Points, Timing, Rev Limit, Frustration...
 

Some couple of weeks ago I decided to replace my distributor rotor since it was cutting out at 5800 and not 6500. Thinking this would would be a 10 min job, of course one thing lead to another ("while you at it" approach) so that I have been messing with the car for the last two weeks. Worst, my new timing gun actually started a fire in the engine!!!

Anyhow, I now replaced the rotor, points, spark plug wires, sparks plugs, coil, and all burned wires (primarily it was the red 15 wire from the coil)

A couple of questions:

1) I read on this forum a different points gap spec than usually found for a 2.7s. I think this was posted by Early S Man, indicating a gap of .035mm instead of .40mm as in other manuals. Does anyone know why this spec is so different?
http://forums.pelicanparts.com/uploa...1243360889.jpg

2) The car now starts and runs. But I can feel a hesitation after 4500rpm. Thinking this might be to do with the yet-to-be finalized timing, could someone please suggest ideas how to properly use the timing gun. On my first experience with the gun I could feel that the gun was draining power from the engine until the motor stalled. It was connected to ground and the fuse box, sensor around wire #1.

3) Took the car for a spin today (without finalized timing). It still cuts out at 5800rpm. Why??

Many thanks.

Jacob

I assume you have a 2.7 based on your post. If it consistently cuts out at 5800 rpms I would think you either have a tach that is reading low or a defective rev limiting rotor.

As Kurt suggests, check the rotor.

I accidently crossed wires and cooked some wiring (coil wiring). When it was all fixed I had a car that would not exceed 4200rpm. My mechanic finally diagnosed that the new points I'd put in prior to my screw-up had been heated in the crossed wiring incident and the spring steel component of the points had 'lost' the "springiness"

Cheers

I'm not sure about this problem but I am interested in the answer you get, I do have a question though. From what Kurt said I'm assuming the 2.7 does have a rev limiter, just wondering if anyone knows where I can get some more information about it? What rpm does the rev limiter work at?

Thanks and good luck :)

Peter, the rev limiter in the 911 is in the distributor rotor button. It works through centrifugal force - if the button spins too fast a connection is broken between the tip of the rotor arm and the centre.

There are 3 versions in the earlier cars, 6800, 7000, and 7300 depending on the specification of the engine - the rev limit is stamped on the underside of the button.

Cheers

Thanks for the responses. As indicated above, I also thought first that the rotor was at fault so I replaced with a new one (6500). This did not help so I have to presume that the rotor is fine. Would timing have anything to do with the premature cut off?


Jacob

thats exactly what mine was doing, 4500 miss. i will get to that in a minute.
check the timing. starting at idle, slowly rev the motor, make sure the timing mark jumps about 15 deg just off idle, this will check the vacuum retard. then check timing at 6K, i dont go that hi, mine is all in before that, so, just whatch it and see when it is all in and set it for the next timing mark. should be around 30 deg. then check at idle, should be close to 0 TDC. after you get the idle reference, you can adjust it at idle, then check at 6K. if you are not at or close to 0 TDC, you may have a problem.
you can also pull the dizzy cap off and gently twist the rotor, it should have a slight movement and return to original position, this will check the mech advance too.

fuel mixture

check plug wires for grounding or missfire

if yours is a 77, you have a vacuum enrichment that comes in around 4k, if that is not working, it will run bad, but i would also think it would run bad at lower RPM's when you give it gas. i am thinking mine was almost undrivable when i disconnected it to see what it would do.

now, back to my final fix.
i found one of my fuel injector lines was clogged, actually a defect i think.
i pulled all the injectors and put them in 6 bottles. with the key on, i lifted the sensor plate for about 30-40seconds. then, i poured each one into a container and weighed it on a postal scale. i found one was suppling half the fuel as the others. done worry about small differences. in fact, i did not need to weigh it, i could see there was a large difference.

the points gap is not that critical. it is not like a convesional points system. the points only provide a ground signal to the CD unit. i just eyeball mine. i make sure they open and close completely and are not open too much.

i was suspecting the same things as you at one time, points, rotor, even fuel distributor and fuel pump.

take care of the simple stuff first.

Wow, T77911S! This approach is incredible. thanks for the input.