OM602 - White Smoke & Low Power-Canada to Argentina-mechanical repairs in Guatemala
 

Hi Everyone - Okay so we are not in a Mercedes car - My wife and I are in a mercedes 410d chassis base vehicle that was made in to a motorhome by a german company called Hymer in 1993.
She has a OM602.940 engine and a 722.393 tranny. 280,000kms.
Both are suspected in the current crime wave of problems associated with us being a little stuck here at Lake Atitlan in Guatemala (I know there are worse places to be stuck - thats for sure).
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We have no turbo, EGR or other fancy stuff just a bosch IP, 5 cylinders and 2.9l of go - or at the moment not so much go.
We weigh 4.6 metric tonnes fully laden with water, waste water, propane and us - we can reduce that by 250kg with no water and waste.
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Problem:
Mountains - steep ones - huge steep ones, but I used to drive the chassis vehicle (410d panel van) in the 90s and, with a manual box, they go, slowly, up anything.
But we are not going slowly up anything other than a shallow 10° to 15° incline and certainly cant make the 30°+ slopes.
This has got worse in the last couple 1000 kms.
Also we are producing a lot of white smoke under high load - smells like diesel.
Summary:
We do not have enough power going to the wheels to make the hills and this vehicle should be able to do this albeit very slowly.
So is it 1: Engine down on power to the tranny OR 2: The tranny not passing enough power through to the wheels OR 3: A mix of the 2!
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What I have determined so far:
1: There is a good vacuum at the tranny modulator
2: There is no ATF in the vacuum pipe whilst running when I pull off the pipe from the modulator - am I right in thinking that I would see wetness in the vacuum pipe when I pull it off the modulator (ie white smoke is not burning ATF)
3: The correct ATF is in use and it is at the correct level
4: The accerator linkages are old and worn but I have adjusted the slack out of them and corrected the bowden cable and it has made no difference
5: Suggested tranny problem is that the Brake Band B2 is not engaging fully - suggested fault B2 Piston and actuator pin combo
6: Diagnosis info - on the flat or shallow incline we pull away in first and can tell that the tranny changes from 1 to 2 to 3 to 4 okay - smooth changes
7: Diagnosis info - on the same steep hills we can't go forward we can go up in reverse no problem
8: When coming down the same steep hills (forward!) the van has a 1st gear selector position - microswitch - which engages and I have electrically tested the microswitch which is good BUT we cant hold first and the tranny changes up to 2nd at normal speed which when you want engine braking to hold your speed down is quite scary.
9: The gearbox has had a recent (300kms ago) oil and filter change and there were no lumps or pieces in the pan
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The engine then:
1: Starts on the button first time every time
2: There is a glow plug not working - just one and so after starting she runs lumpy till a low temp is reached then very even after that - but have been so nervous of breaking the glowplug during removal and the fact that she starts on the button even in minus 0 temps means that I have never risked that.
3: The white smoke at start up - smells like unburned diesel ( i think) doesnt go away when warm - stays the same
4: No black smoke ever
5: Cleaned air filters and checked for blockages in the air intake mainfold - all good
6: checked cam timing and belt is at 3° ATDC - within tolerance for a used belt
7: There is and always has been a small lag between pressing accelerator pedal and the revs coming up - not much but seems like enough to mention
8: There is a small amount of smoke coming out of the rocker cover breather when remove the breather pipe which doesnt increase with revs
9: No pressure on palm of hand when held loosely over the oil filler pipe with the cap removed.
10: Absolutely no loss of coolant - ever - she has had a completely new cooling system in the last 10k kms - water pump, thermostat, temp sender and in the last 20k kms new rad and viscous fan clutch.
11: No oil slick on top of the coolant in the rad
12: temperature guage reads temps that are consistant and vary as expected depending on the incline and ambient air temperature.
13: Fuel sender unit crud guaze in tank cleaned out 4000kms ago and then 300kms ago tank was taken off and cleaned out completely.
14: New fuel filter and inline filter 300kms ago - inline filter still completely clean.
15: We did run with air in the fuel system for several 100kms without knowing getting less and less power until the van finally gave up and died near the grand canyon - that was when the sender unit in the tank was cleaned and all fuel connections were removed replaced and/or remade.
16: With Engine running and warm - I have cracked each of the injectors and a: there is a similar amount of spurt of fuel and b: the effect on the engine note is exactly the same for all injectors c: Cracking the injector lines didnt change the smoking exhaust.
17: I have a temperature gun and the exhaust pipes for each cylinder on the manifold were measured 2" out from the block (at idle at op temp but NOT after a run) at:
cyl 1 - 77°C
cyl 2 - 84°C
cyl 3 - 84°C
cyl 4 - 86°C
cyl 5 - 84°C

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So anyone got any suggestions please.
I am trying to get an order together from Mercedes in the UK (Bristol where we are from) and trying to find a fine line between not ordering things we dont need and ordering too much. Because of the cost of shipping with weight and then not ordering enough because of the time lag between ordering and delivery.
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I have decided to order a new B2 piston and actuator pin set.

