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  #1  
Old 12-30-2008, 06:59 PM
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Replaced glow plugs, still no glow plug light

I thought I'd tested the glow plug system pretty well from Diesel Giant's link. #2 and #5 came up with weird numbers when I tested them, so I figured those were the culprits.

I've FINALLY managed to get the old glow plugs out and the new ones in. Turned the key to see the glory of my work and ..... nothing. No glow plug light, and the car won't start normally (I'm sure if I crank it enough it will finally start).

We tested the relay pins again, and all getting good numbers on everything. Battery is giving plenty of juice, as recommended. Still, no glow plugs. This car has no fuse, so it's not the fuse. (resettable circuit breaker) Maybe that's bad?

Any ideas?

jeff 1991 300d, 128k


Last edited by jbach36; 12-30-2008 at 07:18 PM. Reason: incomplete
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  #2  
Old 12-30-2008, 07:13 PM
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Do you hear the relay clicking off after the glow cycle?
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  #3  
Old 12-30-2008, 07:13 PM
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I'm not sure what you have already tried, but can you hear the relay 'click' after leaving the key in the ON (not start) position for 20-30 seconds? If not I'd suspect a faulty relay. Make sure the relay has a good ground connection. I also assume you have checked the fusible link for the Glow Plugs to make sure the power is in fact getting to the plugs.
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  #4  
Old 12-30-2008, 07:15 PM
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Quote:
Originally Posted by UriahT View Post
Do you hear the relay clicking off after the glow cycle?
Great minds think alike !!
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  #5  
Old 12-30-2008, 07:17 PM
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Relay seems to work fine

Quote:
Originally Posted by Dervman View Post
I'm not sure what you have already tried, but can you hear the relay 'click' after leaving the key in the ON (not start) position for 20-30 seconds? If not I'd suspect a faulty relay. Make sure the relay has a good ground connection. I also assume you have checked the fusible link for the Glow Plugs to make sure the power is in fact getting to the plugs.
Seems as though the relay is working fine. There's a click when on, and then after about 30 seconds.

jeff
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  #6  
Old 12-30-2008, 07:18 PM
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What did you mean, fusible link?

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Originally Posted by Dervman View Post
I'm not sure what you have already tried, but can you hear the relay 'click' after leaving the key in the ON (not start) position for 20-30 seconds? If not I'd suspect a faulty relay. Make sure the relay has a good ground connection. I also assume you have checked the fusible link for the Glow Plugs to make sure the power is in fact getting to the plugs.
What did you mean by fusible link?

jeff
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  #7  
Old 12-30-2008, 09:59 PM
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I think we established in another thread that your relay has a circuit breaker, no fusible link.

Can you check voltage at each glow plug terminal while glowing?

Can you attach an ammeter to the big red wire into the relay? You should see 40-60 amps while glowing.

Feed +12V to the black wire in the small relay connector (disconnected from the relay!) and see if the glow light comes on.

Sixto
87 300D
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  #8  
Old 12-30-2008, 10:31 PM
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Over my head

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Originally Posted by sixto View Post
I think we established in another thread that your relay has a circuit breaker, no fusible link.

Can you check voltage at each glow plug terminal while glowing?

Can you attach an ammeter to the big red wire into the relay? You should see 40-60 amps while glowing.

Feed +12V to the black wire in the small relay connector (disconnected from the relay!) and see if the glow light comes on.

Sixto
87 300D
When he was talking about the fusible link, I didn't know what that was, but I see what you mean now.

We tested when the relay kicked in, that each glow plug (measuring from inside the 5 holes on the pin switch in the relay box area) and we got something like 12.69 or 13.69 or something, to each plug, straight across.

I'll try the big red wire in a few minutes, see what I get. I'm guessing I have to hook the black wire of my tester to the negative battery, and the red to the red wire on the relay?

I don't know how to feed 12v into the black wire.

jeff

Last edited by jbach36; 12-30-2008 at 10:35 PM. Reason: wrong
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  #9  
Old 12-30-2008, 10:45 PM
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I tried that, but ....

I tried hooking up my multimeter, black wire to the battery, red to the relay, and really didn't see any numbers come up. I tried DC amps at first, then
dc v, then ohm. Pretty much flat lined.

I must have done something wrong, because before I changed the glow plugs, the car would at least start. According to one member, if all the glow plugs are out, the car is near impossible to start. Being that it could start, though a bit rough, he reasoned that at least a few of the plugs were glowing, even though the light on the dash wasn't coming on.

But now that I changed the plugs, the car is reluctant to start. It cranks, but that's about it.

What now?

jeff

Last edited by jbach36; 12-30-2008 at 11:00 PM. Reason: wrong
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  #10  
Old 12-30-2008, 10:57 PM
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To check current, you have to disconnect the big red cable from the relay and put the ammeter in series. Most handheld VOMs cannot handle that many amps. I mean look at the size of your probe wires compared to the big red cable.

To test the glow bulb, remove the small connector, identify which connector corresponds with the black wire (should be pin 3, there are tiny numbers next to each contact), run a wire from the big red cable to the black wire connector, check if the glow light is illuminated.

Sixto
87 300D
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  #11  
Old 12-30-2008, 11:01 PM
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read above

Uh-oh, I had just amended my previous reply, please read earlier post above.

jeff
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  #12  
Old 12-30-2008, 11:08 PM
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test the bulb?

Quote:
Originally Posted by sixto View Post
To check current, you have to disconnect the big red cable from the relay and put the ammeter in series. Most handheld VOMs cannot handle that many amps. I mean look at the size of your probe wires compared to the big red cable.

To test the glow bulb, remove the small connector, identify which connector corresponds with the black wire (should be pin 3, there are tiny numbers next to each contact), run a wire from the big red cable to the black wire connector, check if the glow light is illuminated.

Sixto
87 300D
I haven't tested the bulb, but that seems to work fine, at least prior to me doing the repair it was working fine. I guess the plugs aren't working or something else is not working, or the car would start.

jeff

Last edited by jbach36; 12-31-2008 at 02:17 PM. Reason: wrong
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  #13  
Old 12-31-2008, 01:54 AM
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You're getting voltage at the glow plug harness connector on the relay but presumably nothing at the glow plugs because the glow light isn't working? Very odd. I suppose the harness can be so brittle that what movement it went through as you did this job broke all 5 wires. That can't be the prime suspect.

Did you do a resistance check of the new glow plugs at the relay connector? Did you check each plug before installing?

Did you check for voltage at the glow plugs themselves? Touch the probe tip to the terminal on the glow plug.

Just to humor me, is the stop lever in the up position when you're trying to start the engine? And check fuse 7 while you're at it.

Sixto
87 300D
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  #14  
Old 12-31-2008, 01:39 PM
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Relay?

Last night, I could hear the relay kick in and off after 30 seconds or so. Today, nothing. I know it worked prior to me changing the plugs. To make things more exciting, it's New Year's Eve, my multimeter is now not working, and my diesel car is getting no glow plug action. Can I even start the car with no glow plugs?

jeff
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  #15  
Old 12-31-2008, 01:55 PM
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60x engines need their glow cycle. Shouldn't hurt to try if you hold cranking sets to 30 seconds with a couple minutes cooling time in between.

Sixto
87 300D

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