glow plug lights stays on for about 45 seconds after starting - PeachParts Mercedes-Benz Forum

WANT '71 280SEL · #1 08-12-2003, 10:57 AM

Explained it all. Yesterday morning I went to start the '79 300SD when as soon as it started the glow plug light came on and kept blinking. I turned it off but it didn't shut off? Where would the vacuum leak be for not turning off? But anyways, it finally turned off and I restarted it, it blinked for about 45 seconds. It always does that now ever since yesterday morning. It blinks the same amount of times every time it is started. Does it if the engine is cold or hot.
Thanks
David

P.E.Haiges · #2 08-12-2003, 11:16 AM

Want,

The automatic GP system is telling you that you have an open GP.

Do a resistance test on the GP to find the bad one and replace that one only. It might be a good idea to put the new GP in cylinder #1 and replace the bad GP with the GP from Cylinder#1.

P E H

coachgeo · #3 08-12-2003, 12:52 PM

stupid question

cylinder one is on which end. Radiator end or firewall end?

#4 08-12-2003, 01:21 PM

Cylinder #1 is closest to radiator and the rest count upwards toward the firewall.

coachgeo · #5 08-12-2003, 02:31 PM

Quote:

Originally posted by Cazzzidy
Cylinder #1 is closest to radiator and the rest count upwards toward the firewall.

and a front wheel drive will then again throw my wayy off... Just kidding.

Much thanx.

WANT '71 280SEL · #6 08-12-2003, 03:17 PM

what kind of resistance should I get on each one? Are they all the same resistance?
Thanks
David

P.E.Haiges · #7 08-12-2003, 08:22 PM

Want,

The GP should all measure about the same, 0.6 to 0.8 ohms. A bad or open GP will almost always stand out as being different from the others.

Easiest way to measure GP resistance is to take the connector (the one that it's cable goes to the GP) out of the GP relay and use a banana plug in the connector holes for the one ohmeter lead. The other ohmeter lead must goto a good cround. When you find a high reading, just trace that wire to the bad GP.

P E H

P.E.Haiges · #8 08-12-2003, 08:25 PM

Cazzzidy,

Ok we all know where the #1 cylinder is.

Where is the #2 cylinder on a MB V type engine?

P E H

coachgeo · #9 08-12-2003, 08:58 PM

Quote:

Originally posted by P.E.Haiges
Want,

.....Easiest way to measure GP resistance is to take the connector (the one that it's cable goes to the GP) out of the GP relay and use a banana plug in the connector holes for the one ohmeter lead. The other ohmeter lead must goto a good cround. When you find a high reading, just trace that wire to the bad GP.

P E H

I know this is not my thread... just trying to learn from each thread I read. Hope ya dont mind me asking a for more generic explanation here. I dont have a stock GP relay etc. so can you please explain the above in more generic terms. For example I can't tell from the above if you connecting your lead to the Glow plug wire or to the Glow plug relay.

Much thanx.

Kyle Blackmore · #10 08-12-2003, 10:03 PM

Coach , you can check the resistance at the plug or the connector at the relay. The important thing is to have continuity between the glow plug's terminal and it's body (which gets grounded when it's installed), the ohms measured will tell you if the internal resistor is within specs . If you get a reading that is more than 1 ohm at 20C (68F)then there is a problem . Bypass the wiring and test at the GP terminal and if you still are reading more than 1 ohm then replace the GP. What kind of a relay did you install, mine is acting up and $235US ($345Cdn) is more than I want to spend right now

.

P.E.Haiges · #11 08-13-2003, 03:45 AM

Coachgeo,

Once you remove the connector from the GP relay, there is no connection between the relay and the GP. So when you connect one end of the ohmeter by plugging a banana plug in the hole in the connector, you are connecting the meter to the GP thru the wire that connects it to the relay and eliminating spureous readings because by removimg the connector, you eliminate parallel connections to other GP. The only other way to get correct readings is to remove the wire from each GP being tested which is more difficult than removing the connector from the GP relay.

One more test you can do after the GP is out of the engine is to clamp the GP body in a Vise Grip (VG) type wrench (is there ever any end to the usefullness of a VG wrench) and then touch the handle end of VG to one terminal of the battery and the GP terminal to the other battery terminal. The GP should glow red hot within 10 seconds. If it does, the GP is OK, if not its KAPUT.

Be careful handling the GP after the above test. It will be hot unless its shot.

P E H

P.E.Haiges · #12 08-13-2003, 04:14 AM

Coachgeo,

Only if the FWD has a transverse mounted engine.

LOL

P E H

coachgeo · #13 08-13-2003, 12:01 PM

Quote:

Originally posted by Kyle Blackmore
Coach , you can check the resistance at the plug or the connector at the relay. The important thing is to have continuity between the glow plug's terminal and it's body (which gets grounded when it's installed), the ohms measured will tell you if the internal resistor is within specs . If you get a reading that is more than 1 ohm at 20C (68F)then there is a problem . Bypass the wiring and test at the GP terminal and if you still are reading more than 1 ohm then replace the GP. What kind of a relay did you install, mine is acting up and $235US ($345Cdn) is more than I want to spend right now .

the elec. shop that repaired mine when it broke down to far from home used a solinoid and a relay from Radioshack. You can get the parts just about anywhere was his reasoning and since it had its problems in dumbfawk middle of nowhere it was wise choice. I got lucky (I think) the little auto elec. shop I got myself too that day,well the owner was retired diesel mechanic (12yrs) turned auto electric.

Real glad he did it this way if the correct parts are that spendy owwwww. The repair and parts cost me 1500 as it was.