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SV reX
SV reX MegaDork
5/19/24 2:06 p.m.

My friend's daughter has an RX8.  She is a young automotive hypochondriac who lives in rural AL (where there are no rotary folks).  Not a good combination.  She always thinks there is something terribly wrong with the car.  She wrenches on it, but shouldn't.  Any misc thing she reads on Reddit or YouTube...

A couple months ago she parked the car in the evening and found it wouldn't start in the morning.  Eventually a shop figured out it needed plugs and a crankshaft position sensor.  

This week she put it in the garage to clean the TPS and the MAF sensor.  Yesterday it started fine (still unassembled) to move in the garage.  Today she got the whole thing back together (airbox, MAF, intake accordion air duct hose all removed and cleaned and reinstalled).  Also replaced a couple vacuum fittings and bad hoses.

Now the car cranks (strongly), but won't fire.  Didn't note any plugs still disconnected.  I can hear the fuel pump.

The symptoms seem identical to the previous no start.  But a car shouldn't need  plugs and a CPS every 2 months.

 

Any thoughts?

sevenracer
sevenracer HalfDork
5/19/24 2:15 p.m.

Could be flooded if she only started it briefly and shut it off before warmed up.

clutchsmoke
clutchsmoke UberDork
5/19/24 2:59 p.m.
sevenracer said:

Could be flooded if she only started it briefly and shut it off before warmed up.

Yup. I think the procedure is throttle to the floor and crank for... 10 seconds? I'm guessing it's auto thus no option to push start.

Oh! What year is it? The starter could be getting weak. It's a really easy swap for something more beefy.

kb58
kb58 UltraDork
5/19/24 3:20 p.m.

I agree that logically, it's whatever she did last that "broke" it. Back in the old days of carb'ed 13Bs: if it cranks but doesn't start, the apex seals are likely toast. Seems unlikely in this case.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
5/19/24 3:21 p.m.
sevenracer said:

Could be flooded if she only started it briefly and shut it off before warmed up.

Yeah you really really don't want to shut off a fuel injected rotary cold.

triumph7
triumph7 Dork
5/19/24 3:25 p.m.

 

 

Wasn't the procedure for a flooded EFI 13B to pull the fuel pump relay and crank it, maybe with the plugs removed?

Slippery
Slippery UltimaDork
5/19/24 3:34 p.m.

At the end of its life, I had to go and tow start my buddy's RX8 once a month ... he got it to 200k miles, but he was the og owner.

Streetwiseguy
Streetwiseguy MegaDork
5/19/24 4:35 p.m.

She can melt the starter, or get a pull start.  Rotaries flood so easily...

Hope it's a manual.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
5/19/24 5:18 p.m.
triumph7 said:

 

 

Wasn't the procedure for a flooded EFI 13B to pull the fuel pump relay and crank it, maybe with the plugs removed?

Pull the plugs, crank the engine until the white fog stops coming out, add oil into the spark plug holes and crank until compression comes up, install new plugs and start engine.

 

SV reX
SV reX MegaDork
5/19/24 5:34 p.m.

It's a manual. 
 

Had the starter replaced about a year ago. 

BoxheadTim
BoxheadTim MegaDork
5/19/24 5:50 p.m.

Then I'd say first order of the day is to crank it for a few seconds with the pedal to the floor to unflood it.

clutchsmoke
clutchsmoke UberDork
5/19/24 6:09 p.m.
SV reX said:

It's a manual. 
 

Had the starter replaced about a year ago. 

Well in that case pull start. Or pull the plugs and crank to unflood.

SV reX
SV reX MegaDork
5/20/24 7:14 a.m.

First round of cranking with our foot on the floor didn't work. We killed the battery. We'll try again this evening. 

Slippery
Slippery UltimaDork
5/20/24 8:49 a.m.

