Heavy Equipment Repair Questions? Ask an Expert Now.
All I 've seen so far is just the check engine light. I will check to see if the mode button is active on my truck ( it's pretty basic vehicle) tonight after work. The description in the manual was not very clear.
I did check both fuse panels first thing thinking I might have popped something installing the new batteries...all looked good.
k.. it looks like we'll have to do some voltage checks..let me know if u get a code..
sorry for the delay in getting back,next we'll have to do some pin out checks
first the vcu its located somewhere under your top dash panel or bottom of dash panel you will find a rectangular box with either 4 or 3 plugs to it at the 21 pin connector at pins 1 battery 2 ignition 3 gnd verify that first,at the wire insertion side you will see the numbers....very small but they are there next at the pld at your engine,the small plug check 5 and 6 battery 9 and 11 gnd 15 is switched,,check that and get back to me with the results...thanks..this will help
I found the VCU and checked #1 pin @ 12.6 volts, # XXXXX pin @ 12.47 volts w/ ignition on.
The engine plug was a little more difficult. I have 7 contacts and no visable numbers.
Plug attached to engine, toward cab, third contact from top had 12.62 volts, fourth contact had 12.62 volts, seventh contact had 3.52 volts w/ ignition on, eight contact had 5.32 volts w/ ignition on. Plug attached to eng toward radiator, second contact had 12.45 volts, contacts 6 & 8 had no voltage in either position. I had to ground to frame for readings not knowing what contact was ground or the numbering system for this plug.
A friend suggested the camshaft TDC was not working, I tested by cranking and got tach movment.
Hope this helps.
I checked voltage per your instructions and pinout diagram.
Black probe to #11 ground, red probe to # XXXXX contact read -12.63 volts.
Ignition on: black probe to #11 ground and red probe to #15 contact read -9.06 volts.
I strippped the cable covering on the 18 pin connector, but did not understand opening the # XXXXX pin wire and applying 12 volts to the 6 inch section.
I did strip the wire back 2 feet opened the wire ( 439B?D?) as marked, turned the ignition on and got 9 volts. I then traced (439B?D?) to the VCU and with ignition on got 12.26 volts. I disconnected the bulkhead connector to try and localize the resistance problem, but did not get any voltage that made sense e.g. 8.35,8.35 and one at 7.90 volts. Still not shure where the problem is comming from.
Just remember that circut 15 is ignition to the pld cut and strip the wire and applying 12 volts there and the retest will confirm thats the problem,put 12 volts to the wire going to the pld don't apply 12 volts to the wire going to the fire wall.just be sure that you are on the right circut per that diagram i sent..let me know..
I did some more testing since I was getting voltage from pin #6 to pin #11, zero voltage from pin #15 positive side of battery to pin #11
. I reversed to negative side of battery with the jumper and got 12 volts from pin #15 and #11. Is igniton pin #15 positive or negative? ( engine cranked ok did not start).
Could the VCU be doing this? I'll keep playing with it. I'm starting to get fond memories of replacing water pumps and injectors on 3406's and fuel pumps on 12v92's.
15,5 and 6 should all be power at key on,i need you to verify that,check with a head light if you have one,its a good test to check the integrity of the wire if not what are you readings with your meter,once again pin 15 is keyed power..
I went back to original wire connections. Igntion off: red probe to #6 black to #11 -12.72 volts,,red to #15 black to #11 -.112 volts.
Ignition on: red to #6, black to #11 -12.52 volts
red to #15 black to #11 -9.02 volts
My Fluke 77 iis the meter I'm using..
ok if you jumped battery power to 15 thats good,next we need to load down the battery circuts the best thing is a headlight,one side to 5 other to 11 next 6 to 9 when you checked 5 to 11 you said you got -12.5 is that right ? negative? where you multimeter leads backwards?..let me know,its possible your leads are backwards or something isn't right at your batteries,let me know before you do anything..
When I installed the new batteries, I verified connections, having spent the last ten years running and maintaining diesel-generators at an air base it can be critical to prevent damage to switchgear and automatic controls. So yes, the battery negative cables (black) attached to frame and positive(red) atttached, verified with two different DMM's with the possibilty the batteries were mismarked (trying to double check everything)
My Fluke meter com(black) and V,A, ohms(red) This is why I made a point about the (-) reading I was getting.
This does not sound normal per the diagrams I have.(DDEC wire listing and pinout for 16 pin engine plug.)
I'm looking for somethimg to use as a 12 volt load source. I never had a spare headlight laying around even with the three 20-30 year old cars I own( I maintain my own)
This is why I like the old vehicles, simple. If you need verification on anything, let me know.
I set up a 50w 12 volt test light, verified it at the batteries.
I connected it to pin # XXXXX and #11 and got good brightness.
