checking glow plugs

[Anonymous Poster]

If you have access to a DC clamp-on ammeter (i.e. F.W. Bell, or similiar), it can be a better means to verify glow plug functionality. Depending on the factory connections to the plugs, you may have to jury-rig a dedicated lead to each plug (energizing each, one at a time) to take the readings. In doing so, you can compare the actual current draw that each plug generates.

Good Luck.

 

[gyroman]

I got a lot a good info from you guys about my problem. Some updated info about my problem. My tractor is a L285 About 30 years old. I decided to check my glow plugs because its getting harder to start this winter here in Ohio. I am using a digitial ohm meter, and when I checked the terminal to the block the meter showed a zero on the screen. Thanks again guys.
Mike

 

[TWINKLE_TOES]

Out of curiosity I tested the glow plugs on my B21. The B21 has the two material plug type QGS (Quick Glow System) I used a current probe on the feed wire to the three plugs and a two channel oscilloscope, with the second channel monitering the voltage at the plugs (plugs are all in parallel) I left the main switch in preheat position for 30 seconds to see the resistance increase as the plug heated. Results were:

At time zero (preheat on) total current 27.2 Amps, Voltage 11.1 Volts.
At time =4 seconds the current began to decrease and at 30 seconds the current was 17.2 Amps. The voltage at 30 seconds was 11.4 volts. The time to reach 50% of the final value of 17.2 Amps was about 4 seconds (8 seconds from start)

At 30 seconds I started the tractor and the voltage and current dropped to Zero.

So... on the B21 the plugs cold are about 1 ohm and hot about 2 ohms.

I think the best way to test the plug is a flashlight battery and a light bulb. Touch the two wires togather look at the light, touch the two wires to the plug if its good the light will be quite dim, if its open the light will be really dim (out) if its shorted the light will look like it was when the lead are shorted togather. Use a blub thats draws about 1/2 to 1 Amp @ 1.5 volts.
Al

 

[TWINKLE_TOES]

Dub,

<font color=blue>"the 20k position read 2 ohms"</font color=blue>

That's an amazing instrument, who makes it and what is the model number?

 

[TomG]

I've got a Beckman DVM, and I'd expect that sort of performance from it.

 

[TomG]

My owner's manual indicated that injectors should be serviced at 600 hours. My dealer said not to bother until 2000 hours unless it was smoking. Bad spray patterns, wrong spill time etc. and it will smoke. At lot of smoke at start up, and the seals may be leaking down. I have neither, and I'm going to leave mine alone, but I might check the spill time. I believe a dial indicator and base are needed to check and adjust the spill time. I have old Starrett equipment, but an inexpensive button indicator and jig should be adequate.

 

[TWINKLE_TOES]

Tom,

I agree, Beckman is a fine company and has made instruments for a long time. What is the model number of your instrument?
Al

 

[Anonymous Poster]

I agree, Beckman is an excellent company.

We used Beckman's for years in our shop, but it got a little expensive sending them back to the factory for calibration & repair. The last invoices are in the early 90's about $110. then. The Beckman's were very sensitive to High Voltage RF and the guys would end up wacking them.

We switched over to Fluke and never had any more HV/RF glitch problems. As I'm writing this, I'm looking at one of the last Beckman holdouts in the shop, Beckman TECH 360...

P.S.- I've read the posts, maybe I missed something... What is the "original" reason he thinks the glowplugs are not working properly?

 

[TomG]

He says below 'harder to start this winter.' Perhaps the problem includes some missing and smoke at start up.

There are plenty of other reasons for hard starting, but the glow plugs are a candidate. I'd probably start by checking battery condition as well as the battery and starter cables. A starter that doesn't spin fast enough is going to give winter starting problems too.

Didn't know about Beckman and RF problems. I got mine when I was in the sound business, so RF wasn't much of a problem. I worked on aircraft NavAids while teching in the USAF. Some of the frequencies are near the radar range. We used mostly VTVM's or scopes back then. VTVM's probably don't exist today. RF sure is funny stuff. I was working on an omni-range while in school and got across some RF. I smelled something and realized that it was me burning. Never felt a thing.