Gentlmen Help, II have a 941B Track loader , that I use occasionally all , in the winter time I changed the Injectors thinking that would help. It started to loose prime. Changed filter , water separator and hand priming pump. No luck it seems to be sucking air . I found no leaks. My last resort is to rebuild the pump. I would like too find a logical reason. Thank you
Nozzles won't cause air intrusion, the remaining components could but should show signs as filter/separator fuel level when removed low to empty and as this has the fuel tank above the system any air intrusion would be a leak when not running.. The injection pump/transfer pump a potential but they will usually show out as fuel in the oil after use of a period of time. How old is the fuel? Is it greyish or blackening? If is algae contaminated will shut off flow thru the fliters and will require drain, cleaning the tank, flushing lines and replacement of the fuel. Just adding algaecide will clog filters ever faster.
Thank you DMiller, Fuel is not old , , when I bleed it , it is red color. I use the hand pump to prime it , sometime I dont get fuel out when II loosen the the injector. Iam curious if the pump rack or check valve stuck open
DMiller , You have provided a lot of information , just to understand, if there are no fuel in the oil , then pump is ruled out to be OK then all line from inlet to fuel tank need to be checked , I changed fuel filter and water separator. . separator had some bad stuff looked black
If already found black fuel start there. Algae in the fuel will make a slime goo that can block up fittings, lines, sediment screens. Drain the tank first, go from there.
Hello again, drain the tank , fuel looks good , watched drain , 10 Gall. took off and cleaned all fitting , hoses and lines from the pump and back , all looks good and clean Found no cluprit the far
If have tank empty look into the bottom, make certain nothing floating inside that could block fuel.
Noticed the fuel cap center bolt that hold the screen had fallen out , cleaned it and reattached with some locktite
If its kickin your behind to the point of giving up.. Detroit sells a 1 way check valve for the fuel line in different size barb ends, to slide between rubber fuel lines.. You can install 1 between the inj. pump & fuel tank.. just a thought.. I'm sure there are different manuf. of them by now, but the ones I'm familiar w/ came from Detroit.. just google it..
Just wondering which fuel system this engine has, scroll or sleeve metering. Pre-chamber or direct injection? S/N off engine and or machine if they are different might give some more clues of where to look. One idea if it is in fact a sleeve metering pump is in this file:
S/N : 80 H 5236 it is sleeve
Here is the 941 B Running , it lost prime , from the sound of it she sound good
Not sure if this will work but will try to attach the info on the "Systems Operation" for the fuel system. Note that this is somewhat of a generic set of description as it is for various versions of the 3304/6 engine. In the diagrams it shows some with a "Siphon Break" and others with out "Siphon Break" if you read down the pages far enough you will see the statement that,"Siphon Break" is used on a machine with fuel tank located below the fuel pump housing. Hopefully this goes through and after studying how the system works it will give you an idea of how you are loosing your prime. Okay, got a error message saying the file is too large so if you can "Start a Conversation" as the new format of this forum calls it and send me an email address to send it to I'll give that a try.
Kshansen , I posted new post with email
Hey Pumpguysc, This pump has a check Valve , in everything I read about it( in the manual) , I have not been in one of those pumps. in fact it has 2 check valves a and depend on which model you have they suggested to eliminate one of them. Please provide me with a part number if yoou have it
Sent the file direct to your email, hope it is not too big a file.
Just an date , DMiller suggested that I look inside the tank after I empty it. this morning I took my extended light it reach to the bottom , I looked could not see anything that may float , in fact the tank looks real good. took the screen out at the cap , it had some debris junk. good thing still a separtor and filter prior to going thru the pump
That style fuel injection pump has the gerotor style transfer pump mounted in the front of it . A common problem with them is the drive shaft seal wearing out and allowing air into the transfer pump and fuel draining back. You will have to remove the fuel pump to fix it. The seals are shown on the inset to the right on the picture. The transfer pump is at #6
Yes, that's why I was trying to eliminated the "Siphon Break" and any of the check valves in the side cover of the pump first. Actually I believe this pump has two "regular gears" in the front. But still the pump assembly would need to come off to gain access to those seals.
