glow plug lamp on

[markwilson8954]

Hi all, Sprinter 312d on a P plate 1996. i have had a fault with the glow plug curcuit. Ie one of the glow plugs went open curcuit. (HAd to be number 5 didnt it right at the back) anyway decided with it being sunday that i would remove the fualty one and change it with a more accessible one, then get a new one on monday, (today) and replace it so all were back working again. All that done but the glow plug warning lamp is still staying on indicating a fault. Is this normal and will it eventually go out or do i need to take in for the memory clearing. Also since i swapped the plugs around i have had great difficulty starting from cold. Engine turns over for ages with lots or smoke out the back as if its trying to start then all of a sudden after about 45 seconds springs into life. Any idea's.
Still doing this even with the new glow plug. Have double checked all the plugs and the wiring to them just in case but no cure.
Cheers
Mark

 

[Parrot of Doom]

Does yours have a glow plug relay? If so, check the blade fuses within the relay.

 

[markwilson8954]

Hi, thanks for speedy reply. i am getting 12volths through to the plugs so have not checked inside the box. Thought it should be ok if this was the case.
Cheers
mark

 

[Parrot of Doom]

If you're getting 12V then yes the relay should be ok, providing its allowing enough current to be drawn that is I'd assume it is and look at the glow plugs themselves.

I would nip into Mercedes and buy a new set of glow plugs - all of them. Change them all, and go from there, if one has gone the rest won't be far behind.

When I bought mine only 2 plugs out of 6 were working, but even in the coldest depths of frozen winter it would only take about 10 seconds of cranking to get the engine to fire up.

Did you perhaps disturb anything when you changed it over? Is there perhaps a fuel leak? If you can, try parking the van on a hill with the nose down overnight, see if that makes it easier to start in the morning (the theory being that less fuel drops back into the tank).

Sorry I can't be more helpful as I only really know about my own engine.

 

[battwell]

you also need to check that you are getting power to the glow plugs both before and after start. if a plug has been down for a while it can blow the links inside the relay (located under the battery on 312) also the main pos connection to the relay corodes and can snap off. check that too.

 

[wireman]

Before you go silly with the wallet disconnect the supply wire at each plug and check that they are not open circuit. The behavior you describe resembles that of the relay signaling that one or more plugs is dud.

The plugs have a low resistance in the order of 1 ohm which is not easy to measure using normal techniques and a DVM, Better use an ammeter (20A) and connect it from the battery to each glow plug in turn, expect an initial current around 12 -15A, falling as the plug heats up. Mind you dont burn your fingers holding the prods in place.

The total current draw of the heaters will be heavy around 70A or so and a poor connection from the battery to the relay will cause insufficiet heating of the plugs, check the voltage drop from the battery to each plug, if it's much more than a volt or so you may have a wire fault, typicaly corrosion inside a crimp tag.
If all seems well electricaly, test the compression in each cylinder.

 

[markwilson8954]

Hi people, thanks for all your help. Done some more test tonight. on ignition on i have 12v to all heater tops and engine starts fine, (still warm from todays ride home though) But after starting engine 12v seems to remain on the heaters and only dies away if i unplug and then replug the drive wire to the heater relay box. Seems strrange this as i would have thought after starting and a short post glow period of a few seconds the 12v would have been switched off. Going back to other comments about checking fuses and burned out tracks in the relay box itself, the unit seems to be sealed and have no place to open it up for inspection. Do i hace to break into this.
And finalyy, fault now manifests itself only when started from cold and starts as normal even on a morning but then 5 seconds later drops to what feels like 3 cyliders with black smoke out of exaust before 10 seconds later coming back to life and running normal from then on.
Another lecture over with, Any more idea's welcome
Cheers
Mark

 

[battwell]

312 starting problem.

if it starts and runs on all 5 cylinders its not the glow plugs giving the problem.
the glow plugs are on before start to aid initial combustion then stay on to lower after start emissions (you should hear the relay clicking out or feel it if you have a noisy engine(by putting your hand on the relay)
ive never had this fault but would guess at the air temp sensor on the turbo pipe. another thing to check ...there is a black rubber bag which should be hanging off the battery tray, inside there are the loom connectors to all the sensors etc. it is marked oben,top. remove the bag and check for corrosion on the plugs. unplug each one, with ignition off, check the wire entries into the plugs too by a slight wiggle and a good look. use a good spray of magic (wd40) on them anyway and reattatch so the bag is in the upright position so it doesnt fill with water. i have had the main pump solenoid wire snap here which stops the engine totally. if this fails it seems you will have to get the fault codes read and analysed. its no good having your baby off the road.

when it starts and runs rough with the black smoke (usually overfueling) does it clear if you bring revs up or do you just leave it idle

also is your ecu box under the battery? if so check connections on that too.

 

[markwilson8954]

Hi, thanks again for the info, the smoke does clear if revved once the engine has gone back into working mode after about 10 seconds and van runs fine from then on, can stop the engine and will restart as normal. fault only re occurs after van has ben stood to cool off again, probably after about 3 to 4 hours. will check allyou have advised and get back to you
Cheers again
mark

 

[markwilson8954]

Hi all. update on problem
Have sorted out the glow plug problem, was in fact the glow plug relay which had a blown track inside. Unfortunately i still have problems. Originally i had one glow plug open curcuit and a damaged wire on another plug which shorted to the engine hence blowing the track in the relay box so all in all i was only starting up on 3 glows not 5. Right initial problem solved, however i believe this was masking a second fault which is now showing after repairing the glow curcuit. After starting the enigine from cold it starts as normal and runs ok but as soon as the post glow cuts in the engine starts to overfuel and bellows smoke out of the back. As soon as the post glow cuts back out engine runs as normal again. If engine is started from warm this fault does not occur. My theory is that having only had 3 glow plugs running in the past the current draw has been low compared to normal and not effected the rest of the ecu but now i have full current flow as soon as the post glow cuts in it must be dragging a voltage down somewhere thereby upsetting the ecu or other systems. Hence the reason why the fault is only showing after i have repaired the glow curcuit. Is there a regulator somewhere that feeds the ecu that may be faulty. Does anyone have any more idea's. I have changed battery, run new earth to chassis and checkd all other earths i can find. removed and cleaned all live wires from battery and checked for any trapped wires any where.
Any comments appreciated
Cheers
Mark

 

[dava]

Take a look at the harness that runs along the top of the bulk head under the bonnet. This rubs through on the inlet manifold, yet another common fault. Also earth on the engine block, passenger side near starter and while your in there check the harnes that runs to the starter from rubbing through, all from memory now, so dont shoot the messenger.