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CAT 3126 fuel system purging without primer?

fastline

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This engine is in an excavator, but used for everything. Machine fired for me in the cold, then started to stumble, surge die a couple times. I am confident it is a fueling issue. I removed the water separator (1st filter) and rusty crap dumped out of it.

There are two drain lines on the 2nd filter that I opened and neither of them produce a drop, so I unscrewed that filter a bit and there is certainly 'some' fuel hiding in there so I don't know what to think about the drain valves right now. The 2nd filter runs inverted so she is going to dump if it's loaded.

Beyond this, I am unsure about fuel system priming in this situation. The machine does have a lift pump that pulls fuel from the tank, and pushes it through the filters and to the HEUI pump. The book calls for "open the drain and use the manual pump to purge".....Yeah, it ain't got none of that! I can't find any procedure without the manual pump device.
 
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Mobiltech

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Some of them had no pump. I rigged up a pump to put inline . The only other way is to blow in the tank but that’s not easy. They put that filter upside down to save the injectors from the people who like to fill filters with unfiltered fuel.
If you fill the primary and crank the engine it will eventually fill the secondary.
 

fastline

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Would the lift pump not work to purge the fuel system? I noticed that it was working to refill the primary separator but I have no info to know if that pump should load the secondary and fuel line. I am pretty frustrated that the secondary drain lines are not working and I do not want any contamination concerns when pulling the filter.
 

Nige

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am pretty frustrated that the secondary drain lines are not working
That's probably because there is nothing in there to drain. The fact that almost nothing is draining from the secondary filter drains would indicate that the canister is empty, or almost empty.
Would it be worth your while starting by cleaning the tank, or at least open the tank drain and let out the accumulated water & sediment drain until the fuel runs clear.? There should be a ball valve under the bottom of the tank.
At least then you would have half a chance with the water separator & filters, although you might find that there are problems in the fuel suction line from the tank caused by the sheer quantity of contamination that has passed through it.

Regarding priming, please post a photo of the "head" of the primary fuel filter/water separator assembly.
 

fastline

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Couple pics of the filter assy. HEK serial. CAT dealer indicated possibly bulletin REHS2598 is what I am looking for in SIS if someone has that? So far it sounds like there are some known issues with the filter housing/pump. I know the pump is doing 'something' as it certainly refilled the separator but I really think I should at least see something coming off those drain valves when opened. They sit lower than the secondary filter and that filter certain had something in it. I have not yet removed it because I know I really need to be careful here with the known contamination concerns.
 

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Nige

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Jeez, what a fustercluck. How to confuse everyone in one easy lesson...........
The orange and the black wires are the feed for the priming pump. That pump fills the water separator/primary filter and when that's full it fills the secondary. Is it that hard to understand.?

If it's not pumping well enough to fill the secondary then the chances are what I posted above, contamination in the tank and lines, or even in the pump itself. Start your cleaning from where the fuel starts its journey, i.e. the tank.

See attachment. I put REHS2598 in it as well but TBH until you prove the lines are clear from the tank and the tank itself is clean I wouldn't even bother going there to start with.

EDIT: While you're at it make sure to clean all the little ports & passages in the head of the water separator with wire and/or compressed air. This will need all the external ifttings to be removed first.
 

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heymccall

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Confusingly stupid.
Fuel leave the tank via spigot valve or 90 elbow. This is known debris collection point.
It then travels cross chassis to separator/ priming pump inlet.
So, the elbow inlet to the separator is another known debris collection point.

How is fuel stopped from gravity flowing when servicing the separator? Later units have a cute little ball valve in the inlet 90 fitting. I don't see that here.

I also don't see a tank drain for water/ sediment removal.

As an aside...I had to change all the fuel supply hoses on my 8k hour 330C machines for internal disintegration, yet never replace any on my 20k+ 322B machines.

Screenshot_20230224-154604_Chrome.jpg Screenshot_20230224-154625_Chrome.jpg

And, again, why two threads, and, why here, as it IS machine specific?
 

Acoals

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Could there be a fuel gel issue?

As an aside...I had to change all the fuel supply hoses on my 8k hour 330C machines for internal disintegration, yet never replace any on my 20k+ 322B machines.

I had to do the same on my 305C mini right after I got it at 4000 hrs. Actually I had to replace the entire fuel delivery system between the tank and the injector pump due to multiple issues; internally collapsed fuel lines, leaking gaskets on the fuel filter housing causing air ingestion, a lot of general crud and debris and a failing lift pump.
 