Your right. Sometimes I get ahead of myself. I've done a lot of these and usually I end up doing the seals and replacing the gear and key in the transfer pump. It's not a big deal after you've done a few. I wouldn't recommend it for the average backyard mechanic though.
Hi Mobiltech and Kshansen, I reallly appreciate your support, That is exactly the technical support one need . it make sense that the drive shaft seal is worn out, because when I prime the system I can hear ( a hessing sound) right in the front of the pump. That is not something I, ve heard before this time. Mobiltech is right when you do few of these pump it is not a big deal , but am not gona brag about my mechanical ability. typically i love the challenge , but will have to have done more research , and locating source for parts tec. I have to ask you guys this question: earlier in the winter time notice little wetness around no 4 injector, it look those seals needed to changed., So II went changed the injector tips and seals on all of them. The question is that now that new injectors are requiring more prressure than pump was able to deliver this issue with pump occurred .
Right off I would say changing the nozzles in the prechambers would not have any effect on the gear pump leaking. That gear pump's only real job is to suck the fuel from the tank and push it through the filters and fill in injection pump housing. It actually only works at a very low pressure. I would guess without doing any research say it was in the 60 psi range. The camshaft and plungers in the main body of the injection pump are the ones that push the fuel out to the nozzles and into the cylinders.
Hate to keep asking more questions than I feel answers I providing but was wondering if it would be possible to get a couple clear pictures of the two areas circled in the picture below. I'm having a little trouble finding what that part is inside the green circle. Is that a small line from the priming pump hooked to it? In SIS the only pictures I have found either show nothing there just the flat plate on the side of the pump or else the spin-on fuel filter head mounted in that area.
OK , The small line is not hooked to the prime pump , it is actually the fuel pressure line going to the guage
here is the pic the small line is the fuel gauge line , the other is the bleed line
Ok, can see that now. Took another look at SIS for fun and see the spin-on filter head has what looks like a check valve in it. Could be what is suppose to keep it from loosing its prime??? Picture might be a little confusing in the red circle you can see the spring #2 and the disk #4. Item #5 that I colored green is the threaded "insert as they call it" that the filter is screwed on. All I can say from here looking at pictures it would be something to at least check out to be sure it appears to be working!
"back flow preventer" take off the filter & disconnect the lines & blow VERY slight air pressure in.. If its stuck you'll feel air. That's why I suggested the "other type" of 1 way valve between the tank.
Did your problem start before or after you changed the nozzles? Bob
While I don't right off see how changing the nozzles could lead to a "loosing prime" problem I guess a better inscription of this problem and the time line involved may give some better clues to what it really is. Was there a point at which there was no problem? Was anything done just prior to the problem? In my definition of "loosing prime" this is something that happens when engine is shut off and sets for more than a few minutes, usually hours or over night. Is this how this problem presents itself? Or is it more like you pump the hand priming pump and vent off the air with the valve on the upper right side of the cover then engine starts and runs fine for a period of time then starts running bad? Does this have a water separator that is glass cover where you can see the fuel inside? If it does does it stay nice and full with engine running or does it slowly appear to be filling with air? I know lots of questions! But as was talked about n this site just recently getting the full story can go along way to getting to the solution. Here's where I get off on a tangent. Several years back when my dad was still around and after he had had some heart problems he was having pain in his left arm. Mom convinced him to go to hospital to be checked out. All initial tests appeared to be good. Then while talking to the doctors dad mentioned that he had helped push the handicap bus he worked on out of a snow bank earlier in the week. Now that may explain why a 70+ year old guy would have a sore arm! Just goes to show having all the information can be very helpful in diagnosing a problem.
No 4 injector was showing wetness, that is why I changed seal and injectors tips. Then the problem started
I guess the better way of saying it is while the engine running : (Or is it more like you pump the hand priming pump and vent off the air with the valve on the upper right side of the cover then engine starts and runs fine for a period of time then starts running bad?) and shut off The system get full of air again. asking the right question is the only to diagnose the problem. it has a water separator and show low after it shut off. My first thought is I put fresh filter and new water separator , and now drained the tank cleaned the lines, I did not see anything that would present problem can the check valve in the filter base be changed or cleaned etc
I would pull the nozzles and have them checked.You may find the bad one by loosing the fuel line and checking for the one showing air. Bob
I agree with bluox, sounds almost like compression forcing back into nozzle then pump.
