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I'm working on a friend's Huskvarna mower which has a 24hp B&S v-twin. When I got it the engine would just crank and crank, no signs of starting. I found there was no fuel coming from the fuel pump outlet (hose to carb detached - nothing coming from pump when key turned) so I replaced the fuel pump. Same problem. Fuel dribbles at a steady rate from the fuel line from the tank which means the pump would get fuel so I'm thinking it's the pulse line.

I did a quick check of the 3" of pulse line that's visible to me outside of the valve cover and found no obvious issues. The mower is a 2013 model so not much time for dry rot. Rubber still feels nice and soft.

Part of me wants to pull the valve cover but I don't have a gasket to replace the current one with and I'm not sure if there's anything worth seeing in there after breaking the gasket. Can someone tell me what may be going wrong here please? Is there something lurking behind that valve cover that I really need to look at?

Thanks,

Scott

What you are looking for is something in the fuel line. Take it all off and blow it out. You do not need 90 psi so turn it down. I hardly ever tear up a valve cover gasket. take it off and gently remove cover.

BlazNT said:

What you are looking for is something in the fuel line. Take it all off and blow it out. You do not need 90 psi so turn it down. I hardly ever tear up a valve cover gasket. take it off and gently remove cover.

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I get steady flow via gravity from the tank, through the filter and out of the line that goes into the fuel pump. Are you saying I need to check the pulse line for an obstruction?

Take the line off the carb then crank it over... see if you have flow into the carb ...BE careful with fuel lines.....FIRE !!! fuel pump only works when engine is turning over.......not just with key on ...

After you test Boobala said the yes check the pulse line. I personally would check all and the gas tank. May have something covering the drain hole that only covers when pump pulls it down to cover outlet.

BlazNT said:

After you test Boobala said the yes check the pulse line. I personally would check all and the gas tank. May have something covering the drain hole that only covers when pump pulls it down to cover outlet.

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I've already confirmed that fuel doesn't flow from the pump when the engine is turned over. I'll next take things apart enough to get to where the fuel line comes out of the tank - hopefully there's a piece of junk in there that's acting like a flapper over the fuel exit under pressure.

Will let you guys know what I find.

I put some compressed air through the fuel line where it exits the tank and to just before the fuel filter. All clear.

The dip tube fuel sucker straw inside the tank is also clear. The line from the filter to the pump is good as well.

I tried taking off​ the valve cover but it's very well glued to the cylinder head and I'm going to bend metal if I try to take it off with a screwdriver. Suggestions for removing a stuck valve cover?

Also, can someone tell me how the pulse line terminates inside the valve cover? Does it just end, hanging loose in there, or is there something attached to that end that could possibly be causing this issue?

Thanks

Watch this video.
https://youtu.be/jdS36RQkFc4

I used the video suggestion to pull the pulse line and confirm it's good to go. There's no wear, cracks or blemishes.

What else is there to cause this fuel pump to not work? Could it be that there's no or not enough compression under the valve cover?

Very first thing to check is the tubes at the pump.
Most people plumb them together wrong despite the fact that there are generally arrows cast into the pump.
The one on the circle is the impulse line it blows & sucks on the diaphragm the ones on the side are the fuel lines.
Usually the in line is the one nearest the the impulse line and the out line is the one furthest away
Look closely and you should see an arrow on the body or tube somewhere.

Blow & suck on the impulse line, it should only move a little bit both ways if the diaphragm is in a good condition.
With the other two, there is a one way valve inside the pum so you should be able to blow but not suck on the in tube and suck but not blow on the out tube.

bertsmobile1 said:

Very first thing to check is the tubes at the pump.
Most people plumb them together wrong despite the fact that there are generally arrows cast into the pump.
The one on the circle is the impulse line it blows & sucks on the diaphragm the ones on the side are the fuel lines.
Usually the in line is the one nearest the the impulse line and the out line is the one furthest away
Look closely and you should see an arrow on the body or tube somewhere.

Blow & suck on the impulse line, it should only move a little bit both ways if the diaphragm is in a good condition.
With the other two, there is a one way valve inside the pum so you should be able to blow but not suck on the in tube and suck but not blow on the out tube.

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See pic with current configuration. I tried swapping the lines that aren't running to the carb and got the same result - no fuel pumping.

