Hot restart problem!

I put this here only because I had no problem until I installed the sn93. I don't have the fmu on it yet so I haven't had a chance to drive it yet. Just idle time.

It will start when its cold no problem.

When it is hot and I turn the igniton on it will turn over great, start up, rev up and then die.

To keep it running when hot I have to give it gas to keep it alive and slowly let out until it levels off other wise it will die.

I know its not the starter as it turns over very fast just won't hit.
When I do get it running I'm seeing 10-12 lbs vacuum.

Heres the situation. I had no problem last year with this issue. Its a donor 302 from a 89 mustang that has been parked over the winter. Like I said no issues when I parked it last year. I did however have to unhook the battery when I was removing the trans for a pilot bearing and throw out bearing.

This is whats different from last time I ran it.

I vented the drivers side valve cover. Removed the pcv and plugged the port on the intake. Since I don't have the fmu hooked up just yet I have done nothing but idle to burp cooling system. My first thought was that I had a problem with venting the valve cover or the pcv so I put it all back the way it came stock but still no fix.

Could this be an issue of the computer haveing to relearn everything thats in my signature line again. I'm searching as we you read this in the archives as I have been doing for awhile. Any help is very much appreciated. THanks Kris

The Paxton when not in boost is not doing anything. You can even take the belt off and air will still past the unit and the car will run. The low vacuum is probably because your not getting a smooth idle. Have you played with the fuel pressure. Have you adjusted it to high causing a flood/rich condition or to low/lean condition. What size injectors? Stock/Aftermarket.
Do you have a leak at the Mass Air? Have you pulled a plug to see if it wet?

I don't have the fmu on it yet. That doesn't matter right. I haven't driven it just let it idle to get hot. Hope this is a simpler explanation...

When I start it cold it runs like a champ. Once hot it still runs great as long as I don't cut it off. But the moment that I cut it off it doesn't want to start back. It cranks over fast and starts, but it idles up and then back down and die's.

Here something weird!!!!! I was playing around with the vacuum lines to check for a leak. When i pulled the plug off of the port where pcv ran and start it, it starts up and run's. It doesn't die, it just surges. Of course this is a massive vacuum leak!!! But it starts and runs that way. When I put my finger over the hole where its suckin in air it die's instantly.

If it runs while having a massive vacuum leak that means it's starving for air right.

When I go to start it I can keep it running with the pedal by feathering it. After a while of that it will settle down and idle like a brand to car. Shut it off and try again and the same thing happens.

I have the stock fuel pressure regulator and haven't changed it in anyway. Here's everything on my car as of now.

Rebuilt 5.0, Paxton Supercharger, 5-6 PSI,Gt40 Heads, Trickflow Stage 1 Cam, Gt40 Tubular upper and lower,65mm TB,70mm MAF,24lb inj's,255lph pump,

Is 10-12 lbs vacuum low? I haven't pulled a plug yet. They are brand new autolite 103's

Also the plugs are not wet, but they are solid black which to me indicates a rich condition.

You should be at 18+ lbs on vacuum.
Pull the plug off the ISC after it starts and see if it holds idle. If it does not adjust the idle screw to the correct rpm(800) then plug the ISC back on while it is running and see what happens.

Whats the ISC? Did you mean the IAC?

Could it have anything to do with going to colder plugs and not running hte car other than idling. Making them so black that is. I'm getting desprate. I'll go and try what you suggested now.

The car has been sitting for 45 minutes now and still won't start and run on its own. I was able to get it started after feathering the throttle. It was idling around 850 rpm's like normal. When i unplugged the IAC it die's instatly.

Mustang it is the IAC. Sorry, I am also answering questions on the Talon web site and it is called ISC.

Adjust your idle with the IAC unplugged.
Next take the vacuum line off the Fuel Regulator and plug the line and see what happens.

I was able to get it started again. When I remove and plug the FPR hose nothing happens. I can't keep it running with the IAC unplugged. It smeels like it is running very rich and I don't think that it was a hot start issue anymore. I think maybe it is fowling out the plugs. I don't know though as I'm not a gas mechanic.

The plugs are fouling for sure.

Would it matter that my pro maf is only like 6-7 inchs away from the paxton head unit.

Should I install the old plugs back in the car. The one's before I went one step colder?

You really don't need the colder plugs. Do you mean the rear of the meter has only a 6-7" of hose to the supercharger? Have you verified that the meter is working. When you get it running unplug the Pro-M and see what the car does. The MAS/MAP/O2 can cause any of your problems since they all three control your fuel.

sounds like you are having same issues that I am having..

