Matt Hey

My brother has a 1988 TII with...

reman motor with only a few thousand miles
emissions deleted
rc cleaned stock primary injectors
greddy 720cc secondary injectors with resistors
R-Teck 1.7 ecu chip
MSD ignition
stock turbo with ported wastegate
corksport 3" full exhaust
cone filter
hks ssq blow off valve
koyo radiator

It ran fine until he ran out of gas while cruising (not boosting). After putting gas in, the 7 would crank but not start. It was then pull started but did not run well and would not idle. It ran for several blocks but died when the rpm's dropped. We took it home and tried to start it but it acts like it's flooded. Tried the unflooding procedures including...

1. Cranking for a while with the EGI fuse pulled and then with fuel pump disconnected (in case of leaky injector)
2. Put some heavy oil in the spark plug holes
3. Put in some new spark plugs
4. Used starter fluid

The engine sputters and backfires but won't catch. Checked compression and it only shows about 15 psi max on both rotors with a piston compression checker. Another rotary checked over 80 psi on both rotors. I assume this is because the engine is badly flooded and not because every apex seal was blown out.

We changed the fuel filter and put in my old FD fuel pump. We took off the UIM and checked that the primary injectors were working (test light and clicking) and that there is fuel pressure at the rail which there is. We have spark. Found one minor vacuum leak and fixed. Cleaned some grounds. Checked ECU codes and none were set. Checked CAS, TPS, AFM, etc.

We're pretty well stumped. Any ideas would be greatly appreciated.

junito1

I didnt think a rotary could read such a low compression even if it was flooded...

dawicka2

Afm problems could be your issue. You can test it with an n327, 333 or 332. Was gonna say fuel filter and pump til i got too the bottom of your post. Clean your injectors.

John ny

.......make sure throttle all the way open when testing compression.

dvs71990

Try some new spark plugs. My na was so badly flooded I could not get it started for days. Did the unflood procedure numerous times. Finally what I did was took all the plugs out, had some one crank it until I could see no more mist. Put in a fresh set of plugs and she started right up.

Matt Hey

@junito1

I didn't think such low compression numbers were possible either. I didn't think a rotary engine could be this flooded. Surely their must be something wrong that is keeping the flooding from clearing. We have tried everything related to running out of gas though.

@dawicka2

We did test the AFM as per the Mazda manual and we also don't get any ECU codes. Their is also no physical obstructions as testing required holding the flap wide open. I suppose we could still try testing if an N/A AFM works. Are any of the AFM's n327, 333 or 332 from an 86-88 N/A? Is the connector the same size?

We didn't have the throttle open when testing compression. We did use the same technique on the 3 7's we tested and the other 2 had much higher compression numbers. What is the point of holding the throttle open?

@dvs71990

We did try new plugs but may not have dried out the combustion chamber enough first. The plugs do appear wet from a light gasoline and oil mixture. Wiping them off is probably the best we are going to do as $25 worth of new plugs every time we try to unflood gets to be kind of expensive. We have dealt with flooded N/A rotaries before and this acts the same but much worse.

HAILERS

Yeah, try one of those non turbo afm. The engine should start with one. It's a good tool to figure out things.

Mabe pull the fuel line off the engine and jumper the yellow fuel check connector with key to ON and see if there's fuel coming out the line.

philly101

if it floods take the 1st fuse out an then try to crank it4 time then put it back in an it well star right up

Matt Hey

Good to know. We'll give it a try.

Fuel comes out of the primary rail when cranking and injectors are removed. Both primary injectors spray liquid when 12V is applied (removed and tested).

dawicka2

Matt, hold the excellerator all the way to the floor when checking compression. I made that mistake t2 when i got my jspec luce engine. kept reading 75 psi. Then dad held throttle plates open and jumped to 122 or so. 15 is as low as dachhound ***** tho, make sure the spark plug adaptor is all the way in.

john ny

junito1

YEah man something is wrong with the 15 psi..

Even my blown rotor made 55 psi.

g14novak

iTrader: (1)

Get some oil, 2-stroke or normal engine oil, and dump a little bit in each one of the leading spark plug holes. Put in clean spark plugs and try to start it. Oil in the chambers is almost a guarenteed start if its getting fuel, spark, and air. If it doesn't start then, you have some issues with either your fuel delivery, which you say has already been tested, or spark.

To clean the plugs, try spraying them with carb or TB cleaner. Then light the tip on fire and heat it up. A hot plug will spark a lot better than a cold and/or wet one.

red87tll

iTrader: (4)

did you verify the pump is running? pumps like to die when they are ran dry! also there might be air in the lines so you could hot wire the pump and let it cycle for a min or so?

dawicka2

compression tester its self might be bad too. I would test it on a known compression car, or autozone another one for 20 bucks......

how did everything work out?

