97 Cobra Engine Will Start But Soon Shuts Off

tarponboy

Active Member
Oct 12, 2002
50
6
28
St. Louis, MO
So here is a perfect case of "man fixes one problem, but creates another".
Well, it would be a perfect case if I could verify that I fixed the first problem, but I cannot because the engine will not stay running.

The background on this story is that my 97 Cobra has been running hot for some time. I have an SCT Livewire TS that connects to the OBDII port and displays various gauges. I use the SCT Livewire TS to view the digital coolant temperature gauge output as it is more accurate than the factory analog temperature gauge. I still have the factory analog temperature gauge connected, however. So I get the additional reference it provides. As part of my troubleshooting process on this issue, I decided to replace the water pump and serpentine belt. After replacing the water pump, I reconnected the battery, started the engine and checked for leaks. None that I noticed. I then installed the new serpentine belt. It is at this point I would like to say that I resolved the overheating issue, but I cannot verify that as the engine will not stay running. So I introduced a new issue.

It is at this point that the engine would start, but within 30 seconds or so, would bog down and shut off. Just die. The engine will always immediately restart, but again, with 30 seconds or so, would bog down and shut off. I could keep the engine running a bit longer if I elevated the RPMs to 2,000 - 3,000. But despite that, the engine would soon shut off, anyway. Now mind you, this has never been an issue before, so I knew I introduced it somehow. At first, I reasoned it could have to do with the belt I installed, so I removed the belt. Same issue. Now with all the huffin' and puffin' I was doing to remove the water pump, there is surely a lot I could have done to create the issue: pushing on various cables, hoses, wires, etc. I did some basic checks but didn't come up with anything. I then did some more advanced checks.

At this point, this is what I have checked:
--High amp fuses (no blown fuses)
--Low amp fuses (no blown issues)
--Vacuum lines on PCV, EGR systems (all seem good)
--Crankshaft position sensor (seems connected properly)
--Camshaft position sensor (disconnected/connected)
--Inertia switch, a.k.a. fuel pump shutoff (was not tripped)
--Removed serpentine belt
--Removed IAC valve, cleaned with carb cleaner
--SCT Livewire TS has built-in ability to check DTC codes or "diagnostic trouble codes" (but none were present)
--No check engine light on that I notice

As one final note, after going through all of these troubleshooting steps, the engine will now only stay running for about 10 seconds before it shuts off. But will immediately restart.

What suggestions does the greater community have for me?

I appreciate the assistance.
 
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RaggedGT

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Mod Dude
Jul 20, 2014
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Thank you for posting so much info about your car,the issues you are having,and the steps you have taken to fix it. Often times on here we get little to no info and have to ask a million questions lol

My only question for you- is the Security \Theft light on?
 

tarponboy

Active Member
Oct 12, 2002
50
6
28
St. Louis, MO
Hi @RaggedGT. You are welcome about the details.

As for your question, I did consider the passive anti-theft system (PATS), but when I looked in my owner's manual and read through the description about when I would expect to see the "THEFT" illuminated on the dash, my symptoms appeared normal. Just to refresh myself though, I just went outside and tested again and this was what I encountered:
--Car doors were closed, hood was closed (but not latched shut as I continually open and close it during troubleshooting). I mention this because the owner's manual mentioned the PATS system being affected by hood being open.
--Car doors were unlocked
--No "THEFT" left on dash
--Opened driver's side door, THEFT light blinks once per second
--Got inside car, closed door, THEFT light stops blinking
--Turned key to "ON" position, a few lights illuminate, but after a few seconds, all that is left on is battery (I have no serpentine belt on now, so every time I start the engine, the battery is draining) and the parking brake light and the check engine light
--Started engine and the check engine light goes out, but the battery and parking brake lights stay on. The air bag light comes on, though.
--Engine dies within 10 seconds
 

RaggedGT

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Mod Dude
Jul 20, 2014
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Again,excellent info.
The tuner you are using for a code reader,will it read all body/Control modules? If the battery is getting low on juice-might be shutting it down sooner-can you run it hooked to a battery charger?
 

tarponboy

Active Member
Oct 12, 2002
50
6
28
St. Louis, MO
Good idea. Ironically, I do have a Battery Tender Junior (automatic battery charger, a.k.a. "trickle charger"), but had never opened it before. No time like the present, eh? I just connected it to the battery and it appears to be charging. Will keep an eye on it before I try to start the engine. The instructions that came with the Battery Tender Junior indicate that when the battery is 80% charged, the LED will flash green and the engine can be started. The LED is not flashing green, yet. But I imagine it will not be long because the battery voltage was at 11.x when I last checked using the SCT Livewire TS. But once the battery charge level gets above 80%, I will try to start the engine, again.
 