Yes the rear of the maf has 6-7 inchs between it and the supercharger.

Check this out. I take the belt off of the paxton supercharger and the car starts up and runs good, hot or cold every time!!!

I put the belt on the paxton and when I go to start it hot it rev's up and then down and die's.

Whatya think now.

The thing is this is a supercharger that was developed to work specificly on the 87-93 mustangs with no modification needed.

Higher octane fuel and a fmu is all it requires.
I don't have the fmu on it yet but I don't think that it will matter as I have just been idling and its not seeing any boost. Also I currently have 89 cotane fuel in the tank.

have any pictures of the setup. I tried removing belt on mine and it ran the same. Is supercharger working properly? its not clogged with anything? Pully spins by hand with some effort? You had mentioned it was starving for air in one of your posts..

Try putting a socket on a drill that fits blower pulley nut and spin it that way see if it puts out some air?

I've been reading your thread. They do seem similar in some ways. The head unit turns by hand with some resistance. I turned it by hand and can feel air coming out. I will try the drill.

1. So when you pulled the belt of of yours it would run good too? Have you figured out your problem yet?

So do you think that I should try and block off my IAC. I took it apart and its very clean. Also I will try clocking the maf to see if that helps.

The only tune shop said they could maybe fix it by putting on a adj fpr and a blow off valve rerouted back to intake tube. They said it would be $500. Sounds like a shot in the dark to me.

Yeah, sounds to me like its starving for air cause when I create a vacuum leak it runs with the belt on the paxton. The plugs are black and dry.

Black plugs are cause its probably loading up idlin. Adjustable FPR will help for sure, you should have one anyway, then you can probably ditch FMU all togeather.
As far as a blow off, You shouldnt need one unless your blowing more than 6 PSI.
They do make a bypass valve which sounds like what the shop said they would install.

you could also try one of the screw in type KN filters instead of oil fill cap.

My motor runs as good as it is going to untill I get a tune on the computer.

I had a guy tell me that it could be because my maf is on a 90 elbow hooked into the supercharger. What ya think?

could be not 100% sure on that..

Not to sure abouts Fords
But your vehicle may have to relearn the idle after disconnecting the battery. It may have to be driven for 5-10 miles

Just my 2 cents
Mike

I am on my PDA but let me get a couple things said. A adjustable FPR is not needed. You can not use a FMU unless you have at least 32lb injectors at even at only 6psi. The factory FPR when you go to boost always adds fuel 1:1 just like a aftermarket unit. A sharp elbow will cause the problems because the way a Ford MAF works. Just rotate the MAF. The best solution is to install a bov that returns the air back so the MAF can figure things out. If you remove the belt it is opposite of what you think. With the belt on the unit it is running lean and the computer is adding more fuel which is causing a surge. Again the MAF can cause this by not metering air correctly. Sorry got to go my Plane is loading now. Later

It worked.....It bloody worked!!!!!!!!!!!
I moved the air filter and the maf about 12 in away from the supercharger, got rid of the 90 degree bend and it fixed the problem. It starts back when hot or cold and will hold an idle on it's own. I'm so grateful to all of you guys.

Kris

p.s. speedystang, are you saying that I can't use a fmu with 24lbs injectors? I just bought a 8:1 disk so it would be right. I could be reading your post wrong. I think that you mint to say bov instead of fmu in your last post.

yes if your FMU is cald to injectors you should be good to go..

Sorry, Typing at the airport on a Palm my thoughts are faster than my finger touch typing skills. lol

What I was trying to say is that you must use a FMU unless you have 32lb injectors or larger.
Glad we got that problem solved. Now let me get back to the guy that just mounted two VR4s on his '94 Aussie Falcon and can not get it running.
I am such a busy person...lol

Aron you are way two dam dedicatewd to us loosers.

Hobby or Passion not sure which.
I guess I am just CAR CRAZY. Theme song now playing in my head.

Thanks for your time guy's. Kris

idle stability is an issue with 87-93 mustangs period, with or without SC. The SC makes this problem worse. Look up resetting the idle on the web. The idle's made more sensitive by the presence of the SC. More concerning to me is the massive rich condition and low vacuum. My car pulls around 19" at idle with stock cam, it'll actually peg out around 22" with 1000 rpm on and that's fairly normal. Low vacuum indicates a vacuum leak (or, the engine being fragged, unlikely as you say it ran fine before). The rich condition indicates to me the MAF transfer function is wrong for the injectors you have or, the MAF isn't working.

Maybe try switching the MAF to draw through and see if that helps. Draw through works fine on an EFI car.

F=MA