My problem is this:

I have installed new glow plugs and injectors but I am still having problems on cold starts.

The engine starts just fine and runs fine for about 10-15 seconds.

Then it gets rough and plumes of white smoke come out the exhaust.

This morning it was about 50F when I fired it up.

According to the charts I have seen I should have about 30-40 seconds of afterglow at this temp.

I don't think I'm getting that.

From what I can gather from all the posts I've read on the subject, it could be my GP relay or my temperature sensor.

I am getting glow at first and it starts fine so I doubt it's my relay.

Could all of this be caused by a bad temp sensor to the GP relay?

If so, what exactly is this temp sensor called?

I have searched in parts but I haven't found what I am looking for.

The sensor is located between the water pump housing and the thermostat housing.

The wire runs from there to the GP relay.

I have noticed that one of the clips holding the wire onto the sensor is missing but it is still firmly attached to the sensor.

Is this the only temp sensor on the engine?

Is there a way to test it?
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I don't want to confuse the situation too much at this point but I am also having an ongoing problem with my HVAC.

When the A/C is on and I floor it to pass somebody the A/C will stop cooling and immediately start HEATING the cabin.

I have to turn it all off, wait a few seconds and then turn it back on in order for it to start cooling again.

Could this be the same temp sensor or is it another problem entirely?

__________________
1993 W124 300D
-297K on the clock as I type this.

The easiest and best way to get empirical data on exactly what is going on with the glow plugs it to connect an indicator to the system. Get a pair of medium size insulated alligator clips, five or six feet of insulated wire, and either a 12V bulb/socket or better yet a 12V LED indicator from Radio Shack. Attach the alligator clip (red if you’ve got it) to enough wire to reach from GP 1/2/3 (these are usually the easiest to get to but any plug will serve the purpose) to just the other side of the top edge of the engine compartment inner firewall. Connect the other end of this wire to either one terminal of a 12V bulb or the + terminal of the LED indicator. Take another foot of two of the remaining wire attach the second alligator clip (black if you’ve got it) connect the other end of that wire to the other bulb terminal or the - terminal of the LED indicator. If you use a bulb or socket make sure to insulate its outside to prevent it from potentially shorting out when operating, make sure you insulate the wiring connections at the LED lead wires for the same reason.

You have constructed a 12V indicator tool, which you can now connect the alligator clip (red) on the longest wiring leg to the glow plug at its terminal connection to the wiring loom, run the wiring so that the indicator lays a couple inches over the top edge of the engine compartment fire wall, attach the alligator clip (black) on the shortest wiring leg to a good ground on the engine or chassis under the hood.

Now you can shut the hood and the indicator bulb/LED will be held in placed sandwiched between the hood pad and the rubber gasket running along the top of the inner fire wall. The indicator light bulb/LED will be under the rear edge of the hood and visible from behind the wheel.

When you initiate your start procedure the GP relay will energize allowing current flow to the glow plug will simultaneously cause the indicator to light up and lack of current caused by the GP relay de-energizing will cause the indicator to turn off. This way you can accurately identify and time the actual interval of glow plugs being energized. From there you can proceed further to ascertain the cause of insufficient energized glow plug interval.

I have semi-permanently installed an LED indicator of this type (on this installation I added an inline ¼ amp fuse just in from the connection at the glow plug too eliminate any chance of a short in the wiring from the GP to the indicator) on a vehicle that my daughter drives to assist her when she is using the “multiple glow cycle method” of starting in the coldest weather.

It served a secondary purpose last year when she made note of the “failure of the indicator to light” symptom when she experienced a failure to start situation. It was useful element of “failure to start” diagnostic information that prompted me to include a spare GP relay replacement with the tools and parts I decided to bring with me on my 100 mile “daddy service call”.

I thought the 2.5 had a 2-pin temp sensor on the head. If it's a single pin sensor by the thermostat, the part number is 005 545 03 24 and I've seen it for as little as $10 online. That's what I have on my car with afterglow relay since I ditched the BFS which uses a temp switch in the same location.

