Pipe Temp. Sensor

[tchriste]

Hi all, this season has been a trying one for tuning a 925 BB I installed this past summer in my 09HCR. The biggest problem I've been dealing with is pipe temp sensor failure, I just went through my 3rd one in 500 miles the last one making it about 100 miles. The last two sensors failed during a short lake run at WOT at approx. 3,500 ft.
Awhile back there was a very good thread around both the subject of alternate sensors (GM Diesel truck) and some tech info on the resistance/temp the sensor operates at. First I would like to find out why the sensor is failing. Following that I'm thinking of trying a resistor however what one to try as a 200 ohm resistor will tell the ECM that the pipe is cold and leave on in choke mode or do I install a 400 ohm resistor and use my PCV to cold start the engine for a timeframe/engine temp. The local dealer did tell me avgas (lead) would cause the issue, however I'm not running avgas.
Any input would be greatly appreciated.
Cheers,

 

[av8er]

I would call the people who made the 925bb kit

and tel them about your issue, I have put 1000 miles on my Turbo m8 on pure Avgas with zero temp sensor issues.

 

[Mjunkie]

I know the ac delco part number if you need it. I have no idea why they aren't lasting very long though. Too much oil in the pipe maybe causing them to fail? Just a stab in the dark. Something electrical causing them to fail? Good luck man!

Sent from my phone using tapatalk

 

[fast eddie]

I have had the same problem. At least on mine, the copper wire broke near the plug in. I'm assuming it's the vibration cause when I fixed it it worked great for most my trip until it must have broke again. By the way I did buy the gm sensor and it was less than half the price as the cat one. Have not installed yet, just have to change plug to cats. Hope that helps, good luck.

 

[madsledder]

I am useing the gm senser 12639455, on my 2nd one just installed it yesterday. I run 25% av and got a season out of the first one. Also on a 925bb. Mine is rkt, you? I think the wires broke just inside the stem like my first one. Ive also had my pipe out alot trying different pipes. That or the vibration.

 

[tchriste]

Thanks for the info guys;
Mjuckie is the about gm part number the same as yours?
Just for everyones info I have tested all electrical components of my sled, even changed out the stator thinking it was intermittent. I have inspected the wiring, however it may require a closer look. I had just installed my 50mm throttle bodies and was out on my second tuning run when this happened so I had the pipe out however when I installed the sensor I had never seized. I don't think it's a BB issue, at least I can't understand why it would be but I could be wrong. When the sensor starts to go my tuning goes all over the place. I found a couple of very old threads where it was suggested to use a 450-490 ohm resistor however I'm wondering at what wattage, I would assume, as it is a sensor the wattage would be low. I would still like to know why this is happening, it could be as simple as vibration or removal and install of the pipe. One other thing I pre-mix at 40:1, run Shell 91 no ethanol, I run Lucas octane boost.
Again thanks for all your help.

 

[diggerdown]

Have you tried putting some header wrap around the pipe to cut some vibes out.

 

[Mjunkie]

213-4759 or 213-4778 are the ac delco part numbers. I don't know why there are two, but I just found one online and it plugged right in and has worked flawless. I've only gotten 2 1/2 tanks so far but I've also had the pipes off and on many times, and as far as vibration goes I just had to have the front cooler Tig welded because of a vibration crack. Time will tell, but I won't be buying a cat one if and when I have to, I'll stick to the ac delco.

 

[Mjunkie]

Oh btw, mine is on a 1300 running premium with ethanol mixed with a gallon or so 110 leaded. Also premixed 100:1 oil with stock oiling system.

 

[tchriste]

213-4759 or 213-4778 are the ac delco part numbers. I don't know why there are two, but I just found one online and it plugged right in and has worked flawless. I've only gotten 2 1/2 tanks so far but I've also had the pipes off and on many times, and as far as vibration goes I just had to have the front cooler Tig welded because of a vibration crack. Time will tell, but I won't be buying a cat one if and when I have to, I'll stick to the ac delco.

And it plugged right in? Now that is worth looking at. As I understand it there are two sensors on the truck, so which one did you end up getting 4759 or 4778?
Cheers,

 

[madsledder]

Would like top know also as you have to put the plug on the one i get.

 

[m8magicandmystery]

I put hi temp loom on the pipe sensor wire and take it right over the pipe sensor housing and then foil tape it to prevent the stress of the wire separating at the housing crimp which seems to be an issue for failure...some people do a flip back loop as well and zip tie it if length permits..

 

[tchriste]

I too have been installing heat resistant loom on my temp sensor and wire as well as a dab of silicon on the end of the sensor where the wire enter the probe, however I'm still going through them.
I have purchased a 1 watt, 470 ohm resistor which I tried today and it worked very well...$0.30 including tax.
AC Delco 213-4778 is the temp sensor, they're on E bay for as low as $27.00.
But I still want to know why.....

 

[Mjunkie]

And it plugged right in? Now that is worth looking at. As I understand it there are two sensors on the truck, so which one did you end up getting 4759 or 4778?
Cheers,

I'm sorry I can't remember for sure where I got it from. I thought it was ebay, but I looked and it wasn't in my history so I looked thru my receipts but didn't find it either. rockauto.com is ringing a bell but I don't remember which part number I ended up with. All I remember for sure was that I found it just doing a google search and it was the cheapest and that I didn't have to change the plug on it. If I remember or figure it out, I'll post it.

 

[fast eddie]

I too have been installing heat resistant loom on my temp sensor and wire as well as a dab of silicon on the end of the sensor where the wire enter the probe, however I'm still going through them.
I have purchased a 1 watt, 470 ohm resistor which I tried today and it worked very well...$0.30 including tax.
AC Delco 213-4778 is the temp sensor, they're on E bay for as low as $27.00.
But I still want to know why.....

Personally I think the reason why is the copper inside the wire coating breaks in random spots, as I was fixing mine I found two more breaks a half of an inch apart from each other. At least that's what I think because my sled runs no different when codes are flashing, and if the pipe sensor is bad I heard it would not run aswell, supposed to retard the timing? And who knows where it breaks, hopefully that helps. Thanks Kevin

 

[tchriste]

oddly enough when my pipe temp sensor goes out my sled runs like crap, leans out, idle goes up to around 3,200 RPM (due to being lean). My AFR will go from 14.5:1 to about 15.5:1 or higher and my bottom end tuning will be lean as well. Top end AFR does not seem to change and the sled will run fine. I find the lean condition odd as I was under the impression with a sensor failure the system would protect itself, in my case it actually puts the machine in danger. I know I will be setting up a plugin resistor so when I do have a sensor failure I can protect the machine.