Hello all, I have a 1991 FC3C NA that runs great, but seems to have starting problems when warm. If the engine is dead cold, been sitting all night, she comes right up every time with no complaints. If she\'s running and you turn off the ignition, straight kill, no problems, she comes right back up. If you run her for any length of time, long enough for the engine to warm up, turn it off for at least 5 - 10 minutes, then try to start again, it is really hard to get her moving again.
The best way I have found to start her under these circumstances is to put the pedal on the floor (fuel pump cutoff) crank for ten seconds, then release it and keep cranking... she will start to stutter and you can hear combustion happening, but she won\'t start yet. You have to give a little gas and keep cranking even though it seems like the engine is started, or she will outright die again.
It seems like she\'s flooding (maybe?) but I have been killing the engine by revving to 4k and then letting off the throttle, killing the engine as the revs drop. As I understand it, this should clear the excess fuel as she\'s shutting down.
I guess I should try a normal kill-at-idle, since the rev drop seems to be just causing me trouble. But is there anything else I can do to troubleshoot this? Is it really flooding, or am I barking up the wrong tree there?
Thanks for you time.
Try to get a compression test done by someone who\'s got the correct tester.
how many miles are on the engine ??
if its hard to start when hot - then its not a good sign
you could wire in a fuel pump switch - so that when you come to stop the car - you shut the fuel off - wait for the revs to drop and then turn the car off - this might help you
as tim says - a compression test will be your best bet
Stu
Drove her quite a bit today. I\'ll say this, I don\'t think it\'s a flooding issue, because every time I started her today I didn\'t use the fedal-to-the-floor cutoff to start it, and she still came up, albeit sometimes rather hesitantly.
She start quite quickly when \'hot\' that is to say if I turn her off and then start again within say five minutes. It\'s only if she has sat for say, half an hour, then it can be kind of a rough start next time.
I\'m kind of a newbie to rotors but I have read about fuel pump cutoffs and such, that\'s why I thought it might be flooding. But it just doesn\'t seem characteristic of flooding to me, from my very limited knowledge.
Two points that might help: it might just be instrumentation, but the engine never seems to get as warm as I\'d expect. I expect a \'warm\' engine needle to read basically horizontal, but my needle only moves a couple centimetres up from the \'off\' position. Could be a stuck-open thermostat, but I don\'t see that as causing starting problems.
Additionally, and this is probably unrelated, but sometimes I get power dips and falloffs when trying to accelerate in a turn. I had read something about that elsewhere, so I need to go re-investigate it.
Anyway I\'m not looking for someone to give me "the answer", just hoping for troubleshooting tips. I\'ll see about a compression test, I live in rural Indiana though so I\'m not sure where I might take her. I might have to drive her to Indianapolis.
Anyway thanks for the tips so far, if any of this is ringing any bells I\'d appreciate any more advice.
A Mazda dealer that is selling RX-8s should have the necessary compression tester so I hope you don\'t have to travel too far.
What\'s the engine like when it\'s idleing? Get it to operating temperature, let it idle and peek under the bonnet. Is there any visible movement or shaking from the engine?
Also, what RPM does it idle at when hot?
She idles at a pretty low rpm when hot, less than 1k. When she is idling after some driving I don\'t notice any weird shaking from the engine, looks pretty smooth.
I\'ll try to get a compression test done sometime this week.
Low rpm idle is normal and I\'d take this as a good sign - my convertible idles at around 700rpm when it\'s thoroughly warmed up. Idle speed usually drops to about a thousand and after a few seconds, drops further.
In my (limited) experience, a car with compression problems will have to idle somewhat higher and will start to shake sideways if you turn the idle down too low. On my FD with its freshly rebuild engine, there is no noticeable movement. I think it\'s pretty much the same on my convertible but I haven\'t looked at this for a while...
Its probably a combination of old leaking injectors and low compression. You can aleiviate it slightly by running a bit of premix (about 1:20) in the fuel.