Replacing the injector wiring harnesses; any advice or things to wath out for?

[Crunch]

After a long saga I think the cause of my P2146 code is finally isolated. The ECM has been eliminated as a problem, and now so have the injectors. Cummins looked at them under warranty and found no problems. And recently I took the truck to a dealer to get a second opinion on the injectors in case I had to push Cummins on the warranty. The dealer mechanic got the code to pop and checked the injectors but found no problem. The mechanic thinks it is one of the injector wiring harnesses (granted it might be both for the Group 1 injectors), so I am replacing both harnesses for the Group 1 injectors. I've already ordered them from Geno's along with 4 of the clips since they said the clips frequently break.

This will be the deepest I've ever dug into and disassembled this engine, so what should I look out for? The Dodge Repair Manual doesn't have a section specifically for replacing the injector wiring harnesses, but between the process for removing the breather cover and rocker housing cover I think I understand what to do. However, I don't have "tool XXXX" with the guide pins for holes #1 and #5, so I'm going to have to wing that when the time comes. I have a lot of small tubes and rods in various sizes I think will work, or I can cut the heads off a couple of bolts that fit the holes and threads if I have to.

Is there any other advice or things to look out for that I should be aware of? I'm also curious as to how long this job should take. Since I've never done this before, I'm guessing about 2 hours. Needless to say, I'm ready for this to be over. If injector wiring harnesses don't fix it, the only other link in the chain is the main engine wiring harness, which would suck.

Thanks.

 

[Ozymandias]

It is straight forward, been there done that, nothing unexpected to watch.

Only one thing - be very careful with the small nuts on top of the injectors, use a very small wrench on them and listen to your fingers closing them, you'll feel when they are tight.

Take your time, I guess it will be more then 2 hours working carefully.

 

[Crunch]

Only one thing - be very careful with the small nuts on top of the injectors, use a very small wrench on them and listen to your fingers closing them, you'll feel when they are tight.

Take your time, I guess it will be more then 2 hours working carefully.

I'm glad you mentioned the solenoid nuts. The DRM says to torque them to "1.5 Nm (13 in. lbs.)", and warns against overtightening them. I was planning on using my torque wrench, now I'll just use the small wrench you recommended, and be very careful when tightening them.

 

[Ozymandias]

So did I, this torque is so little, I liked it more by hand then with a non calibrated torque wrench.

 

[sag2]

And turn the wrench with a couple fingers, not your hand. Not sure what special tool they are talking about.

 

[Ozymandias]

Back then I used a socket with a screwdriver handle.

 

[Crunch]

And turn the wrench with a couple fingers, not your hand. Not sure what special tool they are talking about.

I'm not sure what "Tool XXXX" is either, but they are referring to the guide pins part of the tool. Presumably, it's to make sure the rocker housing cover is centered and seated properly and keep it from dinging something if it slips. Here's the quote from the Dodge Repair Manual, page 1553 Sec. 9-304:

"Install Tool XXXX guide pins (or equivalent) into the cylinder head at rocker housing bolt locations #1 and #5."

Clearly, I am going to be in the "or equivalent" category.

Back then I used a socket with a screwdriver handle.

I've got a nut driver style handle with a 1/4" drive on it. That and a deep socket, along with a three fingered application is probably the way I'll do it unless I use the two fingered wrench method. No hamming the handle like a motorcycle throttle, that's for sure.

I've ordered the parts from Geno's, but got an e-mail that one of the wiring harnesses is on back order for 4 or 5 days. When they get here I expect Texas weather to be in that perfect Fall sweet spot.

 

[Crunch]

I received the injector wiring harnesses and clips from Geno's on Friday. I'm going to install them on Monday. In examining the harnesses I saw that the connectors are round and have an O-ring to seal them to the rocker housing cover. I expected them to be flat on the bottom with a seal, but because they are round it looks like they slide through a hole in the rocker housing cover. Based on this, I'm thinking that I don't have to remove the rocker housing cover to install them; just the valve cover (I think the Dodge Repair Manual refers to this as the cylinder head cover). Is this correct? It looks like all I have to do is put some oil on the O-rings and the walls of the hole and carefully work them into position.

The only other possible complication I see is that because I am color blind I might have to put some masking tape on the old wires that run to one side of the injector solenoid to match them to the proper terminal. I'll place the tape in two spots and cut the wire between the tape, then remove the connector bracket. It all depends on how they look when I get eyes on them. If I can distinguish the colors that won't be a problem.

 

[cerberusiam]

It will be a lot easier to install the harness if you remove the riser. At this point it is time for new gaskets top and bottom.

 

[Crunch]

It will be a lot easier to install the harness if you remove the riser. At this point it is time for new gaskets top and bottom.

