2012 CAT 120M no hot start

[fordtrucknut]

we have a 120M at the shop. running a CAT 6.6 ACERT

it will start and run fine until the observed coolant temp gets to around 170+/-deg. and you shut down the grader, it will not die and will run fine all day as long as it is kept running.

once shut off it will not start again until the observed coolant temp cools down to 140+/-deg, then it starts fine and runs fine again.

fuel rail pressure will not climb above 2500+/-psi on start up when hot (book says it needs 3625psi to start)**reason we replaced the injection pump/same issue with new pump**

we have gone through the CAT ETM and done every test and check there is.

we have replaced the cam and crank sensors, replaced the injection pump, reflashed the ECM numerous times. swaped out the booster fuel pump/water sep. with another vehicle.

their are only two things left to replace.... and the book says to replace one or the other depending on which test you perform....
ALL 6 injectors and lines.... or the Engine ECM....

We have even had a CAT mechanic that is there for our warrenty equipment, ponder over and help check it out, he too is at a loss....

 

[nowing75]

Have you done the injector bleed of test. Had a d6k do the same thing. Runs great just hard to start

 

[nowing75]

I might have miss spoke. Is that a common rail motor?

 

[fordtrucknut]

yes it is a common rail.
and yes we did a bleed down (today after my post) FAILED miserably....
put out 1925mL of fuel on a 3min run test...goal was 720mL
put out 138mL of fuel on the 30sec crank no start test... goal was 38mL

 

[nowing75]

Sounds like injectors should fix you right up.

 

[fordtrucknut]

I hope so....
funny thing is we have over 100 graders all of them painted either green or tan.... this is the only one that came from the factory with unpainted injector lines, and we just found out yesterday that it has been doing this since new... the instructors that teach the students just made sure to keep it running all day.....

 

[Mobiltech]

I had one doing the same thing. It was hard to start cold too but would not start hot at all. I did the bleed test and it failed terribly. I put in new injectors and it starts better then it has in a long time.
I made up a blocker line during the testing and was able to find 1 injector worse then the rest because my bleed off leakage was way lower without that injector connected. It would actually start hot with that one injector blocked off. We changed all the injectors to be safe though.

 

[nowing75]

Mobiltech did you machine up a dummy injector?

 

[Mobiltech]

Mobiltech did you machine up a dummy injector?

I found a plug to cap off an injector line. Then I unhooked each line from the fuel manifold one at a time and installed the capped line in its place. I did the crank leak test each time and when I had number 3 injector unhooked from the manifold my leakage rate dropped way down. It would actually start fine hot with #3 blocked off but not with it hooked up
You're supposed to replace the lines anyway so it was no loss if I damaged the line by plugging it.

 

[nowing75]

Good idea. Cat says there is no way to find the one leaking so they tell you to replace them all. More profit I guess. Lol

 

[Mobiltech]

I usually read the troubleshooting information from cat and then I find a way to do it easier in the field without all the fancy tools

 

[D11RCD]

I usually read the troubleshooting information from cat and then I find a way to do it easier in the field without all the fancy tools

Have you considered starting a thread sharing some of that information? Because it would be greatly appreciated by some of us newbies :waving

 

[caterpillarmech]

Cat has a block off kit to be able to test each injector. We use these to seal the rail end off to find out which is the problem child. The block off adapters are a rail side injector line nut with a machined blocker stud in it. I had a roller that would not fire . Ended up blocking off injectors and With #3 blocked the dang thing would build rail pressure and fire. Go figure.

 

[Mobiltech]

Have you considered starting a thread sharing some of that information? Because it would be greatly appreciated by some of us newbies :waving

That sounds like a good idea but it usually ends in a debate over how you should always follow the proper guidelines set out by the manufacturer or risk damaging components. Or something like that.

 

[D11RCD]

That sounds like a good idea but it usually ends in a debate over how you should always follow the proper guidelines set out by the manufacturer or risk damaging components. Or something like that.

Fair enough. Bit of a shame though... oh well.