So I have this skidsteer that is not throwing any codes related to fuel. It's a hard start, the only ways I have been able to get it to start are by using ether or bleeding the injectors on the high side, yes I know your not supposed to do the high side. The low side was bleed first. If I bleed the injectors it start and runs fine until I turn off then will not start again unless I bleed again. Look at some captures I see the high pressure if building during crank, but at soon a key is turn off the pressure immediately goes to zero, the other thing to note is there is a fair amount of fuel coming back to tank thru return during crank and Im not sure that is normal or not, seems like when pressure drops maybe if letting air back into the injectors and that's why it won't start without bleeding again. Here are a screenshot and video of what I am seeing. Thanks for the help. Video link iCloud Photos - Apple iCloud View, organize, and share photos and videos with iCloud Photos on the web. Changes will sync across your devices with iCloud. share.icloud.com
That nasty rasp, sounds a lot like a compression issue. Try spraying WD 40 into the intake and see what it does, without the air filters. How many hours on the machine. Is it possible, the machine got sanded. Be very curious what a wet vs dry compression test looks like.
I would look at rail pressure when cranking sounds like a bad injector
It has lots of hours not a new machine by any stretch, it's what I could afford... Any idea how I would take pressure reading other than using ET, with ET it shows it builds during crank and goes to 0 when it stops cranking (screenshot in post) Im not sure if that's normal, build high pressure then drops immediately
I get why you’re thinking compression, especially with many hours, but what keeps pointing me back to fuel/air is that once I bleed/prime it, it will start on diesel and then run fine. If it were mainly a compression issue, I would not expect bleeding the fuel side to be such a repeatable fix. I’m not ruling compression out completely, but based on the behavior I’m seeing, fuel prime/loss of prime seems like a problem
Does rail pressure go above 1400 or 1500 cranking??
In this screen shot it hit 1250, I would have to go back and look at another log that was recorded but I want to say the pressure was meeting the requested amount during crank. I attached a screengrab, the blue is fuel delivered volume and pink here is rail pressure when cranking
Will it start on it's own with booster cables hooked to the battery and being boosted?
Cat used to have a plug kit to block off injectors at the rail so you could find a bad injector you blocked them all and see if pressure went up I’m thinking 1250 is too low
Check the overflow valve on the end of the rail.. If the spring is broken, the fuel won’t hold and ends up back into the tank.. Good luck
I haven't tried that, the battery is new and I charge after every time I work on it
So this is the part I suspected, but Cat does not have a part number for it, after visiting a dealer they told me you can only purchase with the entire $1,500 fuel rail. I also was able to speak to a tech while there and he verified that relief valve should never release fuel unless there is some type of extreme fuel pressure issue, like over 30k plus psi. When I removed mine I could easily blow thru it both directions, on mine it's actually a Kubota engine, I found one online and I'm hoping this resolves this issue.
You could be right as I'm told and researched these systems when running should have about 20k plus psi. So maybe once the leaky valve I found allows it to build up higher pressure when cranking
The system normally operates at around 10k psi. That's one reason why it's not advisable (or safe) to attempt to bleed the HP system at the injectors. The relief valve on the end of the fuel rail is designed to open at 30k. The attachment may help you understand the fuel system a bit better. You can often, although not always, find parts for the fuel system via a Kubota dealer.
Thank you, so that agrees with what cat is saying, the valve should be 100% closed at 7,300 psi or lower and open => 36,300 psi I did call Kubota with my engine model/serial and they can see the engine in their systems, but do not have access to sell parts for the engine, I'm guessing even though it's their engine, Cat has all the rights to it.
That engine should be very similar to the one used in a Kubota svl90-2. (Newer serial would be closer to svl95-2) Differences do exist in the fuel rail and lines though.
It is too low. I don't have the exact spec in front of me, but I'm thinking a minimum of 4000 to 4500 psi before injectors are fired. The rail relief is a good start, also check injector return flow. (Separate from rail relief and pump return)
Sorry. Posted in the wrong thread.