Thanks. This weekend, a combination of fortuitous events and seeing a YouTube video of the rocker housing cover gasket being replaced caused me to make an executive command decision. All but one of the YouTube videos I saw were pretty sparse in details. But one of them showed the rocker housing cover upside down on the bench and I was able to see how the injector wiring harness passed through to the far side. Once I saw that, I decided to go ahead and replace the third injector wiring harness for injectors 5 and 6 in Group 2, along with the gasket for the rocker housing cover. The Cummins shop is only about three miles from where I live, and it didn't make sense to replace just the two harnesses for the Group 1 injectors if I had to disconnect them from the solenoids for injectors 5 and 6 anyway and remove the housing cover to run the ones I had. The Cummins shop had the clips and gasket, but not the wire harness. It should be there tomorrow. The other events that helped me out here were that unexpected rain moved in, and is expected to stick around a few days. I also have a friend that needed help covering a 30' X 100' greenhouse with plastic before cold weather killed the plants. So all these things came together to force a postponement of the replacement. I would have been out there in the rain had I started this morning, and I wouldn't have been happy. Tomorrow is also supposed to be rainy, and maybe Wednesday too, so this is either going to be a late week job or a weekend job.

I may go ahead and get a valve cover gasket when I pick up the order tomorrow. But the Dodge Repair Manual states that it can be reused, and it was replaced when the injectors were replaced, is 10 months old and only has about 10,000 miles on it.

 

[Crunch]

The weather was perfect this morning, so the job got done. No real problems, and from start to finish it took just under three hours, including gathering and putting away the tools.

As I suspected, the hardest part was matching the wires on the new injector wiring harnesses to the terminals on the injector solenoids. The Yellow/Orange wasn't a problem, but the Brown/Red were so close in shade that I wasn't sure if I had it right. I used an old injector wiring harness to try to match them up, but got a neighbor to verify it for me before I reinstalled the rocker housing cover. I also just broke the old wire clips off to remove them since I was installing new ones anyway. Started the truck and it ran perfect

Since the Dodge Repair Manual suggest using guide posts to reinstall the rocker housing cover, and since I've never done this job before I made my own out of 1/4" wooden dowel rods by cutting them to about 3 1/2" in length. I figured they wouldn't scratch or damage any metal parts, and they were cheap. Worked like a charm, but I'm guessing that people who repair these trucks on a daily basis probably skip the guide posts altogether.

Thanks for all the help, people. Hopefully this fixes the problem for good. The only thing left is the main engine harness, and I'm hoping it isn't that. Now it's off to put a few miles on it and check for oil leaks. I may also pay a visit to Sears. The locking ring on my torque wrench split, so it doesn't lock. It still sets, but I have to be careful not to let it change the torque setting while I'm using it. I'm hoping Sears still honors their "lifetime warranty" for hand tools.

EDIT: And the day keeps getting better. I ran the truck about 20 miles to see if the P2146 code would pop, and it didn't. That doesn't necessarily mean anything because it's only popped once in the last two weeks. But it's a start. I also didn't have any oil leaks, so that's good. And to top it all off, one of my stops was at Sears to see if they would exchange my 30 year old torque wrench because of the split lock ring. They did. The new one looks a bit stouter than the old one, but the warranty is only good for 1 year. So all in all, this has been a good day.

 

[Crunch]

This is just a quick update on how this turned out. I've put about 1,000 miles on the truck since changing out the injector wiring harnesses. 500 of those miles were around town in varied driving. Stopping and starting, local highway driving at various speeds, etc. The last 500 miles were today on an out of town trip for Thanksgiving. At this point I am confident that the problem is finally fixed, as I have been code free since I changed out the harnesses. The return trip and the equivalent Christmas trip will seal the deal if the code doesn't return.

There was one hiccup, however. About 250 miles into the trip I started hearing the unmistakable squeaking of a bearing, which sounds like it is coming from the water pump. Seems like mine last about 115K miles before they start to go bad. Fortunately the pump hasn't started leaking and is working fine so far. So guess what I'll be doing this week before the rain and cold weather sets in? The real bummer is that there was a Cummins Central Power right along the highway 100 miles from my destination, but holiday traffic had me arriving 5 minutes after closing time. I'm really hesitant to put in an auto parts store water pump (I equate that with gas station sushi), so tomorrow I'm borrowing a family member's car and trekking back to the Cummins place to get a real one. And a thermostat. And making sure there are gaskets with both.

 

[seafish]

... I'm really hesitant to put in an auto parts store water pump (I equate that with gas station sushi), so tomorrow I'm borrowing a family member's car and trekking back to the Cummins place to get a real one. And a thermostat. And making sure there are gaskets with both.

Good idea on sticking with the OE water pump and thermostat!!!

 

[Prairie Dog]

I'm glad this seems to have cured your problem. I have to wonder how long before I have to address this issue. Kinda seems like the worst part is narrowing it down to the harness! Especially when it's intermittant!

