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Topic: Bad ECM? (Read 18939 times) previous topic - next topic

Bad ECM?

I saw another thread just started regarding bad ecms, and I didn't want to hijack it, so I figured I'd throw my own on here to get some input. I got my 88 XR7 wired up, completed the maf conversion wiring, and wired up a NGS and a css in the pin 30 and 46 circuit. I have the t5 with a manual O2 harness that is hooked to the existing engine harness. When I turn the key on, I have...NO gauge lights, and NO fuel pump prime. However, with the key flipped to the run position, before ever cranking, the coil will spark once. Still no prime. I troubleshot the ecm power relay today, and everything checked out. I trouble shot the fuel pump relay as far as one man can do it himself. I couldn't check the ground on the relay since it required me to crank the car while watching the test light in the trunk. Lol, I'm just not that flexible. However, when I jumped the fuel pump relay connector, I did here the pump running full boar. Primed to 40 lbs with no problem. I disconnected the used a9l that I bought off ebay, and opened it up. Well, I figured by the Nashua a.k.a. Non fomoco tape, that it had probably had a chip at some point. Sure enough the circuit board is wiped clean where a chip had been installed before. Also, I believe it is fried. ill include some pictures to see what you guys think. Should I see about getting a replacement? Or should I get an A9P, lose the NGS and NCS, and roll with an auto O2 harness, like many folk on here have, and seem to be fine with? Any help is once again appreciated. X
XX
1988 Mercury cougar XR7- 302 bored .030 over, gt40p heads, F303, AlexsParts spring and seal kit, explorer upper and lower intake, 70mm tb, maf conversion, 75mm maf, fenderwell cai, 24 lb injectors, T5 conversion, bbk h pipe, Slp lm, 3.73 rear, 4 wheel disc conversion, 5 lug conversion. :D :D

Bad ECM?

Reply #1 –
And a few more. Sorry they're a little hard to see. The unit under the blue cylindrical guy (I lack in the electronic terminology department :hick:) looks like it may be fried where it meets the circuit board. What do you guys think?
XXX
1988 Mercury cougar XR7- 302 bored .030 over, gt40p heads, F303, AlexsParts spring and seal kit, explorer upper and lower intake, 70mm tb, maf conversion, 75mm maf, fenderwell cai, 24 lb injectors, T5 conversion, bbk h pipe, Slp lm, 3.73 rear, 4 wheel disc conversion, 5 lug conversion. :D :D

Bad ECM?

Reply #2 –
its a capacitor

it looks like it leaked but it could also be heat sync material as well.. if you can wipe it off, then yeah... it puked.

so,

back to the other thing you said in your post.

With the eec plugged in
with the key forward

up at the diagnostic connector "BIG ONE"

ground the tan / light green wire out

fuel pump will run if all is well.

repeat by going to the trunk *with* relay installed.
ground the tan light green wire and the fuel pump should run


next
with no grounding in either point, if the fuel pump does not prime *but* you can make it run by doing the above then yes the eec is hosed.

keep in mind that you can ground the tan/light green wire and start and run the car and you will probably be able to do so for a long time.

it means that when you turn the key forward the pump runs all the time.
how is this a problem you may ask,, the downside is that its a safety issue.
the other downside is depending on what is jacked up on the eec, you may not be managing the engine correctly.

If your able to pull codes and get the car to run by grounding the tan/light green wire and all is well,,, I would roll with it.

your not going to find a physical ground on the relay because its provided by the eec.

many eec get spiked up the ground side of the relay coil because people are using a paper clip or something to jump past the relay to troubleshoot, and they are guessing as they go in an educated way but,,, injecting 12v up into the tan light green screws up the eec.

Bad ECM?

Reply #3 –
Alright, I'll try that fuel pump grounding tomorrow. I did already jump power at the fuel pump relay today and got it to run. I'm sorry I forgot to mention the biggest issue....I get one spark when I turn the key to run, but when cranking I get no spark. Then turning the key back past run to the off position the coil sparks again on "run" as I'm turning key off. So, I'm a bit confuzzled as to why it is doing that. Rarely can I get it to spark on cranking. But it has intermittently.

I did just try wiping it off, but to no avail....I'm thinking it's definitely junk. I just found another spot that is definitely toast.
XX
1988 Mercury cougar XR7- 302 bored .030 over, gt40p heads, F303, AlexsParts spring and seal kit, explorer upper and lower intake, 70mm tb, maf conversion, 75mm maf, fenderwell cai, 24 lb injectors, T5 conversion, bbk h pipe, Slp lm, 3.73 rear, 4 wheel disc conversion, 5 lug conversion. :D :D

Bad ECM?

Reply #4 –
these things rarely go bad.. seriously... to e honest they are likely to be the very last thing to go bad on the car.
for as complicated as it all looks , there is some really old but reliable tech inside. 

spark delivery is managed by a separate system all on the distributor.
the exterior module in combination with the inside pick up (replaced points) manages when at what times in the rotation of the distributor will the coil be allowed to actually deliver a spark.

"no fuel delivery" will not prevent "no spark"

if its easier to talk though this stuff, and also have the 88evtm opened up per below, the feel free, 304 772 3411

ideally you want to focus on page 58

Bad ECM?

Reply #5 –
Unplug the SPOUT jumper and see if you get spark while cranking. If you do, the EEC has more problems than just the fuel pump relay circuit.

Bad ECM?

Reply #6 –
Yeah worry about the spark first, as mentioned ECM won't kill that..


