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

[fitterski]

This is a fairly typical Perkins except for the prepended "C" which stands for Compensated which stands for just a little boosted i.e. not as much as the T4.236 which is "real" turbo

I've had to purge ice from the fuel system many times before to fix a lack of guts or even drop-dead situations but this time, so far, my fuel tricks have forsaken me.

#1
On very cold starts (-20c & lower) I can see gases escaping by the turbine gasket, suggestion of a seized turbine?

#2
I gotta keep the rear window open due to lots of exhaust smell in cabin (blown in by the heater)

#3
Once the engine has started performance is so-so but it really falls apart after the engine has warmed up, just will not accelerate above an erratic idle. Oil pressure is OK, no dramatic smoke observed. I've pulled it from service for fear of further damage, or of just getting stuck because it plain drops dead. Certainly can't do any WORK with it.

One piece I have not looked at yet is the inlet screen into the Lucas rotary type injector pump (it was rebuilt 3-4 years ago). If there were ice crystals in this filter screen they might cause others to pile on top of them. I'm not too sure about the temperature inside this fitting where the fuel enters. I'll probably open it in a couple of days, have a blizzard due here tomorrow.

Otherwise my first question is what would the symptoms of a seized turbine be? It might spin cold but if oil starved it would heat up and seize warm?

There is always the possibility of engine damage (7,500hrs) but I'd like to isolate everything else before starting to strip it for a spring-time rebuild.

 

[thepumpguysc]

Symptoms are black or grey smoke.. hard start..
Just pull the boot off the turbo & see if you can spin the blades w/ your finger.. DO NOT do this while running..
A "flick" of your finger & the blades should keep rotating. if they move just a smidge & stop, you have a problem..
Also look for excessive oil leakage in the turbo housing when you pull the boot..
THAT indicates a problem also.

 

[fitterski]

Symptoms are black or grey smoke.. hard start..
Just pull the boot off the turbo & see if you can spin the blades w/ your finger.. DO NOT do this while running..
A "flick" of your finger & the blades should keep rotating. if they move just a smidge & stop, you have a problem..
Also look for excessive oil leakage in the turbo housing when you pull the boot..
THAT indicates a problem also.

Thanks for the input, the blizzard just hit but before it did i managed to open the pump inlet and confirm that it's as clean as a whistle. I started it up to test and beyond the usual requirement for ether it started OK, although it idles hesitatingly at first and is puking smoke of every shade. It isn't cold enough today to cause vapor trails so the traces leaving the turbo gasket area MUST be smoke from burning oil. I decided to test what happens if after a minute I redline it to get the turbo spooled up and spinning cold before it gets a chance to bind or seize. I get good rpm and no exhaust smoke. At that point I quit and surrendered the backyard to the elements for the next 2 days. Looking at the turbo will be next but i have to pull the stack, the muffler and an adapter first, all held with rusty bolts that i'll have break with a 5 foot force-bar. Anyway, it looks like there might just be no need for a major.

Anybody know how to pull the hood on one of these? What does it weigh? Possible without a hoist?

 

[thepumpguysc]

Don't worry about the exhaust side just yet..
Pull the intake boot.. probably rubber & held on w/ a clamp.. 20 minute job.
That'll get you inside enough to do your spin test & give you a good idea of any oil seepage..
The oil will be in the rubber boot most likely..
Don't start the engine.. Check it while the engine is cold.. NOT warmed-up..
Here's hoping for the best.. TPG

 

[fitterski]

Don't worry about the exhaust side just yet..
Pull the intake boot.. probably rubber & held on w/ a clamp.. 20 minute job.
That'll get you inside enough to do your spin test & give you a good idea of any oil seepage..
The oil will be in the rubber boot most likely..
Don't start the engine.. Check it while the engine is cold.. NOT warmed-up..
Here's hoping for the best.. TPG

Just couldn't leave it alone, there's no winter sport like working on an old POS outside in a blizzard

Got to the compressor as you suggested, it spins OK, maybe not THAT free but OK. The shaft end play is at the very most about 1/64" so the problem is not a seized turbo. For the smoke I'll disconnect the oil return to the block to see if it's getting any. There should be oil or there would be no smoke. I think maybe loose clearance is letting some oil go astray and burn on hot pieces. This summer I'll take it off, strip and refurbish it with some casing cleanup and gaskets to make it like new.

On-spec I spliced a transparent piece of hose in between the fuel filter and the injection pump inlet. There is AIR in the flow and more so as revs go up, but I'll have to find out where it's coming from. The mechanical lift pump was bypassed by an electrical one years ago due to similar problems. This means that the only place air could get sucked into the line is between it and the tank, UNLESS the injection pump would be out-sucking the lift pump. I'll need to bypass the tank suction line with one directly into tank filling snout.

Having done some research I'm amazed by the low level of design quality in the case of diesel fuel systems in general, automotive for example, but especially so in the case of heavy equipment. Anyway, that's where it stands now, I think I have the culprit, it's only a question of time before I fix it and this time I'm going to fix it the way it should have been designed in the first place.

 

[thepumpguysc]

What PSI electric pump did you install?? The system only runs on 1-3 psi inlet pressure..[5 max]
IF you replaced it w/ a higher pressure pump, say 10-15-25 psi.. you may be over feeding the system & over-riding the hydraulically. controlled advance mechanism..??
Just another something to check..
Good luck.

 

[fitterski]

What PSI electric pump did you install?? The system only runs on 1-3 psi inlet pressure..[5 max]
IF you replaced it w/ a higher pressure pump, say 10-15-25 psi.. you may be over feeding the system & over-riding the hydraulically. controlled advance mechanism..??
Just another something to check..
Good luck.

I have no idea but it's supposed to be a 'lift' pump, the previous one had been installed by a mechanic and it wouldn't even suck up from about 1-1/2 foot lower. But I read in some pump manual that the low pressure inlet pump elevates the pressure to 'considerably above any internal need' inside the pump before the high pressure output. In this context I don't understand your remark, i.e. if the pressure is raised a lot more before it gets to the governor.

 

[thepumpguysc]

The pumps automatic advance goes hand in hand w/ rpm..
SO, if you have full advance at 400rpm because you over pressurized the inlet.. your gonna get smoke.
The pump raises the pressure internally based on rpm which moves the advance piston..

 

[fitterski]

The pumps automatic advance goes hand in hand w/ rpm..
SO, if you have full advance at 400rpm because you over pressurized the inlet.. your gonna get smoke.
The pump raises the pressure internally based on rpm which moves the advance piston..

OK, I think I get it, the first integral pump at the inlet end ADDS pressure, piggybacking it instead of a regulated value. I'm pretty confident that air in the line is the issue to investigate but the next step I intend to try will use proper pressure as well. Sometime before the weekend I'm going to to hang a litre of filtered fuel some 5 feet above the injection pump, at around 1/2 psi per foot that should give me 2.5 air-free psi.

 

[fitterski]

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

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