I tried the blowing/sucking thing and the new pump worked as it was supposed to. The configuration I have it in now matches the way the diaphragms allow the air to move.

I did find a little gas in the fuel pump which means it may have worked a little bit at some point. It's still not moving fuel though and it's brand new.

Now what?

Remove pulse line and put finger over hole. Crank engine and see if you have a pulse.

I disconnected the pulse line from the fuel pump, put my finger on the end of the pulse line and cranked the engine. I felt no real tugging and even that could have been the shaking of the engine. I put my top lip to the pulse line and thought I felt a little something but it definitely didn't feel like enough to suck fuel from a tank and shoot it into a carb.

Could I have a leak somewhere besides the valve cover gasket, which appears to be solid? Even if that cylinder isn't firing (I've no evidencenyet that it's not) it should still be building up positive and negative pressure when the piston moves, right?

I took it a step further by disconnecting the pulse line from the fuel pump and putting a dab of grease on the end of the line, completely covering the hole. When I cranked the engine the grease didn't move at all. This tells me the engine isn't generating a pulse as it should be.

Another piece of information... when I got the mower there was a lot oily residue on the engine and the oil level was at the bottom of the dipstick. Could this mean that the engine has a leak in a gasket somewhere that's bad enough to disallow compression to build up?

I am not familiar with this specific model but will offer some general suggestions. Put the pre pump hose in a container and let some fuel out while removing the fill cap - deturmines a venting issue if fuel flow increased with cap off. Take the pump off and bench test it in a vise with a small can of gas and supply hose. Put some fuel into BOTH sides of the pump in case a check valve is hung up then re test. Don

have you check compression or did I miss that in a post

Possible problems are Head Gasket, Valve cover gasket(Just because its stuck on does not mean it is not broken in one spot), Valves out of adjustment, and sump gasket. I would start with valve cover gasket and while it is off adjust the valves.

One more thing I just thought of is hole in engine block.

Also re my post bench test you can replicate the vacuum pulse with a turkey baster and length if fuel line....

Don - I've already verified fuel flow from the tank right up to the inlet of the fuel pump. It dribbles nicely with just gravity.

NorthBama - I haven't checked compression - I don't have the tool to do that.

BlazeNT - The things you suggest are beyond my capabilities so I'm probably going to cry uncle on this one and tell my friend to take the mower to a shop for further diagnosis.

Thanks very much for the help here guys, I really appreciate it. I was hoping for a quick fix on this one but it sounds like my friend is going to have to shell out some coin to get this fixed.

I guess nobody told him to give it a shot of gas into the carb to see if it would attempt to run briefly....

I'm aware of that particular step but don't see the point in getting it to run for a few seconds of there's still no fuel coming from the pump. The pulse function is broken here somewhere.

fixitdad45 said:

I'm aware of that particular step but don't see the point in getting it to run for a few seconds of there's still no fuel coming from the pump. The pulse function is broken here somewhere.

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At least if it runs, and it runs for a short time that helps confirm it is the fuel system and NOT something else....
we are beginning to "shoot arrows everywhere" have you tried a different pump..?? might get a used one from a mower shop cheap . .or a GOOD friend ...there is not a lot to the fuel system.. I realize this is not YOUR mower.. and by now you might feel awkward in front of your friend.... I hope he realizes YOU are TRYING to help HIM !!

OOoopps my goof.. just saw you did replace pump ...

fixitdad45 said:

I'm aware of that particular step but don't see the point in getting it to run for a few seconds of there's still no fuel coming from the pump. The pulse function is broken here somewhere.

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Which means that you have to take the "stuck" rocker cover off and when you replace the gasket, put some sealant on the rocker cover side and some high temp wheel bearing grease on the other so it will then strip off easily.
However the "Pump" function is created by the piston moving up and down in the cylinder so the first thing to do is to check the piston is moving by shoving a stick down the plug hole and turning the engine over by hand.
If it is moving then pull the head off and replace the head gasket they blow between the cylinder and the pushrod tubes quite regularly
Clean the outside of the motor carefully before you start looking for holes in the crankcase.
I did have a mower come in with the rod poking out of the crank where it was hard to see.
The owner had spent over $ 500 on new parts trying to get his totalled engine to start.