Backhoe Perkins C4.236 in Cat-426 ...not accelerating, dying

[thepumpguysc]

VERY GOOD INFO there..
I feel your pain.. I'm the guy usually on the other end of that stick..
When I come to help a customer out w/ similar problems & they are at the end of their rope & suggest darn near everything you suggested, all I get is screaming & yelling..
WHY didn't the manuf. do this..??!! WHY didn't the manuf. do that..??!!
I just look at'm & say, "do you want it FIXED or NOT"?? Lol
Now, not "everything" you said is Gospel, so take it w/ a grain of salt.. it might seem that way to you & work perfectly fine for YOU.. but that doesn't make it the gospel truth. {right}..
Hope you get her all straightened out.. Happy Tractoring.. TPG

 

[fitterski]

Re: [provisionally resolved] Re: Perkins C4.236 in Cat-426 ...not accelerating, dyin

Thanks for all the help!

I changed the suction hose to soft polyurethane and then primed the the lift pump by blowing air into the tank after which it pulled a foot from the tank below it. There was no air present in the lines after this nor was there any surging.


..a few more tidbits for those who might be googling for this in the future

Diesel SG is about 0.84 so about 0.37 psi comes from a foot of head. 3 psi output will push up to 8 feet in the design-diameter hose.

The little diaphragm type electric lift pumps are NOT designed to self prime at ANY height, I have two of them with different output volume and untested but suspected low-range output pressure and NEITHER one will self prime to a height of even a single foot. I was very surprised by this and it can be a major factor in machines that sit still for weeks on end! I cannot consider this to be a design flaw because the machine is delivered with a mechanical lift pump, I have no idea if it can self-prime but when the system needs bleeding I want nothing but an electric one. Actually the best design is no need for any bleeding at all, in the form of a self purging layout like on my Deutz 4-holer!

The hoses that many mechanics WRONGLY use to connect both the output and suction input in lift-pump circuits are polyeth or nylon and get very hard in cold weather springing vacuum leaks! Use soft polyurethane hoses for vacuum, the type that remains flexible at any temperature. We're talking suction only here, any leak means air, not fuel, and less likely to occur anyway.


I've had endless troubles with this backhoe since day one and in retrospect ALL of them revolved around the fuel system and its total lack of suitability for very cold weather operations at the design level. So although the issue is temporarily resolved "I" am resolved to fix it once and for all this spring when it warms up outdoors

1
Diesel fuel ALWAYS has water in it, only the quantity varies with the degree of refining. Summer fuel has tons of it causing rust in tanks and lines and filters. Winter grade is more refined (evaporated) which is why it has both less water and less energy. The water however (mostly in the form of ice crystals in suspension giving the fuel a milky appearance) can cause L O T S of problems.

2
For my money an aluminum or SS tank is where it must all begin. Plastic could be ok also but it's too fragile on a backhoe which can be a violent environment. I once had the oil cooler above the oil filter ripped off by a stump, triggering the oil horn!

3
The fuel must be visible for inspection at all times. I'm going to cut a slot in my DIY stainless tank and close it off with a 1/2" thick clear polycarb plate held by a frame and screws with a fuel resistant gasket between the polycarb and the tank. I will cut a similar but round hole on top of the tank for a very bright light that makes the inside (especially the bottom) look like my mouth at the dentist even in ambient sunlight on snow!

4
the electric lift pump will be fed directly from the tank to which it will be fixed, with a protection plate defending against breakage.

5
a 2000 or+ watt heating pad between the tank and the protection plate that will be under the pad. The idea is to raise 28 gallons from -30c to +20c in an hour and keep it there thermostatically. The lift pump will feed a small shuttle tank.

6
metal return line coiled around the exhaust manifold with a thermostatically controlled selector valve to route the output into the main tank when the shuttle tank temperature is 30c or more. This bit gets complicated bu I'll finger something out. At lower shuttle tank temperatures the heated return would replenish the shuttle tank with the rest of replenishing coming from the main tank. In summer the heating coil around the exhaust would be inactive with just a line into the main tank.