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tarponboy

Active Member
Oct 12, 2002
50
6
28
St. Louis, MO
The Battery Tender Junior says that after 16 hours, even a fully discharged battery would be charged. That was not my case. I actually left the Battery Tender Junior connected for about 48 hours and it never charged to 80%. I would know this as the Battery Tender Junior changes from a solid red LED to a flashing green LED at 80% charge and a solid green LED at 100% charged. So I suspected the battery was at fault. But just to confirm, I took the battery out of my daily driver Hyundai and connected it to the Battery Tender Junior. Solid red LED for a few minutes, transitioned to flashing green, which transitioned to solid green over about a 20 minute period. So the Mustang battery appeared to be an issue. I brought it to AutoZone and they tested the battery good (working cells, 12.8V, fully charged). So I figured perhaps the Battery Tender Junior does not work very well (at least from an LED standpoint) with this make/model of battery. So I brought it home and put the battery back in the car. Started the engine... same symptoms.

I decided to take the working battery out of my daily driver Hyundai and put it into the Mustang... same issue. So it seems a few things were discovered during this round... 1) The Mustang battery seems to be good, 2) The Battery Tender Junior does not appear to change LED state with the Mustang battery but it does appear to charge it.

So where to begin my next troubleshooting steps?
 

tarponboy

Active Member
Oct 12, 2002
50
6
28
St. Louis, MO
For S&Gs, I tried to start the engine with the hood latched shut, but it did not help.

After triple checking some of the items I already mentioned, I decided to take another approach and verify the fuel system was working properly. I just had the feeling that fuel was not getting into the engine, sufficiently. I turned the ignition to the "ON" position and listened for the fuel pump to prime the fuel system, but did not hear it. I then disconnected the fuel pump wiring harness connector (which is at the inertia switch in the trunk) the engine didn't behave much differently (starts for a few seconds then dies). I checked the voltage at the fuel pump wiring harness connector when the engine was cranking/running for a few seconds and it was receiving power at just under 12V. Seems to be that verifies the CCRM and PCM and their associated relays for the fuel system circuit are working properly. I then tried some starter fluid in the throttle body opening and the engine stayed running for about 20 seconds. I did that two or three times and it consistently helped. It seems I have a fuel pump issue. Which would be completely unrelated to the water pump work I was doing. I think I am going to drop the gas tank and replace the fuel pump with a high flow fuel pump. And replace the fuel filter while I am at it.

Any other thoughts?
 
Last edited:

tarponboy

Active Member
Oct 12, 2002
50
6
28
St. Louis, MO
Hi @RaggedGT. I have not verified the fuel pressure. My reasoning behind that was as follows: 1) I do not have a fuel pressure gauge to connect to the Schrader valve. 2) My understanding is that the fuel pump provides the pressure in the fuel system and without the fuel pump working properly, I should not expect to see adequate fuel pressure. 3) I believe there should be a certain amount of pressure in the fuel system at all times, being a closed system. I am sure testing pressure could give some information, such as if 0 psi were detected, it could indicate a fuel system leak. That being said, I did eyeball the fuel lines from the tank to the engine and did not see any signs of leaking. Nor do I smell any gas now or in the recent past.

I am not opposed to getting a cheaper fuel pressure gauge, however. Those reasons were just why I had not done so, already.
 

RaggedGT

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Mod Dude
Jul 20, 2014
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All perfectly understandable reasons.
Fwiw Harbor Freight sells an ok fuel pressure gauge set fairly cheap if you go thar route lol.
One more question-You said you verified power at the plug at the inhertia switch. Did you verify power after the inhertia switch to the pump itself?
 

tarponboy

Active Member
Oct 12, 2002
50
6
28
St. Louis, MO
Thanks for the suggestion. I do frequent Harbor Freight, so that is certainly an option.

I did not verify power after the inertia switch... I did not think of that, but now that I do... not sure how to do that. I will take a look at that though, thanks for the suggestion.
 

tarponboy

Active Member
Oct 12, 2002
50
6
28
St. Louis, MO
So looking back at your previous suggestions, I did not test with a fuel pressure gauge nor, did I test power after the inertia switch.

But the goods news is the fuel pump replacement resolved the issue! It took me a few weeks to go through several attempts to get the fuel pump I wanted and deal with several (fuel pump, fuel tank straps) incorrect parts from AutoZone. Weather played a factor as did a lack of time to put against this project. But each experience is a learning one, however, and I certainly learned a lot.

Thanks for the suggestions and guidance, i appreciate it.
 

DualXhst289

Member
Aug 28, 2009
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1
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tarponboy, thank you for finishing your thread by posting A: that you fixed it and B: what the issue was. To many times people dont finish their thread and it can leave others wondering if they are experiencing similar issues. Good job!