Pyro's in La-La Land

[The Warden]

Hello! I think I mentioned this a while back, but I can't find the thread either here or on STD (this cropped up right around the time of the migration). Here's a brief recap:

The pyrometer I have on my truck is an old-style Isspro gauge, purchased used as part of the used turbo kit I have on the engine now, and I have no idea on the previous history, other than that some idiot dropped the gauge onto an asphalt driveway while installing it The pyro worked just fine when I first got it installed, but for whatever reason, a little while later, it stopped reading at all (went to slightly below 100°, which is where the needle "parks"). This would happen intermittently, and after maybe a month of working on-and-off, it seemed to "fix" itself, and I haven't had any problems since.

Of course, it cropped back up the day before yesterday. I hadn't driven the truck in a few weeks, but prior to this, it was working just fine. Two days ago, I used the truck to run to a few stores to get some parts to get my car going to drive to southern California for the holidays. I noticed that the pyro wasn't reading anything, but figured it wasn't a big deal since I wasn't taking the truck anywhere. Of course, then I gave up trying to get the car going and wound up taking the IDI instead (see a thread in the M-B forum for details there). The pyro didn't work at all at first, then started reading...but the readings were a mile off what I'm used to seeing. Cruising on flat ground at 70 to 75 mph, the gauge was reading about 250° (usually reading 450° to 500°). On a climb or while accelerating, the gauge would move...I think the highest it ever got was 450° indicated, while climbing the steep side of the Grapevine. I have no idea whether I should just look at 250° as the equivelant of 450° and adjust the safe readings from there, or what.

I was careful to take my foot out of it, and slow down and/or downshift if the boost got to above 5 psi (I was actually using 3 psi as my max boost before downshifting from 5th), but even still, going over the Grapevine in a truck with a turned-up IP (screw 90° in) and no pyro is nerve-racking to say the least

I'm thinking that I really need to just shell out the $$ and replace the darn thing (been wanting an EV gauge anyways ), but does anyone have any suggestions on what I might be able to look at while down here? I already checked connections; they look good to the naked eye...

If anyone has any thoughts, it'd be greatly appreciated...

Thanks in advance!

 

[soulpatchfr]

Tim, i found your original thread here ...
that's about all i have to offer -

agreed, tho. buck up & buy a new one, i think.

 

[gandalf]

As long as you're replacing the guage because of suspected damage, I'd suggest also replacing the probe and the cable. One of the three isn't working quite right. Unless you want to take the time and effort to find which is defective, the only sure way is to replace all three components. The guage is the most expensive, and you want to do that anyway, so I'd go for all three. You have a nonfunctioning pyro system with an unknown history. Replace the entire system.

 

[tenlug]

Checked my new thermocouple with a torch and IR thermometer. It read about 25 milivolts at 1100 degrees. Did you clean the connections (sand) at the gauge and thermocouple? Steve

 

[Agnem]

Sounds like either the gauge was damaged in the drop, and depending on temperature, moisture or other factors, there is increased or decreased friction in the movement, OR you have a bad electrical connection, which it has been my experience that this is the usual cause. Sometimes just getting a new wiring kit will fix the problem. You could try that first, since it is the cheapest part, and then if that doesn't take care of it, get a new probe and gauge.

 

[The Warden]

Even as I submitted the first post, I had a gut feeling that this would be the answer...since, even if there's a bad connection and I fix it and the pyro seems to work normally again, I won't trust it, I think I'll summarily replace the gauge, wire, and thermocouple as soon as I get home. I had to ask, though... Thanks again!

Tim, i found your original thread here ...
that's about all i have to offer -

Frank, no need to apologize it's good to know that I haven't completely lost my mind and that an original post did in fact exist...