Electrical Weird starting issues

[nissassassassin]

So, first off, I'm new to stangnet as well as working on anything that's not regular maintenance. Recently ended up with a 92 5.0. Its been sitting in a yard for the last decade.

So far I flushed fluids, new alternator, battery, ignition switch, oil and fuel filters. As well as a blown fusable link from the alternator to starter solenoid.

Current issue I'm having is the car will start once when cold. If I throttle it, rpm's will drop enough to either have a very rough idle, or die completely. On the second start, engine will turn over fine, but wont start. If I wait for a bit(over an hour), I can start it back up no problem.

The weird thing is that If I unhook the alternator wire from the starter solenoid, it can start several times. I was thinking I somehow messed up with the fusable link, but if I put a voltmeter to the battery, the alternator is charging the battery fine(12.4V Before start, Drops to ~11V on Startup, Rises to ~14.3V when idle)

Most of my repairs so far have been reliant on decade old forums/videos until now as I couldn't find anything on this. Any help would be much appreciated.

EDIT: I should also point out that the first time that the car runs(with alternator attached) It will start nearly instantly(less than half a second) I dont know if that means anything, but it was something I thought was odd.

 

[General karthief]

Cranks OK, but No Start Checklist for Fuel Injected Mustangs

Cranks OK, but No Start Checklist for Fuel Injected 5.0 Mustangs model years 1986-1995 A word about this checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work...

www.stangnet.com

This will help, keep in mine that there may be more than one issue at play do to the length of time it sat.
I will say the first thing I would do is check for codes, well, honestly I would send off the ecu to get checked out and updated, I use the ECUExchange, you can find them on Ebay.

 

[AeroCoupe]

Can we assume you did a basic tune up i.e. plugs, plug wires, rotor, and cap? Sitting for a long time and not knowing the past maintenance I would do this even if it did run. Can you hear the fuel pump prime when you first turn the key to the run position and then stop a few seconds later? Just making sure the fuel pump is in fact running but this is addressed in the list above.

 

[Mustang5L5]

Dump codes as step #1

Also, when the car won't restart when warm, depress the gas pedal to the floor and see if that allows it to start. That's "flood clear" mode, so if it restarts, then it's a sign the engine is flooding out.

 

[nissassassassin]

Thanks for the quick replies.

Dump codes as step #1

Also, when the car won't restart when warm, depress the gas pedal to the floor and see if that allows it to start. That's "flood clear" mode, so if it restarts, then it's a sign the engine is flooding out.

No changes when depressing the gas pedal

Can we assume you did a basic tune up i.e. plugs, plug wires, rotor, and cap? Sitting for a long time and not knowing the past maintenance I would do this even if it did run. Can you hear the fuel pump prime when you first turn the key to the run position and then stop a few seconds later? Just making sure the fuel pump is in fact running but this is addressed in the list above.

I did a very basic tune up (more like a check up) Plugs are fine and I have hooked up a inline spark tester into each of the plugs(all of them are getting spark). Fuel pump can be clearly heard.

Cranks OK, but No Start Checklist for Fuel Injected Mustangs

Cranks OK, but No Start Checklist for Fuel Injected 5.0 Mustangs model years 1986-1995 A word about this checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work...

www.stangnet.com

This will help, keep in mine that there may be more than one issue at play do to the length of time it sat.
I will say the first thing I would do is check for codes, well, honestly I would send off the ecu to get checked out and updated, I use the ECUExchange, you can find them on Ebay.

I have done a good amount of these. The ones I haven't done are those related to the EEC and the fuel system. But, when it comes to the fuel system, I have been able to run the car for 30+ mins without issue. As long as the alternator isn't hooked up, it'll run until the battery dies. Unless somehow the alternator is clogging the fuel system, I don't see how it could be that.

Based off that forum, I'm limited to the eec or computer, but would the outcome even be different as I could run it off the battery alone

-Also the ecu pulls up no codes.

 

[General karthief]

If the ECU is functioning , you will get codes, the 11 code is the 'all good' code, if you get no codes the computer is caupuit. Send it off to get checked out, I use the ECUExchange

Security Measure

www.ebay.com

 

[Ranger]

If the ECU is functioning , you will get codes, the 11 code is the 'all good' code, if you get no codes the computer is caupuit. Send it off to get checked out, I use the ECUExchange

Security Measure

www.ebay.com

isn't that 14.3v charge rather high for an at idle state? shouldn't the voltage regulator should hold that around 12?

 

[AeroCoupe]

Pretty sure idle voltage is a function of alternator rpm. Regulator is there to control the maximum voltage which is right around 14.3 or 14.4 volts. All you have to due is bump the idle rpm or decrease the diameter of the alt pulley and the voltage will come up.

 

[General karthief]

isn't that 14.3v charge rather high for an at idle state? shouldn't the voltage regulator should hold that around 12?

Stock pulleys?
Well, 14.3v is on the high end of charge at idle but it will depend on the state of charge on the battery, the charge voltage at idle usually is 13-13.5 volts, dependent on current draw/idle rpm ie; headlights, ac, wipers, amp and pulley diameter effects idle voltage too.

 

[nickyb]

What I got from your post is you changed the alt. And it's causing an issue?
Go back over the install very carefully, it's gonna be something stupid simple.