books

iTrader: (8)

car has no power...decided to check the timing..noticed it was off by about 20 degrees..the crank angle sensors checked fine...realizing with the stock ecu we can't change timing...any ideas what would cause this or along those lines how to resolve this problem

thanks everybody

rxrotary2_7

the NE and G sensors are the only thing picking up the timing. the ECU determines the advance. you cant change that. there is only one way it can be put back together. i would *believe* you are barking up the wrong tree for your problem.... if you had a stand alone i would say good idea... but not wiht an OEM ECU

rxrotary2_7

btw, how do you know the degrees it is off? what is your understanding of the timing mark on an FD?

books

iTrader: (8)

thanks for your response...the 20 degrees off is merely an estimate...timing light was connected to T1 plug...while looking from the front of the vehicle the timing mark was at the 1 o'clock position, assuming the timing pin is 12...I do have a Power FC in my other FD but I'm reluctant to stick it in this car...I am just stating what I have observed and attempting to understand why the timing is off...incidentily the test I preformed is outlined in section F page16 of the service manual...again I am trying to understand why the timing has changed...

2-Rotor

Take a look at the main pulley and see if the ring (or the relucter ring as car companies call it) has detached itself from the pulley. If it has, then you will get weird running conditions and maybe the reason your seeing that. The ring has the notches in it and the crank angle sensor (which is a magnetic sensor) measures the grooves as it spins in a circle to measure for timing. Make sure no one has damaged the grooves in the ring as well its not hard to bend them.

books

iTrader: (8)

thanks 2-Rotor

your answer is the type of answer I am hoping for, unfortunately my communications skills seem to be lacking as evidenced by my original post..I looked at the pulley and it appears quite solid. I understand how the sensors work in relation to the crank angle sensor plate and since the sensors are in a fixed position...I assume something has physically moved but what and how..as you know that pulley is keyed and the crank angle sensor plate attaches in a fixed fashion...this is a reman engine from Mazda that has never been driven..just started....on a side note, don't know if this affects anything but just broke the wire at the connector for the CAS G signal...I believe it was probably frayed and about to fail...wondering if this signal were intermittent or of higher magnitude, would it cause the 20 degree offset?

Trout2

iTrader: (5)

If the timing ring on the pulley is only slightly out of line it can give you problems.

When the car is idling timing will jump around constantly. I forget the pins to jump in the diagnostic plug to turn off idle control, its the same thing you do for setting the idle - refer to factory workshop manual. Do this and try reading timing.

Jack

Resource

I serioulsy doubt that the ring can walk or move. If it was out of line at all the pulley would be wobbling bad. The wire needs to be connected to the cas connector or it will not run. Did you make sure the white connector is on the top cas sensor? I've seen many frayed cas wire, some wires were only hanging by one wire and it ran fine. It's just a pick up so I don't think it matters too much, just as long as it connected. Let me know if you need some help. Describe no power?

books

iTrader: (8)

to answer a couple of questions...yes the white connector is on top...and yes the pin in the diagnostic box was grounded...I believe it was Ten to Gnd...also the timing mark stayed around the same position within a degree or two, but 20-30 degrees from the timing pin...didn't notice the pulley wobbling...what about a sheared key???

Resource

you should be able to reach down inside the pulley and feel around. You should be able to slightly feel the pin coming out of the pulley. Or maybe you can see it. I'm thinking your problem might be something else.

Trout2

iTrader: (5)

The timing ring can be damaged so that its not visible but will cause a problem. Steve Kan chased a problem for a while before finding it using a osiliscope.

If the ring has never been off the car I doubt that its the problem.

Jack

books

iTrader: (8)

Jack,

would you please clarify...is the timing ring the same as the crank angle sensor plate...the engine is supposedly a Mazda reman...how would one diagnose this problem?

thanks Dave

Trout2

iTrader: (5)

Yes, I mean the crank angle sensor plate located behind the main pulley. Don't have my workshop manual handy to look up the test.

