Help getting 2nd gen rx7 to start please!

Engine and controls are 87 na rx7.

Transplanted into a 1st gen.

All 2nd gen controls and wires were swapped over from running and driving car along with engine.

We eliminated the fc chassis wiring and ran our own.  We cut every plug off sensors and ecu and ran new, non crispy wire.

The car has spark and fuel.  We hooked up a spare cas and spun it with the injectors still in the rail, but spraying into a glass.  Flow and pattern look good.

Here's the kicker...  the engine will occasionally backfire....  HARD!

Won't start on ether, but sputtered and then backfires.

This is making me think timing, but i checked it with the dot on the cas and the pointer on the front.  They line up...

HALP!

I'm no rotary expert. My knowledge of these engines is as follows: Two stroke magic that resembles spinning chips and revvs up real good. 

So. No valves, cam, timing chain or belt. Problem must needs be ignition timing. Again, not an expert, but Just because the timing marks line up does not mean everything is lined up correctly.

I'd say if it was a normal engine to verify top dead center in no.1 and check your distributor if there is one. Not sure how in the muff you are supposed to find TDC though, oval housing and all.

Did you try pouring some ATF down the vacuum lines?  That's all I know about rotaries.

Have you done the basic compression check-pull plugs and crank to verify evenly spaced pulses? Plug wires on right? Do you have a really good battery and have it actually installed in the car-Jumper cables are doom. I always had the best luck pull starting dead rotary engined cars.

Your ignition timing is off, hard.

I don't know about setting up a CAS but if you ever had the pullies off of the front hub, you can install them 90 degrees out.  180 out will start and run just fine but you won't get over 1/3 throttle without preignition so hard it feels like the engine turns backwards momentarily.

Knurled. said:

Your ignition timing is off, hard.

 

I don't know about setting up a CAS but if you ever had the pullies off of the front hub, you can install them 90 degrees out.  180 out will start and run just fine but you won't get over 1/3 throttle without preignition so hard it feels like the engine turns backwards momentarily.

I didn't think you could install them 90 degrees off because the holes are not in a square pattern.

I will double check the pulleys and see what's up.

Engine has decent compression.  It was around 100 when checked with a regular gage with the valve removed.  Both rotors all faces.

Is there anything with the ecu or sensors that can make the computer change timing?

wvumtnbkr said:

Is there anything with the ecu or sensors that can make the computer change timing?

Probably, like a crank position sensor would be the obvious culprit. Engine temp sensor probably has minor input to startup timing as well, but I'd doubt it'd be enough to make it not start at all.

The temperature sensor wouldn't have anything to do with this.

If I recall (and it's been a long time...), You can stab the cas off of the wrong rotor.  I'll look for evidence of that, though.

It is amazing how "dumb" the old computers are and what they will happily run without.

The fact that it won't run on starting fluid SCREAMS timing problem.  Get a timing light on the wires to the leading rotor and verify that it triggers in the first place, and that the timing is correctish.  Then do it again for the rear rotor, crayon a dummy mark 180 out on the pulley just to gauge off of - you are not looking for exact timing, just verification that spark is happening and in roughly the right time zone.

Will do!

Thanks for holding my hand through this!

My T2 hates to start when it's cold, and if it's cranking slowly, it will sometimes refuse to start and occasionally backfire.  I attribute that to the fact that it's got over 100k on it and my cold start enrichment map isn't quite where it needs to be.  Make sure your plugs are fresh and that your battery is in good shape and fully charged.  I don't even attempt to crank her if it's below about 50 degrees F.

Definitely sounds like a timing issue. If it was an unknown engine I'd say check compression, and also if it's cranking too slow it will have problems starting, especially if the engine is a little worn out.

If you need to stab timing, the easy way to find TDC is to pull the inspection plate by the flywheel and hand crank the engine until the flat side of the flywheel (where you can't see the counterweight) lines up with the side of the iron. The top bolt of the main pulley is now at ~TDC. This is how I had to time my car since my aftermarket pulleys don't have timing marks, and before that, my timing marks were surface rusted away.

Did you pull the cover off the cas to verify that the teeth are pointed the right way?

Dr. Hess said:

Did you try pouring some ATF down the vacuum lines?  That's all I know about rotaries.

ATF in to the spark plug holes. Using a vacuum line to get it there is ok.  Timing is where I would start. If you get timing set roughly correct I would do the ATF trick. Put a table spoon or three in each rotor with the plugs out. Crank it over with the fuel pump disabled then put plugs in and enable the pump.  

You may have flooded it the first time long cranking with no start will flood these. In my FC I wired a kill switch in to the fuel pump so I could manually kill the pump when starting. Crank the motor and then hit the switch. It was also handy for when I had to move the car and it would not get to temp. Kept it from flooding.  I would kill the motor by turning off the pump this reduced the chances of a leaking injector washing the motor in fuel.  It also let me control the semi warm start as the temp sensor will see cold antifreeze but the combustion chambers will be significantly hotter.  This will cause the ecu to put way more fuel in an flood the motor on a warm start.  Being able to manually control the pump eliminates this issue.  

