1989 K3500 8.1 Liter

[BrokenBlazerDave]

It's was on a 200HP shot that day. I like the Camaro. Low 11's on motor is quick. My fat car needs the extra help.

 

[Jermaine Smith]

Your car is fast regardless brother

 

[Supercharged111]

Man that thing gets its **** together pretty violently.

 

[Jermaine Smith]

Any progress on the truck ?

 

[BrokenBlazerDave]

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Any progress on the truck ?

Sorry for the delay. I sometimes forget to check the forums.
I had a few bugs I still had to workout. No speedo, no cruise, temperature gauge reads wrong.
I had to make the speedometer work and I was not sure if I could just tie into the speed sensor wiring for the computer. I was led to believe once, that if you put two things onto one speed sensor it would cut the value in half and each would get 50 percent. Turns out that is not true in this case.
I had to adjust the speedometer to be more accurate once it was working. I had swapped the cluster out for a Kilometers per hour cluster when I first brought the truck home from Phoenix. My donor truck was a half ton 2WD so it had P235/75R15's on it and I am running LT265/75/R16's on the 1 ton. The speedo was out about 8 KM/hr. I removed the resistors on the cluster circuit board and stole a couple from my parts dash and put them in the place for the current tire size. This got the speedo bang on.

 

[BrokenBlazerDave]

The cruise control was an easy fix once I realized what I had done wrong. I had tied into the TCC brake input wire instead of the CHMSL wire. Instead of getting 12 volts when I stepped on the brake it would take 12 volts away. Since this went well, I installed a set of limiting straps. This way I can lift the truck on a two post hoist and not hurt the air bags.

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[BrokenBlazerDave]

The temp gauge in the dash still reads high. The scan tool says the engine is at 190 degrees most of the time. The in dash gauge says 250ish and makes the "check gauges" light come on. Using an infrared temp probe on the thermostat housing the temp is about 190 Fahrenheit when the engine is up to temp. I have tried 2 clusters so I know it not that. If I measure the resistance of the sensor when the engine is warm I get about 180 ohms. If I use my variable resistance gauge tester and put 180 Ohms to the cluster it reads different. I think with load on the sensor it reads wrong. I am going to try a new sensor.

 

[Supercharged111]

Are you using an 8.1 temps sensor or a sensor for the original motor in your truck?

 

[BrokenBlazerDave]

Are you using an 8.1 temps sensor or a sensor for the original motor in your truck?

I am using a new Echlin sensor from NAPA for the 454 threaded into the opposite cylinder head than the 8.1 liter 3 wire gauge for the computer. The head had a 1/2"NPT hole so it fit right in. With the other testing I did I am suspecting the sensor. I also think the gauge read OK on the 454. I have lots of good grounds also.

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[L31MaxExpress]

I am using a new Echlin sensor from NAPA for the 454 threaded into the opposite cylinder head than the 8.1 liter 3 wire gauge for the computer. The head had a 1/2"NPT hole so it fit right in. With the other testing I did I am suspecting the sensor. I also think the gauge read OK on the 454. I have lots of good grounds also.

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On that 8.1 sensor atleast on a Van engine, 2 wires go to the PCM and the 3rd runs the gauge. On the 8.1 in my Tahoe that sensor was broken. GM wanted rediculous money to replace it. I put used a pair of brass plumbing bushings and a standard Vortec 5.7 sensor in the RH head and the standard 5.7 sending unit in the LH head.