Then there are the tools to do a compression test maybe?

A vacuum test kit might be useful and also a fuel pressure test kit as I am wondering if we stressed out the lift pump or fuel pump near the grand canyon and now one of them has finally given up the ghost - but it would be good to know if the fuel pressures were correct anyway after a 280,000km lifetime.

I am wondering about the injectors too - I will order a set of new nozzles - are these easy to fit for a methodical, practical novice?

I am also wondering about the IP timing - having read so much on here about its effect on power and also about advancing (?) to counteract the effect of chain stretch.

Could anyone let me know the correct IP timing ° - I cant seem to find an actual listed number - although I have seen 14° ATDC +/-1° somewhere on my Google orientated late nights

I have basic tools here and am ordering a parcel from the UK at the beginning of next week in which I will put anything that I will need in terms of non-standard tools - like for some reason my wrench set doesnt contain a 14mm open spanner - Injector pipe nut!!
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Any and all advice will be greatfully recieved, many thanks in advance
Regards
Mark and Saskia

Hello from Canada, Interesting issues. Glad its not me. I am happy that it starts and runs. I ran a absolute pressure / volume calculation for you and I am not surprised by the white smoke. The actual air being delivered to your engine at that altitude by your air intake system is just a bit under 80% of what is delivered at sea level. Somewhat akin to running with a really dirty air filter. Sadly you do not have a turbo charger when you badly need one. I think your fuel delivery is also an issue as the lift limitations of any mechanical pump decrease a lot with altitude increase.
Further you have a vacuum pump that is working hard for you that is designed to work at sea level. It too is only capable of roughly 80% . Your transmission has a vacuum modulator designed to work at a carefully calibrated vacuum pressure at sea level. .
I am a engineer and one of the issues all engine manufacturers have to deal with is what happens when someone tries to run our engine far above sea level. One answer no longer in use , was a using a 12 volt pressurisation fan such as a heater fan to act as a cheap supercharger . If you can find one and a flex pipe, plus a bit of wire and a switch, remove the air cleaner and pressurise your air intake, You will lose the smoke and gain the lost power plus possibly gain a bit more.
Spanner size 13 mm is almost exactly 1/2 inch, 14 mm will also fit 9/16
You are staying there how long? Man you are overloaded with that engine at that altitude . The bad news is the road ahead is 10% higher ahead if you are Southbound. Then it gets less. I think based on your letter that in the middle of one of those hills your engine is simply going to loose more power and you will stop. Even in reverse. You will not be able to restart until you are at a lower altitude. I advise this Find a use heater blower and make it pressurise your air intake. Alternately find someone to tow you to your next lower altitude destination Hopefully someone on this forum knows their automatics better than I do. My e mail is .daemdaem@yahoo.com Please feel free to e mail me. Allan

Reply not showing
 

Hi daemdaem
Thanks for your response.
I did reply yesterday but the reply seems to have gone to moderation and not reappeared.
I found your reply informative and have added its information to the pile of information I have gathered in trying to understand our problem.
Hopefully this reply will be allowed and appear here.
Regards
mark

So that worked then
 

Hi Daemdaem
I didnt realise that altitude could lose so much power.
Although there is a barametric valve on the IP so not sure if that is working or not.
Its all a mystery right now and we are working our way through diagnosis sheets and trying to identify some of the issues and then fix them before moving on to the next.
The first lot of parts is due to be sent from the UK this week and then we can fit them and either fix the van or move on to the next likely suspect.
many thanks for taking the time to send me your input.
I will keep this post updated with the results of our trials.
regards
mark and saskia

Mark And Saska, I thanked the Web master for politely forwarding your letter to me. I am a Power Engineer as well a Journeyman Millwright . I will try to explain the math of what your issue is in lay mans terms To help you understand
All infernal combustion engines including jet turbines require a properly atomised amount of a fuel under the correct fuel/air density and pressure to explode at the correct time. Your diesel requires a given amount of air at the correct density to be mixed with a carefully calibrated amount of fuel , injected at the correct time. I think your timing is correct. I am aware of the barometric valve. Its job is to reduce the fuel pressure during injection at high altitude to help prevent smoke. I recommend leaving it alone as you are already maxed out on load.
Let me explain how my brother diamond drills at 7,000 feet. They start the diesel engine at about 2000 feet and make certain that both it and the diesel truck are fully fuelled and warmed up. as they pass 4000 feet both units start to smoke a bit and he reduces a gear. At 6000 ft another gear. Once on site they have about 65% of the normal power. They aim the standard truck downhill before shutting it off. If they stall the drill engine they must go back down the mountain to restart. Sometimes the truck starts with the starter motor, usually not. Using rolling compression works best.
If you have a hair dryer and a bit of ducting, You can simply disconnect the element , duct tape it to the air inlet, turn it on, and start your truck. This is called Forced Induction and you will be at normal power, until the extension cord runs out This is why you should try and find a 12 volt blower out of a old heater . If you can access your blower in place and somehow duct it around the firewall and under the hood that will work but awkwardly. Your engine is suffering from the same issues humans do. Altitude sickness or not enough oxygen. Adding more fuel will not help. Good luck ad please keep us informed Allan

