[DeTomaso] Engine run after switching off ignition

[Thomas Tornblom]

I have finally gotten around to fix the run-after problem after 
installing the EDIS ignition.

My schematic (1984 GT5) shows a resistor in parallel with the alt light, 
close to the speedo. In my car there is no resistor, the bulb acts as 
the resistor.

I installed a 1N5402 3 amp diode in series with the alt light. I added 
it in the speedo harness as I was working in that area anyway. The 
engine now stops when I switch the ignition off, no need to press the 
brake pedal. It can go anywhere in the light circuit, either the 
blue/black wire to the alt or the white wire to the lamp. The ring 
(cathode) should be in the direction of the alt, so that current can 
flow through it and the lamp to energize the field in the alt, but block 
any current going from the alt to the ignition.

This is a simple fix for those with MSD or other after market ignitions 
that makes the engine run after killing the ignition.

The diode specs are not critical. A 1 amp diode should work just as 
well. The current through it is just the amount drawn by the tiny lamp.

Thomas

Dave Londry skrev:
> How did it go Thomas?
> On the L schematic I see a resistor across the charge ind. lamp in the 
> speedo.
> One side (B/BK) winds all the way to the regulator and looks like it 
> energizes the alternator field when there is no alternator output.
> I assume you planned to put a fat power diode in that direction.
> 1N400x or such.  Maybe a Schottky if you care about 400 mv?
> 
> Where was that resistor located. At the back of the original speedo case?
> tks
> dave
> 
> 
> Thomas Tornblom wrote:
>> Dave Londry skrev:
>>> I have this same problem Thomas.
>>> MSD ignition,
>>> Fans not spinning,
>>> All autometer gauges,
>>> No alternator idiot lamp.
>>
>> I assume you still have the resistor that is needed to get the 
>> alternator magnetized on startup. It is connected in parallel with the 
>> idiot lamp and I'm fairly certain that this is the problem.
>>
>> I hope I'll have time to have a go at a fix over the weekend.
>>
>> Cheers,
>> Thomas
>>
>>>
>>> So I really want to hear about your results.
>>> dave
>>>
>>> Thomas Tornblom wrote:
>>>> Larry - Ohio Time Corp skrev:
>>>>  
>>>>> Thomas,
>>>>>
>>>>> Please remember that the cooling fans have been known to cause this 
>>>>> problem
>>>>> as they spin down. They generate enough power to keep things running.
>>>>>     
>>>>
>>>> I know, but I have fixed my fan setup so that it is not vulnerable 
>>>> to this. The fan wasn't running either.
>>>>
>>>> Thanks for the suggestion though.
>>>>
>>>> I do believe I know where I should install the diode as I said in 
>>>> the response to Charlie.
>>>>
>>>> I will most likely have to modify the tacho anyway as the tacho 
>>>> signal from the EDIS system is of much lower amplitude than from the 
>>>> TFI system.
>>>>
>>>>  
>>>>> Larry - Cleveland
>>>>>     
>>>>
>>>> Cheers,
>>>> Thomas
>>>>
>>>>  
>>>>> -----Original Message-----
>>>>> From: detomaso-bounces at realbig.com 
>>>>> [mailto:detomaso-bounces at realbig.com] On
>>>>> Behalf Of Thomas Tornblom
>>>>> Sent: Friday, April 24, 2009 2:48 AM
>>>>> To: DetomasoList
>>>>> Subject: [DeTomaso] Engine run after switching off ignition
>>>>>
>>>>> I fired the engine up last night for the first time after upgrading 
>>>>> from TFI to EDIS (Ford crank trigger). This is nice as I will 
>>>>> finally be able to get rid of the large cap distributor, which sits 
>>>>> too close to the firewall for the engine cover to fit properly.
>>>>>
>>>>> One unanticipated problem is that the engine now runs after I 
>>>>> switch off the key :-| It stops if I press the brake pedal with the 
>>>>> ignition off.
>>>>>
>>>>> Looking at the diagrams it appears that the TFI module and single 
>>>>> coil was fed directly from switched power, while the EDIS module 
>>>>> and quad coils are fed through the EFI power relay, so now the 
>>>>> current drawn from switched power is just the hold current for the 
>>>>> relay, while it used to also be the current for the TFI and coil.
>>>>>
>>>>> I assume the problem is with the alternator idiot lamp circuitry, 
>>>>> which feeds current from the spinning alternator backwards and 
>>>>> keeps the relay engaged.
>>>>>
>>>>> IIRC this has been a problem also for some who installs MSD 
>>>>> ignitions and that it is probably solved by installing a diode 
>>>>> somewhere in the idiot light cuircuit.
>>>>>
>>>>> Anyone have any info on what the simplest solution is?
>>>>>
>>>>> Cheers,
>>>>> Thomas
>>>>>
>>>>>     
>>>>
>>>>
>>>>   
>>>
>>>
>>
>>
> 


-- 
Real life:   Thomas Törnblom             Email:  Thomas.Tornblom at Hax.SE
Snail mail:  Banvallsvägen 14            Phone:    +46 18 444 33 21
              S - 754 40 Uppsala, Sweden  Cellular: +46 70 261 1372