Hello all,

I've been lurking through the forums for about a month and a half now, just reading,searching,reading,searching, and repeating that process trying to take in as much information on FC's and Rotary motors as possible. Now, this will be a daily driver for me, but right now I'm looking at a lightly modified N/A. The owner says the car is running lean and will most likely need a new fuel pump now, so I'm thinking upgrading to an FD fuel pump which seems like the best move I'm an automotive mechanic, but all I really work on is piston motors, but I think I can handle the rotary engine and its maintenance needs. Now, the owner says the car has a "Stage 2 Port and Polish", would this mean it has a Bridgeport or Streetport, or is this just a general Port and Polish job on the motor?

Also, the car has roughly around 60,xxx miles on it, and less than 4000 on the rebuilt motor. Would this be an ideal car to purchase as long as everything is mechanically sound, compression good, all systems work, no known problems.

I don't intend on really beating this car and racing/driving it like nut, but I'm wondering if a lightly modified N/A FC will pack a punch on little Honda hatch's and DSM's.

And finally, the owner said the car was running only slightly lean, would this cause substantial damage to the motor with less than 4000 miles on it? Cause I'll be driving it about 4 hrs back home to my house from where it is located.

Thanks Guys/Gals,
Matt

 

how the heck does he know it runs lean anyway? Ask him for a longer explanation. And an n/a is not going to detonate/be damaged unless the timing is way off. I ran my nonturbo at 13-13.5:1 all day long under WOT and never had any problems. And that was with the timing advanced, on 87 octane.

stage 2 porting could mean anything really, but it's probably just a street port. you will not need an FD pump but you can use one anyway. It may increase fuel pressure slightly and lower gas mileage.

check the FAQ and archives on what else to look for when buying an rx-7, such as the auxilary ports on the nonturbos. But you need to find out more on this whole "running lean" thing. It's likely to be a misdiagnosis of some sort.

 

Sounds like you have done your research and should be more than prepared enough to buy it. I daily drove my TII for a while with no problems. I dont know about beating very much in a straight line, but the car will be a hell of a lot of fun to drive on curvy roads

 

From what he said, the car doesn't seem to be getting enough fuel. When he goes to start the car it needs assistance. So he has to turn the key on and off without actually starting the car so it gets a little bit of fuel along with the standard fuel amount being sent to the motor.

He said, this process is only done when the motor is started for the first time everyday, or when the motor becomes cold.

Any idea?

 

welcome to the forum and thanks for reseaching.
good luck with finding the right rotary for ya.

 

Unless it has been physically verified that the car is running lean (via a wideband, EGT or by reading the plugs) then it's very unlikely that the car needs more fuel. The NAs are overfuelled from the factory and without serious modifications, you aren't going to run out. Putting in an FD fuel pump would just raise fuel pressure and cause the car to run too rich.

Could mean virtually anything. All engine builders do a disservice to the community by describing their work in "stages". The measurement is arbitrary.

If it's a bridgeport, it's going to sound like one of these:
http://www.youtube.com/watch?v=DKaoxJ7dCzw
http://www.youtube.com/watch?v=D3X7Fs5ZDSY
http://www.youtube.com/watch?v=yaKW9sYNcFY
http://www.youtube.com/watch?v=nwT44dEPD8M

It's hard to tell the average streetport from a stock port based on sound.

Porting out the intake manifolds is virtually pointless, as is simply polishing the port runners.

See the how to buy guides in the FAQ.

Nope.

I have no explanation for this. Just turning the key to "ON" does nothing. The stock ECU does not fire a priming pulse, and the fuel pump will not run until the engine is actually sucking air.

 

Compression test...cold start problems are sometimes due to low compression - forget anything else you've been told on the outside or the mileage on the motor. Don't say you haven't been told later. GL!

 

Hmm..I didn't think a fresh rebuilt motor could have low compression?

Any other theories as to why the car needs to have the key turned on and off a few times to start it?

 

It may be something as simple as a sensor that has gone out, unless the rebuild was a very bad one, I would rule out low compression on a 4k rebuild

 

Fresh rebuilds often have low compression if the rotor housings are reused. The Apex seals need time to machine the housings (or vice versa) to achieve maximum compression.

