Fuel pump

[Wvtroutbum81 186]

Needing some direction, old fuel pump on my 312-8 is shot. Looking for a quality rebuild kit. I put a low flow electric pump to get it running but it starts to run out of fuel on a long hill? Tank is clean, removed screen in tank and have new line.

[ri702bill 8,327]

Check with Then and Now in Weymouth Massachusetts. Quality stuff.

[953 nut 55,290]

3 hours ago, Wvtroutbum81 said:

old fuel pump on my 312-8 is shot.

Is that a plastic pump? Don't think Then & Now kits work well on plastic ones.

 

3 hours ago, Wvtroutbum81 said:

I put a low flow electric pump to get it running but it starts to run out of fuel on a long hill?

Did you mount the electric pump below the bottom of your fuel tank? They are good pushers but they suck at sucking.

[Wvtroutbum81 186]

Its metal, i think i mounted the electric pump to high. Going to relocate it this week.

[Jeff-C175 7,202]

36 minutes ago, Wvtroutbum81 said:

relocate

 

As close to the tank, and as low as possible is best.

[Racinbob 11,086]

An electric pump is great especially with the tank under the seat models. Mr Gasket #42s 2-3.5 psi, 28 gpm. Mounted as close to the tank as practical for minimum draw and maximum push. It's ben flawless.

 

[Lane Ranger 10,968]

14 minutes ago, Racinbob said:

An electric pump is great especially with the tank under the seat models. Mr Gasket #42s 2-3.5 psi, 28 gpm. Mounted as close to the tank as practical for minimum draw and maximum push. It's ben flawless.

 

Bob. Did you remove the original fuel pump first when doing this?  And  how did you wire up the pump?    
 

I have a 314 hydro that seems to loose prime in the gas line (my fuel pump may be weak). And I have been thinking about putting an electric fuel pump on. 

[Wvtroutbum81 186]

25 minutes ago, Racinbob said:

An electric pump is great especially with the tank under the seat models. Mr Gasket #42s 2-3.5 psi, 28 gpm. Mounted as close to the tank as practical for minimum draw and maximum push. It's ben flawless.

 

Where did you get that hitch?

[Racinbob 11,086]

28 minutes ago, Lane Ranger said:

Bob. Did you remove the original fuel pump first when doing this?  And  how did you wire up the pump?    
 

I have a 314 hydro that seems to loose prime in the gas line (my fuel pump may be weak). And I have been thinking about putting an electric fuel pump on. 

 

I did not remove the original pump Lane. My thought process was that it would help control the fuel flow and pressure to what the engine was designed for. Then it was suggested to me to bypass the original pump because the electric pump might blow the diaphragm on and pump fuel directly into the engine. I guess that's possible  It's been on there for over 3 years now so I might be on borrowed time. 

 

My biggest issue was that if the tractor sat for a few days the tank is so low it took some time to get the fuel back. As far as wiring the mow in reverse keyswitch on the side of the seat seems to have fallen off . There was a wire right there that was hot when the ignition was on and fused under the hood. Perfect. 

 

19 minutes ago, Wvtroutbum81 said:

Where did you get that hitch?

 

Wheelhorse Parts and More - RedSquare Wheel Horse Forum

 

I have one on my 76 and this 2005. I love them. 

Edited October 30, 2022 by Racinbob

[JoeM 7,874]

The electric pumps are the way to go. No messing around and a lot less cranking. 

 

Removed the mechanical pump and replaced with a piece of flat and some sealant.

 

Used one of these MegaFlint. worked good I have used the Mr. Gasket 42S but they are more pricey. 

 

I like mounting them in the back but in this case low on the frame at engine worked out and allowed to hook into the engine coil plus to turn on. I try to run gas line in as it is like a natural trap feeding into the pump. 

The filter is in back coming out of the tank.

 

 

[Jeff-C175 7,202]

I just received a few aftermarket pump rebuild kits,  yes, I should go electric, but my point is that the screw hole spacing on the diaphragms were too far apart.  About a half screw diameter.

 

I'm wondering if there are two types of pumps, one with the screws a bit further apart?

