jzack

Here is a follow up for those who came here on a search for a fix for cracking fuel lines. After going through multiple sets of lines from Mack, all developing cracks in multiple areas, I have since moved on to fuel lines from PAI for the E7. Thier lines actually look like my originals, a full .25" diameter, double nut with vibration damper at the head. So far so good, I'll keep this updated. Now, with that experience, and an in-frame scheduled for the first week of November, I'm seriously thinking of getting the PAI re-build kit instead of the Muzzle Loader from Mack and probably save some serious money. I've always been a "Mack only" parts guy, but so far, I am very impressed with the PAI fuel lines.

Thanks for all the tips on the input seal, I'll make sure to look for a groove in the shaft. I might try a novel way to pry out the seal I saw on a video the other day. The guy carefully drilled a small pilot hole in the top of the seal. He then screwed in a tall screw enough to grab the seal. Then grabbed the top of the screw with a pliers and used the top of the input shaft for leverage to pop it right out. No mess, easy peasy. If that fails, I can try the messy way!

Well, I'm back at work! All that was done was the re-built pump and replaced all the frost plugs on top the head. Mack said everything else looked good. Fingers crossed I guess. The truck seems to sound and run exactly as it did before except a little stronger. The only issue I have had so far is a leaking input seal on top the steering box. Hopefully it just needs a new seal. Maybe the over-run caused higher pressure in the system blowing past the seal? I'm also hoping my issues with cracking injector lines could be solved. There is much less vibration on the lines now with the new pump. I've had to replace lines 4-6 several times the last six months. Oh, and after driving the 2023 KW T880 for a week, I wouldn't trade my 94 Mack even up. Seriously, trucks have not come as far as you would think in the past 28 years. The ride in that KW was horrible.

Ok, I'll ask about dropping the pan to inspect the cam. The mechanic working on it has been working on Macks for 29 years and really knows his stuff so I trust his opinion. Even though this engine has 1.3M miles it wasn't showing any signs of being on its last legs. I've maintained it since new with regular filter/fluid changes, did the overhead every 300k or so. In fact, the overhead was just done in Dec. along with new injectors.

Thanks fjh. I'll make sure and ask the mechanic about the lifters. I'm curious now.

Well, Mack says it was the fuel pump, no big surprise. Sending it out to get rebuilt now. The oil looked good, no metal. Valvetrain also looked good, other than a couple of frost plugs leaking. The mechanic said he will put the rebuilt pump on and see how it runs. He did start it briefly already and said there wasn't any bad noises. Thinking about putting it on their dyno to see if it can put power down without any issues after the new pump install and go from there. Picked up the T880 today. Kind of surreal going from a 28-year-old truck to a 28-day old truck LOL!! I can already tell my Mack has a better ride. The KW ought to really go though with a 510HP/1,850TQ and 12 speed auto. Amazing they can get that from a 12.9L.

Joey Mack, thank you, I appreciate the sentiment. I was literally across the street from our local Mack dealer when this happened, so I thought it was fate to have it towed there. They do have a few old timers left there that really know their stuff and I'm friendly with the service manager there. I wouldn't hesitate to have them do a full re-build but the $$$ would be crazy. Hopefully a pump is all it needs to get it running, then I can bring it to our shop for a full re-build some time in the near future. I'll keep you all posted.

fjh, thanks, maybe I should consider myself lucky here. The tow truck driver said that many times a runaway engine ends with the truck burning to the ground!! Also, as luck would have it the boss (my sister) is leasing me a brand new 2023 Kenworth to break in while my truck is in the shop. Should be interesting, I haven't driven a new truck since I started driving my Mack in 1995. At that time, it was the best truck I had ever driven. Probably why I kept it so long.

fjh and LtK, very good info, I'll definitely take into account. Thank you!

Joey Mack, thanks, I'll make sure to check the top end and pay attention to the oil. As far as the turbo, I didn't see oily residue in the stack. The accelerator issue (cutting out) and electronic malfunction light don't seem to point to the turbo. The idle had a slight lope to it right before this happened too.....

67RModel, thank you, yes I'm local so I could go in baby steps like you said and see how it responds. Thinking about at least pulling the valve covers and inspecting, send the oil out for analysis too maybe....I would think the shop would have a check list before starting a runaway engine either way. My mechanic mentioned rebuilding or replacing the Econovance too, but they are NLA and the pump shop said they don't work on them either.

Well this was an awful experience. Been driving this truck for 28 years with no major issues. Over 1.3 million miles, 45,000 hours all original engine, even down to the turbo. I left with my second run for the day and the accelerator started acting funny. When I would let up to grab the next gear the RPMs would immediately drop too fast for me to grab the next gear, then they would come back. Like the accelerator lost signal momentarily. Did this twice, then the electronic malfunction light came on and the engine de-rated. Great I thought. So I started moving to the shoulder, pushed in the clutch to grab a lower gear and, BAM the engine immediately went WOT!!! Of course I panicked for a second, turned the key off, no response from the engine. I got it pulled over, remembered reading about runaway engines and what to do, so I grabbed my jacket and stuffed it in the air cleaner intake. That slowed it down to what sounded like a safe RPM but she kept going! White smoke pouring out the exhaust. Now what? Next, I grabbed a wrench and started to crack loose the fuel line to the filter tree. Two or three turns and it finally shut down. Whew!! Not sure how long it ran like that but probably a good 2-3 minutes at least. So disappointing, I'm sure anything in or attached to the engine will be suspect for failure now. An old mechanic at Mack suspects something gave way in the injection pump. We'll see I guess. They are a week out on service work. Three weeks to re-build the pump maybe. The worst part is, short of a full overhaul, not sure I can trust this engine again. Am I right? Before this, she was still running strong with no issues or symptoms whatsoever. On a side note, my Old Man, who I love but enjoys Monday morning quarterbacking, said I should have jammed it in gear and side stepped the clutch? Not sure the drivetrain would have enjoyed that experience though.....

Interesting, maybe I'll try that when I finally get to the end of my rope on this.

I've got a 1994 CH with the E7350. Back in December I replaced #4,5,6 injector lines. They were leaking at the head. Now 4 months later all three have failed with small hairline cracks behind the nipple at the injector. Mack has been warrantying the lines but I'm really growing tired of replacing them every few months. Yes, I make sure all the line clamps are good and tight. The lines stay dry for weeks, maybe months and then bam, they start dripping on the manifold. My original lines were 0.25" OD, the new OEM ones from Mack are 0.23 OD I noticed. I let Mack know about this.... Do I have any other options here?