TR engine turns off by itself

As you look at the engine from the back of the car. Underneath the left air cleaner, there is a round electrical connector. This connector plugs in and threads (screws) into a mating connector on the chassis frame. Make sure that this connector is tight. Solved my similar problem a couple of years ago.

Tony

 

Don't mean to be pushy, but.

Disconnect the described connector, I think it is called the 9-pin connector and reconnect being certain that is is connected all the way in.

Tony

 

The OP has a TR, not a 512TR.

 

Is it a US version TR? -- i.e., engine family F113A040?

 

It would really be easier to figure out if it didn't restart so well Seriously, since it quasi-works almost all of the time, it leaves almost too many possibilities because you can't do tests and rule things in or out (which is the usual way to diagnose problems and zero in on where the trouble is).

On the ignition side, it could be as diabolical as a Gremlin inside the MicroPlex ECU itself or a flaky connection to the flywheel sensors or in the +12V power to run the ignition system. One (easy) thing you might do is there is a small round 4 pin connector for the flywheel sensor under the coolant expansion tank (along with a 9-pin square connector) -- you might unplug/reseat this small round 4-pin connector just to be sure it isn't loose.

On the injection side, the KE-Jet TR have a safety system where:

a signal from the (working) 7/12 coil + power module is fed to the tachometric relay,

when this signal is present (along with power and ground), the tachometric relay is closed,

which closes the fuel pump relays and runs the fuel pumps.

So here too -- if something is flaky in the 7/12 coil + power module or the tachometric relay (either internally or in the connections), this could be causing your fuel pumps to stop running. One way to rule this in or out would be to wire up a 12V test light between the 85 and 86 male tabs on one of the fuel pump relays (while it is still plugged in) and run the wires so you can have the test light inside the passenger cabin with you. This test light should always be on when the engine is running -- so, if it went out while the engine was running, (and then the engine died a few moments later after the fuel pressure fell), this would be a sign that something is wrong in this tachometric system.

Alternatively, it could be as simple as the fuel pump connections in the white connectors at the bottom of the fuse-relay panel are getting flaky/burned, and when one pump stops running, the engine stalls. You might unplug the "y" connector (which requires unplugging the "x" connector first), and look for any burning on the fuel pump connections as shown in these examples below.

Give a shout if you find something interesting, or if the problem get more consistent.
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Yes -- it's not exactly a "new" subject here

But to answer your question, I'd say that there are several reasonable ways:

1. Add some sort of high-current capable connection directly from the output terminal of the existing fuel pump relays to the corresponding P or PN wire leaving the "y" white connector (virtually bypassing the white connector) -- this is what I did. Although ,on your early US TR, I'm unsure if the 30 terminal or the 87 terminal would be the output terminals from the fuel pump relays (because I don't have the early US TR schematics). With the key "off", if you remove one of the fuel pump relays and measure the voltage from the 30 terminal -to- ground and from the 87 terminal -to- ground, the one that is not at +12V is the output terminal that would be connected to the P or PN wire going to the fuel pump.

or

2. Instead of connecting the output terminals of the stock fuel pump relays to the P and PN wires directly, use the output terminals of the stock fuel pump relays to trigger 2 additional relays that you independently supply +12V power to -- i.e., the stock fuel pump relay triggers the added relay that then supplies the +12V (and the big current) to the P or PN wire going to the fuel pump. This requires that the stock connection in the white "y" connector be in good enough condition to supply enough current to close the added relay (maybe ~150 mA), but it won't be further frazzled.

or

3. Remove the stock fuel pump relay completely from the fuse-relay panel, and run jumper wires from the 85 terminal and the 86 terminal of the relay socket to the 85 and 86 terminal of an added relay where you, again, independently supply +12V to the added relay and connect the P or PN wire to the output terminal of the added relay.

Give a shout if something comes up, but, if you do a search on "TR white connectors", you should get a lot of prior backgound/discussion.