Many older diesels run fine on diesel diluted with 10-20% unleaded
regular. In fact, this used to be a trick to keep summer diesel
from gelling when temperatures dropped in the fall.

However 50% is a stretch...
Maybe in hindsight, your best thing to do would have been to drain
the tank into jerry cans immediately when you noticed, then fill
with normal diesel. Later you can test if/how much per tank you can put in of
the 50-50 mixture while still having the engine start and run smoothly.
(Just to use it up in an environmentally friendly way.)

Now, unless you are back to pure diesel in the tank, don't give up
on your glow plugs. Try with pure Diesel first, possibly add some
cetane enhancer (e.g. Stanadyne red) and se if starting becomes smooth.

Cheers,
Martin

   Reply-To: <lamarjohnson@attbi.com>
   From:        "Lamar Johnson" <lamarjohnson@attbi.com>
   Date:        Sat, 21 Sep 2002 16:26:52 -0700
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   Dear Martin:

   I pulled a bone-head stunt a few weeks ago and topped off my fuel tank at my
   favorite cheap Diesel stop across the border; problem was, I grabbed the
   wrong pump handle and topped it off with Unleaded Premium.  I didn't realize
   it until I was well down the freeway, so then I was running about 50:50
   Diesel to gasoline.

   The engine was running normally, no extra smoke, normal water temperature,
   everything looked and felt normal.  I drove for a couple of hours to get the
   tank level down and topped up with Diesel to dilute the gas further.  No
   problems at all.

   However, the next morning,  hard starting at 40F! It was like starting an
   old radial aircraft engine, first one cylinder sputters to life, then
   another, then another, finally all four are roughly running, 1000 RPM at
   full throttle, white smoke of raw Diesel hanging in the air!  It smoothed
   out to normal after a few minutes, but what a fog!

   Driving it warmed-up was perfectly normal, but it was hard starting again
   the next day.

   My big-rig Diesel mechanic friend told me that I probably have burned up the
   glow plugs.  This is an indirect injection engine, C223T Turbo-Diesel Isuzu,
   1986 model with 260,000 miles on it.  The injector flame front is directed
   right onto the glow plugs in the pre-chamber.

   I have been searching the net for glow plug related articles, and found
   yours, so I thought I would share my experiences.

   I am thanking the fates that I did not seize my injection pump, burn a valve
   or hole a piston.

   Now I am facing the horrors of pulling out the twisted and warped glowplugs
   and dropping bits and pieces into the pre-chamber.  Live and learn.

   Best,

   Lamar Johnson
   Beaverton  OR