& the plot thickens.. the nozzle nuts need to be TORQUED.
Does it run good once it's primed and started?
To answer just that problem I would say if, as they show in the illustration I posted, they list part numbers for the spring, seat and disk, yes it can be rebuilt. That said the actual problem might be else where.
I would tend to agree with this, any test you can do without removing lots of parts or throwing money at it is a good place to start. So for a starter loosening one fuel line at a time with engine running to see if there is a sign of air being pushed out or one cylinder that does not seem to make any real difference in how the engine runs would tell you something. If you bought the nozzles from the local Cat Dealer I would also take them there and ask to have them tested. I know that back when these engines were still new that the local Cat dealer told me when ever they replaced a set of nozzles with new ones they would test the new ones before installing them. Also if I had an engine that was not right they would test the used ones for free as long as they knew I would buy new ones from them. If you have the tester it only takes a minute or so to test them.
Just to be sure of one more thing. Is this a pre-chamber engine or a direct injection engine? A pre-chamber engine would be one that has glow plugs to help start it. Wires hooked up next to each injector in the head. Not sure if this will tell us anything but just want the most complete information.
This is what I believe is a key bit of information, if engine ran good then someone replaced a part and now it runs bad I tend to want to point a finger at one of two things. #1 are the parts replaced bad? #2 Hope you don't get upset at this one, Did some one make a mistake installing the part(s)? Some errors I can think of off the top of my head. Not cleaning mating surfaces. Improper torque used. Wrong parts for the application.
Yes it run start, slight miss clears up then run a couple minutes it shut down. Look at the video on post that after I primed it
No 1 seem to be showing air when it shut down. I try to bleed it. I get a lot of comressed air . That is why iasked this question
Ken yes this engine is prechambet engine. With flow plug
I want to wish you all a happy fourth of July . Great bunch , I love all these question, and debates. My engineering background just won't stop over doing it. I am gona Travel to brother in .ca for short while, family business. Once I get back I will test the nozzles , may be put back the old one. Put new check valve in the filter housing. Go from there. This machine I have been trying to make it dependable, did line bore the bucket , arms etc new pin every where. The engine bee running great till this issue. I have leak in the flywheel housing , probably rear main deal. Will fix it little at time
Well when I watched the video I could not tell what was happening as after hearing it run for 15 seconds the video just stopped, engine seemed to be running right up to the end!
You say you are getting "compressed air" ??? Is this when you loosen the fuel line connection at the head, the one that takes a 3/4 inch wrench? You are not loosening the nut that holds the nozzle in the pre-chamber are you? Believe that nut takes a 7/8 or 1 inch wrench, been a few years! Just for fun try running the engine and loosen the fuel line nuts at the pump with them tight at the head. Let us know if you still see air pressure coming out of #1
Yes the line at the head , but is 3/4 wrench. Yes more pressured air than normal bleed.
I would say you've got a bad nozzle on number one. Can you replace number one with an old one to see if it helps. Also try cracking the # 1 injection line at the pump while it's running to see if there is a lot of air coming through the line from the injector tip.
Just to update , got back from trip and started where I left off. took off the filter and check it the valve with slight pressure it spring and it does not appear to be stuck
continue with above post , after taking off the filter , cleaned the mating surface , checked the valve and cleaned around it it appears to be fine. the insert that the filter screws on it , will not come off . cleaned the water separator plate and all the holes, took off the drain plug cock, it had some stuff in drain hole but not pluged, cleaned as well filled the filter and reassembled it.
next step gona inspect the fuel line closer , it is rubber high pressure steel wrapped like the hydraulic type. I replaced the steel one long ago . after which I am gona attempt to start it from a external tank like a gallon to see if it would run
Have you checked for air in the line connected to #1 like myself and Mobiletech suggested on July 3rd and 6th? If there is a problem with the injection nozzle leaking compression pressure into the pump no matter what you do with a external tank or cleaning of check valves in filter heads is going to help! Just trying to know that making suggestions at this end is being heard at your end. Sometimes listening to people who have been there before will save you tons of time and money if you just check one simple thing that only requires using a 3/4 inch wrench and one minute of time.
