I did a bunch of work on my wagon this weekend, most importantly replaced all the GPs (at least one was noticeably bad) and switched to Mobil Delvac 1 (she is much happier now).

I'm 99% sure this is battery related, but when I turn the key to light the GPs the first time no light comes on, but if I turn the key back and then on again the light comes on fine (and it starts perfectly when cold). I notice that the fuel pump is running the first time (maybe to prime the system), but if I let it finish it's cycle it won't come on the next time I turn the key. I'm guessing this extra voltage that's used by the fuel pump the first time is causing too much of a draw for the GPs to even light up, is this correct?

My voltage when cold and not running is 12.7, but I noticed that when the fuel pump is running (no GP light), the voltage can drop down to as low as 12.1 volts.

Never had this problem before, but I guess now that all my GPs are in functioning order there is more of a draw and now they need more volts that my batter cannot provide.

I also replaced my oil level and oil pressure sending units, now my low oil level light doesn't come on during hard left turns, yippee. That oil pressure sender is in a tight spot eh? Had to get a stubby open end 17mm for that one.

Made an attempt at replacing the flex disc joints but couldn't for the life of me get the old (looks original) one out.

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-justin

1987 300TD, 1987 300TD
2008 R32, 2000 Passat Wagon

Have you checked ALL the GP circuitry? Did you check the individual pins from the relay send, and the wires that actually go to the glow plugs?

With the factory GP relay, you can hear it turn off (slight click sound) after glowing for about 20 seconds. My GP light goes off after about 5, but the relay is still activating the glow plugs for 15 more seconds.

Dieselgiant.com has a good page for troubleshooting GP systems.

http://dieselgiant.com/glowplugrepair.htm


Let us know what you find out!

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alimony

Already been through all that type of stuff.

If the light comes on the second try and the car starts perfectly (it didn't start perfectly when cold until now), then I'm pretty sure the GPs are working

I remember hearing that the GP relay won't even give power if it doesn't have the voltage it requires, wanted somebody to give me reassurance that is true before I go buying a new battery (my budget is tight at the moment).

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-justin

1987 300TD, 1987 300TD
2008 R32, 2000 Passat Wagon

12.7 V cold is a good number, I know with gasser models, the fuel pump pressurizes the system then shuts off.

I didnt realize that those diesels had an electric fuel pump... learn something new everday

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1984 Euro 300SDC, (4spd standard)
1986 Toyota Landcruiser Diesel HJ60 5spd X2

Gone but not forgotten (some sold, some stripped)
1983 300 SD, 1985 300 SD, 1983 240D, 1986 300 SDL, 1985 300 SDL, 1983 300 D, 1984 300 D, 1985 300SD, 1987 300 SDL, 1983 300 SD, 1985 300 TD Euro, 1983 380SEC, 1990 300 D, 1987 300D, 1982 300D, 1982 300D, 1994 E420, 1987 300 TD, 1987 300 D, 1984 300 D

Just got back from AutoZone, they tested the battery/alternator and said everything was fine and told me I didn't need a new battery.

What we noticed is that when I turn the key the first time, battery voltage drops down to the low 11 volt range, but after about 10 seconds it slowly crawls back up to the low 12 volt range (no GP light ever). If I turn the key off and then back on again, the GP light comes on and the voltage never drops down into the 11 V range.

What would explain the drastic drop in voltage the first time, but not the second (assuming the battery was tested properly by the AZ guy)?

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-justin

1987 300TD, 1987 300TD
2008 R32, 2000 Passat Wagon

very interesting problem...

have you tried disconnecting the 'lift pump' in the fuel tank?

at least i think it's the lift pump........you can access it by taking out the first aid kit.


i'm not saying your car will run like that...but perhaps you may be able to see if there's still that voltage drop...(perhaps the commutator or brushes are worn a bit on the pump motor?)

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alimony

I lost oil flow to my 87300d after the oil was changed and the most people I have talked to never herd of this but they think it is probably the oil level sending unit causing the problem. If you would please let me know with more detail how to change it it I would greatly appreciate it and thanks in advance.

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Pete.