I couldn't remember the exact problem Steve Kan had but his was break up at high rpm. You may want to contact him at his shop, Gotham Racing. See these two threads and look at the posts by Pluto.

https://www.rx7club.com/forum/showth...ghlight=oscope

https://www.rx7club.com/forum/showth...e&pagenumber=2

I would look at the wiring. Sounds like you've made sure the triggers are in the right position and going to the right plugs. Is your harness old?

Jack

reza

Hey you should not connect to T1. Trailing 1...no no no...trailing is about 15 degree off the leading. Maybe that is why you are reading 20 degree off, 5 degree retard from leading, and another 15 degree difference.

Put in your timing light to leading 1, L1 !!

Well that is my thinking...

Reza

2-Rotor

The main pulley can only go onto the crank one way. There is a key way on the crank that will not allow it to go on any other way. However i do not think thats the problem you are having. I think the gap maybe off on some parts of the ring or you may have a bad wiring harness going to the crank sensor, or even a bad crank sensor.

Check the sensor out and look closely at the timing ring (relucter ring) to see if anyone has pryed in that area or just possibly bent it during shipment (you said it was a Reman.)

books

iTrader: (8)

Jack, thanks for the link to the threads..I guess that is a possibility, but Pluto's problem was at high rpms...I can't even hit 2k without backfiring... I checked the sensors and the wiring harness from the connectors back to the ecu.

Reza, I understand your logic, since L1 should be around -5 degrees at idle...however the service manual section F page 16 clearly states to connect to T1...I have another FD and checked my timing via T1 and the mark was pretty darn close to the timing pin...according to my PFC -5 Leading, -20 Trailing...of course on the problem FD the mark is about 20 degrees off..this is why initially I started looking at the sensors thinking maybe the connectors were switched.

2-Rotor..checked the gap between the ring and sensors and they are within spec

thanks guys for all the help...I sincerely appreciate it

Dave

pluto

I found a new problem on a customer's car two weeks ago where the ground shielding for the trigger wire has an intermittent short to the signal wire, result was that sometimes, it'll throw the trigger signal off and causes some abnormal behavior. Do a continuity test between the signal wire and sheilding ground and see if this could be your case.

Good luck,

Steve

books

iTrader: (8)

Steve, thanks for the idea......this is not much of a revelation..... but after replacing both CAS connectors...I believe I broke one of the wires at the connector while checking for continuity, though it was probably nearly broke already...put everything back together and VOILA the timing was right on....

thanks again to everyone who responded

Dave

pluto

Glad to hear that you found your problem!! I do notice that the car would run with the gnd of the trigger wire cut off and will also throw the timing way out of wack but since you mentioned it was right at 20 degrees, I kinda throw that assumption out since with the wire being cut off, your timing will be different depending on where the trigger sits on the next start up.

books

iTrader: (8)

your assumption,still may be correct...I only checked the timing twice ...the first time was when it was about 20 degrees off .... the 2nd time was after the wire was repaired....and yes it was the ground....I too am trying to make sense out of this

books

iTrader: (8)

Guys and Gals, I hate resurrect this thread but I believe I owe it to the Forum readers who rely on information here to help solve their car ailments to provide an update. Unfortunately for me, I was a little premature with my belief that my timing issue was fixed by replacing the CAS connectors. While the engine does start and the timing is on the mark, this only occurs if the engine is cold. If the engine is restarted after warm up the timing will be off and actually it's closer to 30 degrees off (the width of 1 window on the timing ring). I have repeated this scenario (start and restart) several times with the same results. For what its worth this engine was supposedly a Mazda reman installed by an independent shop, has never ran properly or has never been driven. It has also been to 2 dealerships who were unsuccessful in their attempts. One of the dealerships ran a compression check and the readings were good (8s and 9s). Any help would be appreciated.

thanks Dave