This is no small job, but I've had this machine for 15 years, I knew NOTHING about tractors when I bought it. I've put 5000+ hours on it and absorbed probably 500 hours of DIY service time sometimes under inhuman conditions not to mention $ervice call$. Enough is enough

Although the details are still being kicked around I have already begun actual work on the above. A couple of questions have come up in discussions with various people about the water-separators used with most diesel engines.

a)
Given the small filter size containers how is it possible for any water at all to settle out if suspension with a running engine? I think these WS's are useful only to catch already separated 'gulps' of water while the only place to separate out water in suspension is in the tank itself.

b)
On my Cat-426 (Perkins) space was very badly handled in design and it's anything but easy to open and service the dedicated water-separator on the right side where fuel goes from the tank to the lift pump (this being a fairly conventional arrangement BTW). I want to remove it and instead replace the filter on the opposite side with a combined filter/separator that would be much easier to handle. One pro mechanic is voting against this idea, he doesn't even like my idea of bypassing the mechanical lift pump with a submerged or submerged-equivalent electrical feed pump.

c)
He also claims that the combined filter=separator units are not capable to separate water as well.

Any comments?

 

[MHarryE]

Re: [provisionally resolved] Re: Perkins C4.236 in Cat-426 ...not accelerating, dyin

Although the details are still being kicked around I have already begun actual work on the above. A couple of questions have come up in discussions with various people about the water-separators used with most diesel engines.

a)
Given the small filter size containers how is it possible for any water at all to settle out if suspension with a running engine? I think these WS's are useful only to catch already separated 'gulps' of water while the only place to separate out water in suspension is in the tank itself.

b)
On my Cat-426 (Perkins) space was very badly handled in design and it's anything but easy to open and service the dedicated water-separator on the right side where fuel goes from the tank to the lift pump (this being a fairly conventional arrangement BTW). I want to remove it and instead replace the filter on the opposite side with a combined filter/separator that would be much easier to handle. One pro mechanic is voting against this idea, he doesn't even like my idea of bypassing the mechanical lift pump with a submerged or submerged-equivalent electrical feed pump.

c)
He also claims that the combined filter=separator units are not capable to separate water as well.

Any comments?

Water molecules are larger in size than diesel fuel molecules. Separation is by size. The water separator used on the next gen Cat BHL is the 3054 and uses a combination electric lift pump/water separator/ fuel filter. It has no problem self priming. As a water separator it is 90% efficient, good but not adequate in poor fuel/humid areas. On compactor we added an optional second water separator between the lift and injection pumps due to high injection pump failure rates.

 

[fitterski]

Re: [provisionally resolved] Re: Perkins C4.236 in Cat-426 ...not accelerating, dyin

Water molecules are larger in size than diesel fuel molecules. Separation is by size. The water separator used on the next gen Cat BHL is the 3054 and uses a combination electric lift pump/water separator/ fuel filter. It has no problem self priming. As a water separator it is 90% efficient, good but not adequate in poor fuel/humid areas. On compactor we added an optional second water separator between the lift and injection pumps due to high injection pump failure rates.

That sounds serious, although on the Cat on the left side where I'd like to move all this I'm extremely tight for space. Two additional questions also come to mind.

My son who has some expertise in boats and airplanes as well as grand prix racing (and we do argue a lot) says that electrical feed pumps were NEVER meant to 'lift' fuel on the suction side at all. Are the pumps in the above submerged or at tank level if outside the tank? Last winter while TS-ing a stalling engine I disconnected the electric pump outlet to find no output at all with the in-tank fuel level only a foot below it so that was one that my son won.

The other one is this, if the larger water molecules get separated out on he basis of size I presume they would at first hang-up at a filter element membrane and then settle out and down only after having built up to a certain volume allowing them to become unsuspended. I could live with this, but then what happens when water in suspension freezes? It would presumably mean no smaller molecule sizes and could also hang at a membrane but then it would never settle out being lighter than the fuel. Wouldn't that quickly clog the filter?

In my approach, because the snow blower is a critical-mission link in a chain that must work and must not fail, I will plan to never operate with any fuel anywhere that is below freezing so the question is academic but I'd be curious anyway. All of this BTW will also apply to the blower engine (Cummins 5.9).