I had to replace a similar cap in my '93 Lightning PCM that was leaking(it's a common issue with late OBD-I F-series PCM, seen one that actually flamed, burned a hole in board)... It ran but was hard to start due to it was extremely rich when cold, to the point of flooding and puffing black smoke... Also caused the transmission to shift like it had a full race valve body in it, would bark tires at 20 MPH under light throttle... Once I repl the cap it was fine again... Used 1st gen Lightning PCM are all but unobtainable, and new ones are non existent, have to send them to a rebuilder as there are no cores(or at least were none three years ago when I had my issues)

Bad ECM?

Reply #7 –
Ended up tinkering with the car today for a bit under the cellular guidance of jcassity (thanks for the help!), and we determined the fuel pump relay is gtg. It is getting power from the battery, and from the erc power relay. However, it is not receiving a ground. IM gonna try and work on it again tomorrow before work.
To softtouch, I unplugged the spout connector, cranked it, and got beautiful blue sparks from the coil for days! But only with the spout unplugged. We were thinking the 88s had the spark controlled by the fuel pump grounding by the ecm? What does it mean if I get spark with spout unplugged, but no spark with it plugged in? Still no fuel pump priming, and no warning lights on the gauge cluster. loss of thought for now...back to the EVTM drawing board. Will proceed with more tries tomorrow.
1988 Mercury cougar XR7- 302 bored .030 over, gt40p heads, F303, AlexsParts spring and seal kit, explorer upper and lower intake, 70mm tb, maf conversion, 75mm maf, fenderwell cai, 24 lb injectors, T5 conversion, bbk h pipe, Slp lm, 3.73 rear, 4 wheel disc conversion, 5 lug conversion. :D :D

Bad ECM?

Reply #8 –
It means the EEC is bad, in a nutshell. I'll leave it to the smart guys to tell you exactly what's wrong, though.

I just sold the A9T that I had last week...sorry dude.
'84 Mustang
'98 Explorer 5.0
'03 Focus, dropped a valve seat. yay. freakin' split port engines...
'06 Explorer EB 4.6

Bad ECM?

Reply #9 –
Lol, no sweat. I'm reading other stuff, and I'm wondering if it could be that I forgot a ground somewhere, or I don't have enough grounds....or I could just be in denial of a junk puter that I don't wanna she'll out 170 bucks for a remanned one just yet...atleast until all other tests have been accounted for... But who knows? Just the magic blue smoke creating wizards who live deep within the electrical underworld. ;)
1988 Mercury cougar XR7- 302 bored .030 over, gt40p heads, F303, AlexsParts spring and seal kit, explorer upper and lower intake, 70mm tb, maf conversion, 75mm maf, fenderwell cai, 24 lb injectors, T5 conversion, bbk h pipe, Slp lm, 3.73 rear, 4 wheel disc conversion, 5 lug conversion. :D :D

Bad ECM?

Reply #10 –
Quote from: FOX-XR7;445597
Ended up tinkering with the car today for a bit under the cellular guidance of jcassity (thanks for the help!), and we determined the fuel pump relay is gtg. It is getting power from the battery, and from the erc power relay. However, it is not receiving a ground.
The EEC controls the relay ground.
Quote
We were thinking the 88s had the spark controlled by the fuel pump grounding by the ecm?
Nope, no connection between the relay ground and the spark control.
Quote
What does it mean if I get spark with spout unplugged, but no spark with it plugged in?
With the SPOUT plugged, the TFI is waiting for the EEC to tell it when to fire the coil. With the SPOUT unplugged, the TFI fires the coil on its own at the base timing.
Quote
and no warning lights on the gauge cluster.
List the lights that don't work and which ignition switch position, RUN or START.

Bad ECM?

Reply #11 –
There are no warning or gauge lights at all in run or start. No cel, no brake light, batt light, or oil light. Gauges are all dead with key in run or cranking. Tach doesn't bounce when cranking either.
1988 Mercury cougar XR7- 302 bored .030 over, gt40p heads, F303, AlexsParts spring and seal kit, explorer upper and lower intake, 70mm tb, maf conversion, 75mm maf, fenderwell cai, 24 lb injectors, T5 conversion, bbk h pipe, Slp lm, 3.73 rear, 4 wheel disc conversion, 5 lug conversion. :D :D

Bad ECM?

Reply #12 –
im gonna chime in here in a min,, gotta pull down and show you all something that I found to be totally impossible.

Bad ECM?

Reply #13 –
**this is a 1988 chassis, and the evtm link below

in the car test- symptom= no fuel pressures at fuel rail, no spark
-eec appears to not be providing K2 coil with a ground
-Fuel pump runs when yellow and pink/blk are jumped out
-added manual ground to fuel pump relay
-relay high current contacts audibly click
-power to relay coil is present
-ground is again manually provided
-no power out on ckt 787 to the fuel pump

Fuel pump relay out of the car test
energized k2 manually
found high current contacts to have continuity

first pic below is the 87evtm 5.0 fuel pump layout
next pic is the equal circuit found in 1988 5.0  evtm

next two pics are for 87 3.8L and 88 3.8L pertaining to ckt 787 branch ckt, 1987 its not connected, in 1988 it is.

I am still speculating that there is a revision in engine management in that the eec is given the power to pull out power to the fuel pump and also manage spark for possibly safety reasons
I say this because for the 87 3.8L, the parallel ckt 787 is not connected.
The parallel ckt 787 for the 88 3.8L is connected.
What if this ckt is wired for the 1988 3.8Lonly ?


why would they decide to include the branch ckt 787 for the 5.0L in 1988 only and illustrate it as NC?
Why would they only in 1988 3.8L wire it up to pin 8, yet on 1987 no wire it up?

Bad ECM?

Reply #14 –
here is the 87 and 88 3.8L equal fuel pump layouts