Mack E7 question

thansk, will be right back.


thansk

If anyone is going to try that Mack idle adjustment I mentioned I should also mention a few things first.

1)There must not be active fault codes present (no "CEL" on)

2)This won't work on an automatic equipped truck. You can get the idle to drop with the 3 quick off-on switches of the cruise power, but it won't set to the new RPM, and will go back to it's preprogrammed RPM once the cruise power switch is turned off.

3)The clutch pedal must be pressed atleast once after the new RPM is set. Otherwise it'll revert back to the previously set RPM.

Mack also recommends an idle RPM between 500-750.

FWIW, I found my truck idled smoothly at the 500rpm level, but engagement torque is marginal. I didn't want to be stalling it all the time, and 750 seemed too high to me.

Thanks for the idle adjustment procedure. I think it helped me further narrow down this erratic idle.

I tried it and found that no matter what I set the idle to with the above procedure, my idle was still intermittent. And on the same hand, no matter what I set the idle to with cruise control at idle (whether it be 500 or 1000 rpm and anywhere in between), the intermittent prob would not be there, period. So I'm thinking is has something to do with the sender on the throttle pedal.

Does this make sense to anyone here? :beatsme

Serv said:

I tried it and found that no matter what I set the idle to with the above procedure........

........ So I'm thinking is has something to do with the sender on the throttle pedal.

Does this make sense to anyone here? :beatsme

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Serv, I don't understand the workings of the engines electronics well enough to guess if it is related to the throttle pedal sender, but.................

Here's what I've noticed with mine:
It'll idle "jumpy" at it's current idle rpm of 600 when ever it's not cold (above 150degree's, and no engine load)

It's "jumpiness" is a quick 50-75 bump in RPM at about a once per second frequency.

Any slight load on the engine, whether that's just the AC pump or even the air compressor while building air, is enough to smooth out the idle so it's perfect.

If I increase idle to 700rpm the jumpiness sound more like a slight miss, and at 800rpm it's perfectly smooth.

Mine is the same whether on cruise, or not.

I've been told by other Mack Drivers(not professional mechanics) who've had this idle issue too, that the fix is testing & replacing of faulty injectors, fine adjustment of the rack, and computer reprogramming. No mentions of sensor or sending unit's although that doesn't mean it's not in your case.:beatsme

don't ask, will be right back again, LOL

thansk
KoO
Published Author

Jeff D. said:

Serv, I don't understand the workings of the engines electronics well enough to guess if it is related to the throttle pedal sender, but.................

Here's what I've noticed with mine:
It'll idle "jumpy" at it's current idle rpm of 600 when ever it's not cold (above 150degree's, and no engine load)

It's "jumpiness" is a quick 50-75 bump in RPM at about a once per second frequency.

Any slight load on the engine, whether that's just the AC pump or even the air compressor while building air, is enough to smooth out the idle so it's perfect.

If I increase idle to 700rpm the jumpiness sound more like a slight miss, and at 800rpm it's perfectly smooth.

Mine is the same whether on cruise, or not.

I've been told by other Mack Drivers(not professional mechanics) who've had this idle issue too, that the fix is testing & replacing of faulty injectors, fine adjustment of the rack, and computer reprogramming. No mentions of sensor or sending unit's although that doesn't mean it's not in your case.:beatsme

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That sounds strikingly similar to what mine is doing. Have you tried setting the idle at ~600 then the cruise control at anything above that whether it be 625 to 700? Mine clears up no matter what RPM while idling on CC. I'm going to try putting a load on mine today while normal idling to see if it does the same as yours.

I'm guessing that your idle prob is unrelated to your engine/power cutoff problem.

Serv said:

I'm guessing that your idle prob is unrelated to your engine/power cutoff problem.

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I'm guessing they are not related. I think possibly the problem with the guages and the occasional engine stalling might be related, although they never happen at the same time. The speed at which they'll quit and start working is similair though. And they only happen very occassionally, maybe once a month on average.:beatsme That's why I don't get too worked up about the problems, and as for my idle issue, that doesn't seem to have any negative effects other than sounding weird, but I sound weird sometimes too so............

King of Obsolete said:

don't ask, will be right back again, LOL

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:sleeping Okie Dokie, we're still waiting here patiently...........well CB's getting alittle antsie, but........:cool2

Just to update, my intermittent idle problem completely went away after my local KW/Mack dealer did a top end adjustment of the valves and injectors. Or at least that's what they said they did. It cost me $450.00 but it's getting a little better fuel mileage and idles smoother than it has since I've owned it. I'm finally starting to like this truck now.

E7 overhaul

anybody here know the torque for 350 E7 main, rod bearings, and head bolts?

Do the trucks have an idle step up to increase the idle when the AC is on ? If so it may be a faulty AC sensor . Mack really blew it with these engines , they are garbage . They will do a cam and lifters every 500,000 kilometres and then they will do a crank . The only good one is one that is fitted with a series 60 .

Wow, this brings back memories. I was always a Mack man (still think the old mechanical motors rule)...but had a 2000 CH tractor with an E7 460 with some of these problems. Mine idled OK but it had that mystery "turn on/off real quick while driving" problem, that would leave the electrical malfunction light on. It also had a powerband like a light switch. One hill it would barely pull itself over, the next you would literally think the clutch was slipping because the rpms would suddenly shoot up, then look out, start grabbing gears. The dealer never could find the problem, they even changed all the pins in the ecm wire harness connectors. I recently saw it and spoke to the new owner and he said it is still doing it but said it pulls real strong now.

