2000 Cat 248, every time I hit the glowplugs it pops the main breaker to the machine. Any common areas to start looking? S/N 6LZ00433 Thanks!
This is the circuit. Pretty simple really. If the breaker only trips when you activate the glow plugs, the short must be after terminal 1 on the relay. Split the circuit in half by disconnecting the wire at the glow plug bus bar. If the fault is still there it's a wiring short. If not then you have a bad glow plug(s). Or maybe some debris shorting out the bus bar,
I had something similar a couple years back. Found that it was a bad glow plug but didn't know which. Removed the bus bar and ohmed them, went down the line, very subtle differences. Most were at 0.3 and one was at 0.1 or something like that. Not positive proof because that is not really within the range of the meter but it worked for me to find which one was different. I measured it many times in a row to be sure of what I was seeing first.
Thanks for the suggestions. I'll give them a shot in the next day or so.
I had a chance to look at this today, I pulled the power feed to the metal buss connecting the glow plugs and no short. I pulled the metal buss off and started connecting the power lead to the glow plugs one by one and when I got to number 2 found my short. What I would call the electrode in a spark plug is wobbling around in the glow plug and apparently shorting out. Thanks for the guidance in trouble shooting!! The glow plug has what looks like either a 10mm or 11mm nut on the top of it, does it just unscrew from the head like a spark plug? I'm not going to remove it until I have the replacement in hand.
Yes. Clean out the crud with compressed air or something and unscrew with a deep socket. My personal view it that they should be treated like spark plugs insofar as the whole set gets replaced, not just one.
I have no problem replacing them one by one as they fail if they are not current controlled like the silly old Ford 7.3 IDI system, glow plugs are not cheap.
Already blew it off Cmark, thanks! Wanted to be sure the debris wasn't shorting it out. I did a quick check on Google and it looks like I can get a set of 4 glow plugs for $50 to $100? Does that sound right? I'll call Cat tomorrow and see what their price is.
Cat's price here in Aus is $47 + tax each. If they're getting old enough to start breaking at the top, they're old enough to start breaking at the bottom. Even if they are $100 apiece it's cheaper than a bent valve or a hole in a piston. Once again this is just my personal opinion. Others may disagree.
$33 each, I ordered 4. The machine is nearly 20 years old now and I figured over that length of time it's not a bad investment. One of the service techs said they recommend replacing them all at once when they're in so I decided it was best. They'll be in tomorrow, depending on the weather I may be able to install them in the afternoon
I was able to install these the other day, not much different than changing spark plugs. Cured the problem and now that the weather has changed cold I'll be able to start easily