 

I was able to carefully modify them but thought I would let y'all know that the aftermarket diaphragms might not fit correctly.

[Handy Don 12,233]

1 minute ago, Jeff-C175 said:

I just received a few aftermarket pump rebuild kits,  yes, I should go electric, but my point is that the screw hole spacing on the diaphragms were too far apart.  About a half screw diameter.

 

I'm wondering if there are two types of pumps, one with the screws a bit further apart?

 

I was able to carefully modify them but thought I would let y'all know that the aftermarket diaphragms might not fit correctly.

Those ARE the correct spacing and did not need fixing.

The diaphragms should be "scrunched" in on the screws so there is "slack" that permits the plunger to move up and down without having to stretch the diaphragm material. Stretching severely shortens the diaphragm life and puts extra force on the simple pivot for the actuator arm, which is a non-replaceable part.

Believe it or not, the diaphragm will smooth out and seal properly between the two pump halves as long as you've made sure that they are flat and smooth (think flattening a head).

[Jeff-C175 7,202]

3 minutes ago, Handy Don said:

Those ARE the correct spacing and did not need fixing.

The diaphragms should be "scrunched" in on the screws so there is "slack" that permits the plunger to move up and down without having to stretch the diaphragm material. Stretching severely shortens the diaphragm life and puts extra force on the simple pivot for the actuator arm, which is a non-replaceable part.

Believe it or not, the diaphragm will smooth out and seal properly between the two pump halves as long as you've made sure that they are flat and smooth (think flattening a head).

 

I thought that may be the case, so I tried assembling first, but was unable to get them together without wrinkling the rubber.  I could see maybe a LITTLE slack, but this is more than that.  I don't dispute that it's not good to stretch the rubber,  but there was still some slack after I opened the holes a bit.

 

 

[Handy Don 12,233]

13 hours ago, Jeff-C175 said:

 

I thought that may be the case, so I tried assembling first, but was unable to get them together without wrinkling the rubber.  I could see maybe a LITTLE slack, but this is more than that.  I don't dispute that it's not good to stretch the rubber,  but there was still some slack after I opened the holes a bit.

 

 

The Kohler service manual calls for actuating the fuel pump lever to pull the plunger fully down against the spring before tightening the body screws as the easiest way to get the diaphragm into the correct position. It does sorta take three hands to do that, so I clamped the lower body gently in a vice. There should be no resistance at all from stretch of the diaphragm.

Section 4-2 on reconditioning fuel pumps.

 

[Jeff-C175 7,202]

This sorta makes me think that there may in fact be two 'versions' of the mechanical fuel pump.  I've never seen one as old as this 1972 manual, all three of mine are at least from 1980 and do NOT have the check valves that are removable as shown here.  They are pressed into the body of the pump.

 

 

So with that in mind, I am wondering if the distance between the screws is in fact different.  As I said, if I tried to use the original holes, which I did, there would be no way to get the diaphragm flat inside the pump body.  And yes, I did flex the actuator rod before tightening.  We're talking about almost 1/8" difference !    Whist I had tooken some pics!

 

 

Edited November 1, 2022 by Jeff-C175

[Handy Don 12,233]

17 minutes ago, Jeff-C175 said:

get the diaphragm flat inside the pump body

Sorry that I'm not making myself clearer. The diaphragm is not supposed to be flat inside the pump. It is supposed to shape itself into a bellows.

 

I've done one of each style (age?) of pump, and the older one with the removable valves also had a priming lever. Identical hole spacing on the body halves since I used two kits bought at the same time with the same part number and used the same "scrunch" to get them in. In both cases, I made sure the small bumpiness of the edge of the diaphragm along the pump body seams was evenly distributed and it compressed out as I criss-cross tightened the body screws.

 

Frankly, I'm convinced that a lot of the "not strong enough" flak that Kohler fuel pumps get is a result of a badly-installed diaphragm rebuild that constricts the pump's motion and ability to move fuel. The older pump I re-did is on a 312-H and has no trouble getting fuel to the engine in 3 or 4 seconds after sitting.

