JoshRX7

iTrader: (5)

So, I've had hot start problems since I've owned this car. I recently tested the compression and got 105 on the front rotor and mid-90's on the rear rotor. My injectors have been tested and checked good within the past year or so. What else can you guys come up with for hot start problems. I have good compression and and assumed good injectors. Basically, after running and the engine is hot, the car will not start unless I use the fuel cutoff switch. What gives?

Thanks,
Josh

HAILERS

Got me. Try removing the pin 3B from the ECU smallest plug. It's on the bottom row, far right. Black wire with a Blue stripe.

It's the difference b/t the injectors injecting at a duration of 17ms with the wire in or 6ms with the wire out. Which would you want if you thought it was a flooding problem????? Six of course. Take it out and leave it out. Then drive the **** out of the car and stop and start it.

dennis blackstone

can you jus.t cut the wire and cap each end

88rx7gxl

Why cut it when you can unclip the wire from the connection at the computer? Its easy... But to answer your question, sure you can cut it... if your a dumbass.

dennis blackstone

boy you are pretty harsh with your words we supposed to help each other not call names like kids this is not a honda forum we are supposed to be a family

HAILERS

You could cut it a couple of inches back from the connector so that you can resplice it if you don't like the results. But, somethime take a look at that small plug with it unplugged. Look into the mating side of the connector. The side opposite the wires. Look inside closely and you'll see there is a yellow tab that you can push up while pulling on the wire. The tab locks the wire in the connector. PUll the wire out and put a piece of tape over it. It only has 12vdc when the key is HELD to start. No voltage any other time.

IF you don't get the result you were looking for, then just reinsert the wire back into the plug. No splicing required.

JoshRX7

iTrader: (5)

HAILERS, thanks for the help. I'll definitely try your tip. Do you think the water thermal switch on the back of the water pump might have anything to do with the hot starts if it's resistance is reading out of whack?

AlexG13B

iTrader: (7)

let us know how it goes

NZConvertible

Blah, blah, nancy-boy BS. Who said anything about this being a "family"? This is a technical forum, not a love-in. If you can't stand the heat, get out of the engine bay. We help each other with the info we provide, not by stroking each others' egos and calling each other nice names. Semi-serious, semi-general comment; not a personal attack...

Yes you could cut the wire but not everyone likes to hack up there harness or do mods not easily reversible (for when or if the cause of the problem is found and corrected). Reconnecting a cut wire in a harness is a PITA; plugging a pin back into a connector is very easy.

It's a temp sensor, not just a switch. Generally they either work or they don't, and if they don't the ECU ignores it and assumes the engine is warm (176degF). This will make the engine run crappy when cold, but it's unlikely to cause hot-start issues.

Note that the car comes with a system specifically designed to assist with hot starts. If you've removed the solenoid rack, you've disabled this system.

dennis blackstone

your answer is well appreciated but all you had to say is unclip the wire from the ecu i can stand the heat but if we meet one day i hope you can stand the heat when you come face to face with me you will deffanatly change your tune especially if you know what i do for a liveng we may not all be smart like you

NZConvertible

Wow, you antagonise really easily. First we're a family and now you're making lame physical threats. Do you realise how pathetic that sounds over the internet? Especially after telling someone else not to act like a kid on a Honda forum. You should follow your own advice.

Now settle down and have a nice day.

dennis blackstone

yeah it sound perthetic but if you want to start some drama just say to the persons face we are here to help and discuss car issues not call each other dumbass and trust i have hard skin but dont use this forum for stupid words because as you can see it destroys your very own question you started then it turns into a battle instead of sticking to the issue your hotstart problem ,people like hailers are like pop ups you just wanta close look at the big picture know your thread is a mess because of hailer and me retaliating so when you call some one a dumbass be ready for your thread to be ruined

HAILERS

The water thermo sensor defaults to about 176 degrees if the wires break. That's normal running temp and I doub that's the problem, but you should look into it. With the car fully hot, if you put a meter on pin 2I, the reading will be somewhere around 0.5vdc or if really hot around 0.45vdc. Thats with the connector on the ECU and the engine idling hot. BAck probe the wire. Green/white wire.