I don't have an FSM handy but I'd check resistance between the temp sensor pin and ground when the engine is stone cold and at operating temperature. It should be considerably different cold and hot. Check also resistance across the wire from the temp sensor to pin 5 of the glow relay. Should be close to no resistance.

There might be something more going on if 10-15 seconds of afterglow is insufficient on a 50*F start. Non afterglow engines stabilize within that period. Of course it could be that afterglow relays don't preglow as long.

Sixto
87 300D

What makes the 602 different that the 603 (in reference to the afterglow)? The reason I ask, is that 50F isn't cold. Mine takes a couple seconds (of slightly rough idle) and then it's ready to go.

If it isn't the glow plugs or injectors, what else is there? Compression?

__________________
1982 240D, sold 9/17/2008
1987 300D TurboW124.133 - 603.960, 722.317 - Smoke Silver Metallic / Medium Red (702/177), acquired 8/15/2009
262,715 and counting

That's just it.

I don't think it is afterglowing at all.

I think the smooth running just after start is due to the glow plugs still being hot from the initial glow.

I think that they stop glowing after I start the engine and once several doses of cold/cool diesel hit them they cool off causing the smoking.

I think that is what is happening based upon what I am seeing.

It did the same thing before I installed new glow plugs and injectors but now since my injectors are all working properly there is more smoke because there is more fuel present.

__________________
1993 W124 300D
-297K on the clock as I type this.

What you're describing is POSSIBLY a failure of the AfterGlow system...
(Might be caused by a bad B11/7 ?) [Picture Below]
[engine Temperature sensor for the Pre-Glow system]
(Bad sensor tells the PreGlow relay the engine's warmer than it really is?)


I like BB's suggestion of an "AfterGlow" indicator...
[a quick and dirty would be a 12 volt test light: with one end to ground
and the other hooked up to one of the Glow Plug(s) positive terminal(s).
Then you could "Watch" the Voltage/Current being applied to the GPs
by the Pre-Glow Relay and count your seconds of "AfterGlow".
'Might have to have an "Assistant" turn the Ignition Key to "Glow" and then "Start".
Or do it yourself and jump up and out to see the test light.]

Jeremy5848's earlier post on the "Clean" permanent installation of one in the
dash is an easy modification.
http://www.peachparts.com/shopforum/showthread.php?t=236848&highlight=afterglow
Start reading @ reply #19 ,before that he's giving instructions on how to
install an "AfterGlow" system relay on a OM603 that didn't have one.


If you have the Correct Pre-Glow relay for your 124.128 it will match the pictogram below...NO 80 Amp Fuse.
[AND no G6 terminal,you've got a 5 Cylinder]
The Correct Pre-Glow Relay has the "AfterGlow" system.


TBC in next reply

Attached Thumbnails

         

__________________
'84 300SD sold
124.128

(Kick me for asking)
1.Are We positive All the GPs are Good and Working?
(You "HOT" tested each one with Jumper Cables and a fully charged 12 volt battery,before installation?)
2.Are We Positive the Wiring between the Pre-Glow relay and the GPs is Good?
(You've ohm-ed out all the wires with each end disconnected AND checked for
Clean ,Tight connections)
3.Is the wire from the Pre-Glow relay to B11/7 Good?
(You've tested it with a DMM connected to both ends AND disconnected from
the PGR and B11/7)

Attached Thumbnails

     

__________________
'84 300SD sold
124.128

I did test all the glow plugs before I installed them.

I used a Craftsman battery charger set on 10A as the power source.

They all glowed beautifully prior to installation.

I am convinced the pre-glow is fine.

The engine starts beautifully and without drama.

It's about five seconds after it starts when it starts to smoke.

I checked the relay earlier and it definitely doesn't have a fuse but I didn't take out the plugs to count the pins.

I am operating on the assumption that the relay is the right one.

What part on the relay could cause a faulty "after glow?"

If that's the problem I would have to replace the whole thing I assume.