John ny

Matt Hey

I haven't had a chance to do much lately I'm afraid. I'm making a list of things to try though. I'll post up whatever I figure out. Thanks.

Matt Hey

The pump or primary injectors burning up was what I first thought but that's too logical ;-). We changed the pump to my old FD pump just in case but the original pump seemed to be operational.

Matt Hey

Update:

Compression tested the engine with throttle open and still little to no compression (about 15 psi) on both rotors. Poured several table spoons of oil in and tested compression with same results. Has anyone compression tested a flooded motor? What numbers did you get? How did my brothers engine run with such low compression when pull started? I'm really starting to think something is wrong in the motor but what would affect compression of both rotors? Could the O-rings on the intermediate housing have gone bad and caused the compression to leak out the intake or exhaust of the other rotor? Any ideas?

junito1

DO the leading spark plugs come out wet of fuel when removed?

Turn your motor backwards a couple of times with your spark plugs removed.
Poor some 2 stroke in the spark plug holes and turn the motor with the spark plugs out SO it can spit out excess 2 stroke.
Are you checking compression with both plugs out or something? Make sure you have one in when checking compression. MAke sure you keep a battery charger on the battery so the starter spins ther motor strong.

ANd check your comp tester on something else.... like they said.

YOu should have compression by now.

Matt Hey

Yes, it looks and smells like a mix of oil and fuel. We have tried cleaning them off several times as well as replacing them once.

Only one spark plug was removed during compression tests. We have had the battery tester hooked up while cranking and even switched batteries. Motor acts like it has no compression as it turns over too easy.

We checked 2 other rotary engines with the tester AFTER we got almost no compression on this one. The lowest reading was about 65 psi with throttle closed on one rotor of a tired N/A motor. The same technique was used to check the compression on all engines. The compression tester has also been working fine on piston engines. Everything points to the engine not building compression for some reason, even with oil. It's even more odd that it's BOTH rotors with basically no compression.

g14novak

iTrader: (1)

I find it highly unlikely that you blew at least 2 apex seals on each rotor just from running it out of gas. You sure you set your compression tester up right?

junito1

^^ +1

Matt Hey

We went and tested the other 2 rotary engines because we didn't believe the compression could be so low. I highly doubt the apex seals are blown but what would cause such low compression? Is there a gallon of gas at the bottom of the engine? I've owned and worked on a FC and FD. My brother has 3 FC's. My other brother who is helping is an ASE certified mechanic and we don't know where to go from here. We did pull start it and had it running for a while and it had power so obviously some compression until the rpm's dropped and it died. This would point to a leaky (stuck open) injector? We did disconnect the fuel pump and tried unflooding in case that was the problem. It would be our luck that no one else has had a similar experience.

g14novak

iTrader: (1)

If you think its possibly a stuck injector, why don't you just pull out the "EGI" fuse and the "INJ" fuse to make sure its not getting fuel. The fuel pressure if its leaking will drop eventually. Crank it for a couple seconds with all the plugs out and those 2 fuses out, then put the plugs back in and do your test again. Make sure its at 100% throttle when doing the compression test.

Matt Hey

We unplugged the fuel pump since it was still readily accessible. Same difference as pulling the fuses, no fuel. We then tried unflooding in case an injector was stuck open. It didn't work but maybe there is so much fuel at the bottom of the engine that a few rounds of cranking didn't clear it. Can a large amount of fuel sit at the bottom of the motor or does it get pushed out the intake and exhaust ports while cranking? Do the spark plug holes need to be left open for fuel to run out or to help dry out/evaporate the fuel?

We're doing all the compression tests with the throttle open now. It was just those early tests that we didn't know better ;-).

junito1

YEs having the sprk plugs out helps clear fuel out.

YOu can also take spark plugs out and spin the motor backwards and it should push out all fuel, sitting ont he bottom of the motor, out the leading sparkplug holes.

Go48

iTrader: (7)

Such low compression on all faces of both rotors would certainly be unusual, particularly assuming the engine was running fine before this incident. I suppose it's possible that as you ran out of fuel, the fuel/air ratio went so lean for a period that it caused nearly complete seal failure.

If you blow out any possible fuel-oil in the engine, add a little oil to each housing and still get such low compression numbers, I think the conclusion would be that an engine rebuild or replacement is in order.

As others have indicated, having a fully charged battery and holding the throttle open during the test are important to getting "accurate" readings. It's also nice to have a warm engine, but my testing has shown that is not critical. It would also be useful to have a proper compression test done so that you can examine a graphic representation of what is happening with each face of each rotor.