JoeH

From the vmaciii 8-211 manual. Schematic for MR parking brake blink code 7-2. I don't have the blink code, that's only tripped when park brake is set while moving.

One problem I've heard with V8's in general is that you have 2 connecting rods on each journal of the crank. But I think the E9's weak spot is the heads.

Worth noting, while the park brake dash lamp works, it does not operate the brake lights.

17-A-0.8 is split down from 17-A-1.0, which comes from Fuse 17, 10amp. This fuse supplies several functions.

Also the switch function requires parking brake to be set anyway, so this is a moot point. Gotta fix/hotwire VJ1-10-0.8. any recommendations on lying to that circuit? I'll post a picture of the schematic.

Lol, I thought about that, but the shop foreman didn't think that would work as it's programmed for an automatic. I'm not opposed to trying it but I don't want to fry anything. The task at hand is to find/repair the "VCU Park Brake Switch" circuit. It's wire VJ1-10-0.8. I found the wire near the VECU, but I need to find where the VCU park switch is. So the dash instrument cluster has a parking brake lamp that functions, it works off the park brake sensor on the park brake knob. However, according to my wiring diagrams for the truck there should be a VECU park sensor. Any suggestions on where it'd be on an MR688?

Never ending. Dealer computer can't program idle speed because VECU isn't picking up that the parking brake is set, even though the dash indicator light comes on saying the parking brake is set. 🤣 Brought the truck home to dig into this myself....

What year is the truck? In general these are fantastic engines, if a bit small compared to modern engines. Weak point on these is the valve lifter tappets. They use a carbide face welded on. The carbide can crack, drop a piece off, then shave the lobe off the cam rather quickly. You'll hear a misfire and when you pop the valve covers one rocker will have excess lash from the missing lobe. Someone said on here recently that the E7 motor lifters are interchangeable?? But I am unfamiliar with this detail. Camshaft might be available through PAI. As long as you don't try and squeeze more HP out of the engine it should be very reliable. Mack engineered these engines to the perfect balance of durability and power. Deviating towards power will quickly sacrifice reliability.

The wealth of knowledge here seems to never end. Thank you @fjh! You pointed me in the right direction to sniff this document out!

Throwing this out into the abyss... Idle speed is adjustable by driver, assuming the feature isn't disabled. Punching the right cruise control sequence enters the "reprogram mode", and as you say you need a clutch pedal to set it once you've floated it where you want it. Or you need the Handy Dandy Mack software, which I sort of have but can't utilize because it doesn't recognize the DieselLaptops interface device I own.

Then how did it change in the first place??

Can I reset it with switches myself??

My 2003 MR688S AI350/Allison hd4560 suddenly just dropped it's low idle speed from 650 down to 500 or less. No codes, just had a ton of engine work done at the dealer, see my other "rollover" thread under Modern Trucks. Been running great til now. Firing up computer to check stats, and doing a visual inspection. Any recommendations?

Fan takes power from engine but also pushes you forward.... Like an airplane.Though it's probably inefficient. You should run 180°F thermostat, if the engine runs too cool unburnt fuel can gum up valves, exhaust, etc when idling.

Pistons are usually done in balanced sets. The C probably dictates what weight tolerance range the pistons are in.

Sounds awful trying to pull both heads together. Glad you have the service crane for it though.

Also, when you get those heads off, YOU CANNOT SET THEM DOWN RIGHT SIDE UP!! You will crush the injector nozzle tips!!

Go buy jam nuts they're flatter. Should be able to double nut a couple jam nuts.

Take those manifolds off first.... You're asking for trouble there...

https://www.thedieselstop.com/threads/any-mack-experts-i-need-help-advise.80033/ Reading this ATM.

You'll want to make sure your oil pressure is high at low engine speeds to handle the extra load on the crank bearings.

Maxidynes make 90%+ peak torque from roughly 1000-1200 RPMs up to the governor. I'd expect the fuel pump to be the biggest factor. For 5.9L 12v Cummins engines there's a fuel plate in the pump you can slide or replace to make substantial changes to the fueling. I've never tampered with fuel pumps other than to adjust idle and gov speeds, so this one is above my pay grade.

4 Years ago someone said you're right....

E6 designation started in the early 80's I believe. We've had trucks up to 1981 that still had ENDT676 engine designations. Our 1988 has an EM6-300L, so somewhere between 81 and 88 they changed it. Probably when the 4 valve heads came in.

Typo.