Troubleshooting Pyro

[The Warden]

Hello!

I've got an issue with the Isspro pyrometer on my truck. Specifically, the gauge intermittently doesn't work, with the needle returning to about the 100° mark (where the needle sits when the exhaust is cold).

All connections at least appear to be okay, and I think the wire itself is okay as well (although I'm not certain; call it wishful thinking? ). Since the gauge suffered a 3 foot fall onto asphalt in the process of installation (and I've been kicking myself ever since), I'm thinking it might be the gauge itself.

Is there a way to measure whether or not the thermocouple's putting out current with a "normal" voltmeter? It'd be nice to verify for sure whether or not current's getting to the gauge when the gauge isn't reading. I assume there isn't a way to troubleshoot the gauge itself without more equipment than I have...

Lastly, are EGT's directly related to boost levels except when the engine's being lugged? I'm taking the truck on a 300 mile trip tomorrow (first long trip since I replaced the head gaskets and added the turbo in July), and am concerned about winding up in a hilly area when the pyro decides it wants to take a break. If I can watch the boost gauge and, say, keep it under 5 psi, I'll feel a lot more comfortable. At least the truck's going to be unloaded on the trip...

Thanks!

 

[rthomas]

you can test the thermocouple by using the ohm setting on your meter, i dont know what it should read but thats how most guages work
i dont think egt is totaly related to psi, it also has a lot to do with rpm, example: my truck under 2500 7psi=1150 pre turbo. over 2800 10psi=1175, 12psi=1225
for me the egt goes up faster under about 2500 and is a lot slower and easier to manage over 2500. when in doubt rev it up

 

[Fred Hemer]

I think ya need to kick the guy in the ass who droped that gauge!
Boost and pyro are semi related!As the boost falls off and you keep adding fuel the pyro will rise ,as the fuel that is being installed into the engine hasn't enough air to burn properly and is been expeled and burnt in the turbo itself there inlies the increace in pyro heat!Its a double edged sword ya need the fuel + heat but it has to be burned inside the engine to produce the disired effect!
So on your trip watch the boost go up and watch the pyro go up they will go up as a team for and fairly equal at times but as the engine works harder the the boost levels will climb to a point then max out at a point say 9 10 psi BUT the pyro will still climb and the rpms Drop off below say 1900 rpms (A Guess) thats where ya need to start thinking about changeing gears.
Its been my observation that These engines like the fuel to the engine some where between 1900- 2300 RPMS.

 

[The Warden]

RT, how will an ohmmeter tell anything about the condition of the thermocouple? IIRC, when the thermocouple's heated up, it actually puts out a slight current (measured in milivolts) that the gauge reads and translates into what the needle says. (this is why the pyro doesn't need a 12 volt power source except for the backlighting). Problem is, the thermocouple puts out millivolts of current, so I don't know how a "normal" analog voltmeter can read what the thermocouple's putting out. I'm not even sure it's possible; hence my question. I think my voltmeter's settings only go as low as 1 volt, but I don't have it in front of me (packed up in the truck for the trip), so I can't verify for sure.

I dunno; maybe I should just summarily replace the gauge...problem is, if I do that, I'm going to wind up upgrading to an EV gauge, which means replacing the thermocouple and the wire (not all that easy with how I have the wire routed)...not to mention the $$ factor...ugh...

Originally posted by Fred Hemer
I think ya need to kick the guy in the ass who droped that gauge!

My leg almost reaches...

Seriously, from your response, looks like I'll be okay for the trip if I'm smart about things...keep the RPM's from getting too low and don't let the boost get up too much and I should be safe... *knock on wood*

Thanks again...if there are any more suggestions on seeing if I can for-sure isolate the problem I'm having with this pyro, that'd be great. It's easy for me to jump to the conclusion that the gauge's bad, but I'd love to be able to run some form of diagnostics on the setup...

 

[argve]

Tim,
You pretty much answered your own question in that you know how a thermocouple works (temp vs voltage output) yes your meter should read it if it has a high impedance volt meter. Which sadly to say these are typically on the more expensive side. But My guess would be the guage head would be fine and it's your probe that is actually failing. If I remember correctly you purchased a used pyro so I'm basing my theory off that fact. Do we know if the last pyro was not over heated per sa? I think the guage head can take a fall or two before it goes

Know I know you have already checked the connections but also make sure you have not bent the thermocouple wires in a tight bend anywhere this will effect the accuracty of the reading. A nice easy gentle bend that is double the diameter of the lead wires is min bend rating for them. So double check it anyways, I have seen many a problem in industrial applications because the tcouple was folded/smashed over on it's self. It's worth a look because it's FREE.

 

[Mike]

ISSPRO is great at doing returns, I dont think they care if you were the original owner of the guage. You can call and talk to a tech at ISSPRO, he will prolly tell you to box it up and ship it to him and hell send you a new one. Ask me how I know......

Contact info,

ISSPRO, Inc.
2515 NE Riverside
P.O. Box 11177
Portland, OR
97211

(888)-4-ISSPRO
(888) 447-7776

Ask for a technicican, IIRC the guy I talked to was Jim. Helluva nice guy.....

 

[F350camper]

That's cool. Score one point for ISSPRO!

 

[Darrin Tosh]

Hey Warder,

I know that you checked the connections, but double check them. They have to be perfectly clean because of the low ohm's

Seems like every 3 months or so I have to take my connection apart under the hood, buff them with fine grit sandpaper and shoot a lil Wd40 and it is good to go. Even though it looks like the connection is good with no visable corrosion.

just my .02. Good luck!

 

[JPR]

Darrin, are the connections oxidizing?
If so how about coating them with some dielectric grease like what Ford uses on the factory connections?

 

[The Warden]

Thanks for the replies Haven't had a chance to read them 'till now.

I haven't had a chance to re-check the connections yet; I'll do so when time allows.

I also have to echo JPR's question...would dielectric grease help or hurt with the connections?

If all else fails, I like th eidea of sending it to Isspro...I wonder if they would let me upgrade to an EV gauge?

BTW, I found this pyro tester on eBay; my dad's currently the high bidder...we'll see how it works, eh?

Thanks again