I am definitely going to test/replace the coolant temp sensor to see if that's the problem.

I did test all the glow plugs before I installed them.

I used a Craftsman battery charger set on 10A as the power source.

They all glowed beautifully prior to installation.

I am convinced the pre-glow is fine.

The engine starts beautifully and without drama.

It's about five seconds after it starts when it starts to smoke.

I checked the relay earlier and it definitely doesn't have a fuse but I didn't take out the plugs to count the pins.

I am operating on the assumption that the relay is the right one.

What part on the relay could cause a faulty "after glow?"

If that's the problem I would have to replace the whole thing I assume.

I am definitely going to test/replace the coolant temp sensor to see if that's the problem.

A few days before I replaced the GPs I experienced two instances where the glow plug light came on after I had started the engine(it was running very roughly).

When I removed the GPs and tested them I discovered that only one GP had completely failed and another one had the tip broken when I removed it. I don't know if I did it or if it was already like that.

I rigged it together and it glowed like the dickens.

I have no blow-by at all.

Another thing that might be of interest is that at about 1100 RPMs the engine gets VERY clackety.

Below that or above it and it is much smoother.

At idle it is still rougher than I would like.

Until I drive it about 150 more miles though I won't be able to accurately ascertain whether it is running/sounding right since I have only recently disrupted the fuel injection system.

It always takes this long to sort itself out even when I just do a diesel purge.

__________________
1993 W124 300D
-297K on the clock as I type this.

Some aftermarket replacement afterglow relays have an 80-amp fuse. More telling is the fifth pin (temp sensor) in the small connector set.

Sixto
87 300D

Well, I may be optimistic but it seems to be smoothing out a bit.

I still haven't driven the 200 miles it usually takes to settle down after a disruption of the fuel injection system but it really does seem to be settling down a bit.

It will be much colder tomorrow so that should be a good test.

__________________
1993 W124 300D
-297K on the clock as I type this.

I have posted on this topic before but I now have some video/audio to go with it.

I have installed new glow plugs and injectors but I am still having a really rough idle on a cold engine.

The car starts fine and runs smoothly for about 45 seconds before it starts really getting rough and smoking.

I figure that this is about the time the after glow shuts off but I don't understand how this could be normal.

Any other info anybody could offer on the way my engine sounds is welcome.

It almost "lopes" at times like it does in the video and occasionally I will get a rough idle when warm also but nothing like this.

The engine has 234K miles on it and I am running Mobil 1 Truck and SUV oil.

http://www.youtube.com/watch?v=Hp32ZQSmZVE

__________________
1993 W124 300D
-297K on the clock as I type this.

Nice video. Couple of things.
A diesel will not warm up like a car does at idle. Don't treat it like an gasoline engine.
Is the Mobil 1 Truck and SUV oil Diesel Rated?
Ensure you run an Diesel Rated oil CI-4 or CI-4 Plus or CJ-4.

How does it run with the engine under a load, not at idle?

__________________
92 300D 2.5L OM602 OBK #59

Diesels take forever to warm up at idle, what happens if you just fire it up and drive away....then drive till it is warmed up...does it run ok once warmed up?

Being clackety and rough when cold is fairly normal, especially when its real cold out. The 603 does sound.....wimpier than the 617 though. The 617 is angry for the first 2-3 mins, then it smooths out and is happier.....unless you have the 3 minute afterglow glowplug relay, then it is smooth the whole time.

I agree on making sure the oil is the right type....

It could possibly be the auto-idle control causing it to idle too low....I'm sure others will have ideas too.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

First of all, this is a 602 engine.

Second, the Mobil 1 Truck and SUV 5W-40 is synthetic and diesel rated.

Third, what is the auto idle control?

I have done the GSXR pressure actuated wastegate mod, ripped out the rat's nest and blocked the EGR.

I have never seen any kind of a warning light from the "computer" either.

__________________
1993 W124 300D
-297K on the clock as I type this.

I think Sixto and GSXR need to see this...

__________________
Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)