I have a 2017 t770 that would not start at all. It Would hit on one cylinder if I plugged number 3 injector. So I put new injectors in it. Tonight I got them installed and it would almost start but not quite. I put a pump sprayer of diesel to the inlet of the filter and now it will start but runs rough and dies slowly after about 15 seconds. I’m not sure I understand the cold return valve and whatnot. If I’m pushing fuel in the filter it should have plenty at the pump or am I missing something. I did add a clear inline filter after the filter so I could see if there was air and there’s none there. Is the high pressure pump bad? What else can I try. Next think I can do it replace all the fuel lines and the primer bulb. That’s what I was attempting to bypass with the pump sprayer but I’m not sure I did it right.
Going to need some pictures to see what’s up. How did you hook up the pump sprayer?
I moved it after the filter after posting here. But here’s how it is now. Still cranks up. Slowly gets up to 750 and then slowly dies.
Does it give any error codes? Low rail pressure "should" trigger a fault. Are the injectors new Oem, or aftermarket? If you can keep positive pressure at the pump the cold weather bypass should not matter. Next step really is to verify rail pressure with diagnostic software. You could try capping one injector again, and or removing the main drive belt to reduce parasitic load and increase crank speed. The thing of almost but not quite starting is familiar and usually indicates failing injectors. Are you familiar with checking return flow? Would require removing DOC to individually check return flow. On new injectors I have seen them "stick" and not spray at all till either "buzz" testing/ bleeding or if just one it will usually pick up after a minute or 2 or runtime.
I was just curious why capping one injector? I'm not familiar with that. Maybe a stupid question.
It’s is not showing any error codes on the display on the right. Before putting in the new injectors I had a rail pressure fault. The display on the left is unreadable
No, great question! A common rail fuel system is carefully sized, and a leaking injector can bleed off enough fuel, ( often to return) that the pump cannot provide enough flow to build sufficient pressure at cranking speeds. Capping one injector removes 25% of demand and often allows to start.
The injectors I put in are new Delphi injectors. It seemed to run good for a few seconds once or twice. I don’t see the injectors are causing this although I’m not saying they aren’t. I believe it has to be air still in the system or the common rail pump. I don’t want to change the pump without being sure it’s bad. Would this possibly indicate a failed low pressure side in the common rail pump? Two of the old injectors bypassed a lot of fuel when pressured up with an injector tester. I don’t have a common rail injector tester to activate the solenoid. Only tested with injector closed. Also The pickup clunk in the tank was pretty rusty.
The starts and dies suggests the pump can build enough pressure until the engine starts and requires more fuel. Adding an electric lift pump may help. Verifying and graphing rail pressure will be key. We have changed literally hundreds of injectors, and only several pumps. I would recommend a thorough diagnosis before changing a pump. .
Awesome. I’m setting it back in the shop now. Going to change some more fuel lines and get an electric pump on it. May be able to get rail pressure graph. I have a friend that said he has bobcat software on his scanner. Hopefully it will work with this machine.
Thank you that makes sense. I have seen rail caps for sale and now I know what they are for.
It had been making a bit of a belt squeaking noise when running. I assumed it was because of a misfire and didn’t think much of it. I took the drive belt off and now it idles around 1050 but the squeak was louder and sounded bad. So I took the serpentine belt off thinking maybe something was seized. To my surprise it’s still making the noise. I’ve never been in one of these motors. I don’t yet have any guess what it would be. I’ll see if I can put up a video later.
Maybe I have an engine problem not a fuel problem. This was the first time it ran this long and the first time I got it to idle up at all. It will idle up to 1350 but that’s all. I tried one more time and it sounds terrible. It’s not a noise I’ve ever heard an engine make. It’s doesn’t come through in the video very well but right at the end you can hear it start chirping. There’s still a fuel smell in the exhaust. I’m thinking a compression test is probably in order.
That chirping sounds like a pump loading up. Not very familiar with the V3800 engines but don’t think they have a cassette type pump. I am at a loss for the original knocking sounds, almost think I heard a detonation knock. Did think it sounded like a valve or a rod knock at first. Can you give some background information on the motor at all.
This is a D34 doosan. 2800 hours. Before I put injectors in it, it would spin over but sounded sluggish. (130 rpm) and when it would try to fire It would stall the starter. Plugging off injector number 3 would let it spin without stalling. And it would hit on one or two but wouldn’t start. Probably would have if I had pulled the drive belt. I thought #3 was hanging causing it dump fuel into the cylinder and making it hard to spin past. I probably should have bore scoped it when the injectors were out, but I didn’t think about it. I need to pull the oil cap off. It runs for a second and see what that shows.
It does not have excessive blowby.
That engine does not sound healthy
I’m right in the middle of pulling it out. We’ll see. Bolts that hold the pump bracket to the motor are giving me a fight. Are there 3 or 4?
I am not sure But usually the engine and hydrostat pump come out as one unit
Oh. I figured it was simpler to leave the pumps in the machine.
Took 3-4 hours to get the last couple bolts out and I have no idea how I’ll get them back started. May have to pull the drive pump just to bolt them back together. Found the turbo is shot for sure and the oil filter full of metal. Haven’t pulled the pan. I’ve had enough for today. Probably should have pulled it with the drive pump. But looking at it I’m not sure it would be easier. There are hoses you can’t get to.
Here is the T770 engine removal procedure from the service manual
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It spun rods and mains. So I will certainly be needing some parts. Thank you.
I see. I wouldn’t do it the other way again. It looks like I will probably have to pull the pump out to get the motor back in anyway. Getting those bolts out was hard enough. Getting them back in would be twice as hard.