Nige

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I also don't see a tank drain for water/ sediment removal.
They're shown as being on the front RH corner of the tank. The ball valve for the sediment drain is #8, the fuel shutoff valve is #6. TBH that would be my first port of call before anything else. I've seen those gate-type shutoff valves get partially blocked with sh*t before as well, often in the nipple #5 that screws sinto it.

upload_2023-2-24_21-6-58.png
 

fastline

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All input here imo is on point and relevant. Fuel gel could have occurred. Tank is low and about 15 gal of known good winter fuel was added from the fuel truck just to do 30min worth of work only 4 days ago. It fired and ran at level 6 doing pud worth without any issue at all. The main thing that changed was temperature. It was previous 65F, then dropped to 14F at night and cold start was attempted at about 28F. What was observed coming from the separator was pretty thick.
What I suspect is a combo of cold weather causing thicker fuel, marginal plugged filters, and probably more going on in the tank.

I made the decision today to just leave the machine until warmer weather in a few days because if there is any water in the system, it will be ice right now so I will just chase my tail. Yes, there is certainly a sediment ball valve on the bottom of the tank and I want to open that before even putting in the new filters. If I do that now, no water will come out.

I also need to investigate why the secondary filter drain valves are not doing anything. I don't even know why there is two but I am totally guessing there is one on the inlet and outlet side of that filter section to ensure full draining.

When I attempted my last restart yesterday, she was rolling the white smoke and bumped (hit) only a couple times in a 30sec attempt. That rig has never dropped white smoke, but that usually indicates pumps and injectors are going for it and loss of prime is supect, at least in my experiences.
 

Acoals

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What does "thick" fuel mean? "Gel" is this goopy white waxy snot that plugs up the filters.

Like this:
 

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fastline

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I did not really see any 'gel' so to speak, but viscosity of diesel will increase with temp decrease and if there was any Summer diesel still in the tank, that would make it worse. It poured basically like 5w motor oil. Obviously diesel is oil so not a huge shocker but I suspect the filter was already loaded so the temp change pushed her over the edge. Why the filter is loaded with rust is another matter. I still have a puck of ice that was removed from the water separator and it is still just sitting there....lol I should share that pic just for fun.

The separator is not dated so I suspect it has been ignored for quite a while as the thought may have been that draining the water was doing the job. That cartridge is a first line filter and who knows how long it's been.
 

Nige

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The book calls for "open the drain and use the manual pump to purge".....Yeah, it ain't got none of that! I can't find any procedure without the manual pump device.
So you've obviously read the O&M Manual. Did you miss the bit about how often it's recommended to drain the water and sediment from the fuel tank and the water separator.? During the daily walkaround, that's how often. What does the daily walkaround consist of, climb in the cab and turn the key.?

Now if you have clean fuel and a reasonable maintenance regime it could probably be done weekly and still not cause any issue. Now you're trying to overthink how to fix the problem where all that was needed in the first instance was a bit of basic preventive maintenance, and the clue to what it's supposed to accomplish is in the name..........

So what we have here good people is the parable of Everybody, Somebody, Anybody, & Nobody.
There was an important job to be done and Everybody was sure that Somebody would do it. Anybody could have done it, but Nobody did it. Somebody got angry about that, because it was Everybody’s job. Everybody thought Anybody could do it, but Nobody realized that Everybody wouldn’t do it. It ended up that Everybody blamed Somebody when Nobody did what Anybody could have done.
 

fastline

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Thanks for the helpful CAT documents and advice. The machine lives again! After waiting for warmer temps, I was able to drain off about 1/2gal of water from the fuel tank as well as some rust debris. I then moved to the filters and found a little more water. I found a little water in the secondary filter so no question some has made it to the injection system. the secondary drain valves are not working. The secondary filter was full of fuel so we made a mess. What I found odd is neither filter has a seal for the center threaded part of the filter? I guess because I was in there scrutinizing everything, I noticed this. Not sure if the threads alone are enough to ensure a good seal? Not sure if that makes sense but there is the main outer Oring but nothing in the center section.
There actually is a rubber washer on the separator, but is obvious there is nothing there to even seat against. What I suspect is the washer comes with the filter so people just stick it on there, but there is not a seat for it.

In any case, with the key on, the lift pump was running so I cracked the outlet line from the separator housing to the secondary and there was air followed by spraying. No doubt pressure there! After a few key on events, I attempted a crank and machine fired with only a brief puff of white smoke followed by clean exhaust. Start up did not have a single hiccup and never stumbled. I ran from idle to level 10 many times and worked the machine to confirm all was well.

I talked with a CAT tech I know at the dealer and told the details of my situation and he was not alarmed in the slightest. Just said to get the water out of it and the filters will likely solve the issue. He did say there is a stand pipe on the fuel line fitting in the tank that is up a good 4".
 
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