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MG TD TF 1500 - Electric problem

Hi. I have a problem that prevents me from using the car just now that we have good weather. The issue is that a few days after changing the battery observed that the ignition light does not turn off, I assume that the regulator is wrong and I bought a new one in Moss, but the problem not only does not resolve but worsens, the Ignition light still does not turn off and I have measured a charge in D to ground of 2.5 volts. Just doing this last test the car stopped and has not started again. Looking for the cause I found that when disconnecting the fuel pump (SU electronics), the distributor (electronic CSI) and the radio (modern with classic appearance) I have 13 volts in A3 and A4 of the fuse box, but if I connect any of they drop to 1.6 volts, I do not find any bad ground connection to explain this. I enclose the diagram in case it is useful. Can someone help me?



Gabriel Martínez

Gabriel, you said "..changing the battery...". Did you think to polarize the generator? Do you have a positive, or negative, ground configuration? Bud
Bud Krueger

Yes Bud, I have repolarized the genarator, but It seems to be independent of the problem. It is negative ground, before and after of the problem.
Gabriel Martínez

Negative ground before and after? Why repolsrize the generator.
P G Gilvarry

He maybe referring to “flashing the field”.

Regards, Tom
tm peterson

I re-polarized in case it had something to do with the low battery charge and with this problem, but nothing has changed. The fuel pump works if I connect it directly to the battery and yet there is no connection to the ground of the normal cable that feeds it, this cable has the correct volts until I connect it to the pump, then it drops to 1.5-2.5 volts.
Gabriel Martínez

Gabriel,

From your description it seems that one or more of the electronic units has failed. Below is a step by step list on how to proceed.

1/ Recharge your battery.
2/ Replace the new voltage regulator with the old one.
3/ Disconnect the radio and the CSI ignition.
4/ Turn on the key, Check that the the fuel pump ticks for a few seconds then stops. If it doesn't then the pump is faulty. If OK then go the step 5/
5/ Disconnect the fuel pump.
6/ Reconnect the CSI and try to start the engine. If it does not start check for a spark.

After these tests you should have identified if the problem is fuel and/or ignition.


John








J Scragg

Thanks John, your proposal has suggested an idea. The battery is charged (13 volts.) I have returned to connect the fuel pump directly to the battery and it works, then I have connected the pump directly to IG on the ignition switch, it does not work, the voltage drops to 1.48, I disconnected all light wires from the ignition switch but there is no change. In IG there are 13 volts without connecting the pump. Any suggestions ?.
Gabriel Martínez

Disconnect the pump wire at pump end, the connect the wire to ignition switch.

If there is no short on the wire then the ignition switch is bad when carrying a load.

Peter
P G Gilvarry

That is what I have done. The cable goes straight from IG in the switch to the connection at the pump end. However, I am going to connect the cable in A of the switch, it is assumed that there is no mediation, it is direct connection except for the passage through the regulator.
Gabriel Martínez

We know the pump is good, BUT, do we know the wire to the pump from the Ignition switch is good.

Try it WITHOUT the fuel pump at the other end.

Peter
P G Gilvarry

Gabriel,

Please can you go through the steps 4, 5, and 6, in my above suggestions. these are necessary to isolate the cause of your problem. As the fuel bowls are full,the engine should start and run for a short time even with the pump not connected. If the engine starts, check the if ignition light goes out.


John








J Scragg

Following the route of the stream I finally located the cause: a bad connection in the ammeter that somehow allowed some demand for electricity but not all the necessary. It is even possible that the ammeter is wrong, because afterwards I have lost all the electricity without any other apparent cause. For today is fine, I am exhausted from so much contortion under the wiring, tomorrow I will continue. Thank you very much for all the proposals, in the end they have oriented me to the cause.
Gabriel Martínez

This thread was discussed between 19/06/2019 and 20/06/2019

MG TD TF 1500 index

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