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Old 12-14-2014, 05:00 PM
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Diesel Injector advice needed

I am rebuilding my fuel injectors with Monark nozzles. 1984 300D. 327,000 miles. I do not know when they were last serviced but the car is smoking a lot, has very poor fuel mileage and stalls a few times before it will stay running when I start it.

I have the injectors out and pop tested each one before I took the first one apart. The pop pressure on each is right around 1800. The spray pattern on the old nozzles is, I think, very poor at best. This is my first time doing this so I have not seen a new spray pattern, but I just get a constant downward stream with no popping. I believe it is call peeing. (I wonder why. )

When I finish cleaning the injector bodies and put in the new nozzles, should I expect the pressure to be about the same or will it improve with the new nozzles? That is, is the lower pressure I am seeing because the internal spring in the injector has weakened over time (327K miles) or is it the old worn and dirty nozzles? The FSM says 120 bar or 1740 psi is OK for used injectors. 135 - 143 bar or 1958 - 2074 psi for new.

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Old 12-14-2014, 06:55 PM
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I don't think they will open at the same pressure but it can happen.

vincewaldon.com - HOW-TO: Rebuild Diesel IDI Injectors
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Old 12-14-2014, 07:21 PM
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After much adjusting, I managed to get all 6 of mine to fire between 1950 and 2000 psi. I also put in Monarch nozzles. Runs good at those levels.
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Old 12-14-2014, 08:04 PM
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Quote:
stalls a few times before it will stay running when I start it.
This is more indicative of bad glowplugs
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Old 12-14-2014, 10:31 PM
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Quote:
Originally Posted by dude99 View Post
This is more indicative of bad glowplugs
I guess I will find out once I get the new injectors in. Once it is running the glow plugs are not involved, so I have not suspected a glow plug problem.
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84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
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Old 12-14-2014, 10:50 PM
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Quote:
Originally Posted by Diesel911 View Post
I don't think they will open at the same pressure but it can happen.

vincewaldon.com - HOW-TO: Rebuild Diesel IDI Injectors
Thanks for this link. Good info and tips here.
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84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
00 Toyota Sienna 208K (Sold)
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11 Subaru Outback 67K
98 Ford Taurus 100K (Gertie - Was Grandma's - drove it to church and shopping - really) Daughter's car now.
30 Model A Ford 2 Door Sedan (Sold) 0-60 in . . . Never reached 60
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Old 12-14-2014, 11:27 PM
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Easy to test the glowplugs with a multimeter at the glow-plug relay connector. While you have the injectors out, turn on the glow and peer down each hole to verify they are glowing red. Sometimes they can ohm OK, but have an internal short which puts the hot spot further up the body instead of at the tip (so I have heard).

The pop pressure may be over-rated. I found 3 of the 5 injectors in my 1984 popped at 1600 psig (non-turbo), and the others correct (~1950 psig). Yet, the engine ran fine and about the same when I put all correct ones in. The spray pattern can be hard to judge on a tester. On mine (long ram type pump, electronic pressure recording), some pumps can give more of a stream. You must pump fast enough to get it to "machine gun" pop. Someday I'll add an optical recording to better characterize the spray pattern and fineness than I can do by eye. I used to do academic research on sprays.
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Old 12-14-2014, 11:37 PM
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Originally Posted by BillGrissom View Post
Easy to test the glowplugs with a multimeter at the glow-plug relay connector. While you have the injectors out, turn on the glow and peer down each hole to verify they are glowing red. Sometimes they can ohm OK, but have an internal short which puts the hot spot further up the body instead of at the tip (so I have heard).
Great idea. It did not occur to me to do that.
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84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
00 Toyota Sienna 208K (Sold)
15 Subaru Outback 43K
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98 Ford Taurus 100K (Gertie - Was Grandma's - drove it to church and shopping - really) Daughter's car now.
30 Model A Ford 2 Door Sedan (Sold) 0-60 in . . . Never reached 60
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Old 12-15-2014, 01:12 AM
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To test mine I usually pull them out and use a pair of jumper cables to test them. They should glow nice and bright, almost white hot. Using a multi-meter will only show if they are open and is not a particularly reliable method of testing them.
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2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold
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Old 12-22-2014, 11:47 PM
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Before I put the injectors back in I fired up the glow plugs. 1, 2, 4, and 5 were bright red. 3 looked dead. Is there any need to replace them as a set or just replace the bad one?
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84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
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30 Model A Ford 2 Door Sedan (Sold) 0-60 in . . . Never reached 60
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Old 12-23-2014, 12:09 AM
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Maybe its just been bad for a long time.
Try replacing the one but be prepared to do the rest too.

Im assuming you have confirmed your wire to #3 is good.
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  #12  
Old 12-23-2014, 12:19 AM
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Originally Posted by TnBob View Post
Maybe its just been bad for a long time.
Try replacing the one but be prepared to do the rest too.

I'm assuming you have confirmed your wire to #3 is good.
Very good point. I did not do any further diagnostics on the glow plugs. I just did the observation and then got back to the business at hand, of getting my injectors back in. The glow plugs will be next after I get the motor mounts replaced, hopefully later this week.
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85 300D 75K Anthracite Grey 0-60 in 13 seconds **For Sale**
84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
00 Toyota Sienna 208K (Sold)
15 Subaru Outback 43K
11 Subaru Outback 67K
98 Ford Taurus 100K (Gertie - Was Grandma's - drove it to church and shopping - really) Daughter's car now.
30 Model A Ford 2 Door Sedan (Sold) 0-60 in . . . Never reached 60
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  #13  
Old 12-23-2014, 11:46 AM
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FWIW, glow plugs are relatively cheap, and the job can be somewhat of a PITA. I always like to knock it all out when I'm in there, have the tools handy, and the engine in a temporary state of cleanliness.

Keep the good used ones as spares and do 'em all. Nothing worse than a partial swap you have to redo in 3 months. And they only fail at night, on long trips, while you're sleeping in a hotel far from home, and its snowing/raining/nasty outside. We all know that......
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Old 12-23-2014, 11:54 AM
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Quote:
Originally Posted by BillGrissom View Post
........ While you have the injectors out, turn on the glow and peer down each hole to verify they are glowing red. Sometimes they can ohm OK, but have an internal short which puts the hot spot further up the body instead of at the tip (so I have heard).
....
I do this whenever I have the injectors out because it's cool looking, even though I know my glow plugs are good.
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  #15  
Old 12-23-2014, 11:58 AM
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Check out my signature for a video series I did on rebuilding injectors.

Also, pop pressure is adjusted with shims in the injector body against the base of the spring. I shoot for 1950 PSI for turbo injectors.

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