1995 E7 400-Smoke & Derate Mode

[EWB555]

1995_Mack_Repair_Sheet_2_of_31.pdf

Ok so I've posted on this before however I didn't provide all the information as I had come to the conclusion the 2 issues were unrelated, but now I'm re -thinking.1995_Mack_Repair_Sheet_3_of_31.pdf

The truck is a 95 E7 400 VMAC I I believe (Pump looks just like the mechanical ones however electronically controlled)

My issues are as follows:

Smoke-Truck Smokes a ton at start up, let it idle for a few and clears up. Take off to leave and engine smokes more, and feels like its missing, shift one or two gears and it clears up pretty quick, stops missing as well. Runs fine (that is until derate mode kicks in, I'll get to that in a minute) If I arrive on a job somewhere and idle for more then a minute or two, truck smokes again when I take off, then clears up pretty quick. When going down the road, the truck smokes very little its only on initial startup and after idle.

-When the truck smokes its definatelty an excessive amount, not normal for sure,

Derate-Truck will run strong for about an hour in the mornining (Puts out 34 psi of boost on a pull) then the computer cuts it back and will not allow more then 24 which really kills the pulling power loaded. If I shut the truck off and restart, it goes back to full power, it may last 2 miles, or up to ten or so. Again I though the smoke was unrelated as when the truck goes into derate you are going down the road and it is not smoking.

I have replaced the speed sensor in an attempt to fix the derate, however it did not correct the problem, and the speedometer still acts up every now and then.

I have only owned this truck since june, and it has been having these problems since i bought it (knew about the smoke when I bought the truck and adjusted offer accordingly) I have reciepts from the local Mack dealer that I have attached showing work done to the truck before I purchased, it had one injector replaced and the pump was either replaced or rebuilt. I was beginning to think the problem was in the pump, or injectors however I realized this work was only performed 40,000 miles ago. Does anyone have an idea, I was thinking maybe the econovance is acting up?

[EWB555]

Had the computer scanned today-No fault Codes Found. Mechanic thinks its a timing issue, since when it smokes it misses slightly. However he recommended I take it to Mack.

Last thing I want to do is pay dealer labor rate, anyone have an idea what could cause my issues and not set a code?

When he said timing, the first thing I thought about was the econovance.

[Mackpro]

I would lean towards timing also . I would get the pump timing checked and bump it up no more that 1.5 degrees over what it says on the valve cover. The rings in the Econovance could be shot as well. The intake temp sensor could be going haywire and giving false signal to ECM causing the wrong timing. Rare but I have had 2 bad VMAC2 ECMs that caused no timing advancement. On that last invoice what oil line was replaced? The oil supply line to the Econovance? Oil supplied through that line to the Econovance control valve/solinoid is what make the timing advance/retard.

[EWB555]

First of all thanks for the reply! I will have to look at the truck to see which line looks new, as that work was performed 2 owners ago (Guy I bought it from didnt have it long at all). Looked at the invoice and did the math, they charged for 3 feet of hose so it should be easy to figure out, (unless they just charge for 3) I doubt it was the line from the oil filter to the pressure gauge as that is leaking now, so the econovance oil line is definately a possibility. I called the one owner who had the work done at Mack , and he said its a new pump, and the truck did not smoke like that when he had it, the reason he took it to Mack is it used to shut off on him going down the road. He sold the truck to the guy I bought it from right after he got it back from Mack, The guy I bought the truck from says its smoked since he owned it, so maybe the timing was never set correctly in the pump.

Why do you suggest bumping the timing up 1.5 from the factory setting?

[Mackpro]

The engine seems to be more responsive and run better when the timing is advanced, however going over the 1.5 degree can cause overheating in the summer time. Over time gear wear and pump wear cause the pump timing to lower. I have seen 10+ year old engines thet were never touched ( as far as the pump goes) that had low pump timing as much as 2 degrees. And I'm sure the EPA /emissions had something to do with setting the pump timing where they did.

[24vman]

you should check the econo vein to see if it is bad, ive heard of these going bad and causing the alike symptoms. maybe swap one out and try it, if you have another truck with the same engine. hope this helps.

[EWB555]

So I read an older post on here, titled "Skipping & Blue Smoke" and the symptoms the guy describes seem to fit my truck perfect, and its a 94 so same electronics. The only difference is he stated the "electronic malfunction light" came on, when the engine derated and for the life of me I cannont find the light in my truck, and I am told the computer has no codes (but maybe the derate doesnt set a hard code)

The reccommendation is to remove the screens from the econovance & if that does not fix the problem replace the selonoid. Is there a way to test the selonoid? Owner in the post states he tapped the ecovance selonoid with a screwdriver and the smoke cleared up, so he knew it was the econovance selonoid. Anyone know a more reliable way to make the diagnosis? Those selonoids are pretty pricy.

