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Posted by: second wind Jul 5 2020, 04:59 PM

Hello World,
So my '73 2.0 started acting like it had vapor lock again which is not likely since I relowed the fuel pump up front which totally cured that problem. So out of nowhere it started to not want to start after a several minute drive. Would finally start again after a 10-15 minute wait but this behavior had disappeared since the fuel pump relocation and is now back again. I thought I would use my BG cleaner machine on the throttle body which usually works wonders and noticed that I had a broken wire going to the head temperature sensor on the plenum, which I am told is called the head temperature sensor 2. What exactly does this sensor do and what do my symptoms sound like to you guys? Appreciate the help. Thank you and best regards,
gg

Posted by: JeffBowlsby Jul 5 2020, 09:31 PM

TS1 or the intake air sensor mounts to the air plenum. It senses intake air temp. Unplug it from the harness and it riches the mix.

TS2 mounts to the cyl head near cyl3 and senses head operating temps, which richens the mix when cold, leans it out when warmed up. If TS2 is unplugged the engine will not start because it think s it is full rich.

Posted by: second wind Jul 5 2020, 10:14 PM

QUOTE(JeffBowlsby @ Jul 5 2020, 08:31 PM)

Posted by: BeatNavy Jul 6 2020, 05:51 AM

TS1 (ambient air temp sensor) has a minor enriching effect, but TS2 (CHT) has a major effect and with an open circuit will not allow car to start or run. In my experience, with a bad TS2 or TS2 circuit, a stone cold car may catch briefly but then won't even give you that. An open TS1 circuit should not prevent the car from running in and of itself. Are you flooding? Have you inspected the plugs?

The TS1 on a 2.0 is located directly on top of plenum (under air cleaner), in the vicinity of the throttle body and throttle body sensor. It's sticking straight up and down with a two wire connection.

TS2 is in between cylinders 3 and 4 underneath the engine tin. If you look underneath the intake runners between the cylinders on the passenger side you should see a one wire lead going to a hole (it may still have the grommet covering it). That leads to the CHT.

To troubleshoot the CHT you need to thoroughly inspect the lead from the sensor all the way back through the wiring harness to the ECU. Is the CHT actually connected to the wiring harness? Are there signs of breaks or kinks in the wiring that would leave an open or intermittent circuit? Once you do that, you need an ohmmeter to test resistance from the CHT lead to ground (negative battery terminal). I believe you also have a ballast resistor on this circuit for a '73. If you need to replace the CHT because the values are not correct, it's a little bit of a PITA, but there are threads here describing the process.

The CHT isn't the only possible suspect if you think the car is essentially flooding. The MPS could also be failing.

More with LOTS of good information. Please read: https://members.rennlist.com/pbanders/DJetParts.htm

Posted by: 914_teener Jul 6 2020, 09:51 AM

Early models without TS2 sensors if the ECU sees no ground the car will not start. This would apply to the 1.7 engine running D-jet

Posted by: 914_teener Jul 6 2020, 09:52 AM

Double postr