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Topic: Cranks but won't start--is the ECM bad? (Read 1740 times) previous topic - next topic

Cranks but won't start--is the ECM bad?

88 Cougar LS 3.8L

The car was started one morning and ran fine for about 15 minutes, then it stalled.  Now it cranks but won't start.

When the key is turned on, I hear a click and then the fuel pump starts running.  I assume this means the relay is working and the ECM is getting power.

The check engine light should come on when the key is switched on.  The check engine light does not come on now.

To check for spark, I connected a timing light.  It did flash while the engine was being cranked.

I grounded STI to run the self-test and get codes.  The self-test does not appear to run, and I am not seeing any codes.  Normally, when STI is grounded and the key is switched on, the fuel pump should turn on briefly, then it should run the tests and give out any codes.  Instead, the fuel pump stays on.  It doesn't run the tests, and It doesn't give out any codes.

Cranks but won't start--is the ECM bad?

Reply #1 –
Tell you what..I have two EECs from '88 3.8 Thunderbirds.

If you want to test one of mine...pay shipping, and it's yours.

I've got no use for them...a situation like this is pretty much the only reason they haven't gotten put in a dumpster somewhere...
If you're interested, PM your address and I'll throw you my paypal. I'll wrap them in bubble wrap and send it out in a flat rate box, be just under 13 bucks for you.
'98 Explorer 5.0
'20 Malibu (I know, Chevy, but, 35MPG. Let's go brandon, eh)

Cranks but won't start--is the ECM bad?

Reply #2 –
You've covered the bases from what I can read.  No code 11/system pass?
-- 05 Mustang GT-Whipplecharged !!
--87 5.0 Trick Flow Heads & Intake - Custom Cam - Many other goodies...3100Lbs...Low12's!

Cranks but won't start--is the ECM bad?

Reply #3 –
in my diy link,,, below
click on it
takes you to another thread
in your tool bar go to edit and search then type "codes"
that will quickly get you down to the code pulling section.....

anyway
you are grounding the tan/light green wire and that makes your fuel pump run full time with the key forward and that is normal.
its how you can get yourself a gallon or two of gas to cut the lawn If you need, if You are on the sig rtn unlike you said.  At lease I assume you actually meant you are grounding the SIG RTN??????????  ive never grounded the STI before,,

use a paperclip to jump the sti to the sig rtn via option 3 which is how most people do it.. I just find it inconvenient.

I use a 12v buzzer so I can hear the codes

Cranks but won't start--is the ECM bad?

Reply #4 –
next you want to jam a test light into the back shell of any given injector easy to get to.
back probe the brown wire section,, not the red.  the computer is switching the ground off and on,, power is hot with key on as long as other upstream ckts are working.

crank engine,,see if light blinks.
if it does the computer is pulsing the injectors

next drop a spark plug into the end of an easy wire,, ground the threads and see if you have bluish white spark.


next up,, is not by memory but is in my diy link the voltages you should see on the large connector of  your TFI on the side of the dizzy.

note the 88 3.8L fires all three left and all three right injectors at once.  its not SEFI,, its jut "fuel injected".
And basically the same for pick up trucks.. they fire 4 left and 4 right injectors all at once.


once upon a time long ago on my 87 cfi I had a problem where after the car was warm it would shut off and not start till it cooled down a bit.
even a new TFI and pick up module didn't fix it.
for some unknown reason to this day,,, replacing the ACT and ECT allowed the car to start and stay running ... still makes me wonder if the computer had a safety shut down when the computer thought the engine was too hot or something... I just changed both sensors at the same time cause nothing else was working.

on my 5.0 and 5.8, I remote located my TFI with the aluminum heat sync to get it off the hot engine.

Cranks but won't start--is the ECM bad?

Reply #5 –
Quote from: jcassity;445545
on my 5.0 and 5.8, I remote located my TFI with the aluminum heat sync to get it off the hot engine.

Scott it's heat sink(like kitchen), sync refers to synchronization...

Cranks but won't start--is the ECM bad?

Reply #6 –
You said the pump runs continuously when you try to pull codes.
Does it also run continuously with the ignition in RUN without the STI grounded?
It should shut off after a second or two when the EEC senses that the engine is not running.
The pump running continuously can mean the software in the EEC is not running and the EEC has gone into a hardware only mode called LOS (Limited Output Strategy)
This means the EEC cannot look at any of the input sensors. The TFI goes to base timing (just like the SPOUT being unplugged) and the injectors are pulsed at a fixed pulse with.
It is supposed to be able to run like this to 'Limp Home" but not very well. It will run rich at low RPM. Does it smell like it's flooding?

Of course the pump could be running because someone jury-rigged the wiring to make it run.

Cranks but won't start--is the ECM bad?

Reply #7 –
Quote from: TurboCoupe50;445592
Scott it's heat sink(like kitchen), sync refers to synchronization...

hum,, I did not know that,,

ive always thought it was a sort of "coordination" thing thus "sync"