JoeH

On 1/25/2024 at 3:41 PM, DirtWorx said:

1999 Mack RD688S E7 misfire under load, cuts out sporadically - injectors, EUP, ECM, or wiring harness?

1. Engine runs correct under normal operating conditions unloaded.
2. Engine cuts out sporadically for a split second then comes right back on when loaded or unloaded.
3. Engine sputters under uphill load until throttle is decreased.
4. Engine injector(s) disengages and reengages sporadically under uphill load.
5. Diagnostics shows injector 2 and 3 low voltage.

Find a solution yet?

EA7 is an Australian E7/ETECH i think. On the engine I'd expect the harnesses to be effectively the same.

Id be fixing that motor asap, that's a nice R model. Great history, sorry to hear about your dad's passing, but glad you've got his friend around in your life.

This project chose me, I didn't choose it! Big difference lol! I didn't want my truck put into a ditch!

Your point #2, is the engine shutting off momentarily? This will likely be a loose fuse for the EECU, I'm guessing this fuse is in the fuse box under the hood. With engine running, wiggle the EECU fuse. It'll probably stall out. It should trip a blink code 9-2 I believe. If your fuses aren't labelled in the box lid then just wiggle the fuses one by one. You'll need to pinch the fuse slot connections a bit tighter, and maybe bend the fuse legs a bit to create more connection. That's what I had to do on my MR688.

Sounds like an issue with your #2 and #3 EUP's, anyone able to elaborate on what to inspect? I'd start with inspecting the wiring harness for any rub through, and make sure those 2 injector screws are tight.

46 minutes ago, mrsmackpaul said:

A bit of fair sized task your under taking 

I did something similar on a farm ute years ago

I was stunned when I put it all back together that everything worked first go

 

 

Paul 

 

I'm about $200 into a label maker, between buying it and buying 4-5 roles of the vinyl cartridges that go in it. Pricey, but the utility value is massive.

This harness will go into storage incase we ever need to utilize it and the engine. I'm sure hoping everything works once I get it all together. 

Still need to strip this cab down further, patch a hole in the floor, replace some seized rivnuts, pull windshields, sand down and paint the cab, and a myriad of other tasks. Probably needs a heater core.

The rear window in this cab was a slider, but I'm opting to put the solid rear window from our busted cab into it instead, since the VECU is located just inside the rear window.  Not taking any chances on rainwater finding it's way to the VECU.

He's a narcissist. He loves the center of attention. Some people villainizing him galvanizes others to love him even more.

My brothers and I all learned to drive on my dad's 1979 R686ST. Video e it for 6 years while we built a volumetric mixer for a 95 RD688S triaxle we bought. Now I've been driving that for 9 years, and we're phasing the '79 into backup/retirement.

I like R's. 🤓 Though I do like that Pete, that's the body style I'd chase if I bought a Pete. Though the hood fenders don't have good off-road clearance. Mack's were built for on and off road. Sat up higher.

A nice coat of paint and that'll be a sharp looking Pete. What else does it need other than tires?  Does it have braided airlines or synflex?

Even just a picture of the R by itself is ok ... 🤠

"Deleted" you'll be on your own to fix, dealer probably won't want anything to do with it, so be prepared to work on it yourself.

Generally Mack's and "deleted" is nothing but problems, but I have no experience in the matter. Just what I've heard. Personally I cringe at the thought of buying an MP engine, but the reality is it's gonna have to happen someday. Injector cups are a regular maintenance item or so I figure from a lot of talk about them in the past. Timing gears are all on the backside of the engine I think, which sounds weird to me. Not sure how others feel about that.

What year? The ETECH and AI/AC engines have a fuel gallery drilled through the block, and there's a plug at the front end of that gallery that's inside the timing cover. This plug can come loose and let fuel into the oil pan. But you need to give us more specifics on engine year so we can know more about what you're working on.

43 minutes ago, Macktruckman said:

Ill post up a picture of it if its ok to post a pete on this thread ?  I don’t know the rules very well. 
Josh

As long as there happens to be an R model posted with it I think a blind eye will be turned to the Pete...

Wow that is clean. That truck is a gem.

I'd expect the engine and transmission plus mounts to match, but I don't know what engine/trans you have, I'm unfamiliar with a 747.  Frame I'd assume would match an RW700, I think the first number digit indicates frame profile, though maybe not because the dm600 frame is way different from an R600, though I think they share engine/trans mounts. The U600's have the same frame as R600's though. I borrowed a U model frame rail front half to splice into our '79 R686ST that cracked vertically. Didn't have to drill a single hole.

Those doors look awfully similar to R model doors. 

I will add that our DM was overheating running the blower motor for unloading cement.  Swapping over to the fixed fan made a world of difference. Old fan clutch was probably worn out.

This truck is a good worker for you, I'd swap the fan clutch and see if that helps.

Which cabover model do you have? Just curious what radiator it has.  Our MR688 has a monster radiator. Tons of cooling. Probably half again the size of a typical R model, and the same engine. 

I think the brass fitting cracked that threaded into the intake manifold, and it has some sort of a filter screen in it and it was seized into the manifold, so we just deleted it. This truck doesn't have the transmission torque switch, but we had an identical truck one year newer that did. My dad says you'd hear a click when you shifted into 5th and the truck would kick you in the butt. The transmission switch is unnecessary. The whole system is unnecessary at this point.

You get black smoke til the turbo hits 10-15 psi. Then it clears up. No big deal. I have one truck that's still roadworthy with this same engine, the puff limiter just stopped working a couple years ago so we just capped it off, which I believe just involves pulling the aneroid valve (reversing relay) off the rear intake manifold and putting a plug in instead.

My CAC testing kit. Two 3 inch PVC pipe caps from Home Depot, one with a wheel valve stem for pressurizing. Third fitting is a 2 inch cap wrapped in electrical tape to make the difference to the 3" required by my MR688S. Uses a different size CAC outlet than my RD688S. Just tossing this out there into the Abyss of BigMackTrucks info.

Just had my plugs out the other day, I forget if it's 3 or 4 inch, schedule 40 PVC pipe caps from home Depot. Plugs right into the rubber boots on the CAC.

Drill one and put a wheel valve stem in it. Should be good for 35 psi, if it leaks you'll know quick.