OK, I've cooled down and can now post this question up here without cursing the whole time.

I have a 1976 240d and I believe the glow plug relay is bad. I went to the junkyard and followed every freaking wire coming off the start/stop pull switch on a 73 220d, but none took me to the relay. The shop manual said it is behind the instrument cluster, but I didn't see the "box" that was described in the book. I'm about ready to jerry rig something.

Car runs great but that first start up in the morning is killing me. Will burn out the starter soon, or the glow plus, or the freakin' battery.

Thank you in advance for the help!

Todd

Good luck finding that relay,,,,, it doesn't have one.

Power is applied to the glow plugs when the gorilla knob is held in the 3/4 position.

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Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

If your car does not have the aforementioned knob, the glow plug relay on a w115 would be in a silver relay box above the throttle and brake pedal. It isn't under the hood like on a w123 or w126.

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"spreading a trail of obnoxious where ever we go"
1981 300sd w/ 341,500 miles

http://www.wecrash.com/pics/ddda_banner.gif

I don't recall if M-B continued the gorilla knob arrangement through the '76 MY or not, but if they did, then no, your car has no relay. If, on the other hand they switched to the key-start pre-glow system found in the 300D W115 then there is a relay. Either way, the car you looked at in the junkyard would not have had a relay because it would have used the gorilla knob arrangement and does get its GP power directly from the switch in the knob.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Only the 75 or 76 300D had a GP relay. The 240D models did not. Your problem unless mice ate the wiring is a bad glow plug. Check the power at each glow plug and you'll solve the problem.

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1974 240D 3.0L 4(M) - 250K -OM617.910 + 300D FW + Rajay turbo power!
1977 6.9 3(A) - 84k

Thank you guys. Sometimes I have to laugh at myself. I have the service manual for "engines OM 615-617". I just read, on the first page of course, that engine 615 is in the 220d, 616 in the 240d, and 617 in the 300d (114/115 bodies). And on page 480/1 it describes how the 615 and 616 start with the push/pull knob, and on page 505/1, how the 617 starts with the use of a relay! Duh.

Disconnected the wire that goes to plug four. Believe it is the violet/white wire. Does have electricity going to it. So today I'm gonna pull the plugs (only a few months old) and clean the wire connections today and see what happens.

Thanks again

So let's say you had a '76 W115 300d. I'm looking at the glow plug relay from one and I'm seeing a pin for B+, ground, key on, start, and glow plug output. Is there a 2nd relay that runs the indicator light? Is there a temp sensor at all?

-Jason

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Quick way to isolate the problem on this system,,, take a volt meter or test light and go directly to the nut on #4 glowplug. Pull your.. and I love this term.. Gorilla knob out and hold it against the spring stop. You should see approx 10-12 volts on that connection. ALSO, if you have the alt light and brake light that light up on the intstrument cluster.. you will notice a decrease in brightness when you are on teh correct spot with the gorilla knob. If you have 12 volts at this wire, then go down your glow plugs and see where you are loosing your voltage. It will drop as you go down the line, this is normal. I'm assuming you have the original set up of gp in series, with the squiggly resistor wire between them. IF you have a newer type glowplug (I recommend them for colder areas) then you will have a jumper wire that goes from plug to plug all the way down. These will have 12 volts approx to each glowplug.

The 300D has a "normal" key on to glow system. My friend took the connector apart and the wires got all moved around so we're trying to get it back to stock.