07 AI400 missfire

[Dalton1]

I have an 07 CV713 with a AI400, I'm having trouble with a missfire on cylinder #6, for some background information I've had this #6 EUP break the hold down bolts twice in the past, about 20k ago and 5k miles ago. Both times eup was replaced as well as new bolts. 

Most recently I replaced all the nozzles. As well as re o-ringed all EUPs with new bolts. The truck ran great for about 40 miles, better than before with the new injectors. But then it started skipping, I narrowed it down to #6 cylinder, it was just streaming fuel out with the injector line when cracked instead of pulsing like 1-5 and no change in idle.

So I put yet another new EUP and bolts as well as inspected lifter roller and cam which both look perfect. I also found some damage wires to the EUP (from when the bolts broke) and repaired that.

I still have the same symptoms and am at a loss, there is no fault codes. Also when I jump the terminals on any EUP to test that cylinder the engine shuts right off instead of cutting just that cylinder. Also will throw codes for a short on all 6 EUPs, not sure if that is normal when jumping them. Any help would be greatly appreciated!!

 

[Dalton1]

To update, I checked all wiring going to #6 EUP, pins on the ecm and swapped EUP with another cylinder to make sure I didn't get a defective one, still no change.

[Joey Mack]

so you are getting an 8-9 code?  are you also getting a 9-2 code?  I preach this almost weekly here,,,,,  ground's - ground's - ground's..  

[Dalton1]

No codes at all unless I jump out one of the EUPs it'll throw low voltage codes to all 6 EUPs, is that normal?

I recently went through all the grounds on that TSB about the 9-2 code and it solved that issue. 

[Joey Mack]

how do the plugs on the EECU look?  are the pins dirty?

[Dalton1]

Pins aren't perfect but don't look to corroded, they have dielectric grease on them.

[Joey Mack]

just for kicks... switch the wires on the EUP..  I'm curious.. 

I assume valve adjustment was done by the book??

[Dalton1]

I'll give it a shot, yes valve were done by the book, problem came on very suddenly. Like that cylinder just shut off.

[Joey Mack]

ok

[Vmac3]

Clean off the dielectric. This doesn't help. Switch the injector out with a known good one and make sure you have everything clean. Let's keep it simple first. 

The pumps operate on 2 banks,

1-2-3 (bank one) and 4-5-6 (bank 2).

If my memory serves me right, I believe the engine ecu supplies a ground to switch the pump on and off. If you short out an injector all the supply voltage will drain to ground on that bank, and it will kill the engine. I might be wrong. 

V

 

[Joey Mack]

I didnt care for the di-electric grease either..  

[Dalton1]

I did swap out the 5 and 6 injector, problem stayed with cylinder 6, I'll clean up the pins on the ecu and connector, is there a best way to do that? Electrical contact cleaner?

Thank you for the help, that page out of the manual is helpful. 

[Joey Mack]

yes to elec. cleaner.. (Contact Cleaner) that is sensor safe.. 

[fjh]

So is there smoke accompanying this miss? Possible physical problem valve issue? Engine brake slave stuck? bent push tube!?

[Joey Mack]

Or a rag sucked into the intake port     ask me to show you???   

[Dalton1]

There's no smoke at all, the valve train appears to be ok and is in adjustment. Engine brake still works high and low so I don't think that stuck on. No rag in the intake but I would have been happy to find one! 

Tried swap wires on eup and cleaned ecu connectors with no change. 

I have access to a twin truck, would it be worth swapping the ecu? Or would it not communicate properly?

[Joey Mack]

we used to use ECU's for diag in the shop.. the base program is good..  good luck..  you did say the EUP lobe on the cam is good? 

[Dalton1]

Maybe I'll give that a shot next. I find it odd my scanner won't preform cylinder deactivation tests on any cylinder, always work before on that truck, makes me think there might be an issue in the ECU.

I did check the lobe and lifter both look perfect. 

[Onyx610]

Your ecu is failing, i bet you have much better results with a different one.    

[fjh]

16 hours ago, Joey Mack said:

we used to use ECU's for diag in the shop.. the base program is good..  good luck..  you did say the EUP lobe on the cam is good? 

Yup Joe we used to save the known good ECUs for that purpose  from wrecks  and such  we have several there sill  I believe ! Its better than pulling the trigger on the parts canon with out really knowing! ECUs aren't cheap! 

[Joey Mack]

Yes sir..   we would write any stored codes per/ test ECU, on the ECU with a paint pen, so that it would not fool us to think there are other issues in the truck we are diagnosing. 

[fjh]

1 hour ago, Joey Mack said:

Yes sir..   we would write any stored codes per/ test ECU, on the ECU with a paint pen, so that it would not fool us to think there are other issues in the truck we are diagnosing. 

Great Minds! 😁

[Dalton1]

Thanks everyone, I will try that next and update with results. 

[Dalton1]

Finally got the ecu swapped out, made no change unfortunately. 

When I cracked the #6 cylinder injector line it is a fairly steady flow of fuel and seems very aerated. Even makes small bubbles, no matter how much I bleed it.

Any other ideas? as I said previously it does this same thing with a known good EUP. Any chance the nozzle could cause this somehow? I don't see how but they are new so it's possible I got a bad one or installed it incorrectly. 

I took a video of the way the fuel comes out but not sure how to upload it, I'll work on that. 

[Joey Mack]

If the nozzle has a cracked tip, it will flow too easily.  Low injection pressure.