IF the water thermo sensor wires are broken the ECU sees 176 degrees when the car is cold and makes for a difficult start, but it will start. Just the opposite of your problem.

JoshRX7

iTrader: (5)

Well, from what I can tell, the car seems to be getting too much fuel for hot starts. Say if I shut down the car, go in a store, then come back out 5-10 minutes later... there's no chance it will start without the fuel cutoff switch. Of course if I cut the fuel, I can coax the car to start by burning excess fuel out of the engine, getting the motor to fire up, then turning the fuel back on.

I'll definitely try all the suggestions in this thread and post my results. I have plans for a Haltech E8 and new 720/1680 injectors. Should the Haltech be able to control this hot start problem???

And to NZ... all of the normal idle/emissions equipment was removed by the previous owner... not sure what system controls hot starts.

Josh

NZConvertible

When the engine heat-soaked the fuel in the primary rail can boil, resulting in hard starting and rough idling. When this happens (indicated by high air and coolant temps) one of the solenoids on the rack is used to cut vac to the FPR to raise fuel pressure and push cooler fuel through faster. I don't know if that would help you, but Mazda didn't put it there for the hell of it. Try Hailers' trick and see if it helps.

HAILERS

Unfortunaltly/fortunatly/? during starts the FPR is already seeing full pressure because the engine is not running yet, because there is no vacuum being put on the FPR by the solenoid/vacuum rack.

I know ya'll already realize this but maybe someone else does not. The Hot Start system seems more oriented for once the engine has already started.

Just in case ya'll didn't notice it, on the RX-8 Forum there is a thread that is ENDLESS on flooding of the RX-8. Just FYI.

JoshRX7

iTrader: (5)

I'll tell you what this hot start really reminds of... I'm a pilot. Most high performance reciprocating aircraft engines are fuel-injected and air cooled. Hot starts can be a real problem with these engines because of the "vapor lock" problem that NZ has outlined. Fuel vaporizes in the lines. It reminds me of the exact same problem. The symptoms are similar... I think you both are onto something. Can't wait to try this ECU thing.

HAILERS

About the vapor lock. Now we all know that by just turning the key ON the pump does not run. But, it seems to me one could prove/disprove this idea by jumpering the fuel pump check connector more of less premantley, then when you go to do a Hot Start, turn the key to ON for say a full minute. The fuel should flow thru the rai. clearing any vapor lock, right?

IF you do that and the engine still has Hot start problems, then it isn't vapor lock. Seems reasonable to me. Actually I've been there, done that in the past. Nope. No worky

HAILERS

Here are two jpgs of my Palm. It has four measurements showing.

The bottom left is the Pulse Width.

The other figures are from the top left: AFM Air Intake Temp, then to it's right the Intake Air Temp and the bottom right is the Coolant Temp.

The first jpg shows a start with the pin 3B disconnected.

The second jpg shows a start with the pn 3B connected

I drove the car and pulled into the driveway with the Fuel Cut Switch turned to cut the fuel pump. Then I let the engine sit for maybe five minutes so the intake air temp would rise along with the coolant temp.

Then with the 3B disconnected I logged a start and put it on the scanner. Went back and installed 3B and logged another start on the scanner.

Now some sharp eyed fellow is going to see how the temps rose b/t the two samples, but Trust Me, it's because I had to run to the scanner to make a picute of the first before doing the second jpg. If I do this same procedure one right after the other with the temps the same the results are the same as pictured. Trust Me. Been there and done it tooooo many times.

I'm also going to say this pulling of 3B might not work for someone else for ???? reasons. And pulling of 3B makes for the initial start of the day (cold water temp) bother some with temps under, what? 80 degrees, But for the rest of the day alls well.