EWB555

I was always told White is water, Blue is Oil and Black is Fuel (either too much or lack of air) . My 95 E7 400 with the electronically controlled pump (400,000 Miles) does the same thing but the smoke is more blue then anything. Smokes the whole area out when first started, then if you go down the road and shift a gear or two it clears right up, and doesnt smoke again until you shut it off for at least 20 min then it will smoke again on re-start. The guy I talked to told me its likely the valve guide seals in the heads letting oil leak down into the cylinders when the engine is off, however the truck only used 1.5 gallons between oil changes which doesnt seem like a lot over 16,000 miles given the amount of smoke. Interesting to hear it could be lack out of oil pressure to the econovance-is there something that fixes that or is that inherent to the design?

rhasler- I appreciate your help but I dont think thats the page for my truck because it talks about the self test, and says their is a 2 second delay before you can start the truck. I can turn my key and the truck starts right away, and if the mack self test is anything like a C15 Cat I should be able to hear relays and selonoids clicking every time I turn the key on and dont start the truck. I still dont know whats up with this thing-I replaced the speed sensor a month ago, and the speedometer was reading inaccurate again for a little while the other morning just like it did from time to time before. Does the speadometer head interface with the computer at all, or does the computer only take the reading from the sensor? I was thinking if the ecm gets info from the speedometer head that could be whats causing the derate??

I absolutely love the 12 speed transmission in My RD. Drive like a 5 speed when empty or even loaded on level or downhill, but you can split every gear on a pull (or if you just wanna grab more gears). They do make a bit of noise when splitting the gears if you dont hit it just right, but once you get the hang of it its a awesome transmission. Mine turns 1800 @65 -Tops out at about 72@1950 I believe I have 417 ratio.

I'm not sure where the check engine light is on this truck. I pulled the dash apart today and the light to the right of the speedo had no bulb in it. So I was thinking the previous owner pulled the bulb out before selling the truck. Put a known working bulb in and it did not come on when I turned the key on (I'm not sure it was supposed to). Is the chk eng light normally to the right of the speedo? Also can you check the codes on a 95 by using the cruise control buttons?

Appreciate the info. If there is one thing I'm certain its definately the computer derating the engine. I've had it happen to me loaded, where it cuts the boost back from 30-34 to 25 Max. I get to the plant, dump the load, then shut the truck off for a sec, and its back to over 30psi when I'm back on the road.-It may stay that way 30 minutes or a few hours until she cuts back again. -The torque limit sensor is that on the passengers side top of the transmission? Its the only other electrical plug I can see other then the speed sensor which I just replaced. I checked the wiring and it seems good. All the other things you have listed I think I can almost rule out. Water temp is never over 180- Highest I've seen the pyrometer is just under 1000 i believe after a long pull, usually around 6-700. I may have to break down and have the mechanic look at it with his computer, rather then throw more parts at it. Speed sensor made the most sence to me since the speedo acted up every now and then, and the trip odo is way inacurate (still is even with the new sensor) It's frustrating because the truck runs really good, when the computer isnt cutting it back. I've only had the truck 3 months, and other then this issue the truck is in exellent shape for a 95. I want it to be perfect, but dont want to go broke either.

Ok, truck ran great for 1 load today then back to derate mode. Anything else that can cause this???

Put in the new speed sensor today took her out for a test run, everything seems to be ok. Used the cruise control for about 3 miles and it stayed engauged, boost pressure was good. I guess I'll find out for sure next full day, as sometimes it takes a few hours for it to go into derate mode, but the fact the cruise worked makes me hopeful.

UPDATE-I installed a boost gauge over the weekend. Truck was building 30-32 PSI of Boost Monday Morning, drove it about 10 miles, then all it would build was 22-24 PSI the rest of the day. The truck idled for about 45 minutes before I left the house so its not like it was cold. The only thing I can think is the computer is cutting it back for some reason,I have checked the wires on the transmission and see no evidence of a short. Also the speedo acts up intermittantly (But it was perfect All day Monday) and the Cruise Control works for about 5 minutes then kicks out-Could any of these symptoms be related and make the computer cut the power?

Appreciate the info guys. I am def going to start with the easy stuff, ( will change the filters tonight). In regards to the torque limiter-I just put a shifter in this truck 2 weeks ago, and I was going to change the speed sensor while I had the floor pan out and easy access to the wires, as the speedo reads incorrect every once in a while. I unplugged what I thought was the speed sensor connector, only to realize it went to another sensor on the top passenger side of the tranny. Is that the torque limiter? I plugged this back in, but I was thinking since I messed with the wires I could have broken one. I only see 2 sensors on the transmission, I was going to replace the speed sensor, but It didnt look like the one Mack had given me so I left it alone. The other thing I was thinking of is I had the fuel pedal unbolted to pull the floor out, maybe that could have gone bad and its not letting it get full throttle? Again I appreciate any thoughts anyone has on this.

Name: Mack RD688S (1995) Date Added: 07 August 2011 - 10:01 PM Owner: EWB555 Short Description: None Provided View Vehicle

I was driving my 95 RD688S Tri Axle Dump 400E7 12 Speed this weekend, comming up a long pull loaded down to about 1400 RPM, and was getting ready to drop a gear when all the sudden it felt like I either let off the fuel, or the engine went into some sort of derate mode and just stopped pulling. There was no sudden noise but the sound of the engine changed, (as it would if I let off the fuel). All vitals were normal, water temp just above 180, pyrometer had climbed to about 900 (Which is normal for a long pull). Truck stayed running, just didnt have the pulling power it usually does. Got the load off the truck, it seems to feel ok empty, went back got another load (headed the same place) and I had to consistantly use a gear lower then I needed on the previous load (up until the whatever happened that killed the power). I noticed the pyrometer never got above 800 the rest of the day, so thats an obvious sign of less fuel/less boost? Any ideas what to check first? I was gonna change the fuel filters, it's been about 10,000 miles. Also there is no smoke, everything is the same as it was, it just doesnt pull when you hit the hills loaded. Appreciate any help, this thing just seems dead, I was having flashbacks to the 78 R model 300 6 Speed I drove when I first got my liscense.