Another Starter Relay installation 81 Fi

Gotta love that wiring . . .
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SpiderJim

Another Starter Relay installation 81 Fi

Post by SpiderJim »

Today I modified the starter system on my 81 2000 Fi. We all know that after a time Spiders begin to have false starts when trying to start. This is due to the ignition switch being directly wired to the starter motor. This begins to wear the switch in a very short time and seeing that I installed a new ignition switch it was time to correct this bad design.

Today I installed a Ford starter relay( Stock F492 Starter Relay Autozone $12.00) I opened the straight connector terminal that the red wire fed the starter directly from the ignition switch. This is located a few inches from the starter. I ran a red 12 ga wire from the ignition switch side of this red wire to the S terminal on the relay ( the relay is grounded via its base that I attached to a ground post located just above the emission canister. I ran a yellow 10 ga wire directly from the plus 12v terminal of the alternator to one side of the relay ( always live and easy to get at). I then spliced a red 10 ga wire from the starter (other side of the removed terminal) direct to the other side of the relay. I found it easier to simply splice into this wire rather than remove what was left and connect to the starter post as it is a bugger on a Fi car to get at. Note!!! Do not use the i terminal it is the slightly larger S terminal that triggers the relay.....

So when I turn the key, the ignition switch only powers the low current relay coil that then closes the relay enabling high current through the relay contacts and not the ignition switch as before. This will remove false starts and also save the ignition switch from burning out. Another aspect of this is if the relay fails you can jumper across the relay terminals with the ignition switch in the on position to get the starter motor turning.

Another feature for Fi owners is that we now have a direct connection to the battery plus voltage to connect our timing lights and for voltage testing from the alternator. It was always a pain in the ass to connect a timing light with the battery in the trunk. NOTE!! I suggest adding insulator boots over the live relay contact terminals so as not to zap yourself by accident or damage the electricals.

I also installed a battery ground quick disconnect terminal to the battery ground post. This will save the frustration of having to keep using wrenches whenever I need to work on the electrical system when needing the battery disconnected. Along with this stuff I also replaced all the two pin connectors which where brittle through age.

I hope this helps someone.....

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Last edited by SpiderJim on Thu Feb 17, 2011 10:19 am, edited 1 time in total.
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TulsaSpider
Posts: 1547
Joined: Tue Apr 29, 2008 7:33 pm
Your car is a: 1978 Spyder 124 2L
Location: Tulsa, Ok

Re: Another Starter Relay installation 81 Fi

Post by TulsaSpider »

I'm terrible with electricals how about some pics to help out?
1978 Spyder 1800 make that 2L! Finally making real progress!
majicwrench

Re: Another Starter Relay installation 81 Fi

Post by majicwrench »

Really you have not changed much. High current never flows thru the switch, it flows thru the big battery pos wire.
The way it was the current running thru the switch was energizing the starter soleniod mounted on the starter. Now the current thru the switch is energizing the ford starter soleniod mounted where ever you put it. The ford soleniod is designed for carrying large amount of current, just like the fiat soleniod. If you had used something like a standard Bosch relay, youi would have saved the ign switch a lot of current.
Keith
spider2081
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Patron 2024
Posts: 3015
Joined: Fri Jan 27, 2006 11:45 pm
Your car is a: 1981 Spider 2000
Location: Wallingford,CT

Re: Another Starter Relay installation 81 Fi

Post by spider2081 »

I had the same problem with my 81 and traced it back to the ignition switch contacts. I have access to lots of test equipment at work and I measured the Fiat starter solenoid current. I know I was surprised at how much it was. I am thinking about 8 amps continous and something like 15A on the inital surge. I installed a Bosch 35 amp relay same as the Ford diagram and have been trouble free since. I am sure the Bosch draws less than 1 amp. I think the Ford relay would draw more than the Bosch but less than the Fiats starter solenoid. One of the reasons is the Fiat starter solenoid pulles the Bendix gear into the fly wheel.
So for what it is worth I agree installing a relay is a good idea and I think the smaller Bosh is ample.
Thanks for your post. Too often I neglect to share things I do.
SpiderJim

Re: Another Starter Relay installation 81 Fi

Post by SpiderJim »

majicwrench wrote:Really you have not changed much. High current never flows thru the switch, it flows thru the big battery pos wire.
The way it was the current running thru the switch was energizing the starter soleniod mounted on the starter. Now the current thru the switch is energizing the ford starter soleniod mounted where ever you put it. The ford soleniod is designed for carrying large amount of current, just like the fiat soleniod. If you had used something like a standard Bosch relay, youi would have saved the ign switch a lot of current.
Keith
I would agree with you if my car had a starter relay but it does not until I installed one. The automatic does but mine is the five speed without.
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