Engine electrical ?

[Zithlord]

I have two questions regarding some electrical wiring on the engine:

1. The wire from the oil temp sender, where is that supposed to be lead from the sender over to the wire harness near the coil? I have it on top of the fan shroud as you can see in the pictures but this seems wrong? See first two pics

2. On the left side of the engine(drivers side) there is a "switch" located on the side of the throttle bodies. Into this "switch" there is two wires that i guess should be connected to the "switch" but one of them seems to be disconnected, and I don’t know if this is on purpose? May this be because on my car I think the cold start solenoid(I think that’s the name for it?) has been disconnected and replaced with a button inside the car that I have to press once to get fuel into the throttle bodies before I turn the ignition key the last step to engage the starter. See last two pics

Thanks
John

[304065]

John,

With regard to your first question, if you are asking a concours question, my answer is, I don't know off hand but will look in the shop manual to tell you; but if you are asking a functionality question, well, the oil temperature sender wire runs from the 14-pin connector into the engine harness, which turns into four branches: one to feed the alternator which goes through the shroud, one to feed the oil temp sender (and on my car, the oil pressure idiot light) which is fastened to the lip of the cooling shroud with adel clamps, one for the overrun microswitch (see next paragraph) and one to feed the reverse light switch that goes down under the car.

The microswitch you see is an integral part of the MFI system. Its function is to signal the "speed switch" when the throttle is at idle. A brief description of the system logic is as follows:

Engine RPM > 1800 AND microswitch CLOSED = Solenoid ON
Engine RPM < 1300 AND microswitch CLOSED = Solenoid OFF
Microswitch OPEN = Solenoid OFF

In practice, suppose you are blowing down the back straight at Lime Rock Park at 7300 RPM and you get to the braking zone and abruptly close the throttle. Without this system, the MFI pump will continue to dump fuel into the cylinders even though the throttle is closed. This will cause a huge backfire. With the system working properly, the speed switch senses what's happening and operates the solenoid to move the MFI pump's control rack to the full lean position, effectively shutting off the fuel.

You probably have a defective speed switch for those wires to be disconnected. To test the system, hook the wires back up, the polarity of the microswitch contacts doesn't matter. Now, start the engine and raise the revs with the hand throttle to 3000 rpm. Then go around to the back of the car and manually operate the microswitch until it clicks with your finger. Don't get anything caught in that beautiful fan, you could lose a limb as well as losing the concours. When the switch clicks the revolutions should drop and then oscillate between 1300 and 1800.

If it doesn't perform exactly like that, search over on Pelican for the term "speed switch." Warren Hall, resident elecronic guru (who took the trouble to explain all of the above) has written volumes on this.

Good luck!

[Zithlord]

Thank you very much for your good explanation on my problem with the speed switch, I will hook it up again and do the test you recommended. When it comes to the wire from the temp sender I just wandered exactly where it originaly should run, over or under the fan shroud?

John

[304065]

Mine runs over it, on the outside. I used adel clamps attached to the M6 bolts that hold the shroud to the fan housing to guide it. That is NOT the way the factory did it but it holds nicely and doesn't come off.

[Zithlord]

My English is not good enough so I stated the question wrongly. What I ment by question # 1. was do the temp sender wire run under or over the FAN HOUSING not the fan shroud.......

John

[Zithlord]

I have reconnected the two wires that are supposed to be connected to the speed switch, one of the connectors where broken off. I think the switch works BUT... the part of the throttle system that is supposed to "hit" the speed switch does not press the switch down far enough for the switch to "click" when the throttle is closed at idle, is it supposed to depress the switch at idle? I see it is possible to adjust the screw that is supposed to "hit" the speed switch. How should the screw be adjusted for the system to function properly?

John

[Zithlord]

Hi

I set the hand throttle to 3000 rpm, and then went to the back of the car and pressed the micro switch, noting happens, the rpm does not drop at all? Is the switch broken or could this problem be from some other part connected to the system? As I have mentioned before I have a button inside the car for cold start and I don’t no if this conversion has done anything to the same system that the micro switch is connected to(cold start solenoid?)

The car and engine runs perfect and start perfect, no smoke no backfire, BUT it uses a lot of fuel. I have read that the bad fuel consumption could be related to the micro switch not engaging and continuing to dump fuel into the engine.

The car also have a non original coil and volt regulator, by Lumenition. Have anybody heard of this ignition system?


John

[304065]

They are different circuits. You may have a defective speed switch, which is the metal box on the electrical console that controls the system.

If you apply +12v from the top fuse on the console to the terminal on the solenoid, does it click?

[HarryD]

Hi

I set the hand throttle to 3000 rpm, and then went to the back of the car and pressed the micro switch, noting happens, the rpm does not drop at all? Is the switch broken or could this problem be from some other part connected to the system? As I have mentioned before I have a button inside the car for cold start and I don’t no if this conversion has done anything to the same system that the micro switch is connected to(cold start solenoid?)

The car and engine runs perfect and start perfect, no smoke no backfire, BUT it uses a lot of fuel. I have read that the bad fuel consumption could be related to the micro switch not engaging and continuing to dump fuel into the engine.

The car also have a non original coil and volt regulator, by Lumenition. Have anybody heard of this ignition system?


John

Hi John,

I cannot help you witht he MFI Stuff.

When the pointless electronic ignition in my '79 Spitfire died, I replaced it with Lumenition. It is a replacement for points (or the pointless electronic equivalent). It is ok but uses an optical sensor to decide when to open the contacts to fire the CDI or Coil. If the optics get dirty, the system becomes unreliable. Most here prefer Pertronix which uses a magnet that is imprevious to degradation by dirt.