m_snoby

Hello,
I’m interested in hearing from anyone that has experience with this problem. My FD has a one year old KDRotary rebuild in it and 10k miles on that new motor. Everything has been running just fine except… The car runs GREAT, except after it is warmed up and I park at a store then come out and try to start it up, it’s somewhat difficult to start. It spins over for a while (just like it sounds when it is flooded), then it catches and runs normally. I haven’t gotten out of the car to see if it smells like gas or not just yet. When the car is cold it starts up super quick no problem. However, just after startup it does sounds a little bit rougher then usual for the first minute. Other than that it runs just fine. My initial impression is that I have a fuel injector that is leaking a little bit into the intake manifold. FYI the primaries are only a year old where as the secondary injectors were rebuilt by RC engineering one year ago.

Anyone here with this type of experience I would be grateful to hear you stories. Thanks again.
Matt

DamonB

Could be the fuel pressure regulator solenoid. This is the solenoid closest to the firewall on the rack. Its purpose in life is to control fuel pressure during hot starts. Failure symptoms are just as you describe.

m_snoby

Normally I would agree with you however Dave at KDRotary took care of this back during the rebuild. Here is his quote when I asked him about it.

"Hey Matt..the orange solenoid is the fuel pressure reg solenoid...we bypassed it and went directly to the fuel pressure reg with a vacumn line for two reasons...it helps get rid of that 3k skip...and we have found that fuel pressures stay much more stable during dyno testing...that solenoid has a real tendency to stick when under hood temps climb....so we have to plug it in electrically..but it is going just for a ride..."

Thank you for the suggestion though. I wonder if it could be the fuel pressure regulator it's self?

dubulup

Bypassing it will do what Damon said.

m_snoby

Bypassing "it"? Bypassing the solenoid will cause the hot starting issue? It's been that way for a year with out any problems, so bypassing the solenoid doesn't immediately seem like the right answer. Or did you mean the fuel pressure regulator?
I'm just trying to clearify

DamonB

Your symptoms are because the solenoid is bypassed. Like I said, its sole function is to aid hot starting. Mine was bypassed for a short while and I changed it back because of the problems you describe.

m_snoby

Yeah I can see your point, and I thank you for your input. I just can't explain it working for over a year now with out this issue then all of a sudden it being a problem.

Cihuuy

mayb ur plugs are fouled?? dat symptoms is what happend to me... i changed the plugs and it was fine again..

m_snoby

I wish Cihuuy, but I replaced the plugs about 1k miles ago. Speaking of that I could really tell the difference! Plugs only last about 10k miles in our cars.

Thanks for the input!

Rated R1

Have you checked the compression?

m_snoby

No I haven't checked the compression. I have read a few threads here on the forum and I just can't believe that compression is the problem. If it was compression you would think that it would have a terrible time starting when it is cold. I mean the seals would be "contracted" and there would be less compression, verses a warm engine where the seals have expanded and are at there full size.
Am I wrong here?
Matt

yy4u

mine would start fine cold and wouldn't start warm - final conclusion - bad compression. When i posted, others reported the same problem. Do a quick compression test to make sure. But mine wouldn't start at all warm, whereas it seems your's just takes a while. I don't know why your theory is wrong, but it is

m_snoby

Well that doesn't make me a happy camper. Humm I sent an email to Dave at KDRotary. Boy I hope that I don't have to buy some POS car while my RX-7 is getting ANOTHER motor in it. Boy this is really weird.
Thanks for all your great advice.

Rated R1

Yeah you have it backwards. Sometimes motors will run with bad apex seals until they warm up. I hope this is not your problem, but I would check it so you don't go chasing other problems. Good luck.

matty

but why would this only occurr during startups....if he is loosing compression wouldnt it contiue to run like ****?

yy4u

my car ran fine with bad compression, it was only a problem with startup and the vaccum at idle wasn't great. But it built boost fine and seemed to have as much power even with the bad seal (compression).

Don't know why a motor with 10k on it would blow though, unless you were running lean or maybe got a bad tank of gas...

m_snoby

Yes it's very strange, I never really run the car hard. My early thought is that it ran too cold during the winter. I don't think the car got warmed up enough and maybe that caused to much wear on the housing???? I'm not sure, it was always in the 170 degree range on my autometer temp gauge.

Mahjik

iTrader: (1)

m_snoby,

You should follow DamonB's advice before jumping to conclusions. If removing the bypassing job on FPR solenoid doesn't solve your problem, then you might want to look into getting a compression test done.

However, there are other problems that could should low compression when there really isn't a problem with the seals.

BNA_ELLIS

It could also be an air leak, I have a similar problem at the moment, and it's my inlet manifold gasket.

rgds

Brian

m_snoby

Thanks guys your right, I've been thinking of doomsday senerios here instead of being positive. I think that I'll have a compression test done, I'll spend the money on that just because it's something an experience rotary mechanic should do it(MazCare). Brian your suggestion does peak my interest because I swear I'm hearing the turbo's loader lately like rushing air. I thought that I would check for if one of the turbo pipes going to the intercooler had loosened...
Thanks again all of your suggestions are great!
THANKS
matt

Snook

iTrader: (12)

Calm down. Your motor does not have low compression.


You are totally off track. Remember your car starts fine when it is cold out. You would think that if you had a vacuum leak it would be equally hard to start it when it is cold right? Actually it should be harder to start when it is cold with a vacuum leak and easier to start in cold if you had low compression. All of my points say that it is low compression but we know it isn't because you have taken care of the car and the motor is fairly new. Do you still use your oil metering pump or do you add premix? Have you been doing that? Maybe check the omp to see if it is working. Try flooring the gas while cranking the car over when it is hot and see if it starts right up. If those things check out then it has to be something else and not low compression which I believe it is for sure.

m_snoby

Snook,
Your post is quite confusing! The first line is "Calm down. Your motor does not have low compression" Then your last sentence is "If those things check out then it has to be something else and not low compression which I believe it is for sure." I just thought it was funny. Anyway the research that I have done on the forum and here in this thread have made me come to the conclusion this is something that is far from trivial. I think that I am still with in 500 miles of my warrenty so I'm going find a way for KDRotary to solve this problem.
Thanks again everyone your help has been greatly appriciated... you know what... this internet thing might just catch on!
Matt

Snook

iTrader: (12)

haha yes I was just trying to get you to not worry about it.

I listed all of the things that would cause low compression so you could think about it one by one.

Then I told you that if all of those checked out positive than it isn't low compressioN!

haha
yes very confusing but I have problems of my own and car problems that I'm clueless about. Been working on a boost leak or something for weeks. Taking the frigen car apart with a knife and penny as my only tools

hahaha!

Nathan Kwok

Check the compression (do it hot obviously). "Big list" wisdom says that low compression shows up on on hot starts first, although some people on here have reported it starting on cold startup first. Don't rationalize that the engine seals better when its hot therefore compression is automatically better when hot, this is not necessarily true. Bottom line is this, the shop manual lists "low compression" as a possible cause of hot start problems, so check it. There are a million other things it could be but it can't hurt, its easy to do, and its always nice to know.

Nathan Kwok

Check the compression (do it hot obviously). "Big list" wisdom says that low compression shows up on on hot starts first, although some people on here have reported it starting on cold startup first. Don't rationalize that the engine seals better when its hot therefore compression is automatically better when hot, this is not necessarily true. Bottom line is this, the shop manual lists "low compression" as a possible cause of hot start problems, so check it. There are a million other things it could be but it can't hurt, its easy to do, and its always nice to know.