So I'm having some serious hot starting issues. The problem is even worse now that it's 100+ degrees in so cal. This is so upsetting considering I've done EVERYTHING to make sure this engine stays healthy and reliable! Can someone PLEASE point me in the right direction on what to check? I'm on the brink of going LS1, no joke.

Mods:
1500 miles on rebuild w/ 2mm atkins seals/springs, mazda corner seals/springs
apexi PFC tuned at 13lbs
99 spec twins
M2 intake
SMIC w/ ducting, greddy elbow
aluminum radiator/ast
AEM water injection kit
Fast reacting AIT sensor
banzai racing block off kit (retained IACV)
3 inch DP/MP/catback
hks twinpower/NGK 9's all around/new coils and plug wires

I think that's all for relevant mods.

The car stayed below 4k rpms for the first 1k miles, went through 3 oil changes, and had water injecting into the elbow before it ever saw any secondary boost.

Please point me in the direction of what to check (aside from compression, taking it to Lucky 7 this week). Save this R1 from an LS1.

 

Forgot to mention, eliminated the OMP, been premixing with idemitsu since startup.

 

Thats a bummer man. Didnt know you were in the same boat as me. I've only had 2 hot starting issues so far but she still fired up. And im 2100 miles on a lucky 7 rebuild.

 

How much idemitsu are you premixing? What are the specs on the rotor housings used in the build?

 

Yea...it's really aggravating :/. The car will start if i sit there cranking it to all hell, and once it sounds like it's going to start, I need to keep the starter cranking until it fires up...it's sad.

I'm really hoping that there could be other things besides low compression that could be causing this problem...

 

I was advised by a reputable shop to mix .5 ounce p/g. That also seems to be an acceptable ratio per HC's premix thread. The housings were in GOOD usable condition from what I was told, and 100+ compression was expected.

 

Fwiw, my engine was hard to hot start for a while last year. I think my issue came down to tuning as I changed some parameters on the PFC on amount of fuel in the start up cells and also fuel enrichment following Chuck's notes and experimenting a bit.

My coils are also suspect as they are pretty old. Need to change them soon.

 

Alberto brings up some great points, I doubt it's a compression/engine issue. It certainly can be tuning related.

 

Good advice, thanks. I'll talk to the tuner and see what he thinks. The coils are low mileage as i replaced them when I put this engine in.

 

Agreed. I would put my money on the aforementioned.

 

Going out a limb here but there is a fuel pressure solenoid. Its there to help with hot starts. The hose goes from the solenoid to the fpr. Was this bypassed?

I say this because I was trying to diagnose a problem with my fd and bypassed this solenoid. After I did this it took more cranking to get it to start.

 

Did you replace the fuel injectors as well, or are they still original oem? I've never had this problem myself, but i've read threads of FD owners that started that their leaky fuel injectors were the cause of the hot start issues, or something fuel related

 

If you used old housings and have yet to do a compression check, I'd do one. Its and easy thing to do and will save you alot of hassel and time trying to sort things out, especially if you never had the problem prior.

 

Car has underwent a simplified sequential setup. There is no fuel pressure solenoid, but I've had this same setup on previous engines and it worked fine. As for a leaky injector, I'm on 550/1300's, so I guess that's a possibility, how could I check this?

 

I had the same problems. If the car was running and I turned it off, I'd have to wait 20-30 minutes to be able to start it again. I bought the car knowing this because I got him down very low in price saying it needed a new engine. What were my results? Well you can check my build thread

Anyway, all depends on what you want to do if you have to go with a rebuild which I hope you don't. I bought my car a year ago basically on this day. I started pulling the engine myself in November, rebuilt and it is back in the car right now and I'm waiting on trying to get the correct fuel pressure before I start it up again. I don't know how I would take it if I worked this hard and my engine was having the same hot start issues just a few thousand miles in. I think I'd give into the LSx too but that is just me and hopefully for both our sakes, we won't have to get any rebuilds sooner or later.

Good luck my friend

 

assuming there are no major mechanical failures (and I'd be surprised if there were) advance the timing during cranking

try 15 degrees leading, 15 degrees trailing in P9-P10 N1-N2 cells



see
https://www.rx7club.com/showpost.php...4&postcount=34

you may have to play with cranking fuel as well. I would adjust timing first.

Assuming the crank angle sensor is syncing correctly (not normally an issue on a PFC) ultimately the key questions are:

does the engine need more/less fuel?
does the engine need more/less timing advance?
does the engine need more air (throttle valve angle, ISC)?
does the engine have sufficient compression?

in principle it's no different from getting a lawnmower started

 

Can I do this with the commander? Are there instructions on doing this? I don't have a manual or anything.

 

That is output from the datalogit (FC-edit is the program)

Do you have a datalogit?

 

read the link I posted. It explains how to change cranking fuel and cranking spark using the Commander only. Almost everything you would ever need to know about how to make changes with the Commander is in that thread.

 

Thank you so much! I had posted before I saw your post, I appreciate it. I'll check it out as soon as I'm home.

 

here's what I would do:

-- write down settings before you change anything

-- try cranking advance of 15 degrees L&T and then try 10 degrees L&T and 20 degrees L&T. From memory, according to training manual specs it is 5 degrees L and 5 degrees trailing on the factory ECU.

-- After you've messed with cranking timing try increasing and decreasing cranking fuel in 15 or 20% increments for the 50C and 80C temperatures--take the existing value, multiply by 1.15 (or .85 if attempting to decrease) and see how the engine responds. that's exactly what a tuner is going to do if he knows what he's doing and he devotes enough time to it. so if you are starting with 12.0 msec of cranking pulsewidth at 80C, try 10.2 and 13.8C . As you add/take away fuel It will either get better, get worse, or stay the same. Worst case scenario is that it will flood, but a 15 or 20% increase in cranking fuel probably won't do that.

it's no different than turning some screws on a mower carb. I built my engine with good used housings and it starts every time without flooding--no AI, no premix, hell I actually reused my apex seals

 

Makes perfect sense after I've read your other post, thank you. One question, since the problem occurs during hot start, should I get the water temp over 80C before adjusting the settings?

 

it doesn't matter

If anything, advancing the cranking timing will speed up cold starts as well.

 

To everyone who contributed to this thread, THANK YOU!

Arghx, you are the man. My hot starting problem has been reduced to a bearable standard. Car will start up every time now! Not perfectly, but I can't ask for too much considering most of my air/idling components are eliminated.

I played around with the ignition timing in P9/10 N1/2. Went through 15/10/20 degrees advance like you said. She liked 20 degrees advance the most.

Played with the water temp/fuel cranking injection time as well. The car liked an extra 15% @ 30C and below, and an extra 10% to 80C and 50C. Car starts in a few seconds now as opposed to 10+ seconds and keeping the started engaged till it's actually running.

Once again, thank you for taking the time to point me in the right direction

 

Another LS1 swap prevented