Also get a battery that is really good then put s jump box on it and a set of cables from a running vehical. I have found that these things when left to sit for a while need to be spun over fast and hard to bring back to life. In some cases we would tow them behind another vehical in 1st  to really get them spinning just keep an eye on the tachometer so you don’t over speed the motor.  

Lastly a tank of fresh gas. For some reason all my RXs wanted fresh gas when started after sitting for a while.  Once running I could run them on just about any swill as long as you had a good filter.  They liked 93 and I would run it on general principal to avoid knock but there were times I had to put 87 in it and there were no issues.  

In reply to dean1484 :

I know almost nothing about Rotaries but that answer seemed like, REALLY GOOD!

That kind of stuff is why I’m here!

edit: the other answers were good too, I meant only positivity!

I'm following along to learn here. I don't really have anything else to add.

"put ATF in the burny part of the engine" is probably my new favorite thing. I LOVE how un-EPA friendly that is. Don't get me wrong, I don't want to watch the world burn, and I like to conserve wherever I can. I just think that if this is a serious, used and actual fix for something to do with wankel engines, then I really need to own a wankel at some point.

In reply to dean1484 :

All of this is great advice. I had an 87 RX-7 with slightly low compression and it would flood terribly in cold weather during startup...even just a few minutes after a warm shutdown. There are 3-4 different levels of un-flooding these bastards. As Dean1484 pointed out, disabling the fuel delivery while holding wide open throttle during cranking can help clear out the raw fuel. I pulled the injector fuse. Also, fast spinning of the engine is critical. Check out RX7club.com 2nd gen forum. They have a lot of excellent advice on unflooding. Note: the ATF trick is to get compression back after the raw gasoline has scrubbed all of the lubrication off the combustion chamber walls. If you use ATF, be sure to immediately change your oil. You don't want ATF contamination hanging around in your oil.

Good luck and have fun with the RX7. They handle great, but that rotary...(be sure to rev the snot out of it!!!)

In reply to barefootskater :

Yep. The “ATF Trick” is a real thing. Super high detergent oil that will lubricate the seals and tips that get washed with gasoline when you flood one of these. Not only will the flooding kill the plugs but it causes the side seals and tips to not seal as well lowering compression. Adding the atf removes the fuel and ups the compression similar to a standard motor but is much more effective due to the shape of the combustion chamber and the comparatively large amount of sealing area as compared to a piston. It will also dissolve carbon that can cause rotor tips to loose there seal. This is because of the high detergents in it. This is a fix for rotary motors that get carbon build up due to them not being driven hard every now and then. Rotary need to be run up to redline every now and then and driven at temp to keep the carbon buildup at bay.  If a rotary gets all carboned up you pull the plugs and add atf one a day ant turn it over by had. Repeat for a week is best but even two or three days will often help a lot. 

Oh I would not use synthetic atf standard stuff is better.  And on a side note use standard oil unless you are using premix in the gas

Thanks guys!  Time to rethink the basics....  

For the record, fuel pump is on a switch.  

This is my 13th rotary vehicle.  11 others being 2nd gen s4 rx7s.

I think my pulley is wrong.  Tried the flywheel cutout on the side.  Timing is better, but still not sure if right.  

I will take the 12a pulley off that engine and stick it on 2nd gen engine... yes, I know about Torrington bearing.

That way I know timing is right.  Next step,  more revs through starter or pulling.

I might try atf before that.

Pete, how much for a successful house call?

Why would the 12a pulley make a difference if you're running the 13b with the stock pulley? And as long as you're not removing the pulley by the big bolt in the middle and only by the 4 small bolts, no need to worry about the bearing. The main thing is getting that ignition stabbed near TDC. It will run if the timing is close, or at least pop or try and kick over.

I think you/we might be overthinking this. What has changed since the running engine was pulled and been transplanted? Did you swap front covers? Anything that has been changed is a possible problem, anything that hasn't changed is likely not. Take a step back and think about what the problem could be before chasing something it can't.

If this is efi, check the polarity of the hall effect sensor, wether its crank/cam/flywheel.

I have swapped the two wires before, and gotten some really berkeleyed up behaviors until it was sorted.

This was bothe electronic ignition mopar with a carb, and tpi corvette. 

May be a red herring in the rotary world though.

Hope you can get it running. This thread makes me want to see if I can get my 2nd gen to run before I pull the engine.

At one time, the pulleys were removed from the engine.  I found out recently that not all of the pulleys and hubs are the same.  

Since I have a few of these engines around, I want to make sure I have the timing set properly.  I have a known good 12a hub and pulley that I can swap over and mark the pulleys I have.

In other words, some years pulleys and hubs were drilled differently.  There is a strong chance that I mixed up the pulleys about a year ago before putting this engine in this car....