Check the resistance of the old plugs that are not broken. They should be somewhere around 1 Ohm, maybe a little less or up to 1.8 Ohms.

My question about the broken tip is, I want you to be sure the whole plug came out berfore the new plug was inserted by your "mechanic." Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Jim, it's not entirely academic. If the black lead is used in the - socket for the meter and the red lead is used in the + socket, the meter (analog) will peg itself on the bottom end of the scale (attempting to read -12V). It's not the most beneficial exercise for the meter.

So, the polarity of the cabling is somewhat important, although the selection of red or black for the + or - lead, respectively, is not.

Yeah, but an analog gage? Can you buy them anymore? An old geezer like me wouldn't be able to read the meter without terminal eye strain - I have not used an analog meter for twenty years! The idea of having that little mirrored strip and those skinny little lines and scales and a freaking needle to get all lined up to read makes my sinuses ache. I like the big LCD displays that people with aging eyes can read without a strain.

There is something to be said for reading the manual that came with the tool before you set out to apply it to various items in the car and in the house. If you are new to the tool and don't like reading instructions, buy lots of fuses. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

LOL........yes, I can commiserate. I still use the pocket Radio Shack meter (pack of cigarettes) for most of my work. But, I don't actually read the numbers on the meter..........I just estimate where 12V would be (80% of full scale......15V).

My major problem is with sockets.........it's damn near impossible to read the numbers on the sides..........I might have to get a new set of Craftsman with the huge laser marked numbers..........the existing sets are driving me nuts.

Oh, I sympathize with the socket markings! There are just too many, as well. All I want is the size, who cares about the other stuff? It is that and light. Under the hood on a sunny day is the worst. I actually have to get a drop light out to see anything in the shade!

Getting old sucks. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

I have two 8' flourescent light fixtures in each garage bay. Total of 440W of flourescent power in the bay.........right over the hood.

Now, you'd think that such light would be on par with the sun. But, once the hood is open and you need to peer down near the alternator and find some fasteners...........it cannot be done. I recently bought a flourescent drop light.........rugged and covered in rubber..........it's been a lifesaver for me.

I really cannot figure out where all the lumens go.........because they are not headed toward my eyes.

Agreed........

Much easier to check glow plugs if you do not have to remove them! Take the wires off each glow plug and apply battery power in series with an ammeter (the aftermarket round gauge type) and measure the current to each glow plug. An even easier method which does not require removing the wires or glow plugs is to use a starter motor ammeter by placing it on the wire to each glow plug.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I am not familiar with your engine. Did the so called 'mechanic' remove the manifofold and injector hardlines to change the glow plugs? If the hardlines are not reinstalled properly and there are leaks, it could cause the starting problems you're having even with good glow plugs. If the hardlines were disturbed, I'd install a clear return hose to the IP and make sure there are no bubbles before going further.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Following Brian's instructions I tried to test like this:

Tested battery got a 12.5v reading.

Then while in #2 key position placed black to ground and red to
the glow plug (touching the exposed plug right below the head)

I got no reading at all.

My test meter instructions say use black for the -pole so I did
it that way (taking from the +/- discussion that it doesn't matter).

Did I do it right?

I didn't test the old ones for resistance because I'm not sure
how to do that. I know I can find the instructions via the search
function so I'm doing that now.

other question:
Manifold was removed but not the injector lines. It was
incorrectly reattached and 3 lines are bent significantly and
one is pushed out of place so that the clip won't reattach. None
of them are broken though.

__________________
k. darkman
1987 300D Turbo 200k

No. You should be testing the glow plug for resistance. On your meter there should be a scale for Ohms. You select the low end of the available ranges of Ohms (on my Sears model 982406 the choice is 0-200 Ohms). Then, you unplug the connector between the glow plug relay and the glow plugs. The relay is located on the left front inner fender, near the top. It is a black plastic box, that has a kind of flip top that comes off. You open the box and will see a typical six pin electrical connector plug. You have to work it a bit to get it off the mating connector, and I don't recall if the part you pull off has the pins or the sockets. In any case, each pin or socket is the end of the wire going to a specific glow plug. When you test you look for resistance from the pin or socket to ground. The circuit includes the glow plug. One of the halves of the connector has an identifying number cast into the black plastic adjacent to each pin or socket, so you can know which plug you are testing.

