JakeFairley

I’m a pretty new Rx8 owner and don’t know a lot about cars in general but I’ll do my best to describe the issue. My engine has taken a while to turn over for a couple months (about 2 seconds or so) But recently when the engine is warm it takes multiple try’s and around 6-8 seconds to start. One day I drove it home from work with nothing out of the ordinary, parked it and it sat for about two weeks (I don’t drive it too often) When I went to start it cranked but wouldn’t turn over.

Coils, Plugs, Wires?
Loss if compression?
Where should I start and how should I go about it?
Thanks for reading, anything would be appreciated.

CaymanRotary

It could be ignition system related but it could also be low compression. Get the compression test done first as I’m assuming it starts and runs while cold right? Any engine codes?

JakeFairley

Yes it has a cylinder 2 misfire. and also no, even cold it’s just cranking but won’t start.

CaymanRotary

In this case you want to remove the spark plugs and inspect them for any damage. Even a low compression engine should crank cold. Could also try to deflood the car if the spark plugs are in good condition.

JoeBlow

After sitting for 2 weeks sounds battery related, it might be on it’s way out. Also If the cold cranking amps (caa) rating of your battery is less than 660 it won’t turn over fast enough to start easily.

Check the plugs for spark. Pull plugs one at a time and feed the plug and wire up so it sits on top of the strut tower (where your strut bar is bolted) so as not to ignite the fuel coming out of the empty spark plug hole. Threading a spare plug into that empty hole while you do this is best. You will be able to see the spark from inside the car while the hood is up. If there is no spark try a known good spark plug. If there’s still no spark it’s probably the coil. To double check, replace the plug wire with one that you get spark from. Be careful when you remove the plug wire from the coil (turn before you pull).Also take note of which coil goes to which spark plug before you swap plug wires.
It’s a good idea to have fire extinguisher handy when there is an empty spark plug hole or any time you’re working on your car really.
if you’re not comfortable doing any of this then get someone who is to help you or do it for you, better still.
PS you’ll need to jack up the front of the car with emergency brake on and or wheel chocks on the back wheels and secure with jack stands and then remove the drivers side front wheel to access the plugs.
I apologize if this is more than you want to take on.
Best of luck.

shawnstasiuk

yeah JoeBlows advice is pretty solid. Only thing i could add is get an obd2 app and adapter for your phone. with that you can monitor your battery voltage while sitting, cranking, and running to see how dead it really is. can also monitor your rpm (cranking speed) while turning it over. But truthfully the hot start problem sounds like it might be out the door on compression.

Friertuck45

I hate to post my own problems under someone else's post but I have no idea how or if I (being a fairly new member) am able to create my own threads. I'm stuck and don't know how to proceed so I'm trying to see if anyone has had a similar issue, or if anyone knows the solution to such a complicated mess.

ANYWAY...

I recently rebuilt my 13b, replaced all seals and springs, rotor housings, resurfaced irons, even went as far as painting certain components. Needless to say, I spent A LOT of time researching, doing my hw, and rebuilding this motor. I torqued everything to spec, and I am confident the motor is in the best condition possible. The engine went back in fine, hooked up the upper intake manifold and the AEM cold air intake (the only engine mod on the car), along with everything else within a day. My old battery was shot so I went with an Optima Yellowtop D35. After doing some research you'll find Optima does not recommend the Yellowtop D35 but instead the Redtop 35. They have the same dimensions, only a difference in cranking amps. *According to the Optima rep I spoke to, they recommend the Redtop for the higher cranking amps*

Here is where the problem begins.. The front of the car is pitched up on jack stands with the front wheels off in order to get under the car, the key turns to ON, turns to ACC, cranks over and within seconds, its running with the expected cloud of smoke of the Vaseline burning out of the engine. It sat at idle very very smooth, right above 1K RPM. Every once in a while I'd give the gas a small tap, never went beyond 2K RPM. I noticed the gas tank needle was below E. After running smooth for maybe 3 minutes, the RPM slowly began to drop and the car shut itself off. I immediately added gas and tried again but since then I have not been able to get it started. It cranks around 200 RPM but doesn't seem to want to catch.

