How can you tell the glow plugs are going bad? - PeachParts Mercedes-Benz Forum

veg_hed_300d · #1 02-11-2007, 05:27 PM

I know it's been cold for the last few weeks but I have not been able to get the Benz started up without a jump over the last week. It cranks and cranks until it finally runs the battery dead. When I did get it started with a jump and a little ether, I had the battery and alternator checked and they were both good. It ran fine last year with a mix of biodiesel and petro-diesel. Now it has all petrodiesel in the tank and still it won't start in the morning. Also, no block heater, but I did purchase a coolant heater that goes in the lower radiator hose. So how can I find out if the glow plugs are bad? I checked them with an ohm tester and all tested well. But just to make sure, what are they supposed to test at?

angst · #2 02-11-2007, 05:37 PM

Here is a good link with plenty of pics. http://dieselgiant.com/glowplugrepair.htm
Dont forget that unplugging the relay plug is important. Otherwise your ohm reading is no good.

Most here considerer .8 as the threshold with your meter set on the 200 ohm setting.

veg_hed_300d · #3 02-11-2007, 05:38 PM

mine registered at .6 on the 200 ohm setting

toomany MBZ · #4 02-11-2007, 05:53 PM

The CD plugs are at .7 ohms. This is with a cheap multimeter, has only a single ohm setting.

mybenz123 · #5 02-11-2007, 05:57 PM

Quote:

Originally Posted by veg_hed_300d

I know it's been cold for the last few weeks but I have not been able to get the Benz started up without a jump over the last week. It cranks and cranks until it finally runs the battery dead. When I did get it started with a jump and a little ether, I had the battery and alternator checked and they were both good. It ran fine last year with a mix of biodiesel and petro-diesel. Now it has all petrodiesel in the tank and still it won't start in the morning. Also, no block heater, but I did purchase a coolant heater that goes in the lower radiator hose. So how can I find out if the glow plugs are bad? I checked them with an ohm tester and all tested well. But just to make sure, what are they supposed to test at?

When was the last time your valves where adjusted?
If more than a year, it should be done asap.

Louis.

cmp · #6 02-11-2007, 06:19 PM

I'm having a similar problem with my 240. It starts, but only after several glow cycles and it still barely bumbles to a start.

I replaced the glow plugs with the cheap ones (Autolyte, old-style), and had a valve adjustment and a block heater installed. It's still having problems starting, so I have ordered the glowplug upgrade kit from Diesel Giant. Hopefully I can get that installed and solve some issues.

Could it be the cheap glow plugs causing rough starts?

GRIESL · #7 02-11-2007, 07:40 PM

Quote:

Originally Posted by veg_hed_300d

I know it's been cold for the last few weeks but I have not been able to get the Benz started up without a jump over the last week. It cranks and cranks until it finally runs the battery dead. When I did get it started with a jump and a little ether, I had the battery and alternator checked and they were both good. It ran fine last year with a mix of biodiesel and petro-diesel. Now it has all petrodiesel in the tank and still it won't start in the morning. Also, no block heater, but I did purchase a coolant heater that goes in the lower radiator hose. So how can I find out if the glow plugs are bad? I checked them with an ohm tester and all tested well. But just to make sure, what are they supposed to test at?

If you really want to see if they're good, pull 'em and juice 'em with some jumper cables. It may be overkill, but it is kinda cool to see them glow.