Pulse pump... governor or valve cover.

[frostyflammable]

So I am doing my first pulse pump install, and have seen it done both ways. I see quite a few YouTubers use the governor hole and some use the valve cover with the current "pressure release" (or whatever it is called but I am not a fan of this) or some drill a new hole and tap it with a NPT fitting on top of the valve cover and use that for the pulse pump.

Just wanted to see if there are any pros and cons to using either of these locations.

Thanks,
Dan

 

[bob58o]

I vote none of the above.
Which engine? Which Carb?

They make intake manifolds and carb isolator/insulators with pulse fittings.

 

[frostyflammable]

I vote none of the above.
Which engine? Which Carb?

They make intake manifolds and carb isolator/insulators with pulse fittings.

It is a Predator 420cc, stock carb, governor still in but may remove it.

--Dan

 

[bob58o]

https://www.ebay.com/itm/Isolator-w...a-GX340-GX390-VRX420-VRX440-460-/171911247602

 

[frostyflammable]

That is nice and convenient. Would you happen to know if this is a 1/4in pulse fitting?

Thanks!!!

 

[anderkart]

Yes, the pulse-fitting in that carb spacer will be made to fit a 1/4" line

So I am doing my first pulse pump install, and have seen it done both ways. I see quite a few YouTubers use the governor hole and some use the valve cover with the current "pressure release" (or whatever it is called but I am not a fan of this) or some drill a new hole and tap it with a NPT fitting on top of the valve cover and use that for the pulse pump.

Just wanted to see if there are any pros and cons to using either of these locations.

Thanks,
Dan

Pulse pump fitting in the Governor hole will work, but you typically end up with quite a bit of engine oil in your pulse-signal line running to the pump. The fuel pump would typically keep working with oil in that line, but at a reduced level of fuel pressure & volume.

Pulse pump fitting in the Valve cover will work fine too, It usually supplies a little weaker pulse signal than using the Governor-hole location, but you'll get less oil in the pulse-line.

Pulse fitting in the Carburetor spacer works too. You wont get any oil in the pulse line, but the pulse-signal is quite a bit stronger than using either of the valve cover or governor-hole locations. This stronger pulse signal results in the fuel pump creating a higher fuel pressure/volume level; that can sometimes overwhelm the Needle & Seat valve in the Carburetor of engines like yours, causing flooding Issues.

But If you ended up with flooding Issues, you could install a fuel-return system like I had to do on one of my karts. Here's a couple pics of the pulse pump fuel system I installed on one of my old karts:

I installed an In-line fuel shut off valve in the return line, so I could adjust how much fuel is allowed to return to the fuel tank.

I also installed a Marine Primer bulb in the fuel-supply line from the tank, to make staring the engine much easier.

My round Mikuni Pulse Pump had 4-fittings (dual-outputs). But If your pulse-pump only has 1 fuel output fitting, you could simply install a T-fitting into that fuel line to connect your return line...

 

[frostyflammable]

That is a lot of good info anderkart, really appreciate it.

I am using a spun aluminium gas tank and have no way to weld in another NPT fitting for the return line. I ordered the isolator with the pulse fitting just in case so I have it on hand. I may try valve cover way and hope that it pulls enough fuel (not a fan of oil from the gov hole gumming up the pump). Worst case I have a spare 420 valve cover in case this does not work and then I can take the fuel tank to a shop to weld in another NPT fitting. The pulse pump I have only has three fittings as well (in/out and vacuum) so I would need a T fitting for the return line.

Thanks,
Dan

 

[bob58o]

That is a lot of good info anderkart, really appreciate it.

I am using a spun aluminium gas tank and have no way to weld in another NPT fitting for the return line. I ordered the isolator with the pulse fitting just in case so I have it on hand. I may try valve cover way and hope that it pulls enough fuel (not a fan of oil from the gov hole gumming up the pump). Worst case I have a spare 420 valve cover in case this does not work and then I can take the fuel tank to a shop to weld in another NPT fitting. The pulse pump I have only has three fittings as well (in/out and vacuum) so I would need a T fitting for the return line.

Thanks,
Dan

I've also heard of people reducing the pulse signal by sticking something in the vacuum line. If the carb was flooding, they'd add a restriction in the line - something they could drill out bigger to make it "adjustable".

