Unable to start my FD RX7 when warm.

[Myrotarylife]

Hi All,

So I figured out the cranking tables etc and she starts first time every time now and idles fantastically.

The issue comes when I try to restart the car. time doesnt matter with this one. It refuses to start. If I wait until the next day I can start it again without issue. Plugs were getting fuel but not flooded by any means. All values look good for sensors etc.

I have included a copy of my map that I am running, please can someone take a look if there is anything obvious thats wrong.

I have looked at most tables and dont really want to adjust anything because when I do get it started its pretty much perfect.

I just compression checked the engine and all faces are very good. Lowest value was one face with 80PSI most were 90-100psi.

So mechanically were OK. It must be something in the setup.

The car will sometimes try and catch but then instantly dies. AFR is reading high after cranking. I have tried playing with the ECT vs. Injector duty when cranking table to induce more fuel volume but it hasnt helped.

 

Any ideas?

Mazda RX7 Charlie Link Base Map Backup.pclr

[Myrotarylife]

Hi Folks,

It is looking like its a compression issue....Not an ECU issue at all......

[Pete_89t2]

Sorry to hear it's a compression issue - I assume you tested with a rotary specific compression tester and did the test with the engine hot and at wide open throttle? What were the compression #'s? If just one chamber is reading low, it's probably just a sticky side seal - you can often free those up with Seafoam treatment (or equiv. solvent). Might want to give that a try before tearing it down for a rebuild.

[Myrotarylife]

Hi Pete,

 

I used my rotary compression tester v5. It was warm after the running of the car. 
 

Rear rotor was awesome. All around 100psi. ( races for 4 years!) Front was 73psi on one face and 78 and 82 on the other faces. 
 

the whole reason I moved to link was my adaptronic had failed and wasn’t fueling correctly. I do t have an OMP and lubrication is purely based on premixed fuel. So the issue with the ecu caused a lack of lube and hence the wear. 
 

good news is it is nothing catastrophic that has failed. A master close out kit will refresh the whole thing and give me hopefully another 4-5 years of racing just like it has Since my last rebuild of it. 

at least I have plenty of time before next Time attack race season starts. 

[Myrotarylife]

I tell you what is strange Pete. When it does run I’m still pulling -12in/mg. of vacuum which for a heavily ported engine is actually pretty solid numbers. It’s the only thing that’s kept me away from compression checking it previously. When it was fresh built and broken in it was sat around -16in/mg. 

[Pete_89t2]

Interesting, the reason I mentioned the sticky side seals and Seafoam treatment is I have a similar weak compression issue on my FC that appears to be seasonally tied to my car's usage. I get to a track day maybe once a year if I'm lucky, and my FC gets some spirited use on the twisty roads when the weather is nice but it's basically street driven much of the time from about March - Dec (or whenever the roads aren't salted and the weather is decent). I give it an annual flogging at Deals Gap when I do my annual pilgrimage to Deals Gap Rotary Rally in April/May and rack up around 1700 miles over that week. I have the same RCT5 compression tester you have, and I discovered that if my car is consistently driven frequently & hard, I get better compression figures. And when the car comes out of winter hibernation, my front rotor is marginally weak on one chamber. Eg, my normal "good" readings are ~118's on the rear, and ~108's on the front, all faces. I attribute the "normal" front to rear difference to the fact that I built up the front rotor first, so I probably took off a little too much material when I was setting side seal clearance. The post-hibernation readings are typically 105's rear (all faces), and mid-90's front, but with one chamber in the low 80's. When that happens, I'll add 2 cans of Seafoam to an almost empty tank of gas and take a bunch of full throttle rips to redline in 3rd/4th gear, and then retest the compression, which will magically bounces back to the "good" readings.

I built my FC motor 2 years ago, it's a 13BT, but a bit of a mutt - started with all new parts, S4 housings, and S5 irons & rotating assembly. Put a big street port on it with Pineapple racing intake & exhaust templates. I'm running the S5 OMP with the RA OMP adapter so it's apex seals only see pre-mix, which is gravity fed from a separate tank; engine management (and OMP control) is with an AEM Infinity ECU. Reason I'm on this forum is I just picked up an FD that is running a Link G+ Fury with a single turbo. Trying to climb the learning curve with the Link, which seems much easier that my AEM Infinity! Previous owner chucked the OMP and is running a DBW setup on it - I'm going to have to rewire it all so I can get the OMP back and plan to set it up just like my FC

[Myrotarylife]

interesting. Maybe I should try it first. The car only idles about once a week with some off load revving and then gets thrashed for a weekend a month. 
 

might be worth a go before pulling it apart. 
 

it may buy me another season yet. Who knows. Thanks for the heads up.  
 

also I went from adaptronic to link and I am not regretting the move. Both have plus and negative points but the links depth far outweighs the adaptronic. 
 

I was supposed to go to DGRR so many times with my FD but running the shop made it impossible to leave. I was part of the Nova Scotia bunch of rotary heads that make it down each year.