I hooked it up to pin #15 and #11 and did not get a light...checked voltage under light load
light off -9 volts
light on -.002 volts
I jumped from the red...positive side of the battery terminal to pin #15 pigtail.
Clipped the light to pin #15 and #11......no light.
before plugging in with your light confirm all circuits are good...confirm polarity is right.reassemble and retest,,
Wired system back to normal and took the following readings from the 16 pin conn:
Ignition off using fluke DMM ---black to #11, red to # XXXXX volts
" " " " black to #11, red to #6.....-12.57 volts
" " " red to #11, black to #15.....12.50 volts
" " " red to #11, black to #6.....12.57 volts
Ignition on " black to #11, red to #15.....-8.9 volts
" " black to #11, red to #6.....-12.42 volts
" " red to #11, black to #15.....9.07 volts
" " red to #11, black to #6.....12.40 volts
I have the VIH to DDEC-ECU connector wiring print from June 17th answer that shows the picture of the connector.
It says at the bottom of the picture " looking into the Pins on the Harness"" Front"
Reading the picture.....On the Right, pins 1-8....On the Left, Pins 9-16, is this OK?
Is this correct? If so, those are the readings I'm getting. Is there a relay or something else that could reverse or dimminish the voltage on #15? I get -9 volts going from pin #15 diectly to frame ground as well.
According to the drawing on the print, by reading the shell markings, I've been reading everything upside down.
Took new readings....pins #5&6 (battery) to pin #11 reads 12.4 volts.
Pin # XXXXX and pin #11 ign off...zero volts....ign on read 12.48 volts.
sorry for the confusion,im glad we got that figured...so pld and vcu are good yes?
when you key on the check engine light comes on?
if so when cranking does it come on or stay on ??
also reconfirm that cicuts pass headlight test..
I rewired everything back to normal setup.
I light tested both battery pins to #11 ground.....light OK.
I hooked light to pin #15 and #11, no light w/ ign off....good light w/ ign on.
Turn ignition on with original factory connectors plugged in....no check engine light.
Cranked engine a good 10 secounds twice...no check engine light
pld and vcu good? I guess...voltage checks to vcu were good.
have you done anything else to this vehicle besides batteries,lately and hey its good we got that wiring thing sorted out.sorry for taking as long as it did..
has there been any work done to transmission clutch flywheel ?
I'Ve had the truck since this time last year and the only problem I had was the hvac relay went bad. I had it replaced in Abilene and the front disk brake pads replaced. I was getting a coolant and transmission temperature indications that were funny and had both replaced at the same time. They have been working good on my last two trips.
I changed the oil once....that is all I've done to the truck.
with the key on does the check engine light come on? does it stay on ?does it go out?
confirm foul level is good in both tanks
confirm no fuel leaks anywhere along driver side of engine
pull black covers off that say mercedes benz and confirm
let me know of all results
The check engine light does come on when I turn the key on...then goes off after the gauge test.
Fuel level is 60 percent...visable check OK.
Checked fuel lines by engine look good( did that when I replaced fuel filters).
I pulled the covers when I cracked a couple of the fuel lines to check fuel to injectors when cranking. No leaks seen at that time. No fuel in oil indicating loose injectors. No obstructions or debri in old fuel filters, no water found in racor prefilter when changed and refilled with fresh JP5( from D-G day tank at work.)
ok next i want you to check the crank sensor,its ontop of trans and to the drivers side of engine,you may have to remove shifter boot or 1/4 fender to access,there are 2 back there cam and crank,,go after the one pointing towards the ring gear remove inspect and clean...reinstall and make sure it bottoms then retest.next go to your electronic unit pumps and in between 5 and 6 you'll see a fuel line that goes into a tall fitting...thats your fuel pressure regulator.remove and inspect let me know what you find..
that regulator is basically a check valve
has a ball and spring and what happens is the ball moves off to one side and doesn't seal proper and thus fuel will pass through it prematurely and thus low fuel pressure.have a look but man.its just so odd that this problem off yours came up after doing the batteries none the less lets have a look or perhaps we can check fuel pressure and this is done by removing fuel temp sender and plumbing in a guage.that sender is in front of all your electronic unit pumps ..in front of number one actually.let me know how you did..
I checked the the fuel pressure regulator...ball is centered and passes the puff test.
Testing fuel pressure is going to be a little harder as all my high accuracy test gauges are allready in Texas, also I'm not shure I would get much pressure just cranking the engine. I did check flow by disconnecting 1&2 lines to the block and got a little flow when I was checking for blockage in the fuel lines.
Sorry for the delay, it took awhile to do some more troubleshooting....The engine has no compression...looks like a dammaged head. Would not start on ether and has blowback out of the intake. Pulled the rocker shaft to veryfy. ( all valves shut)
Thanks for all the help.