MadScience_7

I remember a thread from a while back that had a fix for hot start flooding problems. It had something to do with a relay and maybe a resistor on I think the starting wire of the ECU? Too bad I can't remember enough about it to find it in the search. Doesn't look like it got moved to the archives. Anyone remember it?

Anyway, my S4 NA has the classic hot start problem. After I shut it off, I can restart it for about the next 20 minutes, but after that I have to wait for it to cool off. I just got newly cleaned injectors so it isn't a problem with them. I'm assuming it's just that the cranking map in the ECU is too damn rich and until RTek adds the ability to adjust that for the S4 NA, I'm pretty much SOL. I don't really like the idea of hacking stuff into the factory wiring since it just adds another component to fail on me, but I can't keep getting stranded at the grocery store. If I can find someone willing to reach under the hood and crack open the secondary butterflies while I crank it, it starts fine, so it doesn't need to be leaned out too much.

Thanks,
Andy

RotaryRocket88

iTrader: (7)

This one: https://www.rx7club.com/showthread.php?t=499744?

The "fix" involves the water temp sensor. That does suck the Rtek 2.0 for S4 NAs doesn't have crank map adjustment. It's one of my favorite features on my S4 TII 2.1.

MadScience_7

Aha, that's the one. Looking at that, I should probably spec out my water temp sensor and make sure it's correct before hacking into the wiring.

I can understand that the S4 NA RTek is lacking in some options. It's probably the least popular one. Meh.

Thanks again.

MadScience_7

Well, didn't quite get to this yet, but now I'm 0-7 for first try starts. It doesn't seem to matter if it's hot or cold, it floods regardless. Looking at the diagram from the other thread(attached here for convenience), the ECU doesn't take any input from the TPS or the AFM? So I would think I could just open the throttle to give it more air, but that doesn't seem to work at all. The ECU has been intermittently throwing a code for the intake air temp sensor while running, so I've ordered a new one, but that doesn't seem to figure in to the cranking mixture either. I'm starting to run out of ideas.

Please don't tell me to check the compression. I know that could be the problem, but I just spent all my money to rebuild it 6 months ago and if it's already going bad, she's off to the junk yard.

satch

iTrader: (1)

Have you tested the Water Thermosensor voltage at the ECU yet?

armen505

iTrader: (3)

Sounds like a bad water thermo sensor. You can also wire a switch to your fuel pump relay as a back up to prevent flooding.<-------Band Aid method, but at least you won't be left stranded.

MadScience_7

Not yet. It's such a pain to get under the floor to the ECU.

satch

iTrader: (1)

It really only takes about 15 minutes to do and while your down there you could survey the territory and get more pin readings. Pin 2I would read 2 to 3 volts cold and .5 when warm. Some folks will remove pin 3B, which really lowers the amount of fuel injected upon start up, but it might be too little for cold weather starting.

sharingan 19

iTrader: (16)

fuel cut swtich.
wire it up and you can figure out a more permanent solution while remaining confident AAA won't have to find out about your trip to the adult video store...

I really can't believe rTek wouldn't put the starting map adjustment on the S4 N/A, I've forgoten where my fuel cut switch is its been so long since I've used it.

MadScience_7

It's mostly the carpet I hate dealing with. It already has 2 big creases in it and I don't want to make it worse. The fuel pump wire has to be accessible from under the dash somewhere, right? I can't get to it back in the hatch with my subs back there.

Adult video store?? You mean there's a place where people actually have to go and pay for ****?!? Wow, glad I didn't grow up in the old wild west.

Edit: Oh wait, the fuel relay or something is under the dash right? That should work for a cut switch. Need to go look thru the wiring diagrams.

satch

iTrader: (1)

The fuel relay, called the Circuit Opening relay, is located to the right of the steering wheel column and is Yellow.

MadScience_7

Well, the thermo sensor was reading a little high, so I replaced it, but no change. I did finally put in a fuel cut switch though. As much as I dislike bandaids, at least the car will start now.

