worth rebuilding my engine?

[Silver86]

is it even worth the effort? it runs like garbage... not entirely sure whats wrong with the engine, i know theres either a stuck or blown side seal in one of the rotors... NoDOHC came out the other day to give me a hand and he said it almost sounds like it is running on 1 rotor. maybe hell chime in and give me some professional advice.

saving up for this 20b N/a project is gonna take forever and i would like to at least drive and enjoy the car before i put her under the knife...

looking at this beautiful paperweight i have sitting in my driveway makes me all emo...

[JShiz]

Open it up and see the damage so you can make a good call.

[Max777]

Dude, mine ran kinda crappy, the compression was low, it was only pulling about 12" of vaccum at idle, and the transmission had about 140K on it. I priced out a rebuild, and all the work/tools/time involved, and decided that unless there is some concrete reason you want to keep the N/A powerplant, a TII swap just makes more sense. Also, if a TII engine blows, there is more reason to rebuild IT, rather than the crap N/A.

[Silver86]

Dude, mine ran kinda crappy, the compression was low, it was only pulling about 12" of vaccum at idle, and the transmission had about 140K on it. I priced out a rebuild, and all the work/tools/time involved, and decided that unless there is some concrete reason you want to keep the N/A powerplant, a TII swap just makes more sense. Also, if a TII engine blows, there is more reason to rebuild IT, rather than the crap N/A.

good reasoning, but a TII swap is not something i want... i would rather rip out my N/a powerplant, rebuild it and re-install... thus getting a chance to enjoy the car (even if its slow) while i buy/build/prep for the 20b swap.

[need RX7]

Since you're trying to save for the swap, I'd look for a known-running, low-ish mile engine and throw it in for the time being. It won't cost as much as a rebuild and it'll get you back on the road. Of course, there's always the chance that there will be something wrong with it and it will put you even deeper in the hole...

[RETed]

Did anyone mention doing a COMPRESSION TEST before opening the engine up???


-Ted

[Phoenix7]

Do a compression check first and then just stare at it as you gather the 3-rotor stuff (or you buy it all at once, dunno your situation).

Honestly, I wouldn't rebuild an NA but that's just me. I currently have a blown FC that I haven't touched because it's not worth my time or money to rebuild it (also have very little time) but I'm looking into a drop-in spare motor for it to get it on the road by spring..... If it was a 13BT then I'd have it apart and trying to rebuild it as we speak.

If it IS blown then look for a spare, decent running motor and drive it till it blows again.

[need RX7]

Did anyone mention doing a COMPRESSION TEST before opening the engine up???


-Ted
Yes, do this if you haven't already. I assumed it was always a given.

[Phoenix7]

Yes, do this if you haven't already. I assumed it was always a given.me too, blown motor = compression test showed 0 psi on 1 or more rotors.

[Silver86]

Did anyone mention doing a COMPRESSION TEST before opening the engine up???


-Ted


lol... im no noob Ted... of course if did a compression test. it was the first thing i did after i got the car home after buying it. its been a few years... so i might as well try it again, just to see if anythings changed. the last i did check it though... i do remember now... i did get 3 decent pulses on the front rotor... and only 2 on the rear... that was also 3 years ago.

[TitaniumTT]

Rebuild it. If you've got good comp in the front rotor and only one low pulse in the rear, it's definately worth rebuilding rather than let it sit for 2+ years

If you don't expect the motor to last forever pull it apart, clean everything up really well and reuse most of the seals. Buy new oil control o-rings, dowel rings, fire/coolant seals and just do the bare minimum. Even if a housing is chunked a decent N/A housing should be able to ba had for a bill or two. At that point you're looking at your time. Total time to do that should be in the 30-40 hour range. So wake up saturday morning and work until Sunday night and you'll be 90% of the way there.

Seems like a no brainer to me.

[RETed]

i did get 3 decent pulses on the front rotor... and only 2 on the rear... that was also 3 years ago.

Only 2 on the rear might mean just a stuck side seal.
Try soaking the rear rotor in ATF or MMO or whatever your fav is.
1 good and 2 bad / no pulses is indicative of a bad apex seal and guarantee a rebuild.