As always I appreciate anyones input!

[krismoriah]

I have a 1998 model with an E7400 that did the same thing..i think. Mine smoked a ton at startup then cleared up..then after awhile would lose power..and jakes wouldnt work. There was a solonoid on the side of the pump that someone had been taking a hammer to.. so i got to looking and the solenoid was nearly beat to death..and was sparking. I went to a junkyard and got a solenoid off an E7350 and fixed the derate and jake problems... still smokes like crazy at startup but after that runs like a champ.

Replace the solenoid as cheaply as possible... will fix your power problems. As for the smoking like its on fire at startup... i still havent figured that out... I have heard maybe the puff limiter? I couldnt find any screens?? maybe someone can post a picture of the screens so I know what to look for?

[NorthernWhiteman]

I have the same E7400 in my truck & the f**ker smokes more then me but only on start up. I'm suspecting that it could be the valve guides. My motor has 20 000 hrs on it.

[EWB555]

Well, Took the $500 gamble. I've been thinking it could be the econovance solonoid, and between the mechanic saying the timing is off, and the posts i've read about the econovance I mean the "Skipping and blue smoke" post I could have written about my truck.

Installed the new one today, I too could not find any screens in the old or new one. It still smokes like hell when you start it, but clears up as soon as you go down the road. At like 1400 RPM of part throttle this thing pumps out smoke and feels like its missing, it clears when you mash it, and as long at the water temp is around 180 it doesnt do it at all. So if i leave the house, drive an hour to the quarry, then sit for 30 min to get loaded, water temp falls back, and the think smokes like hell at part throttle, but again clears up if you hammer it. I'm praying the econovance fixed the derate problem, however it certainly did not fix the smoke isse, which doesnt leave me too hopeful. I drove it for about 30 minutes, and it did not derate, but sometimes it lasts an hour. I figured I might have blew $500 so I shouldnt ride around and waste fuel, we'll see what happens this week.

[krismoriah]

No it did not fix my smoke issue either.. my mechanic thinks there is o-rings leaking under the injectors somewhere.. but mine only does it on startup. It definately fixed the de-rate and my jake brake issues as soon as I put the solenoid in.. I got by with $100 from the junkyard for mine. Whatever it is lets the fuel leak past the injectors after you shut it down. Which loads up the cylinders with fuel.. I was worried about vapor lock or washdown with the amount of fuel that must be loaded after shutdown.

[EWB555]

Well, I hope it works the same for me. My Jake doesnt quit working when it goes into Derate mode, just the cruise control quits. With your truck being a 98 i'm pretty sure the fuel delivery system is different, the newer ones have the individual injector pumps, where mine is the single pump with electronic control (looks the same as the mechanical but with an electrical connector in the back instead of a throttle linkage) If it didnt take care of the derate, I'm definately going to bite the bullet and put the truck in the shop.

[EWB555]

Ok do def wasted $500 bucks, engine still smokes and derates. On the positive side I found the engine malfunction light, the bulb socket had fallen out of the indicator and I kept noticing a light shining under the dash when I drive the truck in the dark. The truck flashed Code 3-4 the first several times I hit the cruise button, however today it only flashed 3-5, according to what I can find the first code is engine position sensor, and the second is jake brake output 1. Can anyone tell me what to check/replace to fix this issue? I'm hoping this could be the key to all my problems.

[EWB555]

Anybody? I've looked all over the internet can can find very little information about these codes. Would really appreciate some help, I feel like I'm finally close to fixing this thing.

[EWB555]

Here's a little more info I figured out yesterday. Before the derate the code is 34 (Engine Position Sensor) After the truck goes into Derate mode it spits out code 35 (Jake Solonoid output 1)

Is the engine position sensor on this truck on the front of the flywheel housing below the starter? Had the wife pick up the part from Mack and I can find nothing that looks like what they gave me, so I'm thinking they gave me a sensor for a newer model. (it has an 0-Ring and looks like a Crank Sensor for a car) The sensor on the flywheel housing of my truck appears to be a screw in type, and looks exactly like the speed sensor I replaced on the back of the transmission a few months ago.

