Fuel 89 Mustang LX sport 5.0 stick, cranks, no start, fuel pump comes on with key doesn't shut off after 1-2 seconds

Dan2017

Member
Aug 13, 2016
16
5
13
69
Texas Gulf Coast
I might be in the wrong place, but the car was running fine, let off gas coming to a light and the engine died at 2000, was doing 15 or so, tried to let the clutchout, but wouldn't start. came to stop, and would crank but not start. NOTE: When I turn the key on the fuel pump doesn't stop running after 1 second, alway has in the past. I can't do the koeo tests because the engine won't start to get it warm, tried OBD-I reader, goes through the motions, gives code 11. coil, spark, timing all good, fuel pressure 44 at pressure up, drops to 36 while cranking. stays at 36 until I turn the key off, then over about 10 minutes drops to 26 and stays there. new fuel filter, fuel pump delivers 6 to 8 ounces in 2 to 3 seconds.I have tested the PIP, timing, all good. Sprayed starter fluid in throttle body, will catch and run briefly, every time. As I have been testing different things and cranking the engine on several attempts it started and ran a couple of minutes, nothing was wrong, sounded great, then the mil blinks, and it sputters and dies, no codes set. Last time it started it kept running so I attempted to drive it around the block, drove like nothing was wrong, shifted fine, all was good then it sputtered and died. The fuel pump not shutting off after pressurizing the fuel rail makes me think its the EEC-IV controller. The inertia switch is good, the fuel pump relay is good, I've taken all the connections between the eec-iv and the eec-iv relay and fuel pump apart, cleaned them and put them back together. Every checklist I've seen so far, and they are legion, says to run the check list, and I'm a big believer in check lists, but they all go to the koeo test, which yields the clear code 11. I show power to the injectors, but I'm not getting the ground signal when testing with an led power/ground tester.
 
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Dan2017

Member
Aug 13, 2016
16
5
13
69
Texas Gulf Coast
The mustang (89 LX sport convertible 5.0 HO 5 speed, all original, 206,000 miles.) stalled and died about a month ago. It would crank but not start... had spark, fuel pressure, etc., etc, Odd thing was the fuel pump when the key is turned to on always cycles for 1 second and shuts off, until when it died, then it would come on with key on, and keep running. The way the Mustang engine control works different than anything I have ever worked on; instead of opening a path from positive to the the engine sensors and controls, they all have the path to the positive battery terminal when the key is turned to on, then when the key is turned to start the path to ground is completed and opened and closed as each device is needed by the engine control module. This makes reading the electrical circuits a lot of fun. I'm writing all this because I couldn't find anywhere any explanation for why the fuel pump wasn't shutting off after 1 second of cycling. I ran through the cranks but doesn't start checklist several times, and everything checked okay, except I was not seeing the ground signal on the injectors and they were not opening and closing.

The engine control module [ecm] supplies a path from power to the injectors and controls when the injectors open by closing the path to ground. The ECM also provides a path to ground for the electric fuel pump, which it opens about a second after power is provided to the ECM. The ECM wasn't opening the path to ground, thus, the fuel pump kept running, even though the engine wasn't running.

I had the ECM rebuilt by "EcuExchange" on eBay (https://www.ebay.com/usr/bmwsalepro?ul_noapp=true) and I followed their advice that before reconnecting the battery, to unplug each plug to and from the ECM 3 or 4 times (an arduous task, for 31 year old plugs with a catch or two on each plug) to ensure a good connection at each. I recharged the battery while reinstalling the ECM and unplugging and reconnecting the plugs. I reconnected the battery, said another prayer, and turned the key on listening for the sound of the fuel pump running... the fuel pump came on and ran for about 1 second and stopped. Yay, test one complete. I disconnected the Idle Air Controller (IAC), made sure all the accessories were off and turned the key to start... and the engine started and idled at about 750 rpm. Yay, test two complete. 1.) I let the engine idle for 2 minutes with the IAC disconnected and all accessories off... this clears the ECM's memory. Then I ran through reprograming the ECM's memory with the engine running conditions: 2.) shut the engine off, reconnect the IAC, restart the engine and idle 2 more minutes with all accessories off, 3.) while running, turn everything on, idle another 2 minutes and 4. 5. and 6., drive for 5 minutes at 30, then 5 at 45, then5 at 65. This resets the engine running conditions in the computer. It's running great again.

Thanks to HemiRick and Blown88GT for indicating it was most likely the ECM (aka ECU) was the problem.