I picked up a 91 na in the midst of a jdm s5 tll swap. Finally ready to start and nothing. So I checked fuel pump, (working) when I pulled the spark plugs to check for spark and front rotor is fairly quiet, but the back rotor is pretty loud. This cant be good right. oh yeah they all had spark.

 

I've moved your thread over to the Technical section.

Sounds like you're low on compression on that front rotor. You may want to get the engine compression tested.

For cheap, you can get an idea of the compression your engine is putting out by using a piston engine tester.

Here's a couple examples:
http://www.banzai-racing.com/compression_test.htm
http://www.rotaryresurrection.com/2n...ion_check.html

It's not the ideal test and doesn't get you 100% accurate info... But it'll get you approximate numbers, enough to get the engine started and running.


Also, you verified fuel pump is moving fuel... But do you have a reading on the pressure? Do you know if your injectors are getting power and/or firing?

Go to the local parts store and find a set of "Noid Lights" to test your injector wiring.

 

this is off topic, but pele why is it a compression tester made for piston engines wont be accurate when all it does is read PSI?

 

Ok so looks as if I got a jdm 13b 3s5 tll no compression in front rotor at all, and the rear is at like 90 psi. I'm gonna attempt to tear down, inspect and rebuild. I've read alot about the different seals. (2mm,3mm,hard,soft, rotor housing warring, detonation, etc.) So many different opinions. Need some advise as to what seals would be best for my app. I would like to run higher boost than stock in the near future maybe 10 to 12 lbs or so I don’t have emissions where I live so, won’t have cats. If within budget, would also like to do a port of some type not too sure on that. I'd like to have some reliable power in the future from this build. (Say 350 to 450 hp). I can’t hear anything ominous sounding when I turn it over, so I'm hoping I can use my current rotor housings, in case ones damaged can I use one from a left over s5 na or are they different. Anybody know someone in Houston who does good port work. Is this something a fairly competent guy could research and do himself? If so where could an instruction video be found. Thanks for the advice

 

A rebuild is something any fairly decent mechanically inclined person can do, if you have patience and take your time. Helps to have an extra set of hands to help. Porting is another story all together. Best leave that to the pros. any slight mistake and your housing or iron can be garbage.

 

They're intended to read the pressure generated by one cylinder, so having it not vent pressure is just fine.

On a rotary, each spark plug hole gives access to 3 separate combustion chambers. If the bleeder valve is not depressed (or the schrader valve isn't removed), the tester will only show you the highest pressure generated by one of the rotor faces. Holding the bleeder valve open gets around this, but the needle will be bouncing all over the place. Hence the reason it's hard to see if it's 91psi or 92psi, etc...But a ballpark measurement is still reasonable.

 

o . . .ok, so a piston engine compression tester works fine with the pressure release in but since the needle jumps its hard to tell what the needle is EXACTLY.

thanx , this is similar, how come a coventianal rpm guage not work right with rotorys?

 

seems weird that the front rotor would lose comp... any i've seen have always been the rear. where did you get the motor?

 

the motor is a jdm

 

I'm getting ready to tear down my s5 tll. Not sure what I'm gonna find when I get'er open. Hopeing my housings are ok. But if not can I use one from the original s5 na motor. Or, I guess a better question is what all is interchangable.