Good kshansen, I am totally with you on taking people advise seriously . I was taking by surprise when this problem occurred. as I tried to back track all my steps and this I have changed too understand all possibles problems. Today I will remove all Nozzles inspect them and replace them with the old ones. I have a discussion with a friend whose a service manager at the Thompson cat dealer. he suggested that I may be getting compressed air from the injectors tips. The reason he said if they are not seated right. To install them I should be able to feel a snap that is indication that the tip is properly seated. Well , that is new information for me and a key information. I hope that will be reporting good news
Now more than before I'm confused! This is a pre-chamber engine going by the S/N. I'm not understanding this "snap" this guy is saying you should feel. The nozzle screws on to the end of the adapter finger tight and then the two parts drop into the pre-chamber lining up the splines. Next the nut with the oring screws in and is torqued to proper torque. Then you put the oring with the steel ring molded into it on and hook up the fuel line and tighten it to the proper torque. Does this "service manager" understand what engine you are working on? Sounds like he is thinking you have something with electronic injectors that have oring seals around the outside, like a C15. If I heard a "snap" while installing nozzles in a pre-chamber engine I would get worried something broke!
https://photos.app.goo.gl/kb5WrYCWcGb2fGVI3
hello Kshansen, I think you all called it , give the credit where it is due. I pulled the all injectors tips this afternoon. starting from the back forward. And voila , the no. 1 injector tip all covered with fume Now I need to to fix that and what to know what caused it . if you click on the link above you will see a video of no 1 rotating.
Check the seat in the prechamber, make certain it isn't cracked. One cracked they are all suspect.
Yea, I think on that engine I would be draining the coolant and pulling all the chambers to get a real good look at them. All those nozzles have what I would call suspicious marks where they seat in the chambers. Not sure how good a job you can do cleaning the seats down in the chambers, especially that number one! If I was working on this for the company or a customer I think I would be leaning heavy towards new chambers and nozzles. Not sure how good the "Classic" brand chambers are but looks like they run about $50.00 or so depending on exact serial number of engine. Nozzles/Fuel Valve Body in the classic version go for about $15.00 so for around $70.00 a hole on a four cylinder engine you are only looking at under $300.00. Would be a bit more for sure if you went to all original Cat parts so one has to factor in how much this machine will be used and how critical downtime might be. As this machine has been sidelined for over a month as of now I can't think it is a mainline machine in a major quarry so I would be leaning towards the Classic parts and some careful work installing them. Probably go for a set of new glow plugs to avoid problems with those next week! One will need the correct tool to install the new chambers and the instructions on how to do it but that should not be a problem, just ask. And if he has a friend who is a service manager at a dealer that should be no problem getting hold of either.
Looks like a simple fix. Make sure to torque the pre-com chambers and the fuel nozzles to the correct torque. That may be the cause of your trouble if someone put too much torque on the fuel nozzles when they tightened them. It can deform them.
Good Morning All, Finally had sometime to get back on the machine. Well my surprise all the new injector were bad, I tested them at the pump shop. the old ones tested excellent . so reinstalled the old ones. Torqued them to them specs, bled and primed and couple start it fired up ran for while and it did not shut off as usual
Here is a link while the machine running: https://s.amsu.ng/70iEHTRAoavN
Where did you buy those "new" nozzles? Have you contacted that place and asked for a refund? I could understand maybe one being bad but a full set sounds like they have a major problem in manufacturing! I do know back when this type of nozzle/cartridge was the "normal" style the local dealer recommended testing all new nozzles. More or less to be sure they did not send a mechanic half way across the state to do a job then find a bad one. I don't recall ever finding a bad new one in all the years I worked on those machines. And even used ones never failed to let engine run!
You are right , I contacted the dealer it is an aftermarket place , now I am going back to recontact them and ask for refund. This place is in Knoxville Tn called OFF road equipment , I buy most of the time from Regal never had problem like such as this one. good Part are reliable and fit well from the picture of No 1 injector it appear blowing compressed fuel back . II did clean the PC chamber well used various buffing tools and made sure I SEATED the Nozzle and torqued according to specs 105.