Did I mention it was also one of the lucky ones that came from the factory with all the cooling galleries full of casting sand. Five air compressors and five dryers later they finally got it all cleaned out. Then it dropped a valve while parked idling at 125,000 km. Then the starter wiring caught fire while running with the pto on. Then the camshaft went at 300,000 km. Along with an air conditioning system that would freeze solid (was an update on that) and a recall on the engine oil pump that was too low on pressure.:Banghead That's why I bought a Cat powered International.
I still like Macks though and I hear good things about the new MP engines. Just wish I could still get a new R model with an E6 350:notworthy

A few years ago I was an employee for a short time for a big petroleum transportation company, and drove a CH Mack. It had a 400 and when it ran, it ran just good enough so I wasn't mad all the time. It also developed that electrical gremlin one time where I was going along and it'd literally shut off. One day it happened 12 times in an hour, I was loaded with 8500 gallons of gasoline going up the NY Thruway from Albany to Saratoga to a station. I had to keep starting it back up going 65 mph to get to the station to unload. Something about electrical problems...and GAS...I'm not sure what it is, but it was making me a little nervous.
I called the so-called "mechanic" for the outfit, and for the first time in his life admitted he didn't know what it was, so bring it to Mack. It ended up being the wiring harness that plugs into the firewall that feeds ecm and a few other things. 4 feet of wire and labor was over $600.00.
Shortly after that I remedied the entire problem by purchasing a '97 Peterbilt and became an owner-op again even though I said I'd never do it again. Electrical problems ended, but a whole new series of problems developed at that point...like all truck owners can relate to.

I used to drive for a local food chain a number of years ago. One of our outside vendors always ran Macks, they had the R model when I started, but updated to the CH when they came out. I can't tell you how many times one of their trucks would be sitting behind the store dead in the water, it would crank but never fire off. I made quite a bit of overtime due to their trucks blocking the dock.

This problem was so common it tarnished Mack's reputation as being a bulletproof truck. I had driven a DM600 for 2 years in heavy construction and had only seen one minor repair in that time from a 50 cent hose clamp blowing off the pressurized air line to the intercooler. I was really impressed with the beating that truck took and kept coming back for more. The problems that plagued the early CH series would make me think twice about buying one of them after having such good experience with the DM model.

I have to agree on the earlier Macks being close to bulletproof. I did my time in a few (B-61, B-81, DM 800, DM 600, R-Models,) but never really aquired a "love" affair with them. I was always partial to a normal Cummins, Cat, Detroit powerplant with Roadrangers or two stick combos.
I am surrounded by them (Macks) currently. Today I was in about an '85 R-Model waterwagon doing dust control for an hour. That was about all I need of it now for another month or better, and as long as nobody I know saw me in it, I'm cool.:laugh

I do'nt know how the Big Chiefs at Mack can sleep at night . With a proven and documented history of these trucks shutting down at speed it's only a matter of time until someone gets killed . The litagation will be severe and ongoing once a precident is set . And even if it was'nt the cause of the accident , what truck driver would'nt say "it just shut down and i could'nt control it " and if the shut downs do'nt get logged in the computor how would anyone dispute it . I'd be starring at the ceiling at night waiting for the call....

I have a old CH model with elec. 350. It has some electrical problems also . My top bank of fuses and relays in the glove box lost power , sounds like a easy fix , guess again :Banghead. I ran a wire from the lower bank of fuses to power up the upper row , works sweet . My truck also shuts off for a split second , I always contributed it to needing new fuel filters but sounds like its common on other trucks and its electrical. I still love her , she's never left me walkin.

Any of you guys running the E7, check your exhaust manifold. Specifically around the turbo flange. Mine was broken all the way around and leaking hot exhaust onto a plastic diesel return line. Luckily, I recently purchased a spare engine for this truck (just in case) so I had a spare manifold. But guess what, the manifold on the spare engine is cracked as well. I'll be melting some nickel rod in that one later on this morning. I spent all night grinding the injury out. I just need it to hold until the new one comes in. But that manifold is on national back order and there are none to be found anywhere. I wonder why?

This post makes me glad that our RD688 is as old as she is a 97, mechanical motor! knock on wood she has treated us well, just over 250k miles. It was a lumber truck that we had T&T Body king up in Latham build for us! Ill get some pics soon!

King of Obsolete said:

buddy barry has the blue mack which is a E7and the thing is acting up. driving it at highway speed, all it does is act as if sme one is turning the key on and off. the electronic malfuction light comes on and goes off. we have to drive the truck 1200 kms to the nearest mack dealer which treats us pretty good. they can't guess what the problem is on the truck over the phone.

thansk
KoO
Published Author

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My 2001 Vision 427 use to do that, 1st owner did not properly remove the qualcom programs from the ecu local mack dealer fixed it in a sec. hasn't acted up in over a year

To all. No ur gear train is not coming apart. All u need to do is contact ur local Mack dealer n order u a couple of timing sensor shims. Most of the time they already have one on the sensor. But people leave them off not knowing. Majority of the time on the position timing sensor if there’s metal on it it’s because it’s not shimmed correctly and it’s riding to close to the cam gear. On the timing sensor that’s on fly wheel. There will b some metal shavings from time to time from clutch etc. normal where. Will need cleaned. But it also is supposed to be shimmed if needed