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Old 06-11-2012, 08:57 AM
Registered User
Join Date: May 2012
Location: Edwardsville, IL
Posts: 8
Yesterday I removed and tested the old plugs. Only #1 and #5 glowed at all, and only #5 glowed like it should. It really is no joke that a resistance test doesn't prove that you have a good plug.

Reamed the holes, and installed the new plugs (with anti-sieze). Problem solved. The car started this morning with no problem at all, and ran smooth immediately.

Thanks to all who offered advice. It is very much appreciated.
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Old 06-11-2012, 11:24 AM
Registered User
Join Date: Nov 2004
Location: Nova Scotia, Canada.
Posts: 6,510
This is a case everyone should keep in mind. Good normal resistance on all plugs but only a couple working properly.

We may have to switch to an amperage consumption type of troubleshooting test if there is any concern at all they may be marginal . Yet pass the resistance test.

This car probably had some bad plugs all along in it's recent moderatly long term past. Then just one or two too many glow plugs went bad.
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Old 06-11-2012, 12:48 PM
oso oso is offline
'87 300TD
Join Date: Oct 2007
Location: San Antonio, TX
Posts: 189
Lift pump

Originally Posted by Phillytwotank View Post
If not the glow plugs i think it would be something fuel related.

I had the same problem with mine once and it turned out to be the lift pump. $10 kit from peachparts fixed the check valves on the lift pump did the trick.
What's the part number on that kit? I am having problems with my '87 300td with overnight hard start and suspect that the excessive cranking is due to the slow dissipation of the fuel pressure ( return line). Unless the car is sitting for a while it starts just fine. So far I had replaced the fuel lines and the O-ring in the fuel thermostat unit. Also, craked the injector lines to see if getting the fuel was the problem and so far all checks out.
Glow plugs replaced a couple of years ago, the check light goes out as it suppose to. There must be some kind of check valve that "bleeds"....
Please feel free to chime in if I am not seeing the big picture. Thanks in advance.
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Old 06-12-2012, 11:14 PM
oso oso is offline
'87 300TD
Join Date: Oct 2007
Location: San Antonio, TX
Posts: 189
hard start

Update- since I was not getting anywhere following the fuel supply issue, I decided to inspect the glow plugs system as per Diesel Giant's DYI write-up (eveni though in-dash glow plug light was showing up and disappearing beautifully...)- and there it was: a hairline fracture of the strip fuse in the relay!!! Replaced the fuse and my car starts perfectly again. My hard starts were hard because the engine had to relay on compression alone! So ,lesson learned as it is shown so many times on this forum: inspect what you expect and assume nothing!!!
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