Leading and Trailing Spark Direction: Which Way Does Engine Rotate?
 

From my current understanding, the leading plugs are the lower plugs, thus the trailing plugs are the upper plugs. What I don't know for SURE is which direction that implies the rotor spins, which is important for me to know if I'm going to crank a motor by hand.

So is a leading plug the first plug passed by the apex? Is it the first to fire? Both first passed and first to fire? It makes the most sense for it to be both, but I wanted to make sure.

no offense bro and i dont mean to sound like an a-hole but, if you had searched you would have found a longer thread that was maked exactly about this and one of the higher ups even had a link to an animation that showed how the plugs worked

Motor spins clockwise.
About the only motor that spins CCW is some of the older Honda engines.

The rotor will sweep over the trailing first then the leading.
I don't know why is important to you?


-Ted

Also the leading plugs fire first, then trailing. Actually, both leading fire simultaneously (waste spark method) and trailing fires depending on rotor position. As I understand it, the trailing firing contributes much less to engine power than leading, it's mostly used for more complete combustion.

Yeah I realize there's the two spark system mostly for a clean burn (but still, a clean burn will typically perform better).

It's important to me in case I want to turn it by hand to at least check for blown seals. Maybe it doesn't make any difference which direction you turn it, but either way I'm more comfortable spinning it the way it was meant to go.

Yes, I could have searched more than I did, but I had a couple specific questions past 'which plug is which?'.

well like i said i wasnt out to flame or anything i was just sayen, anymore enemies is the last thing i need on this forum

no problem

any other ideas? I'll be on the phone with the owner tomorrow so I'll try to ask some more questions then. I'm also considering ordering some parts from Advance so we can hopefully make sure the difficult to test stuff is good when trying to turn it over. Things like the TPS, ECU, ignition control unit (I assume it has one)... any other suggestions? I have a commercial account at Advance and O'reilly's, with credit on both, as well as a high limit credit card with only ~$50 owed at the moment, so I can shell out a lot for parts if I'm just going to use them to test stuff, and then I can keep whatever I'd need to use as replacements. What I want to avoid is burning up a whole day going to a parts store in an unfamiliar area just to test existing parts. I want to get the sucker to turn over, and possibly run.

Aren't they labeled L and T?

idk, but now I know how they're arranged whether they're labeled or not.

Right.... but.... All you need to know is which rotor is 1 and which is 2... The rotor nearest the radiator is 1, the rearmost one is 2. Look at the coil.. They say L1, L2, T1, T2.. Think you can figure it out from there? I sure hope so. :)

Maybe you were just curious how it all worked......

It's great that you have access to discounted parts, however I have seen so many people diagnose their cars by throwing parts at them instead of obtaining factory service manuals and checking things the right way. Not wanting to come across as being rude, but it seems a potential waste of money to buy parts that you don't need. Most often, rx7s don't need several parts at once to fix them, maybe one failed part and the rest of the repairs due to cracked vac hoses, wiring connectors, bad grounds, lack of maintenance, etc. From my understanding, the car won't start, correct?...then start with the basics.....buy a spark tester (spark plug with a wide gap), a compression gauge, and fuel pressure gauge, and while you're at the parts store, at least grab a Hayne's manual, not nearly as good as a FSM but better than "diagnosis by substitution".

I knew the front side of the motor is 'coincidentally' facing the front of the car. Typically the front of a motor is whichever end has pulleys on it. I don't see why I would need to know which rotor is '1' and which is '2'...

Anyway, I'd like to hear suggestions on which parts I might want to pick up.

no start
 

i agree with scrip7 dont just buy parts and put it on..if you need to know if u have a blown seal ....remove the shrader valve from the compression tester......plug it into spark plug hole ,,,, crank a bout 4 times looking the guage....if you get lets say 125 , 123, 124 your ok on that rotor, do the same on the next....then if you get lets say 123, 124, 100....you may have a chipped seal or something......also sometimes wire harnesses can wreak havoc on diagnostics, check for spark at the wires....if non, check for ohms at the crank angle sensor, or if you have access to a scope that is better. if that is good , pulll a fuel line and check carefully and quickly for fuel......sometimes a faile pump is all it is...........and on and on and on

I don't think you read what I wrote. I'll return whatever parts I don't need, and Advance has been more than happy to allow me to do that in the past. The reason I want to do that is so that if I run into parts that have possibly failed I don't want to be running around all day trying to find them. I want to get this done in a day if possible, and I know fully well that trying out all the possibilities can be extremely time consuming, I was working on one car that wouldn't start, it would turn over well, but no firing. There were a large number of things that could have been wrong, and I had to test for spark, fuel pressure, ignition control module, and the starter coil before I found the culprit. I'm not an idiot, I'm trying to be prepared.

I have a compression gauge and spark tester, both of which I'll be taking with me. Coincidentally, I also already have a Chilton manual (by Haynes) because it's the same one for my '88 323. Again, I'd like to hear suggestions on parts to get, including vacuum hoses and such. Anything and everything that could be related to not starting or parts related to common problems with neglected RX-7's or ones that might not have run in a while. I'm going to hit up Advance pretty soon and browse their list of parts and pick up anything I think could possibly be useful.

