ajsuper7

ok, i have a 91 na. when i start the car when its been sitting fora long time ie cold it starts no problem. but when i let it sit for 15 or so minutes i have to give it alot of gas to get it going, what could the problem be, its just started doing this, its always started right up. i just changed the plugs and oil and its still having problems. i had the injectors cleaned not too long ago less than 10,000 miles and i put some injector cleaner in anyways. thanks in advance

rico05

Never start a rotary hot, and never turn a rotary off before it warms up. This is usual, it is just the nature of the beast. Basically, it floods when you try and hot start it. Install a fuel cut switch, and that will solve all of your problems. Do a search for "How to install a fuel cut switch on a series 5". I have one on my 91 n/a, and it never has a problem.

Silkworm

My suggestion would be one of two things.

Either it's the result of dripping injectors, in which case, send them off to be rebuilt (3-4 days without the car)

or it's the fuel pressure solenoid not actuating, which is supposed to adjust pressure for hot starts.

That's my .02$

PaulC

NZConvertible

There is no reason why a rotary can't be started hot. None whatsoever. The turning it off cold problem is also an elctronics problem, not that it's a rotary.

Like Silkworm said, check the FPR solenoid valve. It increases fuel pressure for 50sec when the engine is hot started to stop fuel aeration. It's covered in the FSM under "Hot Start Assist System". Logical place to start, eh?

blinkdog182

hi there...

so i have a very similar issue: 87 Turbo, stock (hollow pre-cat), original engine, 156K miles or so...

this hot start problem just started after i took the car in to have the fuel pulsation dampener replaced b/c it was leaking (with a strong fuel smell). other than that, the car ran great!

they also replaced a fuel line and lots of brittle vacuum hoses with silicone hoses. also had the oil metering pump hoses replaced while the intake manifold was off because they were leaking badly.

i took it back once because i began to have both cold & hot start problems after i got the car back from this shop.

the cold start problems were apparently caused by a broken/faulty water thermo switch on the bottom of the radiator... possibly due to age (i've seen this is a common failure point in other posts), or possibly due to a mistake made with the servicing mentioned above. they replaced this part.

i am still having hot start problems similar to the original post in this thread. if the car is sitting for about an hour after it's been driven a moderate distance (10 miles or so), then it'll usually start ok... but when the engine is hot & i kill the engine, and try to start it within 15-30 minutes, it will not catch... and appears to flood (pulling the egi fuse, cranking, and then replacing the fuse will let me start the engine). needless to say this makes short trips to the supermarket very inconvenient and embarrassing.

is there anything that i had done in the original servicing of the car that would lead you guys to think the problem would be more likely caused by the fuel pressure solenoid valve or leaking injectors (or vice versa)? or is it a toss up? i've gone thru 2 tanks of gas with chevron fuel injector cleaner, to see if it would help... it didn't. the thing that gets me is that the car started fine before i had the work done!

i took it back to the same shop, left it for 2 days while they cracked the intake open again to check for vacuum leaks. just got it back after they said they think they fixed it... but i still have the same hot start problem!!! i guess these guys don't know how to troubleshoot this... and they are supposed to be an rx-7 specialty shop....

thanks for any further comments/insights...

NZConvertible

I can't explain why it started after you had the work done, but these are classic symptoms of dirty injectors. The injectors can't seal properly and leak when the engine's off because of residual pressure in the fuel system. This washes the oil off the chamber walls when you try to restart causing loss of compression and a dead engine. My theory (and that's all it is) on why the engine can be started if it's cool is that the oil is colder and hence more viscous, so it clings to the chamber faces better than hot oil. Get the workshop to pull the injectors and have them professionally cleaned. Try to get a "no result, no pay" deal! Because the primary injectors are used so much more than the secondaries, maybe 80-90% of the fuel (and cleaner) goes through them, so the secondaries don't get treated nearly as well.

ZachSpazz

Check your compression at Mazda. Sometimes the corner seals lost their sealing ability and when that happens, your hot compression goes out the window. You'll be able to start fine though when the engine is cold/warm. Plus, you get a good idea of how powerful your car is and what your gameplan for maintainence is.

ajsuper7

well i read in my haynes manual that it might be a bad battery terminal, and my negative terminal is in really bad shape so im gonna replace those and see what happens

blinkdog182

I actually did have a recent compression check and it looked fine, I think: (7.0,7.0,7.3) & (7.7,7.6,7.5)

Also, after I got the car back, it no longer does it's 3000 rpm warm up when dead cold. I've read in another post that this is controlled by the Air Bypass Solenoid.

Can anyone who's taken off their intake manifold tell me - do those 4 solenoid valves get touched at all? Trying to get an idea if that got screwed up when they opened the manifold.

Another theory I've been tossing around about why everything went to crap after I had the car serviced (but need more expert opinions to shoot it down or not):

since my fuel pulse dampener was leaking (perhaps even a small amount before it was big enough to smell), is it likely that residual fuel pressure could just escape easily when i shut down?

then, after the fuel system pressure was presumably brought back into spec by the fixed dampener, there was more residual fuel press. to cause the injectors to start leaking significantly???

I don't know... just a thought.

also, at what rpm do the secondary injectors get used? do you think using fuel injector cleaner while cruising regularly at XXX rpms would allow better cleaning of the secondaries?

thanks for your replies.

NZConvertible

The secondary injectors are only used above 3800rpm and when there’s enough load (based on manifold pressure, dunno how much). So they’re really only being used when the car is accelerating. This would make it difficult to deliberately use the secondaries a lot for a whole tank of gas.

ajsuper7

ok well i no longer have any starting problems, i got under the car to discover that the starter was almost falling off the car. the top bolt has totally come off and the bottom bolt was almost gone too, luskily i found what was wrong, it would of been really bad if i lost my starter. thanks for the info though

Silkworm

I dunno if they get touched, but they can break. Two of mine had cracks in the lines.

ajsuper7.. DOH!