Alternately you can check from the threaded end of the glow plug to ground, which can be any convenient surface on the engine or head.


If the plug is out of the engine, you check resistance again, but this time between the end that has the electrical connection (on older cars this is the small threaded end, and a smooth pin on newer cars) and the large threaded surface that engages the threads in the cylinder head.
It is not a good idea to bend them at all, and then to leave them essentially unsupported is asking for a fatigue failure from engine vibration and the pump pressure pulsations. So, I would try to either coax them back into their original orientation and fit the clamps and fixtures to them, or replace them. Sorry. Others may disagree, and I have no specific analytical engineering basis for my concerns - just practical experience.

Good luck, and post back when you get the results of the RESISTANCE checks for the glow plugs. Once you have that data we can go into measuring voltage. The way you had the probes positioned you were measuring the voltage difference between the ends of a copper wire, which should be zero unless the wire is way too small for the current being passed. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Jim, his test was valid. He measured voltage directly at the glow plug tip and found zero.

All the resistance checks in the world are meaningless if there is no voltage at the plugs. I wouldn't bother wasting time on them.

Naturally, I'm presuming that the plug was inserted in the relay end.

If the fuse has not been replaced in the glow plug relay...........now is the time to do so.

Additionally, it's time to see if there is voltage at the relay. See if you get 12V at one...........or both..........screw terminals that hold the fuse in place.

I believe that the FSM recommends replacing any lines that are bent or damaged. I might be remembering this from my CAT manual, but I believe it is in both (for high-pressure lines).

The "mechanic" should be replacing any lines that he damaged or bent, but he probably won't, and probably won't own-up to causing starting problems either. Best of luck, and I'd suggest staying far from this part-changer in the future.

__________________

Gone to the dark side

- Jeff

I apologize. I misunderstood his test, but still don't find it definitive. if you measure the voltage from the tip of the connector to ground with the key in the #2 position you have to be sure the time on the relay has not expired and you have to be sure the relay actually has power. And, at that point about all the test would prove is the wire from the relay to the plug was broken.

Checking the health of the glow plugs is typically done by measuring resistance. Checking the health of the circuit, including the relay, is typically done by looking for voltage when the relay is supposed to be sending the plug power. If the relay has voltage, and the glow plug doesn't either the switching element in the relay is kaput, or the wire from the relay to the plug is shot, or, as has happened to me, the connector plug was left unplugged at the relay and then you get squat to all the plugs. I have done this twice - left the plug off - and it is immediately obvious. I had some plugs working and now none. But it is still irritating.

So, I thought we were investigating the health of the plugs he has installed. I still maintain RESISTANCE is the measure of glow plug health.

When looking for voltage at the fuse, you again need to make sure you turn the key to position #2 within a minute or so of when you take those voltage measurements. Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Please refer to post #12.......herewith repeated:


If this post was followed, as instructed, we have a definitive answer and can make a reasonable conclusion that the relay is non-functional. The chances of a broken wire to the one plug that he selected is very slim........but, I'll grant that it's not impossible.

No additional tests are required for the resistance of the glow plugs.

I'd pursue the fuse as the culprit and, if not, the relay is the next choice.

Brian,

I agree that checks the relay circuit (go battery to the relay fuse to check the relay circuit alone), but, if the relay checks out ok, how does this test identify which plug is bad? If you recall the original problem was an apparent issue with one or two plugs that went awry when the "mechanic" got involved. I guess it is feasible the relay is now bad, but I was still back in the phase of the problem eliminating the plugs as the issue before expanding the scope or jumping to something else.

And, I have actually left the plug connecting the glow plugs to the relay unplugged/not fully engaged before, twice, in fact. That can be checked visually or by just pulling it off and making sure everything is aligned, and then pushing the plug back into the sockets.

Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)