1990 2.9 - Engine Cranks, won't start - At my wits end!

[rusty ol ranger]

As far as I know a bad PCM can't cause a No Start with 50/50 test on a 1994 or earlier Ranger

1994 and earlier have a separate Spark system, the 60-wire PCM is only used for Load spark advance

In 1995 and up the spark system was in the new 104-wire PCM

Doesnt the ECM ground the coil to make it spark?

 

[fastpakr]

Doesn't sound like it, based on OP's previous comments about testing for spark.

 

[bobbywalter]

Should have nothing to do with spark.


But if was getting zero fuel and there is some sort of ridiculous vacuum leak or blockage....this is a check off....If the pcm isn't bad out of the box.

 

[bobbywalter]

So I actually watched the videos.....didn't realize there were that many.


It's cranking like there are no spark plugs in it.

It sure as hell don't sound like 165 cold compression. Which is awesome for an old engine...

If that was ether....it would have popped off.

Do a leak down.

 

[fastpakr]

That cranking speed is impressive. I'm guilty of not watching the videos earlier.

Just a thought... have you tried starting it with the throttle held open partway? Seems unlikely that you haven't, but you'd hate to have gone through all this and the root cause was some combination of the IAC not opening and/or the throttle set too low.

 

[RonD]

Doesnt the ECM ground the coil to make it spark?

No, not on 1994 and earlier, these years have separate Spark modules, TFI or ICM or EDIS, these are autonomous, they have their own 12v and grounds
ECM/PCM in these years just ran fuel system, these spark modules sent OUT timing to ECM so it could time injectors, and ECM did send the spark modules back spark advance suggestions as engine load changed, called the SPOUT signal, its what Vacuum Advance did on older systems

 

[bobbywalter]

That cranking speed is impressive. I'm guilty of not watching the videos earlier.

Just a thought... have you tried starting it with the throttle held open partway? Seems unlikely that you haven't, but you'd hate to have gone through all this and the root cause was some combination of the IAC not opening and/or the throttle set too low.

She was holding the tb open feeding it the Cosby sauce while someone else was cranking.


The amount alone was good for half point compression increase...any more would have been in rod bending territory ..

Not really . .but it made me laugh...to say Cosby sauce like peg....

 

[RonD]

Cosby sauce, I like it, had to look it up

Where is this video?

I discounted flooded out engine because "smell of gasoline" was never mentioned

If OP has a vacuum gauge try cranking engine and see what vacuum reads, 3" to 5" is expected
Wondering if a Cat or Muffler collapsed blocking exhaust so no air out = no fuel/air IN
0" cranking vacuum is no compression or completely blocked exhaust

 

[fastpakr]

Where is this video?

12th post of the thread

 

[RonD]

Spark is very weak and intermittent, should see white/blue spark, looked orange to me red/yellow is a very weak spark

How old is the Coil?
Test voltage at coil with key on, should show Battery Voltage

Hook up spark plug directly to coil(using spark plug wire), by passing the distributor, see what color spark you get, spark will be much faster, lol
As said you want white/blue
If its white/blue directly from coil then you are losing spark voltage in coil to cap wire or distributor cap and rotor

If its still orange then coil or its voltage, + and -, is the issue

With spark plug hooked up to the coil and key on, unplug the coils "-" terminal or both terminals and you will get 1 spark, each time you connect it and disconnect it you get 1 spark, see what color that spark is

If the coil is not getting full battery volts or TFI is not fully disconnecting the Ground, "-" terminal, then you don't get a full discharge from the coil, so weak spark

 

[Munchie1615]

Hey All,
Finally had time to look into the Ranger again today... went with my gut feeling that the ignition coil was providing a weak spark -- even though it tested good on the primary and secondary coil resistance, per the OEM manual. Guess what, she started right up! SO FREAKING STOKED!! Now I can get to some of the fun stuff! I did put in the new ECM I ordered, everything seems good. Just figured I'd let you all know what I found.

 

[bobbywalter]

Get some run time on it

 

[Frank de la garza]

My 89 would crank but no start. Replaced module and started right up. The module gets pretty hot, so I ordered a hot temperature grease that goes on module and it’s being starting up fine for 5 yrs.