1994 Mustang Hot Start Issue

The title really says it all my 1994 mustang (V6) has developed a hot start issue. The car runs and drives fine when cold and runs fine when up to temp but if you turn it off and then try to re start it when it is up to temp it cranks and cranks and cranks and will eventually start after 5 min and just at the point when the battery is starting to die.

The only clues I can give are that I did head gaskets on it a while back and I broke the temp sensor on the intake. I replaced with a new one. Other than that everything is the same.

The car did not have the hot start issue immediately after the head gasket replacement. It developed about 3 weeks after so i am not sure that the two things are actually related.

I guess I really need to do more diagnosis and see if if it is fuel or spark related but I was hoping that maybe someone here could shorten up my search.

This is an OBD 2 car by the way I should also see about pulling codes. Yes 94 mustangs are OBD2 before anyone says they are not. The GT's in 94 were not but the V6's were.

First thing I would check is for corrosion on the battery cables. Next thing I would check is to see if there is a voltage drop at the starter when hot vs cold start. Did this car sit for a while recently?

The car has not problem cranking over it just will not start when it is hot. Sorry if I was not clear on this. I could probibly drive it home on the starter except that it is an auto trans car.

Fuel pressure. You can get a gauge for $17 at harbor freight. Or, if you find that too exorbitant and want a $3 diagnosis, buy some starter fluid and see if it will run on starter fluid on a hot restart.

Probably either the check valve on the pump is leaking, or the regulator is leaking down pressure, and on a hot restart the pump has to push all the boiling fuel out the injectors or through the FPR before you can get liquid fuel coming out of the injectors again and actually run the engine. "Vapor Lock"

Or mat the accelerator to induce a "Clear Flood" condition?

Ford has a recirculating (regulator in the front) 2 line fuel system, no "vapor lock". At any rate the increased pressure in the EFI system would prevent any boiling. Unless the check valve was bad. But then it would have a cold start issue as well....

Thanks for the replies and keep them coming. I am going to try the starter fluid test and see if it is fuel related. Obviously I will check spark as well.

TFI issue? Or maybe ignition coil?

The TFI module doesn't like heat and even though Ford moved it from the distributor to the passenger side fender on the SN95 cars, they still can go bad.

Here is a pretty good checklist to run though: http://www.allfordmustangs.com/forums/5-0l-tech/120806-fuel-injected-mustangs-crank-no-start-checklist.html

Ford has a recirculating (regulator in the front) 2 line fuel system, no "vapor lock"

There's nothing about a return-style fuel system that changes the boiling point of gasoline. I did say:

on a hot restart the pump has to push all the boiling fuel out the injectors or through the FPR

. Unless the check valve was bad.

Which is what i said.

But then it would have a cold start issue as well....

Fuel doesnt boil when it's cold..

My 2000 V6, had a hard restarting and rough running after a heat soak problem. I changed the coil pack without effect. I was working on a plan to insulate the injectors when it went away and never came back. If it does I will probably put a bypass circuit on the fan to cool it off. I know my heads and intake are different than yours so this may or may not help.

I put a 97 motor in it about 10 yeats back so it is closer than the oe 94 motor.

sounds like coil. TFI usually will die at random while hot, then come back after a cool down, though TFIs are cheap. id recommend this one:

http://www.latemodelrestoration.com/item/PDI-000555/1986-93-Mustang-50L-58L-Dyna-Mod-Tfi-Ignition-Module

that TFI cured a lot of issues for me in the past with stock/mild engines and ignition issues.

also try a spare coil if you have one. wires could be worn as well, heat soak can affect spark transfer. i would assume a head job would involve 8$ worth of plugs, but it never hurts to ask, did you replace the plugs when you did heads?

-J0N

One could go on at length arguing theory without actually addressing his hot start issue.

Quick and easy diagnostics are to check for,

spark

remove fuel (clear flood)(mat throttle when cranking)

add fuel (spray can, I like Berryman's carb jiz)(it has a happy smell!)

If the problem is easily repeatable one of these checks will quickly point out where the problem is with basic or no tools.

Check the idle air control.

dean1484 wrote: I put a 97 motor in it about 10 yeats back so it is closer than the oe 94 motor.

The change occurred in 99.

Does your engine have a dizzy?, people keep talking TFI and I thought they were gone in '92.

So Dean, $17 test or $3 test?

bentwrench wrote: Ford has a recirculating (regulator in the front) 2 line fuel system, no "vapor lock". At any rate the increased pressure in the EFI system would prevent any boiling. Unless the check valve was bad. But then it would have a cold start issue as well....

Nope. Cold start will be no problem, hot will be extended crank. I'd be shocked if a bad checkvalve were enough to make it a "kill the battery" length of time. Can you hear the pump run when you crank the key? I agree on the fuel pressure gauge suggestion, but I would also be looking at fuel pump relays and weak coils and other electronics that may get stupid after a heat soak.