MP7 04 model missing erratic

[br549]

2000 miles 1 trip missed 1 time, cut off engine start back up fine. Next trip 800 miles missed 2 times. on the return trip Missed 13 times till got back each time he would cut truck off and restart than it would go for a while. Code in system 128 sid 5 fmi 5 13 times. Truck starts easy and idles good, Drove for 1 hour this morning and cannot get it to do anything. I know it has to do with # 5 injector. When you get injector seat gasket blown will it show the same injector or various ones with air in system, I hear they are hard to start with air in system but this truck stars easy.. About 80,000 miles ago head was replaced, along with new wiring harness. truck has 590,000 on it now, and ideals

Its BACK We replaced #5 Injector and has run about 30,000 miles. This last trip about 2400 miles it started missing on #5 again. 128 SID 5 FM 5. You can cut off truck and restart and it will run fine for a while. I found the package were we replaced the harness in November of 2012 and it showed a package date of 10-12-1012 I would think it should have the new terminal on it. any ideals? 1-24-14

[Challenger]

FMI 5 is an electrical problem. Open circuit, Bad injector, break in the harness or bad EECU. First guess would have been a bad connector to #5 injector. Mack had problems with the connector terminal heating up and loosening. But since you already replaced the harness its probably a bad injector. If it was me I would replace the injector.

The air in the fuel system would be from bad cups. You would have, hard starting, low power and maybe injector codes with FMI 7.

You could swap injector 4 and 5 and see if the code follows the injector. I would replace the injector and be done with it.

[Mackpro]

Unless it's missing all the time, For an injector code with an FMI-8 we just replace the harness end. Be careful as the harness will be brittle and the insulation will break off. I have put alot of these on over years. Mack says replace all ends but if the harness is brittle and coming apart when you touch it, I usually just replace the bad one. But its up to the customer if he wants to risk damaging the harness to replace all ends. My friends MP-8 has almost 800000 miles on it with orignal harness and I have replaced 2 ends on 2 different ocassions. His truck runs fine but his harness is about toasted. In his case he would rather be down a couple hours 2 times versus having a new engine harness installed taking at least a day or more( depending on who installs it). The injector harness and the rest of the engine harness is all one piece.

injector harness.pdf

[staxx]

Check where the injector harness goes over the oil control valve under valve cover have seen a lot of pinched harness there . If harness is not tied back in correct position it will get crushed by the valve cover and eventually get cut on bottom side and shot to ground on top of oil control valve.

[boyd]

Also these injector harnesses are notorious for engine oil seeping down inside the harness itself and causing the wires to rub raw within the loom and causing shorting issues,, it will normally happen 6-8 inches from where it comes out of the rear of the engine..

[turckster]

With a FMI:5 (open circuit) and happening intermittent, I would guess it was loose/bad terminals on the inj. connector. We have seen a few '04 emission engines, even with new/fairly new harnesses, still have issues like what you describe. I'm not sure if all the '04 emission harnesses got the higher tension terminals.

Last week we had a truck with the same issues you described, has a new harness. The injector connectors didn't feel like they had enough tension when you pulled the connector out of the injectors-kinda loose. We replaced all the terminals with the higher tension ones and the connectors felt "tighter", problem solved.

[Rogerhays]

I have a 07 Mack mp7 it will do this daily it starts and runs fine as the day goes on it will start missing I stop and shut the truck off and let it set for 2 minutes start it back up and will run fine the rest of the day. Just had an overhead done and it didn’t do it before then

[steeler]

On 12/3/2019 at 10:58 AM, Rogerhays said:

I have a 07 Mack mp7 it will do this daily it starts and runs fine as the day goes on it will start missing I stop and shut the truck off and let it set for 2 minutes start it back up and will run fine the rest of the day. Just had an overhead done and it didn’t do it before then

All of the above advise applies here also. Very well could be that the harness is pinched between valve cover and oil valve, or bad terminals at injector.

Figure out which cylinder is the culprit first.

As far as the new harnesses having the high tension terminals, I've ran into both 04 and 07 emission new harnesses that do not have the new terminals. The last harness I changed out, I replaced the terminals before I put it on the engine. (After I confirmed it didn't have the good ones)