Check Engine Light, Glow Plug Light Stays On - PeachParts Mercedes-Benz Forum

hobberslobbers · #1 06-13-2011, 04:52 PM

Need some help on this one. Pics below are taken with the engine running (very smoothly and fine, I might add) on my wife's '98 E300 Turbodiesel. The two lights on the right are Check Engine (top) and Glow Plug (bottom) with the message below the speedometer, "Check Engine -- Engine Electronics." Could this simply be that I need to put a new set of GP's in?

kerry · #2 06-13-2011, 05:00 PM

Could be as simple as one bad glow plug I think.

hobberslobbers · #3 06-13-2011, 05:19 PM

Thx kerry. The reason I posted this is b/c I have heard that a GP light doesn't necessarily mean that it's a glow plug problem, and that it could mean other things. I guess I'll get my multimeter out and have a go at trying to isolate it.

hobberslobbers · #4 06-13-2011, 09:18 PM

P0380 was the code at autozone. Looks like some new GP's are in the near future for "Merry." Question, I am assuming the air intake manifold has to come off to get to all the GP's. Does this gasket need to be replaced too?

Aquaticedge · #5 06-13-2011, 09:44 PM

I dont recall, but if your engine is (I think) the 606 be very very careful.

hobberslobbers · #6 06-13-2011, 09:56 PM

aqua, your comment meaning?.... it is a 606. referring to broken GP's possibility?

sokoloff · #7 06-14-2011, 12:16 PM

Good plugs read about 0.7 ohms. Can find which one(s) is/are bad by checking at the glow plug relay connection on the drivers side (left) fender well. Manifold does have to come off. There is an excellent write up here on the process done by Lightman several years ago. A search ought to bring it up. I highly recommend you change them on a hot engine and use anti-seize on the new ones.

vstech · #8 06-14-2011, 12:50 PM

yes.
broken GP's are very common on this motor.
read up on the procedure for changing them. be very very very studious before beginning this trek, and be prepared for the car NOT to be running while you arrange for the tools and such to drill out a broken plug.

spark3542 · #9 06-14-2011, 01:11 PM

There's a 6 pin connector on the driver's side fenderwall. Disconnect this and measure resistance with an ohmmeter from each contact to ground. The contacts are numbered, but very tiny. Low resistance means good gp. Open resistance is bad gp. I would only change the GP that's bad. Some think "change all while you're in there", but that's 5 more opportunities to break off a gp and cause a big headache.

To change the gp: Lots of PB Blaster, warm engine, and use torque wrench to remove. Never exceed 50 Nm of off-torque. If it doesn't come loose at 50 Nm, spray more PB Blaster, go inside and watch a hockey game for an hour (go Bruins!). Then try again. Repeat as needed.

TMAllison · #10 06-14-2011, 01:14 PM

P0380 trips when the start sequence is attempted on cold plugs.

Is usually operator error; soemone turns key before GP light is out.

That code will clear itself after 3 cold/hot run cycles if the fault doesnt re-occur during that time. Usually 1 day for a daily driver with a quick trip to lunch or the grocery store thrown in.

Ignore it unless it remains lit.

hobberslobbers · #11 06-14-2011, 08:34 PM

thanks to all for the pointers! yeah, on my two old 300D's the gp's are easy to change. last set took all of 15 minutes. on the '98 i will go slow, use lots of PB Blaster, on a warm engine. man that stuff stinks! it works great though. i probably was the operator who err'd. my 83 starts great without a full gp cycle in the summer. starts like a normal gasser does, turns over twice and fires. it really is an amazing car! 310k miles and starts all the time. but i digress... i will be replacing the gp's on the e300 this weekend. wish me luck. next project after the gp's will be rebuilding the injectors on the same car.

TMAllison · #12 06-15-2011, 10:48 AM

Unless you've tested them at the relay and a GP is bad, why tempt fate replacing something that isn't broken???

Mine have been in for almost 200k miles.....I won't put a wrench on one until it doesnt work anymore. I used OEM Beru plugs, the same as came from the factory. They are slightly larger where the barrel connects to the nut/head than bocsh plugs are. Also cost more.

hobberslobbers · #13 06-15-2011, 09:07 PM

TM, I'm glad you asked and your advice is well-taken! Ok, so I finally convinced myself that the price of a digital multi-meter pales in comparison to the "price" in sweat and aggravation of a broken glow plug on one that didn't really need to be replaced in the first place. And here's the results of my ohm/resistance test on my DMM:

Pin Ω's
1 - 0.7Ω
2 - 0.8Ω
3 - 0.6Ω
4 - 0.7Ω
5 - 0.L (infinity)
6 - 0.6Ω

So, it looks like #5 is the offending plug. Question: To which cylinder does the #5 pin on the plug refer? I am assuming cylinder #5, but am asking the question nonetheless to be sure. If it does, in fact, refer to cylinder #5, is it cylinder #5 in the firing order or is it simply the 5th cylinder counting from front to back? Obviously, I am looking for a definite answer on this. Many thanks in advance for your answers.

spark3542 · #14 06-16-2011, 07:41 AM

It's cylinder #5, counting from the front. Confirm this with your ohmmeter once you have the manifold off. This eliminates any possibility that the open is in the wiring somewhere.

spark3542 · #15 06-16-2011, 01:53 PM

And speaking of ohmmeters...Harbor Freight just sent a grand opening ad (Braintree, MA) and coupon for FREE digital multimeter. No toolbox should be without one when they're FREE!!!

Where's that "skinflint" thread again??