1, The spark plugs are sparking good (apparently Mazda updated the PCM at some point in history so that only the leading plugs/wires spark on startup, then the trailing spark while running ?). 2, The coils and wires are working properly. 3, The compression is about 70 PSI on both front and rear rotors. 4, I have a code for the APV stuck open (not sure how that would affect a no start condition. 5, Cranking the engine with the spark plugs removed, I do not see, or feel any spritz of fuel coming out of the plug holes which leads me to think its not getting fuel. 6, I've sprayed starting fluid into the manifold but still, the engine barely sputters. 7, My brand new battery has already drained even though being charged and then jumped (obviously leading to a separate no-start condition and probably indicating a different issue). 8, I performed some sort of reset by depressing the brake pedal 20 times.

As of right now, I can't think of any other details related. My mind tells me maybe blocked injectors from the fuel that had been sitting for months in the tank ? But even still, spraying starting fluid into the engine should result in at least a slight sputter, being the spark is good.. am I wrong ? How would the engine start up so smoothly, run so easily, but then die off and not start again ? Is there a condition where if the car runs out of gas, the dealer has to hook up a scanner to it to manually reset something ? I thought I remember that being the case on some Toyotas when I was working there.

Sorry for such a long post but I figured the more clear detail I can provide, the better others can understand the situation. Please help

CaymanRotary

This is extremely low. This number corrected for 250 RPM and elevation with a rotary compression tester? Its possible the rebuild leaned out and damage was done when you ran it out of fuel. Even at 2k RPM you really don't want to starve the engine of fuel.

Friertuck45

I actually did not correct it. I remember seeing a graph somewhere, but I'll have to see what I can find in order to correct it. I did not use a proper rotary compression tester (too damn expensive). And I agree that 70 PSI for a freshly rebuilt rotary seems way way way too low, but the last thing I want to do is pull the engine apart again :/ even still, the low compression shouldn't be causing a no start condition.

CaymanRotary

Can't really take that result too seriously then. Your engine should start. Assuming it's cranking at 200RPM that should put in high 80's / low 90's. It should start and run. Getting any codes? Did you try to deflood? Are you getting fuel to the engine? Can you hear the fuel pump prime?

Friertuck45

Yeah I have 2 fault codes, one is for ABS, the other I believe is a P2004 APV stuck open. I stripped the LIM down to get it cleaned and painted so I almost expected something to be wrong with the APV system. Although I'm not sure why that would interfere with the engine not starting. As you said, It should start. I have spark, I have air, and I think (I'm going to dig into it a little bit) I have fuel. maybe there is some was the air:fuel ratio is off ?

CaymanRotary

Make sure you are getting fuel pressure. APV shouldn't cause a no start scenario. The only clue is that it ran fine until it went out of gas. When you put new gas in it wouldnt start. Points to a fuel issue.

Friertuck45

That's what I'm thinking as well. It's just such a complex and unique system, I've been second guessing everything..

Friertuck45

Turns out, depressing the brake pedal 20 times cycles the oil pressure gauge on the dash and resets something int vehicle's computer.. Combined with disconnecting and reconnecting the battery - allows the car to start (still trying to figure out why this works when nothing else would). I checked the fuel pressure at the same time by tapping into the line by the brake booster and got ~ 58 PSI when in ACC, then ~ 62 PSI when the car was running. Unfortunately the car ran rough for about 2.5 maybe 3 minutes, trying to find a smooth idle and then stalled itself out. I also tripped the same P2004 code regarding the APV stuck open.

I believe my next move is going to include taking the upper intake off, along with whatever else I can easily remove, and attack the APV issue the best I can. If anyone knows anything on this issue, please let me know. I'm going to be doing some research on it to see what I can find.

Red line envy

You do have to pull the engine to take the Lim off but first you can test the apv motor by jumping 12v to it. It is the black electrical motor on the Lim. Access by removing passenger front tire. You should see it.

Friertuck45

I can hear it actuating which is the odd part.. when I turn the car off I hear the APV motor working, I can also feel it with my hand.. I'd hate to pull all that off again, just to find out it's working normally.

Red line envy

It could be working but if the small magnet on the gear is worn out or gone the the ecu won't know it's open triggering the code.