Got few more nagging items to fix 1- Temp Gauge , probably ground wire 2- loosing anti freeze 3- torque converter temp gauge install Fuel pressure and oil pressure is good
About #2. is this an external loss? Or is it going someplace else? You don't want anti-freeze going into places it is not suppose to be can cause major problems.
Actually, I dont see where it is going , I have new water pump , new hoses etc. I know it is not in the engine Oil.
Are you sure it wasn't just an air pocket in the engine and after running a bit it worked it's way out? Or have you had to add coolant several times each time you check it? Also how much are you loosing? Five Gallons a day, five ounces a day? As we always say the more information you give us the better chance of getting a reply that will actually help find the problem.
I will be monitoring closely . I added 2 gall A WHILE BACK when I was diagnosing the problem yesterday I added a gall I dont see a leak , but gona look closer
How is the temp running? Is it smelling of antifreeze from the operator seat where the cap is burping from too much pressure from getting hot? Possible loaded core, both IN and/or Outsides will cause enough overheat to get coolant to boil and blowdown to the cap pressure rate, can also be a bad cap not sealing and blowing down all the time.
DMiller, I ran it today I did not smell any antifreeze and is holding pressure good. I dont have temp Gun something II will need to buy. The bad news it lost prime after It sat for few days. I can see the water separator is low at the top not even 1/8 in in top. anyway when it run it does not cut off . we are getting somewhere
That would be step one.
Hello DMiller started the Machine today , did not need to prime it , the water separator was not low. I ran it for while . obviously the injectors Nozzle was the problems. but will need to continue to ran and repair as I go
You would be well off to replace the existing temperature gauge, if is known good(new is probably +/- 5 from reading) then you will know if is cooking. Have you cleaned the exterior of the radiator? Was the engine or any underhood components leaking to where dirt accumulation is thick on the core? Another step is getting the radiator professionally cleaned IN and OUT.
Hey DMiller, Thank you for you response , always challenging. Just as a background, this machine had new water, pump , and thermostat because it was boiling. allso had the radiator professionally cleaned . when I got all that done, the temp gauge broke the wire coming out of the engine. so had to replace the gauge, got new one installed, but i must have left a ground wire off , or wired it wrong. I also got the trans oil temp gauge. that is my stories , now that I got it running , am gonna make sure the temp gauge work. I dont have a good wiring diagram for the gauge panels
Gauges work pretty simple, power feeds to them the ground is the sensing unit, make sure you are getting power at the cluster feed. If it IS still getting hot after all that AND pushing coolant you are probably looking to head work at a bare minimum. Most likely prechamber seals, potential cracks in prechamber seats or threads, worst is just a cracked head.
I will open up the Dash panel and check the wiring, the fuel pressure and oil gauges works. You know Iam fixing and restoring on this machine , new pin and bushing at the bucket and links. but there are something about the engine bothering for long time , and you may have touched on it which is the head. I should have it worked. it would eliminate a lot of issues. such as blow by , oil consumption. I have what I consider a lot blow by . These things that I fixed are really minor. the machine always started well
The original temp gauge is mechanical with no electrics at all.
If the machine was later modified it could have a electrical gauge. Has to have a power feed if electrical and must be the voltage specified on the meter IE: 12v, 6v or 24v. Rusted is correct in that originally these machines had strictly mechanical gauges with a sensing Bulb and capillary tube to the gauge. No electrical power and the gauge will not function as the sensor for electrical is a controlled or heat/resistor based ground for the electric feed thru the gauge. Yours may have a warning lamp sensor to which it will only go hard ground at excess temperature that someone tried to use for a electrical gauge.
I guess it is possible that over the years someone has replaced the mechanical gauge with an electric one. asleiman, is the water temp gauge you installed a Cat gauge? If so how about a part number to help us understand what it is. Also if it is an electric gauge did you also replace the sender? If someone had installed a generic electric gauge and you replace it with a Cat electric gauge it could be the sender is not compatible with the gauge! DMillier, I have to type faster if I'm going to beat you in the morning!
Morning!! Hansen!!
Hell, I have already been up almost three hours! Damn muscle in my AZZ is a major PITA and wakes me at the most awful of times.
