allowed to re enter the tank!!!!!!!

John T

onefarmer · Jul 10, 2013

I have a G8 Yamaha Golf Cart and had the same trouble with it. Never could get the pulse pump to work right. So I got mad and put a Mr Gasket elec pump on it. It works great.

retired farmer · Jul 10, 2013

Had a lawn mower engine do that once, replaced the new fuel filter with another new one and cured the problem. Filter must have been defective.

Janicholson · Jul 10, 2013

A stiff diaphragm will make it difficult to pump against a closed needle or air. Moderately bad check valves will let low vapor pressure fuel maks vapor where liquid should be.
If rebuilding the pump is no help. I would put a primer electric (for carburetor) on it with a push button to make first pressure. If the engine runs well generally leave it alone. Jim

john *.?-!.* cub owner · Jul 10, 2013

get a piece of hose that fits the pulse port, and blow-suck rapidly on the hose. that is enough to operate the fuel pump for a test. You should not get a fuel taste in your mouth if the diaphragm is good. Use the number on the pump itself to do an internet search, the pumps are pretty cheap.

Hendrik · Jul 10, 2013

Worse than billy bob:
Put your gas tank on (or just under) the cart's canopy (if it has one); remove or bypass pump.

Another thought: is the "other" side of the pump's membrane sufficiently vented?

HTH

ben there · Jul 10, 2013

alot of folks claim snake oil but my 08 Kawi Teryx will not run right without Sea Foam...its cheaper than rogaine

DoubleR · Jul 10, 2013

I messed around with the 8HP Kohler on my tiller on and off for what seemed like a couple years trying to get it to run right. I replaced the fuel pump a couple of years ago and it hasn't missed a beat since. I took the old one apart and didn't see anything wrong with it. Go figure?
Sea-Foam also gets my vote as doing wonders for a bad running gas engine.

Edwin Koberle · Jul 10, 2013

Been working in the golf car business since 1972.
In my experience you can loose crankcase pressure due to seals,dipstick not in properly,not having the oil fill plug not sealing or crank case gaskets failing. But most likley the pump needs a repair kit.

Gene Davis (Ga.) · Jul 10, 2013

I work at the local golf course and we use this type pump for several applications. The line from the crankcase will sometimes fill up with oil or sludge if the engine has a lot of wear on the rings and has blow by. To check for proper operation of the pulse line from the crankcase. Pull the line loose on the pump end and place some soft grease over the opening so that it completely covers the hole. Run the starter to crank over the engine, If the grease does not suck in and blow out, you do not have enough action to operate the pump. Sometimes the line is full of crud also. The OEM pulse type for a Yamaha will choke you with the price. Go to the local small engine place and they will have them that fit, Tecumseh, Briggs and also Kohler. All the same pump just the lines are oriented differently. These will often be 1/2 the price of the OEM pumps and do the same job. I use the Kohler style most often. You will have to be sure the pressure from an electric isn't too much or the needle and seat to control. The plastic ones are usually less expensive than the metal ones. The pumps we have tried rebuilding did not ever work satisfactorily so we decided to take the price of a kit and applu it to the new one. One other thing, small engine gasoline filters are made in 2 types. One type is for fuel pump and the other type is for a gravity flow tank.

jm. · Jul 10, 2013

You are right on the low pressure but usually the most common problem we find is the valve cover bolts loose and loss of the suction there.

Geo-TH,In · Jul 10, 2013

JohnT,
I had a bad fuel tank on a Jubilee. So I installed an in line fuel filter. MISTAKE. The fuel filter was made of a clear plastic, paper inside and you could see when the fuel stopped. No fuel pump on the Jubilee, just gravity. Well it worked fine until the gas temp reached 135, then the fuel stopped flowing through the paper filter. Vapor locked. When it cooled off, the fuel flowed again.

Remove your filter and see what happens.

I purchased a new tank and went back to the sedimen bowl and the 3 screen filters that was OEM.

Some lawn mowers can't use paper in line filter. The gas won't go through them, they use a screen filter instead.

Think you could go to a shade tree mower repair shop, Billy Bobs,LLC and pick up a used fuel pump for testing?

How cheap are electric fuel pumps?

Now is you really want to be cheap, get a gas hose like on a boat with a priming bulb. Let your passanger pump the fuel by hand.
George.

JD Seller · Jul 10, 2013

John Look at B&S part number 808656 on Ebay. It is the type of pump you are talking about and you can get aftermarket ones for around $12 including shipping. The OEM B&S is only $23.

Small engine Pulse Fuel Pump

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