Scott

 

[Crunch]

I'm glad this seems to have cured your problem. I have to wonder how long before I have to address this issue. Kinda seems like the worst part is narrowing it down to the harness! Especially when it's intermittant!

In researching it, I found out that it's not that uncommon of a problem either. That's reinforced by the fact that Geno's sells both the injector wiring harnesses and the clips for the wires. I look at it this way: If you replace your injectors yourself, you may as well replace the injector wiring harnesses at the same time. It's going to add less than $300 to the total cost, but save you about 3 hours of labor if you end up having to do it later. Plus you avoid the aggravation, and avoiding that is priceless. The labor is pretty much an additional 10 bolts: 7 on the rocker housing cover and 3 that hold the injector wiring harnesses in place. The parts are the three injector wiring harnesses, 6 wiring clips, a rocker housing gasket and the 6 O-rings that slip on to the valve cover bolts (I actually didn't replace these, as the old ones were still good). All are available from Geno's.

The dilemma arises if you have a shop replace your injectors, as they will upcharge the parts. Their additional labor will be about 30 minutes to remove, clean and reinstall the rocker housing cover. But then it's done and over, and should last as long as the new injectors.

As to how one or two (most likely one) of the wiring harnesses failed, who knows. Geno's says they do go bad, but since it happened a few months after the injectors were replaced I have to think it is related. I see three reasons and points of failure. First, the Cummins shop steam cleaned the engine before doing the injectors. It's possible that water got deep into the injector wiring harness connector and corroded where I couldn't see it. They looked fine to me when I examined them. Second, the connections at the nuts on the wiring harnesses where they connect to the injector solenoids. When the shop removed them they could have loosened the connectors or damaged the wires while moving them out of the way. Third would be damage to the wires between the injector solenoid connectors and the main plug connector. The wires are pinched between the ribs that span the rocker housing cover and the bolt channel in the rib. They are protected by a sleeve that covers the wires. The harnesses are subjected to cycles of heat and cold, and covered in oil for their entire life, so I can see how that would take a toll on them. There is no reason not to replace all three if you go down this road.

On the bright side, be glad you don't have a later model, where the wires are incorporated into the gasket. I think the dealer price on the gasket is about $800. Probably easier to replace, but a lot higher in cost and I've read that the design is subject to leakage.

 

[BigPapa]

On the bright side, be glad you don't have a later model, where the wires are incorporated into the gasket. I think the dealer price on the gasket is about $800. Probably easier to replace, but a lot higher in cost and I've read that the design is subject to leakage.

We're giving @ $125.00 for them. Cummins #5367847.

 

[Crunch]

Well, I'm back to square one on this. After changing the injector wiring harnesses on November 1 the truck ran great for 3,000 miles. I did a Thanksgiving trip and Christmas trip for 1,000 miles each, and another 1,000 miles locally. Then the dreaded P2146 code popped again in January. I limped home and tried clearing the code so I could track the problem, but my code reader couldn't establish a link. The last time a link couldn't be established I sent the ECM back for a warranty repair and the truck ran fine after reinstalling it, even though the shop didn't find an open circuit. They replaced the high side diode for, as they put it, "CYA". The P2146 popped again a couple of times before I changed out the injector wiring harnesses, but the loss of 3 cylinders only lasted a few seconds. I'm expecting my ECM to be returned this week after its second warranty repair.

I've had the injectors checked out twice--two times by the Cummins shop and once by a dealer. The ECM has also been looked at 3 times. Since it ran solid for 3,000 miles after I replaced the injector wiring harnesses and the ECM and injectors seem to check out OK I'm starting to think there is a problem with the main wiring harness between the ECM and injector wiring harnesses. That makes me recall the steam cleaning the Cummins shop did on the engine when the injectors were changed out. My thinking is that there was corrosion at the connections for injector wiring harnesses 1 and 2, and replacing them cleared up a lot of that. While the ECM has been out for repair I've hit the main wiring harness connectors with Deoxit in the hopes that would clean up the surfaces.

So my questions are can corrosion on the main wiring harness connectors can cause the code reader to fail in establishing a link? Are there sensors somewhere that can be causing this problem? And the big one, what does a main wiring harness cost and what's involved in switching it out? In looking at it I can see that it runs to more than the injector wiring harnesses, but since it is bundled up and shrouded with the protective tube I can't really tell how it fits together. Is it hard to switch out, or is it just a matter of disconnecting things one at a time and removing the bundling and electrical tape to trace it back?

It's really a bummer, since after all kinds of driving and 3,000 miles I really thought that the problem was solved. If it isn't a sensor somewhere the only remaining link in the chain is the main wiring harness. Jiggling the wires at the connectors hasn't helped. But since the only code being thrown is the P2146 I'm thinking it has to be something in the wires between the ECM and either the first injector wiring harness or the two wires for injector 3 on the second injector wiring harness. Definitely befuddled about this.