Edited November 1, 2022 by Handy Don

[Jeff-C175 7,202]

32 minutes ago, Handy Don said:

I'm not making myself clearer

 

Absolutely clear, understand completely what you are saying, no problem... and I'd like to add that I don't intend to be argumentative, just discussing and trying to understand.

 

Here's a couple pics:

 

The old is 1-3/8" between centers:

 

The new is 1-1/2" between centers:

 

It's not possible to 'scrunch' the diaphragm that much.  Also, check the distance of the holes from the outside edge of the diaphragm.  If you used the holes on the new one and were able to scrunch it that much and get it flat at the mating surfaces, the diaphragm would be 1/16" from the edge of the pump body.

 

 

 

Edited November 1, 2022 by Jeff-C175

[Handy Don 12,233]

Yep. Gotcha. Info back and forth. 

 

In the top picture, the bellows are already formed in the center and the edges have been compressed via plastic deformation pushing the holes closer together. The material at the edges will be slightly thicker than the material in the center as a result.

 

The diaphragm you would like to have is one where the bellows is already formed but that isn't how it works.

 

If you were able to pull the edges of the old diaphragm outward to "flatten" the bellows, you would get to the same hole-to-hole dimension as the new diaphragm or extremely close.

[davem1111 2,030]

On 10/30/2022 at 8:18 AM, Lane Ranger said:

Bob. Did you remove the original fuel pump first when doing this?  And  how did you wire up the pump?    
 

I have a 314 hydro that seems to loose prime in the gas line (my fuel pump may be weak). And I have been thinking about putting an electric fuel pump on. 

 

I'm not Bob, but I'll add my 2 cents here.  

 

I have 2 of the Carbole 12v pumps, one on a Kohler 12 and one on an Onan 16, and have had very good results so far.  First one has been in service for maybe a year, so that's not a long trial.

 

As far a wiring, at first I just put a toggle switch on the positive wire where I could reach it below the hood, because it was expedient at the time.  Later, I tested various wires coming out of the circuit board and found one that came on when the switch was turned on, and tapped into that. 

 

I like that these come with a backflow valve - i.e., it doesn't let fuel flow backwards, so there's not much distance for the gas to refill the lines depending on how long it's been sitting, I suppose.  I mounted mine under the hood, but I do like the "under the seat" idea too.

[Jeff-C175 7,202]

3 hours ago, Handy Don said:

same hole-to-hole dimension as the new diaphragm or extremely close.

 

Well... I don't agree... IMO, there is no way that you can 'scrunch' the diaphragm enough to make up that much difference.  

BTW, there's some parallax in the photos below, the micrometer is actually quite close to the centers of the holes.

 

It's about 0.2 inches corner to corner that you would have to make up.

OLD:

 

NEW:

 

The 'tell' is the distance from the edge of the rubber (and this measurement shouldn't change because this part does not get stretched) to the hole center:

NEW:

 

OLD:

 

The overall width of the diaphragm is the same on both parts.

 

I am still not disputing that one should not 'stretch' the diaphragm when installing, but am maintaining that the hole spacing on the new diaphragms is incorrect.  I could see a LITTLE BIT, but NOT this ginormous amount.

 

One last point... the 'groove' that is colored blue below is not part of the 'bellows', its the groove that has a recess on one half and a raised part on the other half of the pump body.  This captures the diaphragm and helps create the seal.  If you were able to 'scrunch' the diaphragm enough that those screw holes would line up, the edge of the diaphragm would fall into this area.  In other words, to get it scrunched enough to fit, you would have to pull it back from the edge of the pump body almost an 1/8 of an inch.

 

So... let's just agree to disagree!  K ?

 

I wish someone had a new OEM Kohler diaphragm that they could measure.

 

 

 

 

Edited November 1, 2022 by Jeff-C175

[953 nut 55,290]

On 11/1/2022 at 1:19 PM, davem1111 said:

Later, I tested various wires coming out of the circuit board and found one that came on when the switch was turned on, and tapped into that.

I always wire the electric fuel pump to the volt meter/hour meter wires, that wire is powered with the key ON and is fuse protected.