Help me sort out my engine wiring!!
 

My engine is a 1974 2.7S, the body is a 912, and I am trying to tidy up the chaotical wiring in the engine compartment. Some wires were litarally connected to nothing, or somehow connected to themselves. I slowly make progress, but now I have a few questions:

1. What should the two connectors of the micro switch be connected to? The one was connected to the cold start enrichment valve and the other one to the oil temperature sender. Doesn't sound right, does it?

2. What should the two connectors of the oil temperature sender be connected to? I believe one has to go to the temp guage, and I guess the other to the ignition (positive). Please tell me which one should go where.

3. What should the two wires of the cold start enrichment valve be connected to?

Please don't refer me back to the wiring diagram, I am wiring diagram illiterate.

Thanks in advance

Is that an MFI engine? I don't think '74 CIS engines have or need a microswitch.

Warren and Patronus, I believe the microswitch in question is on the throttle linkage and it exists on a 1974 with CIS and is called the throttle valve switch. Assuming you have the correct engine wiring harness, then in 1974 the throttle valve switch is connected to yellow wires. One of these yellow wires should be connected the thermo-switch for the cold start valve. The cold start valve itself has a gray and white wire and a red and black wire from the thermo-switch Note that the gray and white wire and the yellow wire are connected to the same terminal on the thermo-switch. The WUR (warm up regulator) mounted on an intake runner base on the driver's side of the engine should have a single red wire with white stripes connected to it. I'll comment on the oil temp. sender in another post. Cheers, Jim Sims:D

There should only be a single green and black wire from the oil temperature sender; in a 911 this wire goes through 2 connectors and is then connected to the back of the oil temperature gage. The other side of the oil temperature gage should have two red and black wires attached to it. I am confused by your statement that your oil temp. sender has two wires. The oil temp. sender is screwed into the case at the back of the engine (fan pulley side) on the passenger side and it should only have the single green and black wire attached to it. Perhaps you are looking at an oil pressure sending unit in the oil line to the passenger side cam tower that also incorporates an oil pressure switch. If this is the case then the green and red wire is the oil pressure signal and should be connected to the oil pressure gage; in a 911 this wire goes through two connectors before reaching the gage. The other wire is for the oil pressure switch and is green and white and goes through a single connector (in a 911) before attaching to the oil pressure indicator light. Please note the usual place for this oil pressure switch is on the engine top back by the flywheel side of the engine. However, I've read about some units having a combined oil pressure switch and sender in the right cam tower oil line. Cheers, Jim

One additional bit of information: the other yellow wire from throttle valve switch (micro-switch) goes to terminal 50 on the starter solenoid. There should also be a white wire on termianl 50 of the starter solenoid and this white wire goes forward (in a 911) to the ignition switch through 4 connectors. At the first connector it changes to a yellow color. :D Jim

Hi guys,
i just want to know, if before with the 2.7 engine cable we have a sportomatic transmission with wires we don't used?

i presently change engine from 2.0 to 2.7 cis to weber and without the sportomatic,and i have wire over...
Thank You
Raynald
the french canadian !

Raynald, The 2.7 CIS sportomatic wiring for 1974 is different. If you've gone to Webers then the following wires are probably not needed: a gray and red wire(*) to the throttle valve switch (micro-switch - you probably no longer have this switch if you've gone to Webers), a gray and red wire from the throttle valve switch to the shut off solenoid, a grey and white wire(*) to the cold start solenoid, a red and black wire(*) to the thermo-switch and a yellow wire to the thermo-switch, this yellow wire goes to the starter. Note these colors are for 1974 and they may be differnet if your engine is from another year. (*) means these wires come from the 14 pin connector that attaches the engine to the electrical chassis/panel on the drivers side of the engine compartment. I would recommend taping off the ends of these wires but not cutting them. :D Jim

Thank You Jim,

my engine is 1974 , one more question...
on my transmission i have two wire for reverse speed...
and on my new cable from 2.7l with sportomatic
what is the wire i will used for it?

Thank You Again
Raynald
the french canadian

Thank You Jim,

my engine is 1974 , one more question...
on my transmission i have two wire for reverse speed...
and on my new cable from 2.7l with sportomatic
what is the wire i will used for it?

Thank You Again
Raynald
the french canadian

Raynald, I will assume you are referring to the wiring for the reverse gear switch which turns on the backup lights. There are two wires from the engine wiring harness to this switch; in 1974 one wire is green and yellow and the other is gray. The wires should be the same for both manual and sportomatic transmissions.:D Jim

OK Jim
i will check for it tomorrow,
i apreciate your help...
Thank You Again
Raynald

Jim,

Thanks a lot for the info, I will now start digesting it.

Yes, the microswitch in question is right next to the throttle linkage.

I unfortunately don't have a complete wiring harness, the previous owner made his own. All the wires are either red or black, so I have to trace them one by one to see where they lead. He did a pretty good job, but I think at a certain point he became confused and the result is a microswitch that is connected to the temp sender, a few wires that are connected to themselves, and a few wires that go nowhere.

After studying your replies (for which I really have to thank you) I will probably come up with one or two more questions.

Patronus,

The unit in the left side chain cover is the Thermo-Time Switch which is the basic control for the enrichment solenoid during the starting phase. There is a test procedure in the following thread:

http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=33347&highlight=thermo+ time+switch

Here is a fuzzy scan of the Bosch parts catalog:

AHA!! It is slowly starting to make sense to me. In other words, I mistook the Thermo-Time Switch for the oil temp sender.

The wire connected to the warm up regulator, I assume it should be live (ignition)?

Jim and Early_S_Man, thanks so far!

Hello

Just a dump quest:

What year is your 912 body ?

The Sportomatic has a own temperaturesensor on the housing and so the enginesideed temperature sensor is deletet ( Just the hole pluged )

Also sportomatics have a starter lock out system and the electric clutch actuator in the haness.

Pitty you can´t read wire shematics yet the early versions are very easy to understand even for double left handers.

Grüsse

Roland,

My 912 body is a 1968 model, RHD.

I have compared my wiring diagram with the explanations of Jim and Early_S_Man, and I am now slowly figuring out how it works. A simple explanation still means more to me than the diagram itself, but I'm getting there. The fact that all the wires in my engine compartment are either black or red makes it difficult, but I'll sort them out, one by one.

Red and black! Oh well, that's better than a 356 a friend of mine is restoring. One of the PO's rewired the car with a single color and then left the wiring unmasked while the car was painted. Now that's a puzzle! My listing of the standard '74 911 2.7 CIS engine wiring harness colors probably doesn't help you much. Okay back to basics. Cold start valve circuit: There should be a wire from the ignition switch to terminal 50 (this is a small blade type lug that receives a female type connector) on the starter, from terminal 50 of the starter a wire goes to the throttle valve switch. From the other side of the throttle valve switch a wire goes to the thermo-switch (this is the one Early_S_Man describes in his 2nd post on this thread) on the driver's side chain case, this wire from the throttle switch attaches to one terminal (this is the non-ground side terminal) of the thermo-switch, a second wire is also attached to this same terminal of the thermo-switch and goes to the cold start valve. From the other side (ground side) of the thermo-switch a second wire goes to the cold start valve. A lot of words to replacea wiring diagram. Good luck!:D Jim

Thanks Jim, the info I have will keep me busy for a while. I am printing out these valuable posts and will paste them in my workshop manual, right by the wiring diagram. During the week I will continue working on the car, and as I encounter problems I will post them here.