Hot Start Problems. Please Help
 

Hi all,

I have been experiencing a starting problem that I can't seem to fix. The car starts fine when it is cold, but when up to normal operating temperature it turns over but won't fire up. I thought it might be something related to the fuel pressure regulator, or maybe a coolant temp. sensor. So, I replaced all of these items along with fuel thermosensor, all vacuume lines, plugs, wires, and tested all solonoids.
I can usually get it started with some throttle work, but its not easy. The motor is fresh, no oil in coolant or coolant in oil. It doesn't seem to smoke when I do get it started.
Any help at all is greatly appreciated.

Thanks,
Garrett

Possibly low compression. Rotarys start ok when cold and not when hot if the compression is low. Even if the engine is "fresh" I would suggest checking the compression, to confirm or eliminate as a possible cause.

Thanks, I'll check the compression.

Garrett

Could be your thermoswitch, when the car is hot the car uses the thermoswitch to up the fuel pressure.

Is it blowing alot of brown(fuel rich) smoke when ya start it up? It could be that its flooding...

I also had this problem, I couldn't suss it out so I bought a Power FC and it fixed it right up.

Hope you find out whats causing it.

I have the same problem, although I have the PFC. All I have to do is blip the throttle right now and it smooths out. I have a partially re-built motor( done by reputable shop) so there could be something other then compression.

I replaced the fuel thermosensor, located on the fuel rail, when I did the hose replace. The old one actually tested within tolerance, I was just trying to cover everything since I had it all out.
Not really noticing any smoke when it starts.
The problem came on very suddenly. It went from turn the key, no throttle, starts right up to hard starting overnight. I wasn't even messing with anything. Quite aggrevating.

Thanks,
Garrett

Maybe your injectors are in need of a good cleaning/flowtesting?

Sounds word for word the problem I had. I replaced just about everything you listed as well. Turned out to be low compression. There was no smoke at startup, no bubbles in coolant, no coolant in oil, ect. Even the first compression test I did looked fine, but a few months later the rear rotor was at 60.

charlie

Garrett, you mention that the motor is 'fresh,' but what exactly does that mean? Who built it, and about how many miles are on the housings and how many miles are on the internals?

Actually the fresh part is mostly an assumption. The car has 80,000 on it and I have no actual history. From what I have seen working on it, the motor has definately been out at one time. The motor is basically stock. All mods are reliability based (intake, exhaust, rad., knock retard, turbo timer, guages). I have some experience with the 13b from racing Formula Mazda but that motor has very little similarity to this animal. Fresh is mostly just a somewhat educated guess.
A compression test is a great idea. The car has always run well and I never gave it much thought.
Good idea on the injector also. I think that a sticking/leaking injector could cause a similiar symptom. Would it be smokey upon startup? I'm sure that a good cleaning is a good idea no matter what.
I'll get after it.

so say it is just low compression. Low but even compression on all faces. What are his options?

I'm having a hot start problem to...i noticed today that after i tried starting her up there was a bit of white smoke coming out the exhaust, very little amount, but noticeable if you were paying attention...do you think the problem is low compression as well? my 87'FC has 219,000 km on it, never been rebuilt, it had it's injectors and fuel rails replaced a few years back. It seems to start up just fine in the cold (it started great in -32, not plugged in, after sitting there for 8 hours in the work parking lot) but as soon as it gets hot, it's hard to start, and the idle becomes pretty rough around 750 rpm or lower.

Why are FC guys suddenly posting in this forum for help???

Anyway, typical causes of bad hot starts (other than low compression) are failing fuel pressure regulator or the associated solenoid. Have you tried hot-starting the car with the throttle wide open? If it starts easier while doing so, it is an FPR problem.

So because i do not currently own a FD, to you, means I should not be curious about them and find solutions to problems I may encounter with my - to be purchased - FD down the road? Perhaps you meant "suddenly posting in this THREAD for help" granted it is about 3 or so weeks old. I don't see how that matters. uuunless u want this FC guy to open up a new noob thread in your elitist FD forum instead?

He's talking about Kazikan's post:

Kazikan,

My suggestions:

1. Ask in the 2nd gen forum. ;)

2. Get a compression test

3. Pressure test your cooling system

Those will give you an idea on where you stand with your motor.

Actually, i posted this in an FC forum:P then someone told me to search "hot starts" I was so excited when i found this thread that i didn't check to make sure i was aloud to post a similar problem that my FC was having....here's the link for the original thread i started in the FC forum

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/monthly-pms-630694/

I'm sorry that i offended you somehow?...i wasn't trying to be rude or post something out of context, considering it's the same engine type (13B) with the same type of hot start problem. I thought I'd let him know i was having the same problem to possible rule out an FD spesific problem, and maybe we could work together to discover the problem:P...instead of reading the topic and wondering...geee i don't have an FD i should just back away slowly keep eye contact and don't speak...

I hope not everyone on this forum is stuck up about a generation difference? Like c'mon we ALL love rotary's, we all own RX7's or we're interested in them, I can see the help for seperating the generations for some problems but i don't see how that should prohibit someone in another generation with the SAME problem from posting?....it's not like i came on here talking about a suspention issue or somthing completely off topic...I'm new to this forum so I hope we can all just get alone alittle better and worry less about generation differences (I'm planning to buy a 3rd generation in the future as well, so it's not like i'm pro FC, i'm PROUDLY pro rotary:P)

that's what should define us, not a few years of improvements over latter models, I'm sorry if i came off alittle harsh there...I knew this guy who owned and FD who thought he was ALL that and would treat other RX7 owners like "underlings" if they drove anything less than an FD....(i'm not saying that's what people are like here) I just felt like someone was saying that because i own an FC and not and FD i don't deserve to post here?

that's it for my little rant!

i'm not trying to start a flame war here, i just want people to remmeber we've all got rotary RX7's here, why try to seperate into smaller groups?

peace ^_^

edit* and thanks for your tips on what to test for my engine! very helpful! :icon16:

I've got no problems with FCs...I think a few of you are being a bit defensive for no reason. The 13B and the 13B-REW may be similar but the control systems are quite a bit different in many cases. That's why there are generation-specific forums....

I agree, the systems are different, alot of things are, i agree there should be generation specific forums. It just doesn't feel so good when you get "shooed" out of a thread because your car isn't the same generation. Even though it has the same engine type and pretty much same problem (i realize it could be a different system problem, but it also could not.) ^_^ anyway, doesn't matter, It was my mistake for not carefully checking to see if this was a 3rd gen post or not, it just matched the problem i was having, and thought i'd add in that my FC was having the same problem, so that could possibly rule out some of the systems that are different between the two generations. I wasn't trying to cause problems...i guess FD threads are offlimits from now on...