Even though I can't do anything about it now, I did check the compression. I got a nice even 60PSI on all chambers. Taking into account the altitude compensation in the manual, and figuring that it's just a cheap piston compression gauge with the schrader valve removed, that isn't nearly as bad as it seems. However, it's far from optimal. I'm thinking about steam cleaning it to see if that helps. I built it with all new seals, triple checked clearances, great rotor housings. WTF??

AGreen

iTrader: (11)

Used housings + New seals = low initial compression. Takes some wearing in. Try adding a little premix too, it helps with new rebuilds until they break in.

Anyways, you've probably got a high resistance connection somewhere. I can't find what the voltage is supposed to be at the temp sensor, but it's either going to be +5v and ground, or +12v and ground. Probably the +5 volts. And as the wires age, they sort of mystically turn into thermistors, meaning their resistance will go up as they get hotter. You could try running new wires to fix your situation as well, it'll only help.

Also, farther down the thread Hailers ended up saying that his final opinion was to ditch the relay and 220 ohm resistor, and to just REMOVE pin 3B. It'll take a little longer for you to start the car stone cold, but once it heats up, you'll have no problem.

Black Knight RX7 FC3S

iTrader: (7)

is there a hot start solution to inject less fuel in a S5??

dennis blackstone

ive rebuilt dozens of motors with new and used housings and if you check your side seal clearance is on point you will not have hot start

when i stared rebuilding engines i didnt check anything ,when i used old housings none of them had a hotstart problem

MadScience_7

My side seal clearances were all checked religiously. I probably spent more time carefully sanding down the seals than I did on any other part of the engine. I've put over 5k miles on this engine, I would have hoped that it would be broken in by now. My previous build using Atkins seals was happy after 2k. This time I'm using RA classic seals and T2 rotor housings instead of N/A housings. Could those take this much extra time to bed in?

I do premix and I even bumped it up to a little more than 1oz/gal after the rebuild. The previous engine failed due to extreme seal chatter on the bottom of the rotor housing. Driving in the mountains I spend a lot of time coasting (fuel cut). I was afraid that was the cause of the failure so I have changed my driving style to go downhill in neutral and just use the brakes more. New pads are cheaper than a new engine.

AGreen: I haven't checked the ECU voltage since I replaced the thermo sensor. Maybe you're right and it is a bad wire. Damn 22 year old wiring.

erknee916

iTrader: (1)

does this fix thread also apply to a s4 t2??? and is there a thread with a step by step process to building a fuel cut switch. thanks

dennis blackstone

i use ra seals on all my builds never a hot start issue

i think its in the ecu where the problem is
even the rx8s have hotstart issues so its not the engine

hailers no more about it
i do no when you go with a standalone 98% of the time the issue is gone

HAILERS2

You sixty psi compression is a bit low and probably causing the start problem once the engine is warmed up. I assume it starts just fine when cold.

RTEK for the series four non turbo now has the fix for the start fuel map. I think this is right. Go to the Digital Tuning site and take a look and see if I'm right or wrong. Seems if one has the early non turbo chip, you can send it back to them and purchase the new one with the fix for just twenty/thirty bucks or so.

A fuel cut switch will work as you've found out. How to make a fuel cut switch can be found by doing a SEARCH on this site and going thru a lot of threads til you find one. The person who is looking for this might put in the name NZCONVERTIBLE when doing a SEARCH for FUEL CUT SWITCH. Seems he had a faily good write up.

I did several things prior to RTEK 2.0 to fix hot start problems. One was to install an electrical circuit using the water thermo senor switches input to the ECU to disrupt the START SIGNAL from the ignition switch when the water temp got over 120*. That worked fine til the RTEK came out. I've used fuel cut switches in the past .........then when I figured how things work disconnected the START signal from the ECU and that worked but made starting in cold outside temperatures very difficult. Might work year round in Miami or Cuba with no problems.