If it's a stuck side seal, there's a chance you could resurrect the engine without opening it up...


-Ted

[Silver86]

Only 2 on the rear might mean just a stuck side seal.
Try soaking the rear rotor in ATF or MMO or whatever your fav is.
1 good and 2 bad / no pulses is indicative of a bad apex seal and guarantee a rebuild.

If it's a stuck side seal, there's a chance you could resurrect the engine without opening it up...


-Ted


how would i go about positioning that side of the rotor down so itll soak? crank the engine by hand?

err i worder that wrong... how would you do it Ted?

[RETed]

Yeah, crank by hand.
I typically use the 19mm bolt in the center of the main pulley.
I'll pour the liquid via a hose and funnel through the leading spark plug hole(s).
Crank just enough just to get the liquid to go through.
Don't crank it too many times, and it starts to get spit out the exhaust.
Allow to soak 24 hours or overnight.
With ATF, it should fire up.
Just be warned that ATF burning causes a HUGE SMOKE CLOUD.
It'll take a few minutes to burn off.


-Ted

[Silver86]

Yeah, crank by hand.
I typically use the 19mm bolt in the center of the main pulley.
I'll pour the liquid via a hose and funnel through the leading spark plug hole(s).
Crank just enough just to get the liquid to go through.
Don't crank it too many times, and it starts to get spit out the exhaust.
Allow to soak 24 hours or overnight.
With ATF, it should fire up.
Just be warned that ATF burning causes a HUGE SMOKE CLOUD.
It'll take a few minutes to burn off.


-Ted

easy enough... any particular brand of ATF? not sure if i can find MMO in my area.

[RETed]

Buy any of "cheap" ATF.
Don't buy the stuff that's specific to one model - i.e. Honda.

[NoDOHC]

A few additional pieces of info:

The engine idles rather smoothly for a dead face on a rotor, but revs very slowly (like it is running on one rotor).

We unplugged each rotor in its turn. The engine sputtered and died if the front rotor was unplugged, but did try to stay running. The engine sputtered and died almost as fast when the rear rotor was unplugged (still trying to stay running).

The engine would not start on either rotor alone.

This goes against my previous experience with blown rotaries, when they would start and run and drive fine (except for extreme gutlessness and very hot exhaust).

I guess I am not sure that this is an engine issue or if it is a fuel injection issue.
It almost acts like it is running very rich or has very retarded timing.

Maybe we can pull the exhaust manifold off and look at the apex seals, that will indicate if the engine is worth rebuilding.

[Silver86]

Maybe we can pull the exhaust manifold off and look at the apex seals, that will indicate if the engine is worth rebuilding.

youll have to let me know when youre free next. well have to get something going.

[RETed]

You need to try and do some basic troubleshooting then?

Eliminate ignition (spark) first, since this is the easiest.
First, confirm all 4 spark plugs are firing.
Then, confirm (with a timing gun) that they are firing at the proper moment.

If ignition system looks good, move onto the fuel...
I would swap the fuel injectors just as a test - does the problem change?
Swap either front to back (primaries) or swap primaries for secondaries.
Also, might want to check spray pattern from the primaries by tying the fuel injectors to the rail and crank the engine with the injectors out of their holes - helps to have a friend here.


-Ted

[TitaniumTT]

Before fiddling with swapping injectors I would make sure that there is proper rail pressure. It could literally be as simple as a bad pump, regulator or even a clogged filter.

[NoDOHC]

For that matter, I have lots of good S4 injectors, I will bring a set down (but I am guessing that is not the problem, I think it is sensor related). We will check the timing too. (I know all coils are firing, we already tested that). If the engine didn't idle so smoothly, I would be guessing vacuum leak.

Fuel pressure is also a good one (I think I have a gauge somewhere).

It is also possible that I have driven my Haltech '86 so long that I forgot how slowly stock rotaries rev. (although I think the '91 revs faster).

[Silver86]

what i think ill do before we get busy with this... im gonna buy a new fuel filter and some newer gas... the 1/4 tank thats in there now is the same 1/4 tank that was in there when i bought the car.