Nice I will look up that engine model if the part doesn't work out.
You're right on the money, so I replaced the rail relief valve and now it no longer has fluid coming out from there. Weird thing is started right up on first try, i shut off after a few minutes, then it would not start again. So I went back looking at et and the fuel rail demand is around 4200 psi but the rail is still only reaching around 1200, so either something is loosing pressure or the hp pump is t getting commanded on or not functioning completely is my guess,,,, do you think it's safe to say the hp pump is somewhat being activated if it's hitting 1200 psi? I think I'm going to try and bleed the low side again to verify there is no air in there, do you know what the low side pressure should normally be, seems like last time I tried to measure it was in the 14-35 I really cannot remember it's been a few weeks since I tested that.
Injector return is the fuel return from each individual Injector. On your engine the return line is under the valve cover, however, it is possible to separate the Injector return from the rail relief and pump return to at least see the total return flow from all 4 injectors. You cannot diagnose which Injector may have failed, but for a no start condition we only want to very that there is basically zero flow from the injectors while cranking. This video shows the test on a running engine. The attached image shows the return line circled in blue, and the external test locatin circled in green. Again, you want nearly zero fuel here while cranking.
Seems like a good quick test to do, I was look at getting some rail blank caps for the injectors hoses and see if the pressure goes up, but this seems like a faster way to see if there are indeed leaking if I understand you correctly. Was there a video link, I see the image. Thanks
The link is the word video , it is slightly grayed.
Ok I find the video, thanks, being frustrated I ended up capping of the 4 injector ports at the rail and the actual pressure is now the same as the desired psi, this machine sat for about 3-4 years so maybe fuel decay or water in there at some point? So does this test not 100% prove there is some leak at or around the injectors?
That is likely so. Injectors are the most common failure. I wouldn't actually advise capping all 4 injectors, as there is nowhere else for high pressure fuel to go and could end up popping your new rail relief. After too many relief cycles the relief tends to fail. . .
Now connect injectors one at a time and see how pressure reacts
Ok, thanks for the advice - I only did the test once and wont do it again that way. Because of how the metal injector tubes are routed and without bending them, I may have to either remove the valve cover or remove the piece where the EGR housing is (see picture) because there are some brackets that hold all the tubes together and without bending them it's difficult to attach a test fitting to and individual one. But please tell me, at this point, after my last test..... it really doesn't matter how I go about it, the valve cover is going to have to be removed no matter what to fix the problem, correct? I have heard maybe a cleaning might fix it if there is no metal debris, or rust in the injector. In theory I guess as a quick test I could send a small amount of low pressure into the overflow line that exits the motor that you first mentioned and I think I would hear which individual injector(s) are leaking I suppose?
On the topic of Injectors, my CAT has a Kubota engine: Engine C3.8 Arrangement 345-3555 Serial 2GL0419 And the least expensive set I have found is $800 for a set of four, but I came across these and to me they look like they are exactly the same as the ones recommended but only $400 a set, 095000-9690 1J500-53051 And I was able to cross reference them thru and 3rd party, https://www.dencodiesel.com/product...gnUYmoTeTTdj4RKC3PDlFQ0-5-Y1_Bnc4bxAOgJz3h61O I'm just wondering if I need up replacing has anyone gone this route and is it best to just replace one or all while I'm in there..
The old adage. “Buy cheap, buy twice” (or maybe more than that) comes to mind, especially when you are talking about fuel injection parts. Not sure if @ozarkag can give you some direction but a Kubota engine outlet might be your best source for replacement injectors.
Well by least expensive and the angle I was was coming from was I meant buying from Kubota and paying Kubota prices instead of paying CAT prices for a Kubota engine.
Gotcha. I misunderstood what you posted.
So this was unexpected...when I removed all four injectors that all just slipped right out, I was expecting some resistance from the seals when removing, but they all literally just lifted right up with no pressure.. I wonder what caused this and why