That being said...that processes should be pretty much over by 4k. But like Aaron said, turning the off and on does nothing, so maybe its got a weak start/ battery, or a vaccum leak that makes it difficult to start.

If the compression checks out, it starts cold as well as hot, and it doesn't smoke, you should be good to go.

 

Rebuilt engines need time to break in.

When you say you turn the key on and off, do you actually crank the car or just turn the key on and off?

If you are cranking and it takes several attempts, it's flooding out or still being hard to start after the rebuild. As the compression comes up it will be easier to start. Also if the injectors have a lot of time on them, you'll want to have them professionally cleaned.

If you are just keying the car on and off, then I don't know. As I mentioned, the ECU does not prime the pump or fire a priming pulse of fuel. It may just be that the key switch is worn.

 

I consider a compression test mandatory before any rotary purchase. Learned it the hard way, after having the engine go one year after I bought my car in '96. No offense to the seller, but I don't take 4k on the rebuild as Gospel. I wouldn't trust anything that's been said about the car or engine. This is why I reiterate *compression test*. If that's good, before buying, also look at the oil pressure as the engine warms up from cold to operating temperature. See how warm it runs when warmed up. Search for more rotary buying tips by Aaron Cake and company.

As far as the cold start matter, if you mean key on and off cranking, it could be flooding as mentioned due to old/leaking injectors. This would be easy to verify by unplugging the fuel pump connector with the engine on. The plug is near the rear left shock tower. Once the engine stops, crank another five seconds. Connect the fuel pump. Start the car after the usual time it tends to give trouble restarting. See how it starts. If you have a fuel pump cutoff switch (commonly installed on older rotaries by their owners), the above is much simpler. On S5's, holding the throttle all the way shuts off the fuel pump while starting.

Other causes of difficult starting could be the fast idle mechanism not working (you may have to push the gas once down and let go before starting for the fast idle cam to move to fast idle) well, water thermo sensor, BAC valve, Air bypass Valve, etc., but they're nothing to worry too much about as far as cost/labour.

If the car looks good everywhere else, it's worth spending some time on it.

 

When he turns the key, it is only turned to the "ON" position without actually cranking the vehicle, then back off, then back to the "ON" position. He said that the car doesn't do the "warm-up" procedure with the idle increasing and then dropping down, he said he has to hold the car at 3000RPM for about 30sec or so then it will idle.

He said that the car has had new Primary Fuel Injectors installed, and in regards to knowing it's running lean. The vehicle had a "Fuel injection Diagnostic " done on it, where I'm assuming that's how they know it's running slightly lean.

Don't worry, I intend on performing a compression test,auxillary port test, as well as any other lookovers and tests I can find I don't feel like spending a few thousand dollars on something that isn't going to run right for very long.

 

Keying the car on then off again won't do anything. It just powers the ECU up and down.

For the 3K startup, check that the BAC and ASV are installed and connected, and that the thermo switch on the bottom of the rad has not been shorted.

The car should idle around 1.5K when it's cool and then gradually drop to 750 RPM once it has warmed up. If not, check the operation of the cold start cam and thermowax. Could have been removed, or maybe it's just stuck.

It would be very unlikely that "new" injectors are installed. The cost from Mazda would be astronomical. A "fuel injection diagnostic" could mean almost anything. And none of the standard tests (exhaust gas sniffer, wideband, etc.) will detect the cause of flooding.

 

Hey Aaron, what if some previous owner installed a connection to the fuel jumper wire circuit so that with ignition on it would prime the fuel pump? Seems like one of the only reasons to need to switch the ign. on and off, maybe to band-aid not enough fuel during starting? Maybe something with the ECU not getting a start signal. /rambling

 

Would there be any serious harm to the motor or electrical system if the car had to be started like that, and revving the motor on startup at 3000rpm due to the "cold-start" system not working as it should?

Or is this something that needs attention ASAP?

 

No harm will come from a nonfunctional 3K startup system. However if you find those systems to be removed/hacked, then be very careful about what else on the car may be hacked.

I still can't explain why you need to turn the key several times to start the car. Some electrical troubleshooting will be necessary to figure out the problem.