Car pops and goes completely dead when I turn the key

CapeCobra

New Member
Jul 7, 2009
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Hi fellow Stang owners. I have a unique problem that I couldn't find solutions for on the forum. My car was going into fits when I took it out of storage. At first, the PATS in the trunk was going nuts clicking and killing the car when I hooked up the battery, which I replaced thinking the old battery was at fault somehow. After many failed attempts with the PATS engaging each time I hooked up the new battery, it finally let me crank, but the fuel pump was dead (wasn't priming, inertia switch was pressed). Now the fuel pump is back, but it won't start crank at all. The most common problem now is when I hook up the battery, turn the key and let the PATS cycle off, fuel pump primes, turn the key, hear a pop and the whole car goes dead. Then after a second or two, the PATS starts clicking but the car acts like the battery is low. the only way to get it to stop is to unhook the battery. Rehooking will either trip the PATS clicking (coming from the driver's side trunk), or it'll let me try and start it again and the same pop, goes dead. the cycle continues. I tried two batteries and got the same result. There is no voltage drop from the battery posts to the cables. There are no obvious loose connections. The starter relay checked out. This has always been an issue on some level. for many years, the first time I'd hook up the battery after the car was in storage, this would happen, but unhooking, rehooking would always fix it. It's an 98 cobra. There is a clifford ignition kill on it, but that seems to be working fine. plus, if that was killing it, it just doesn't let you crank, but all the lights stay on. This is different. it pops and goes completely dead. I plan to check all the starter fuses and even if the starter is getting power, but because of the click and dead, then PATS thing, I don't think this is an issue. Would the PATS act like this? it's the pop and dead that is so weird. The key fob works. I tried both keys with the same result. I'm at a total loss and getting to the point of considering a tow to the local dealer. If anyone has any experience with this, please help. Thanks!
 
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wmburns

SN Certified Technician
Aug 14, 2009
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Houston Texas
If this were my car I would bring all focus to bear on the battery, battery terminals, battery cables, and grounds around the radiator core support. Pay special attention to the battery negative as it's bad about splitting. This problem REEKS of a problem in the battery and charging system.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

When it is known that the charging system is in tip top shape, then the real trouble shooting can begin. Don't be "that guy" who changes a bunch of parts only to find out it was a loose battery connection. If the voltage drop method is followed it will point to where the problem is.
 

CapeCobra

New Member
Jul 7, 2009
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Thanks for the reply. I checked everything including the grounds. it's all fine. That problems seems to have disappeared. no issues since. however, a new one has started with the car randomly dying at idle and won't restart for 15-20 minutes. That's the latest challenge
 

wmburns

SN Certified Technician
Aug 14, 2009
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505
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Houston Texas
It does sound like some progress has been made.

Please review the crank with no start check list. Pay special attention to the part about how to "prove out" PATS. Also note the part about what the check engine light does during cranking.

It would also help to know operational PID's (ODB2 scanner needed) such as:
  • Fuel pressure
  • MAF flow
  • RPM's
  • Operating mode (open/closed loop).
Having access to an ODB2 scanner might make very short work of this problem.

How old is the gas? Could it be "stale"?

Finally it may prove useful to know the base motor's health. A compression test and/or a leak down test.

1996+ Crank with no start check list
https://www.allfordmustangs.com/forums/4-6l-tech/336452-1997-mustang-wont-ignite.html

ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/
 
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CapeCobra

New Member
Jul 7, 2009
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Thanks for engaging me on this. I had an actron scanner and it has no codes and bought a OBDII to work with forscan, but I can't get it to connect. I can only connect with a different app with limited data. But let me explain the sequence of events before I answer your questions

The car will start and run fine. then at an unknown, unpredictable time, at idle (only ever at idle), it just cut out. completely dies. not sputter and die, just cut out like someone killed the ignition. in the past when this would happen, it would restart no problem and might not happen for years. now, it cuts out. then it's dead. it'll crank, but not turn over initially. I actually don't think the pump even primes. then after a few minutes, the pump primes, the car will start, but immediately die out. hitting the throttle has no affect. once, I was able to catch it with the throttle, but it ran like the timing was severely off and eventually cut out. wait a few more minutes, it'll start up normal and off we go until it does it again. for your questions

my understanding on PATS is it won't kill a running car. it's more a startup thing. however the theft light goes off during this process, or at least when I have looked I thought it did. the last two successful restarts, I waited until the theft light went completely off. I did have that clicking issue from the alarm unit in the trunk and blinking theft light, but that seems to have gone away.

the car is a summer car. only has 46K on it. It sat in storage with a full tank and a bottle of stabil 360. When the car is running, it runs normal. no apparent loss of power, no drive ability issues. the idle isn't completely smooth, but I don't recall it ever being smooth even with I bought it with 10k on it.

the app that I can get to connect to the scanner has verified a few things. there are no historical, pending or current codes. it's not operating in open loop. the MAF at idle is between 5-7 at about 900 rpms. the next time it craps out, I was going to check for spark and fuel pressure, but, of course, it's completely unpredictable when it'll do it although it has done it the last two times I have driven the car.

I'm working on getting a compatible scanner with forscan. I greatly appreciate you help with this. I would venture a guess it's not mechanical, but having something to do with sensors, computer and possible heat trigger, but I am not well-versed in modern car electronics. Thanks
 

wmburns

SN Certified Technician
Aug 14, 2009
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Houston Texas
It's an 98 cobra. There is a clifford ignition kill on it
^^This is my vote as to where the source of the problem is. To be able to kill the ignition it HAS to be wired in somewhere. In the case of a complex after market alarm likely there are several points where the factory wiring has been altered. My theory is there's one of the field splices that has come loose or corroded such that it's not making a good solid connection.

I don't agree with your logic regarding why the after market ignition kill system couldn't be the source. Image for a moment that somewhere in the car the ignition power just HAS to pass through this device. How else could the device actually disconnect power otherwise? Consider the possibility that the field splice to the device has gone bad. Wouldn't the effect to the car be the same?

For you to be able to trouble shoot this issue you will need to know exactly WHERE the factory wiring has been modified and HOW the system works. This will give the information needed to devise a trouble shooting plan to either rule in or out possible problem sources.
 

CapeCobra

New Member
Jul 7, 2009
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what i meant is the ignition kills device itself isn't causing the issues in the sense it isn't malfunctioning. It's very possible where they spliced in is an issue and maybe when things get hot, something trips. However, the device itself is just an ignition kill, not an alarm. it only has the ability to kill the starter, if I understand it correctly. If you don't disarm and turn the key, nothing happens. you can't even crank it. it kills the power to the starter. Also, when I say the car goes dead, just the engine. I do not loose any of the electronics. It has to be disarmed to crank so far, there has not been an issue with cranking it after it cuts out. It also (this model) doesn't have control over the fuel. I'm not saying that the splice can't somehow be involved. I will try and locate where it tapped into the ignition wiring. It's worth knowing if those connection are secure and protected