Results 1 to 5 of 5

Thread: Coolant sensor woes. '91 5.7 TBI

  1. #1
    Fuel Injected! pma4x4's Avatar
    Join Date
    Jun 2014
    Location
    Apache Junction, Arizona
    Posts
    91

    Coolant sensor woes. '91 5.7 TBI

    So I found out the coolant sensor on top by the thermostat housing is bad via a ohms test. I have a copy of ALLDATA and I then come across a connector image. It shows (#3) the one on top everyone knows about and its called "coolant temperature sensor". the other (#19) is called "Engine coolant Sensor".

    I can not find a diagram of BOTH circuits. only the one on top. If there are two I want to verify the other is functioning as well. My gauge in cab has been showing cold for some time. Like I said the sensor on top is in fact bad Ohms are all over the place and the engines runs like crap when not plugged in.

    I just came across this exploded connector view a little bit ago and I know there is a sensor there as I just saw it when I was testing today. Its between #1 and #2 cylinder and is a single green wire. Is the single wire sensor (#19) be the gauge unit? and the #3 on top just for the ECM? This is what I am starting to getting out of it. Any light shed on this would be great.

    This whole thing started because engine seemed to be running cold a lot lately and mpg is down, found sendor on top bad now wanting to test or replace other unit (if it is that). Going to be doing a new thermostat as as well and checking clutch on fan.

    Capture 1.JPG

    Capture 2.JPG



    Current: '91 1500 Suburban (3rd owner), 350 TBI, 700R4

    TBI system: RV Morse Bored TB - Matched FIs - Adjust. fuel psi regulator - Injector pod spacer - RV Morse Powerplate - Hypertech "salad bowl"

    Full write-up here

    Follow the build here



  2. #2
    Fuel Injected!
    Join Date
    Dec 2012
    Location
    Naches, WA
    Age
    76
    Posts
    64
    A quick search on the AutoZone repair guide wiring diagrams show the two circuits. Your assumptions for the location and use of the two component appear to be correct.

  3. #3
    Fuel Injected!
    Join Date
    Feb 2015
    Location
    New Zealand
    Age
    54
    Posts
    280
    On my 94 TBI 350 the sensor for the temperature gauge only is the one in the head between cylinders 1 & 3.
    The sensor up on the intake manifold lets the PCM know what the engine temperature is, when you unplug that sensor it sets a fault code and the engine goes into limp home mode (and runs rough).
    From memory the sensors have different part numbers and a different number of pins.

  4. #4
    Fuel Injected!
    Join Date
    Aug 2012
    Posts
    386
    My 94 tbi 454 is the same as yours.
    6395, BHDF, 7.4 BBC lightly modded now 6395 BMHM back to BHDF

  5. #5
    Fuel Injected! pma4x4's Avatar
    Join Date
    Jun 2014
    Location
    Apache Junction, Arizona
    Posts
    91
    ok so I am right that the sensor on the left head is for the gauge. Thanks for verifying guys

    Would anyone know if testing the ohm is the same as on the ECM sensor?



    Current: '91 1500 Suburban (3rd owner), 350 TBI, 700R4

    TBI system: RV Morse Bored TB - Matched FIs - Adjust. fuel psi regulator - Injector pod spacer - RV Morse Powerplate - Hypertech "salad bowl"

    Full write-up here

    Follow the build here



Similar Threads

  1. 4-Wire O2 Sensor Woes
    By 350yj in forum GM EFI Systems
    Replies: 12
    Last Post: 04-05-2016, 05:10 AM
  2. Replace Engine Coolant Temp Sensor or ECM?
    By Karms20 in forum GM EFI Systems
    Replies: 9
    Last Post: 06-16-2015, 04:58 PM
  3. Should the Coolant Temp Sensor really be located @ the H2Opump?
    By LeMarky Dissod in forum GM EFI Systems
    Replies: 7
    Last Post: 06-14-2015, 11:34 PM
  4. Coolant Temp Sensor Location
    By notime2d8 in forum GM EFI Systems
    Replies: 8
    Last Post: 03-29-2014, 12:32 AM
  5. Coolant Temperature Sensor Diagnostic Test CTS
    By EagleMark in forum GM EFI Systems
    Replies: 0
    Last Post: 03-28-2011, 04:33 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •