Cat D8T Engine Miss Firing

[Kiwi Craig]

I am operating a Cat D8T here in New Zealand.
It has an engine miss firing problem, usually later in the day when fuel gets lower in the tank. No problem early in the day
We have had the Cat dealer look at it twice, but nothing shows up on their computer, making us think it may be a fuel issue. Have replaced the fuel filters early in the piece, but problem still persists.
The engine will go onto 5 cylinders, sometimes even 4, after 2 or 3 minutes it will clear itself and continue for maybe 15 or 30 minutes, sometimes longer before the issue returns. After it started doing this, they found the alternator was faulty leading to a spike in charging , which may have lead to damaged components, ECM etc. Everything is OK according to the Cat guy.
Does anyone have any ideas on what may be the cause.

 

[rmllarue91]

My experience with d8ts miss firing is injectors sticking mechanically will probably get worse usually to the point where when hot at low idle will smoke black with dead miss. at wide open throttle won't be as noticable. Can be tough to diagnose when it is acting up cylinder cut out will show stuck cylinder.

 

[Kiwi Craig]

My experience with d8ts miss firing is injectors sticking mechanically will probably get worse usually to the point where when hot at low idle will smoke black with dead miss. at wide open throttle won't be as noticable. Can be tough to diagnose when it is acting up cylinder cut out will show stuck cylinder.

Wouldn't that show up on the laptop diagnostics, that there had been misfiring, technician said it came up all clear?
Doesn't seem to do it in the morning, just in the afternoon. Can you think of a reason for that?

 

[Tinkerer]

"Later in the day when the fuel gets lower"
I saw it several times with 8N's. Defective fuel transfer pumps every time.

 

[rmllarue91]

Hey kiwi they will not though any codes if injector plugger mechanically sticks the solenoid on top will work just fine when it's stuck wide open. No guarantee this is your issue but it is possiblity. If it is fuel related try filling up at lunch or something along them lines to narrow issue.

 

[rmllarue91]

As far as I know only up to 2010 ish ( my experience ) on d8ts weren't capable of detecting a missfire like a car with nock sensors and such they just watch return volts from solenoid to determine injector issues.

 

[Kiwi Craig]

As far as I know only up to 2010 ish ( my experience ) on d8ts weren't capable of detecting a missfire like a car with nock sensors and such they just watch return volts from solenoid to determine injector issues.

Not sure what year this one is, it has the " D8T" on the side of the bonnet, not on side by fuel tank, so later model, it has done 6600 hours.
We tried filling up at lunchtime, but still did it once or twice, which isn't as bad as other days. Very intermittent which makes it hard to trace. Some days it gets really bad in afternoon.
With the fuel transfer pump issue, would that be the same on a 3406 in a D8N as a C15 Acert in a T?

 

[rmllarue91]

Here's my 2 cents wait till it gets consistent enough you can have someone on site when it's acts up we had one that was getting pretty predictable dad ran it for 3 hours started acting up all ready had et plugged in confirmed and changed it out. our local dealer will usually swap a set of injectors in this situation witch will fix issue but they are not cheap and originals seem to last longer than remains another thought would be try a fuel additive ( can't recommend one but there's always stories of magic additives ). I don't think it has anything to do with fuel level. Fuel pressure and volume of fuel flow usually make these boggy and such not missing like other engines in my experience and throw codes . fuel temp probably played more of a role do to cooling with more fluid in tank. This is assuming maintenance is affecting and dealer check fuel pressure and basics.

 

[Bls repair]

Have you tried to find missing cylinder with a non contact thermometer?see if it changes

 

[walkerv]

an injector mechanically failing wont throw codes as mentioned above if you can get it to do it non stop for a little while you may be able to pinpoint it with a non contact thermometer on the exhuast manifold as Bls repair stated directly above this comment , if supply pump tests out propper pressure and volumn as tinkerer stated above could be a problem , which is probably the cheapest option if you want to throw a part at it , that only really leaves throwing a set of injectors in it which is costly and time consuming as you have to take that mess apart and off above the engine . being a d8t im assuming that is an emmission model with def fluid like mine and having 6600 hrs on it if the emissions hasnt been serviced yet it was due at 5000 hr you didnt mention any emmissions warnings on display so maybe it was done already

 

[Kiwi Craig]

an injector mechanically failing wont throw codes as mentioned above if you can get it to do it non stop for a little while you may be able to pinpoint it with a non contact thermometer on the exhuast manifold as Bls repair stated directly above this comment , if supply pump tests out propper pressure and volumn as tinkerer stated above could be a problem , which is probably the cheapest option if you want to throw a part at it , that only really leaves throwing a set of injectors in it which is costly and time consuming as you have to take that mess apart and off above the engine . being a d8t im assuming that is an emmission model with def fluid like mine and having 6600 hrs on it if the emissions hasnt been serviced yet it was due at 5000 hr you didnt mention any emmissions warnings on display so maybe it was done already

Thank you for all your input and advice.
This one is not an emission engine, so none of those issues apply.
Sometimes it seems to drop 2 cylinders, sounds really sick then.
That's the problem, getting it to do it when we have the serviceman on site, you cant have those guys sitting around waiting at the rates they charge.
Its a hire machine, so unless we tag it out, they dont seem to care while we are just putting up with it. Trouble is we need it, working on major motorway project between Auckland and Hamilton in New Zealand.

 

[walkerv]

Thank you for all your input and advice.
This one is not an emission engine, so none of those issues apply.
Sometimes it seems to drop 2 cylinders, sounds really sick then.
That's the problem, getting it to do it when we have the serviceman on site, you cant have those guys sitting around waiting at the rates they charge.
Its a hire machine, so unless we tag it out, they dont seem to care while we are just putting up with it. Trouble is we need it, working on major motorway project between Auckland and Hamilton in New Zealand.

so it is a lease machine ? and they are charging you to fix a rental ? is that what im gathering here , if that is the case we woulda had it shipped back to them and told them to send us a different one .

 

[Bls repair]

X 2^^^^^

 

[Kiwi Craig]

Yes it is a hire machine, and the owner is paying to fix it, but we have to put up with the inconvience.
We actually had a second D8T , because we had so much trouble with the damn things. All sorts of issues, so when one went down we would use the other.
Unfortunately they have now taken the other one away.
I am a ' Cat Man' through and through, but this experience has shaken my belief !!!

 

[Bls repair]

All machines have lemons .If you don’t fix it,it won’t heal by itself

 

[Welder Dave]

Tell them to bring the other one back and you're not paying to rent a machine that doesn't operate properly.

 

[epirbalex]

Hi Craig , difficult to understand why two late model dozers are not up to the job . Is that one of Gough's technician's looking for the fault ? going by what I have read its long past due that some old grumpy bugger that knows what he is doing has a look at the problem . Was a time finding which cylinder is missing was simply to crack the diesel line on the injector , no change in sound , bingo . Pulling off a lead might be the go now but could poke the electronics . Won't make much difference to this dozer . Guess we can expect to wonderful low hour D8T's to grace the pages of Trade-me .