I appreciate anyones help or Input! (I know I've been talking to myself last 4 posts, but hey at least the process is documented!)

[Olivetroad]

(I know I've been talking to myself last 4 posts, but hey at least the process is documented!)

Hey, don't feel bad - keep it up - idiots like me can't help you with your problem, but you are helping me in the edge-U-kay-shun department

[EWB555]

Thanks! I figure eventually I'll be able to talk it out myself!

[krismoriah]

I had the same problem awhile back. The jakes werent working right, and it was derating. I replaced both jake solenoids..no help. I replaced the econovance and it fixed it. It has always smoked a ton at startup.. It clears up within 30 seconds. From what yours is doing..something says the econovance isnt getting the proper amount of oil to do its thing. It will derate by advancing or retarding the timing if the oil pressure isnt right. Have you looked at the lines going into the econovance? is it possible your new econovance isnt working properly? Have you tried pecking on it when its acting up to see if it clears up? I am by no means an expert but except for the smoking at startup (which i think is the timing related to the lack of oil pressure at startup at the econovance)... mine had the same problem and was an easy fix.

[EWB555]

_{Well, here is some good news. I fixed Code 34 by replacing the engine position sensor (easily screws in the side of the pump) -Mack had given me the wrong part as I suspected. Bad news is it still smokes and still derates, and still spits out code 35 for the Jake Solonoid output 1. Kris, I have tried beating on the old econovance however that did not make a difference. Oil pressure is good, and I really hope its not an internal problem. I did read that a sticking Jake solonoid can cause the engine to smoke. My Jake works fine for the most part (it doesnt come on full in the morning until the engine gets warm) , and the smoke clears up when you go down the road and get the engine warm. Who knows at this point. I'm glad I fixed a code, however it sucks the code wasnt causing any of my symptoms.}

[LuceExcavation]

Check your timing. Had it happen to me when a shop rebuilt the heads and they didnt know how to time the engine

[EWB555]

Put the truck in the shop finally...they had a hard time and its a long miserable story but it seems the problem was the ECM. They also fixed my exhaust manifold leak & installed new injectors (they put high flow ones in, I'm told they are mild) It was ran on the dyno to verify the repair & that the timing is correct, It put 369HP to the wheels (I was given the printout). The torque number on the printout is crazy high, I think you have to divde by the gear ratio which gives me 1549 ft lbs to the wheels which seems consistant since from what I can find on the internet an E7 454 is rated @1660 to the flywheel. 2 days so far with no derate!

[Timothy B Demarco]

First off check your engine position sensor on the side of the pump. When they go bad it screws up the timing. Then have your injectors tested, while in there adjust your valves and jake unit. Give that a shot if that doesn't work have the pump rebuilt.

[EWB555]

Thanks! Yes that sensor was replaced early on and was causing the 3-4 Code. The 3-5 was a conbination of the econovance needing rebuilt, which made it go longer between throwing the code, however the problem was not fixed until they swapped out the ECM. I drove the thing myself for the first time today, and wow what a difference in the power, the high flow injectors & new ECM really make the thing very responsive & able to cruise up hills without being in the fuel all the way. All symptoms I had are gone, no smoke & no engine derate. I cant wait to drive it loaded (my dad works the truck during the week, I just ran it to the truck wash today)

[dieseldaddy24]

Ok this is my 1st post. I'm working on a 95 Mack e7 manual pump with electric governor,the truck has been to 3 other shops and no one can figure it out. Her are my issues.

Truck starts up and dies.

When ruck finally ckanks and stays running it idles fine no smoke. When you raid the engine rpms it goes it to derate mode I guess,where the engine surges the rpm come up and back down with the pedal on the floor. The prolink shows throddle % at 100 and isworkibg fine.

Also found injector not fireing , replaced injestor.

Checked all timing sensors ohm out sensors all checked good.

Also found when the derate mode is acting up it throwsa engine speed sensor code and a file rate sparagic code and when u let engine ldle codes go inactive.

Found timing was set at 10degrees past TDC,adjusted timing to .5 degree past what valve cover says. And now engine starts and dies won't stay running. Thinking about pulling the pump off to have checked. Does anyone know anything about this mess??

[theakerstwo]

When you give up and get in the shop were it can have the ecm montitored and timing checked you should be there when they check it. Then you will find that all we can do here is guess what the problem is and you have found it cost a lot of money changing parts. It is too hard to trouble shoot some of the electrial problems with out hands on.my guess is you need the timing checked and that can only be done with a reader on that pump. good luck. glenn