Too much fuel pressure - restrict the pulse signal line.
Not enough fuel pressure - drill the hole in the restriction larger.

In my head, I'm thinking about something like a fuel jet stuck in the signal line. Small jet = less pressure. Large jet = more pressure. Unless I'm backwards again.

Wonder if you could add a 1/4 turn shut off valve in the signal line to adjust the fuel pressure?
If that would work, that seems like the best bet. If flooding, close the valve a bit to weaken the signal??? Watcha think???

 

[frostyflammable]

I've also heard of people reducing the pulse signal by sticking something in the vacuum line. If the carb was flooding, they'd add a restriction in the line - something they could drill out bigger to make it "adjustable".

Too much fuel pressure - restrict the pulse signal line.
Not enough fuel pressure - drill the hole in the restriction larger.

In my head, I'm thinking about something like a fuel jet stuck in the signal line. Small jet = less pressure. Large jet = more pressure. Unless I'm backwards again.

Wonder if you could add a 1/4 turn shut off valve in the signal line to adjust the fuel pressure?
If that would work, that seems like the best bet. If flooding, close the valve a bit to weaken the signal??? Watcha think???

I like the idea, I have a fuel shutoff valve that will be going right after the fuel tank followed by the fuel filter. I have not looked at the shut off valve itself to see if its a full on/off or if I could regulate the fuel flow by partially turning it. I'd hate to flood the 420 may try this with the shutoff valve at half, at least in my brain it easier to add fuel than have to change the oil from flooding. May be overthinking it but I do that a lot

This is the shutoff valve that I have, still in the box have not even opened it yet.
https://www.ebay.com/itm/InLine-Str...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Thanks,
Dan

 

[bob58o]

I like the idea, I have a fuel shutoff valve that will be going right after the fuel tank followed by the fuel filter. I have not looked at the shut off valve itself to see if its a full on/off or if I could regulate the fuel flow by partially turning it. I'd hate to flood the 420 may try this with the shutoff valve at half, at least in my brain it easier to add fuel than have to change the oil from flooding. May be overthinking it but I do that a lot

This is the shutoff valve that I have, still in the box have not even opened it yet.
https://www.ebay.com/itm/InLine-Str...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Thanks,
Dan

I was talking about adding the shut off valve in the pulse line, not the fuel line.... To adjust the fuel pressure by "regulating" the vacuum pulse signal.

 

[frostyflammable]

I was talking about adding the shut off valve in the pulse line, not the fuel line.... To adjust the fuel pressure by "regulating" the vacuum pulse signal.

Oh, that makes even more sense. Will order another one of those switches for that side of the fuel system as well.

Thanks!
Dan

 

[anderkart]

That is a lot of good info anderkart, really appreciate it.

I am using a spun aluminium gas tank and have no way to weld in another NPT fitting for the return line. I ordered the isolator with the pulse fitting just in case so I have it on hand. I may try valve cover way and hope that it pulls enough fuel (not a fan of oil from the gov hole gumming up the pump). Worst case I have a spare 420 valve cover in case this does not work and then I can take the fuel tank to a shop to weld in another NPT fitting. The pulse pump I have only has three fittings as well (in/out and vacuum) so I would need a T fitting for the return line.

Thanks,
Dan

You could connect the return line to you fuel tanks Cap. You could purchase a 1/4" brass - barbed fitting with a nut to install/secure it, at most any Ace Hardware store. You could use a 1/4" O-ring and Flat washer on the fitting to help make a perfect seal...

If it isn't possible to install the fitting in your fuel cap, you could drill a hole in the top of your fuel tank to install a 1/4' barbed fitting that's equipped with pipe threads, and use Teflon tape around the fittings threads to help make the seal...

PS: You might not even need a return system, even when using the carb spacer-pulse fitting method.

I used a High volume Mikuni pulse pump on my kart. I suggest you just use a normal Walbro pulse pump like this link, and you probably wont even need a return system or any of the other suggested mods: http://out2win.com/catalog/fuelpump.html

 

[65ShelbyClone]

Increasing the internal volume of the signal line might also work. Perhaps using either a large diameter hose with reducers or adding a fuel filter inline with it.

That's if you need to to do anything at all. It may not be necessary.