Hey Hansen & DMiller, the temp gauge was working till the cappilary tube broke at the sending unit , II replaced it from Regal with part No 3S4824, and converter temp p/n 6H6692
Well while you all were waking up , II opened up the Dash Panel. shortly II will post some picture of the back of the panel. in mean time got hit with few wasp or yellow Jacket
Well if it has a capillary tube then it is strictly a mechanical gauge so no need for any wires. Only thing electrical in relation to the gauge might be a light so you can see it at night! If you want to test the gauge remove the sensing end from the engine and stick it in a hot cup of coffee or some boiling water! If you use coffee don't drink it afterwards as if there is some coolant getting into the coffee it could be poisonous! One more question, does this engine have a good temperature regulator? If not it might never get hot enough to move gauge. That is a bad way to run an engine!
Here is how the pic of the panels looks . there some wires coming in the picture
here are the Pic earlier post did not work
Okay so there are wires connected to one of the mounting studs for the temp gauge, but they are in no way involved in how the gauge works or does not work! Check out where the other end of those wires are connected and I'm sure you will find they are just ground wires for dash lights or possibly one of the other gauges. Probably was just a handy place to hook up a ground wire by some past owner. I tried without much luck to find a clear and simple description online of how a mechanical temperature gauge functions, could be they are a thing to old for the internet to know about them! Any how I'll try to put it in words of my own. First off you need to know that the temperature gauge is in many senses just a pressure gauge. If you don't know how they work go here: http://www.marshallinstruments.com/faqs/detail.cfm?id=22 The only difference is the temperature gauge reads the pressure inside a sealed system. That bulb like thing that you put in the fitting in the cylinder head of the motor, it is filled with ether just like the stuff in the starting fluid you might use to get an engine to start on a cold morning. Connected to this bulb filled with ether is a piece of copper or steel tubing that is connected to the back of the gauge. Now if you know any basic science you know that when a liquid or gas is heated it will expand. If this liquid or gas is inside a sealed system this expansion will create pressure. Well as this now heated ether is expanding and creating pressure and it has this nice little tube hooked to the gauge in the dash this pressure works on the gauge just like oil or air pressure. The more you heat the ether the more pressure and the more the needle on the gauge moves. No need for any outside power other than the heat from the coolant in the engine. Just be careful to not kink or damage the tubing running from the bulb in the head to the gauge, If you crush or kink the tube pressure can not get to the gauge. If you break or crack the tube any pressure will vent out and cause the gauge to also not work. If anyone knows of a good link to a better description or has suggestions on edits to this feel free to let me know.
Yep, better off going back all mechanical and installing what was there.
Great guys , gona check it out with the coeffe cup . need to find a plug ,, and going back with all original. Probably should take another pic of this machine , it is full Cab with ROPS on top of it what do you mean all mechanical. Iam trying to restore to original parts
Like Kshansen said, you have an all mechanical gauge. Looks like the OEM. That tube is very important, if you break the tube the magic is gone and it won't work. You can remove the sensor from the engine and put it in boiling water, or 250 degree oil, and see if the needle moves to the red. If not, you can tap around the gauge to see if it's just stuck, unusual for a new gauge but common in the old ones. OR, you can get the engine up to temperature, confirm by an temp gun, and tap around the gauge. If it doesn't move, then the magic has escaped
I always hated releasing the 'Magic Smoke' from electrical devices, just can't seem to catch enough of it to stuff back in!! I guess the same is true for the old capillary systems, release the magic fluid and all gone!
For the electric smoke you might want to contact Lucas to see if they have a 24 volt negative ground version of this product: And if you are really set on repairing a mechanical water temp gauge there are people who can explain how to do it: http://www.avi-plus.com/repair-tips...repair-of-a-mechanical-temperature-gauge.html Not worth the effort for something like a Cat loader, but if you have a museum piece antique car you want to be 100% original that's another story!
Good morning guys , I have 2 gauge coming one Eng temp and one converter temp. and one 40 Amp also coming. Called regal , they were happy to replace both of them. I am sure from the picture you noticed that I have a melt down on section of the harness . I inspected further and noticed that 40 Amp fuse is gone. there are 2 big orange wire connect to the fuse.n I guess that is something I have to fix.