If its flooded and has weaker compression, the only way to start it will be to pull start with another car. It will take quite a while and you will need to get it up to a good amount of speed. I'd say 1/2 mile and 30 mph, it will want to start and bog repeteadly until it finally comes to life.

93gsxturbo
93gsxturbo UltraDork
5/20/24 9:41 a.m.

Old rotaries don't like to sit as you know.  

I got a good deal on a non-runner, pulled the plugs and flooded it with ATF through the spark plug holes.

Let it sit for a week.

Spin it over to clear the ATF

Install *new* plugs.

Fire that bad boy up and drive it like you stole it.  

Don't let it sit.  

Brett_Murphy (Agent of Chaos)
Brett_Murphy (Agent of Chaos) MegaDork
5/20/24 10:06 a.m.

Add another rotary guy saying to pull start it.

 

SV reX
SV reX MegaDork
5/20/24 10:36 a.m.

Hmm... I was prepared to start pulling the plugs and trying to dry it out that way this evening, but maybe I'll try pull starting it first. 

Keith Tanner
Keith Tanner MegaDork
5/20/24 10:49 a.m.

I'm not a rotorhead, but to me this sounds like a case of "something was reassembled wrong". Car was working, someone took it apart, car no longer works.

Assuming RX8 wiring is related to other Mazda wiring, it's almost impossible to keep them from cranking as long as you have power in the battery. The cranking circuit is fairly simple. If the fuel pump is priming, then I'd be looking at why the ECU doesn't think the engine is trying to run. A crank position sensor unplugged or with the wrong air gap, for example. Or a MAF that's installed backwards. At this point we're possibly getting into rotary specific stuff, but no matter what I'd be looking at what was done between "car running" and "car not running".

codrus (Forum Supporter)
codrus (Forum Supporter) UltimaDork
5/20/24 11:03 a.m.

Did you check it for codes?  If there's an unplugged sensor or something that's stopping it from starting, that would probably set one.

 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
5/20/24 11:35 a.m.

In reply to codrus (Forum Supporter) :

On an RX-8?  It's probably low compression due to weak ignition coils.  Or a slow starter.  There's a much faster upgrade starter available.

 

I've been a rotary nerd since the mid 90s and I still don't understand the RX-8 voodoo where weak coils = low compression.  Like, replace the coils and compression will come up 20-30psi.

codrus (Forum Supporter)
codrus (Forum Supporter) UltimaDork
5/20/24 12:26 p.m.
Pete. (l33t FS) said:

On an RX-8?  It's probably low compression due to weak ignition coils.  Or a slow starter.  There's a much faster upgrade starter available.

"started fine, took it apart, put it back together, now it won't start".  As Keith says, that usually means you screwed something up when you reassembled it, rather than that some long-standing progressive problem suddenly got bad enough to fall over the cliff of not starting at all.

Flooding is certainly possible, due to short distance moving around while doing the service, but otherwise the general rule of thumb is "it's the last thing you touched".

SV reX
SV reX MegaDork
5/20/24 12:28 p.m.

In reply to codrus (Forum Supporter) :

I agree. But there really isn't much you can screw up removing and reinstalling the air box. 
 

...although Keith's idea of the MAF being installed backwards is an interesting theory...

fidelity101
fidelity101 UberDork
5/20/24 12:48 p.m.

In reply to Pete. (l33t FS) :

this

 

also has a compression test been done yet?

SV reX
SV reX MegaDork
5/20/24 1:18 p.m.

In reply to fidelity101 :

RX8 seems to be the only car that everyone automatically jumps to "compression test". There's a lot of other stuff to check before assuming the motor is shot (some of which effect compression like Pete noted).

Im pretty certain internet lore has retired a lot of RX8's for "compression" when they may have only needed an ignition coil or starter.

Ill go through other steps first. 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
5/20/24 1:45 p.m.

In reply to SV reX :

Well, it's not like timing can be screwed up.  Compression is the only thing you really can check.  And rotaries, especially injected ones, have a penchant for flooding if you short-start them.

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