6 Hole Multec Injectors? 7.4L Vortec

[Tom P]

Was always under the assumption that the OEM Multec injectors on the 7.4L L29 engine were single hole? The ones I just pulled to replace with the "bosch replacements" are 6 hole? Wondering if I should even be replacing them?

 

[Christian Steffen]

Thats a good question, I can't remember for sure what mine were (its been like 4 years) and a quick google search was no help. Hopefully someone that has their old set laying around will chime in, otherwise I'd just swap them for piece of mind.

 

[Tom P]

So I'm going to admit something here that I'm not really proud to admit. I did the swap months ago... The reason I said "bosch replacements" were because the injectors weren't even bosch's... scammed on eBay so let buyer beware. Unfortunately this scam and my own oversight coupled with some ignorance of the previous owner put my family in a reasonable amount of danger while we were on vacation. When I did the injector swap I accounted for the orings of each injector I took out. Apparently, the last time the injectors were changed, not all the orings were accounted for and at least one or two were left behind. Thus once the new, fake bosch injectors were installed created a leak because the injector was not seated properly. We were pulling a mountain pass towing our travel trailer when the injector blew out of the common rail and dumped about 1/4 tank of fuel along the highway. When I was able to pull off the road, the truck died so I shut the key off, popped the hood and saw gas boiling on my intake manifold. Had I not replaced the cracked spark plug wires the week before we left, i'd probably be showing you guys pictures of a burnt hulk. Luckily my wife and two daughters were able to get out of the truck safely and jump into my parents truck. Long story short, had to tow the truck to a shop 45 minutes away where they discovered my injector blew off because of additional orings, and while they were about to reassemble it noticed that the injectors I installed were not bosch, but some crappy alternative used in some volvo applications. So i spent a small fortune to have the OEM Multecs installed because the shop refused to put anything cheaper back in. I was on vacation and had few options and no room to argue so there we went.

 

[Christian Steffen]

Man that's a ****** deal, but it could have been a lot worse, glad it wasn't. Ebay is indeed a dangerous place to injector shop.

That really sucks having a shop do something you could have done yourself, at a premium price for the stock injectors.

Honestly, if it were me I would run the oem injectors until they show some sign of issue. There's no way that they are going to be garbage from the get go, it seems like more of these trucks don't develop the hard start issue until after 100k miles (someone can correct me if I'm wrong, just my experience). So I would run them, at least for awhile until you forget about how expensive they are, then upgrade down the road.

 

[Tom P]

Yes I have very much learned my lesson and hopefully other people can learn from my mistakes. And of course because the injectors were installed back in February I have no recourse with the seller so I'm screwed there too.

At first we were going to sell the truck. Once something like that happens it leaves a bad taste in your mouth, however now that the fury has calmed down a bit I realize I still really like the truck and instead of spending more money on a truck I dont want to make payments on, we will just keep this one and fix it up further. So now I have a few things that need to be upgraded including exhaust, and some stuff that needs to be repaired like rusty leaf spring mounts and front end bushings and tie rods. Wondering how much longer I can go before an engine and tranny rebuild will be necessary. The thing is a gutless pile pulling a pass. My 2004 Nissan Titan would have walked away from this truck pulling the same trailer up the same pass and would have averaged an mpg or two better while doing it, and engine and tranny overheating wouldn't have been an issue either.

 

[Christian Steffen]

When you say rusty do you mean rusted through, or surface rust?

How many miles are on it? Exhaust and a tune will go a long way to wake these up. The stock power enrichment delay is like 60 seconds, and the timing is pretty conservative. Adding a cam will help quite a bit too. The mileage while pulling mountain passes probably won't get much better, but cruising should get better and it should well outperform the titan ( I'm a little surprised it doesn't in stock form).

How hot was the engine and tranny?

 

[Tom P]

Not exactly rusted through, but metal is flaking off at a rather alarming rate. Truck came from BC, Canada where they use nothing but massive amounts of rock salt in the winter Luckily only the back half of the truck is cancerous.

I was down to about 40 MPH near the top of the pass at 3000-4000 rpm in second gear and losing speed fast. Truck has 175K miles on it. I put a 180 degree thermostat in the truck when I bought it and she heated up to about 220? My gauges are all in metric but it was over the 100 degree Celsius mark (~212 F?). Not boiling over by any means but took about 15 minutes of running at an idle to cool down. No tranny temp gauge but I checked the dipstick and it smelled pretty hot.

My titan did the same hill two years earlier pulling at 55mph and the engine temp never faltered and the tranny didnt even come close to max temp.

 

[Christian Steffen]

Have you ever changed the transmission fluid? Might not hurt. I can't remember, what year is your truck? Mine has a temp sensor in it, but you have to read it through the computer. I wouldn't get concerned about the engine hitting 220 degrees.

What gear ratio is your axle? Just doesn't seem like a titan should outpull it.

Do you know the history of the truck? Was it used hard? My engine was pretty much worn out at 180k, but that was 180k of mostly towing.

Transmission should be fine if it's well maintained and kept cool.

 

[Tom P]

I have not changed the trans fluid yet. Its on my list to do a complete drivetrain fluid change, but its still fairly clean looking and doesn't smell burnt yet. My truck is a 2000 so I'm guessing it has a temp gauge installed as well. I guess I'm not as worried about the tranny as I am everything else. I read a thread somewhere where a guy was disputing the argument that a lower temp thermostat actually helps your truck run cooler while under load. Without going into too much detail he argued that when a say 180 degree therm is installed, it spends more time open and the coolant spends less time in the radiator cooling down. Under normal driving conditions this isn't an issue but when you're pulling a hill in 90 degree weather you need that coolant to spend as much time in the radiator as possible. The other thing that was noted was the water coming into the radiator isn't always hot enough to cause the fan clutch to kick in thus taking more cooling capacity away. And when you have the A/C going, the auxiliary fan wont kick on unless the truck is reading like 200 degrees or so you lose some capacity there as well. Again, just a theory I read. I may swap in a 195 degree thermostat before winter.

The truck was used as a tow horse. Had a 5th wheel hitch as well as camper mounts. The most recent owners pulled a 5th wheel with it. They're a retired couple that used to go between campgrounds almost year round before finally landing at a semi permanent campground and becoming the hosts i suppose. Of course they sold it because it needed a ton of work which I know now. But the truck is straight and the interior is in great shape for its age. Needs a massive cleaning though. I'd like to rip the interior out and clean it and either put down some sound deadening material or like a rhino liner on the cab floor. I'm also chasing a short in the power door lock circuit, which i believe also has the main cigarette lighter and the lumbar support pump as well. And there's a short in the cabin lights as well. Put the fuse in and its lit regardless of whether or not the doors are open.

 

[Christian Steffen]

If you get an OBD bluetooth adapter and torque pro on your phone (if its android, not sure what the options are for IOS, this is also assuming you have a smart phone), you should be able to read the tranny temp, plus monitor other stuff like fuel trims which helps for troubleshooting and monitoring those injectors. As far as the Tstat goes, I'd just run the 195 all the time, or you could compare the two while its still hot out. If you got a mail order tune for the truck, you could have the aux fan turned on earlier than 200*.

Is the body clean, no rust? If so it is worth the work to get everything else fixed up.

Does it have good oil pressure when hot, >20 psi? Might not hurt to do a compression check.