GUYS. Please read what's already out here. It doesn't turn over. That has nothing to do with the fuel pump, nor the spark. IF I get it to turn over and it still won't start, then I'll be testing those things, which I already know how to do. I also know how to check the compression, I don't need a tutorial, I just wondered if there was a way to do it without the starter if I couldn't get it to turn over on its own. Like I said, hooking power straight to the starter is a good idea that I will probably try out.

Speedoflife: You start the post with newb questions (which is perfectly fine, because I am less sensitive about people not searching) and a horrible approach to diagnosing the problem (getting a bunch of parts you may not need, even if you can return them), and then feel like we're patronizing you for telling you basic stuff. We're just trying to help...and BTW, scrip7 was dead on.

I'll offer the following regarding your first post for you and others: As far as rotor direction is concerned, you know the intake manifold is on the top left of the engine, whereas the exhaust manifold is at the bottom left (you know this, but others may not). When I was new to these engines, it helped to think like this...fuel goes in..but it can't just go back out, which would happen if it spun counter-clockwise, so it must turn clockwise, for the fuel-air mixture to go past the spark plugs. Therefore it spins clockwise (standing in front of the car). Also, I see you want to turn the engine manually - turn it this way. Some people say spinning it counter-clockwise may help free some carbon up, but this may later break an apex seal. As far as the leading versus trailing spark is concerned, this helps the engine rotate by having the flame front begin where you want the engine to rotate. Because of the shape of the combustion chamber, the trailing spark helps maximise combustion.

As far as the current problem is concerned, it sounds like the engine may be carbon locked. It seems like you have little time and you want to get a bunch of potential parts. I don't know if you're planning on doing any thorough diagnosis (es), but replacing parts may end up costing more time. Also, have a FSM nearby and use the Haynes/Chiltons (I have/had a Haynes myself before I got the FSM) as filler in the bookshelf.

For the FSM, training manual, and Parts Fiche, see...

http://www.wankel.net/~krwright/cars...als.html#parts

See, we're nice people here...

I know you guys are just trying to help, I do appreciate it. But unless I buy the car, the parts will ultimately cost me nothing, because I would return them. Like I said, I'd do that to save time in the event that something needs to be replaced or some sort of sensor or control unit needs testing, in which case I'd temporarily replace it to see if it was in fact broken versus going to a store to have it tested.

I'll read up on carbon lock so I know what to do if it won't turn.

question then...??? can you turn it manually IE with a wrench or socket? if yes and it is a manual and you have juice, why not try a kickstart? i may have missed where you talked about this so dont get all pissed if i did ok..i am just trying to help someone as if it was me...

I re-read what's already "out here" and from what you wrote I would have never known you had a cranking problem. The more specific and accurate your first post of each thread, the more helpful we become and the less likely you will be fried to a golden brown by forum nazis.:)

If adding power and ground to the starter doesn't help, assuming the battery is good and fully charged, you should be able to turn the engine over by hand. If you still can't, remove the starter to eliminate it as a cause if it is binding and won't release from the flywheel. If it still won't turn, it may indeed be carbon-locked. Some have been successful freeing them up, later to have problems. It might then be necessary to do a teardown and inspection.

I ordered up a few ignition and spark related parts in preparation, including a starter and the neutral detecting switch (I forget the exact name, but I understand its purpose). I also picked up some sea foam, this is a good option in case it's carbon locked, right? I read that some people have used it to loosen stuck seals and clean out the chambers to improve compression.

And you may be right, I think I assumed that everyone would read the for sale thread in which I'm pretty sure it was stated that it won't turn over. That was a poor assumption for me to make, sorry.

Yeah, I think you can hook a large socket to the front of the motor to crank it. That might be necessary if it's carbon locked, but the most it can do for a compression check is help determine if seals are blown or not, not numbers. HOWEVER, I just talked to the owner and (w00t) he said that when trying to start it it won't click or anything as if power isn't reaching the starter, one way or another. So that sounds more promising and not a result of carbon lock (if it was locked you should still be able to hear the starter click on, right?).

I'm still open to suggestions, and we changed the time to meet to Sunday.

Intake manifold is on top of the exhaust manifold on the passenger side of the engine?

Not tooooo hard to figure out? :D

ok so best bet then is first bridge soloniod to see if it is stuck, starter should run when you do that.....if not push start, now for compression you can remove the plugs and turn with socket and put your finger in leading hole..you should get 3 faint swoosh sounds and a slight push on finger.....

I know, I felt dumb when this was first mentioned... :wallbash:

L stands for lower while T stands for top...idiot proof way to put in ur spark plugs......i remind myself that every time i have to put them in...

um... I thought they actually stood for 'leading' and 'trailing', especially since 'lower' and 'top' are kind of self explanatory just by their position...