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Old 03-10-2003, 08:05 PM
Posts: n/a
Fuel Injector Replacement

I would like to increase my fuel mileage in my 1984 300D TurboDiesel. Reviewing the past service invoices, it appears that all of the injectors are original at 253000 miles except one. One injector was leaking around the housing requiring replacement.

I recently replaced the air filter. At present the car gets ~23 mpg.

Should I expect a significant increase in fuel economy and performance by replacing the old injectors? Must I also invest in a refurbished injector pump along with the new injectors? What is the best mostly-highway-driving fuel economy that I can expect. How can I determine if the pump start timing is off by observing performance? What indicators should I be looking for?

What is the procedure to correctly change injectors? I have been told that it is not difficult, but this car is my first diesel. I have a quality break-away torque wrench. What should I avoid or be careful with in this procedure?

Finally, I hear of experimenters who are fueling their engines with biodiesel (100% processed vegetable oil.) Would some kit or special adjustments be required to accomplish biodiesel use? I understand others are doing nothing to accomodate biodiesel use.

Thank you,
Michael Smith
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Old 03-10-2003, 08:30 PM
sixto's Avatar
smoke gets in your eyes
Join Date: Jun 2000
Location: SF Bay Area
Posts: 18,745
Replacing injectors is easy. You'll need a deep 27mm socket. Make sure the inside is deep enough as some such as impact sockets have shoulders that make them not so deep in effect. The one I got at Home Depot was cheaper and fit better than the Sears one.

Don't forget new heat shields and note which way the heat shields are installed.

I'm not sure about 617s but there might be value in replacing the delivery valve seals while you're at it.

If you can do a 0-60mph run in 15 seconds I doubt you'll gain anything from replacing the injectors.

See if a station near you sells biodiesel. Check the ARCO website as some ARCO stations sell the stuff.

If the stuff if offered from a regular pump then it's just a matter of buying it.

If you go with something like waste vegetable oil (WVO) then you have to consider a heater of some sort because that stuff will solidify overnight or sooner in cold climates, and also a filter so you don't get bits of french fries and the Colonel's herbs and spices in your fuel tank. Check out

91 300SE
87 300SDL
83 300SD
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Old 03-11-2003, 01:02 AM
haasman's Avatar
Registered User
Join Date: Jun 2001
Location: San Francisco, CA
Posts: 3,096

Your MPGs would improve slightly, my guess .5 ~ 2.0.

Do you have the standard size tires on your car? When I owned a 300D Turbo when the tires needed replacement I changed from over sized tires back to the factory recommended sizes and it upped the MPGs.

Compression contributes alot to MPG, have the valves been adjusted recently?

Keep us posted,

'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)
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Old 03-11-2003, 01:48 AM
Senior Member
Join Date: Sep 2002
Location: So. Calif.
Posts: 323
253K . . . Geeeezzz DUDE . . . QUIT while you're AHEAD ! ! !
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