Hi Allan
Thanks for the further explanation.
As I progress through this problem I am coming to the conclusion that there are several medium to minor things acting to manifest this situation.
The potential for the transmission to be not passing whatever power is developed by the engine to the wheels is our first port of call. These 722.3 autoboxes seem to have a weak point in the B2 brake band system particularly the wear on the band and the length of the actuator pin to take up that wear. Also I have now determined that the kickdown solenoid is o/s - and although not directly related to driving forwards up hill it is a problem because we cant use engine braking down hill in first (the gearbox wont hold first and changes up to 2nd - alarming on a 25 to 30° slope.
So the first lot of parts will contain repair parts for these problems.
Once I have satisfied myself with the tranny being as good as it can be then on to why the engine is not producing enough power - and while I am waiting for these first parts I am now determined to find and buy an inline impeller fan to do as you suggest - it cant hurt and can only help if i understand your information clearly.
What I was wondering though is whether to set it up before the filter or after - push or suck? any suggestions?
And then when we are at sealevel or thereabouts and the fan is off would the restriction on airflow - caused by the fan body being inline - be detrimental to the incoming air flow enough to cause similar problems at low altitude?
From all that I am reading and the responses I am getting on other posts and forums most people are concerned with a lack of air at the point of combustion ... so I should be too as everyone has experience or is skilled in areas such as yours or being a mechanic of many years.
Your continued thoughts are and will be appreciated.
Regards Mark and Saskia

question regarding power loss at specific altitude
 

Hi Allan
So I am just doing some calcs for required extra air flow produced by an inline fan.
In your first post you say that its 3% loss per 1000' - but in your second post you say that the engine is down by 35% at 7000' feet.
Is this not a linear relationship then?
I am calculating extra airflow required at 2100m - 7000' and at 3600m - 12,000'
Regards
Mark

Hello, The theoretical number is roughly 35%. I slipped with a dropped zero. Theory and reality differ. To properly calculate it requires using Boyles law P1 x V1 x T1=a constant where absolute temperature and volume are taken in to consideration. If you use 10,000 feet with out considering temperature differences and no use of relative humidity differences the published tables Show 35%, and it is a curved graph. I rounded my estimate up quite a bit to allow for engine blow by, and laminar flow losses and air filter losses and intake / exhaust valves and finally exhaust system losses.
The whole fact is you need forced induction to supply more available oxegen by turbo charging, by a fan or supercharging , or by impractical means. You should ask the locals what is available. We can scheme and calculate to our hearts content, but you need something practical.
ON a paved road, your engine can be run quite safely without an air cleaner for short distances, once you are over the hump, simply stop, leave the engine running and reconnect air filter.
Regarding the transmission . I hope your parts solve the issue. Yes I live in an mountain area of Canada where we respect grades. While waiting you might consider having a look at your brakes. I prefer not to have an automatic at all, and loosing a driveshaft or stalling on a 25 % or more grade could be a life changing event Allan

HI Allan
Thanks for the further information.
I attached a 16" 12v fan via some serious ducting to the intake before the filter (air) yesterday to see if extra air reduced smoke output. (standing still not on a climb - we now do not have enough atf in the box to go anywhere and I am loathe to refill only to drop it all next week when the parts get here). It may help with power on climbing but standing still it didnt change the smoke output at all. There are other things acting up here. So I have tracked down a simple 12v 3" inline fan that will take a variable speed controller that moves 130CFM and our intake is roughly 3" so when this is all done - as in good enough to go up again - the last install is gonna be a dash mounted controller for a switchable inline fan. As far as I can work out the ducting and bends in the system and the filter will reduce the airflow to around 60CFM and according to rough online calculators that I found this should go full or part way to increasing airflow up to around 10,000 feet. Due to the restriction on airflow when not in use I have to get a y-connector for the 3" intake so I can have natural aspiration at sealevel - or up to 3000 feet and then be able to switch the fan in after that.
Variable speed controller making sure that the mixture isnt air rich at lower altitudes.
Would you be able to offfer any comments on this arrangement?
Regards Mark

Mark , Sounds like you are on the correct path. I consulted with a elderly long retired Mercedes mechanic. He said it should help. He told me that a tow, to the top of the pass might be a wise idea, but only if you deal with the transmission issues. His advise is to stop at the top, get out, check all wheels for heat build up. Then proceed very slowly downhill. Good luck and I hope it works out well . Allan