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Old 07-07-2001, 02:10 PM
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If they check out at .9 ohms, then they are obviously O.K. as far as the electrical heating element is concerned. But does this necessarily mean that they are definitely O.K. as far as to their FUNCTIONING? (Assuming that they are receiving currant.)

The reason I ask is that my 84 300D “misfires” on a few cylinders for about 10 seconds when started from cold. It also takes about 4-5 seconds of cranking even when warm. The compression is good, the valves are adjusted, etc. The car runs beautifully otherwise.

The injectors are original with 199,000 on them. Is it likely that these symptoms are indicative of the spray patterns or opening pressures being off?

Also, I have seen a tool for “reaming” the prechambers where the glowplugs are inserted. Is this a necessary or recommended procedure when replacing the plugs?

Thanks for the help!

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Old 07-07-2001, 05:29 PM
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MB specifies that 1 ohm or less indicates a good glow plug. However, you can do an amp draw test on the glow plugs. This is the recommended method on later model diesels and the one I prefer. The amp draw test will tell you exactly what the glow plug is doing. You will need an amp meter capable of handling at least 30 amps. What you will be reading is the initial draw when you connect the meter to the glow plug which, should be somwhere between 17-22 amps. After that the amperage should begin to decrease. I usually let drop between 5-10 amps before I disconnect.
If the initial draw is around 10 amps for example, that would indicate a faulty glow plug.

Reaming the chambers is definintely recommended. This cleans the carbon deposits away from the glow plug. A 6mm allen socket works just fine too.

Scott Diener
89 300E
93 300E
92 Volvo 740 Wagon aka "Mutt mover"
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Old 07-08-2001, 12:51 PM
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Thanks guys for the input. MUCH appreciated.

Chowpit, I saw the amp draw test in the CD, but I do not (yet) own an amp-meter or current draw diagnostic meter. I was thinking that maybe there is a ‘typical’ type of problem (or failure mode) that is experienced with some degree of regularity – the lazy (or ill-equipped) persons way of “diagnosis” .

And MUCH thanks for the tip on using a 6mm hex key – you just saved me $40 that can be better spent, like on an amp-meter . Just wondering if there is anything that I need to watch out for while using the allen wrench – is this a job where delicacy is needed, or do I use the Neanderthal approach & just shove it in there and start grinding away? Do I need to be concerned about any chips/chunks of carbon ending up in the chamber?

And tkamiya, thanks for the info regarding the accuracy & window or margin of error on the multimeters – I was not aware of this.

MANY Thanks! And considering my questions, I better include one of my ‘tag’ lines on the sign off…

Ignorant, but working on it.

“Ignorance is due to the lack of information; Stupidity is the lack of ability to utilize information”
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