1995 F150 4.9l

-truck been sitting for about 2 years.

-Replaced: ECM, distributor cap & rotor, spark plugs/boots, battery.

-with old ECM: would crank & crank for as long as you wanted (but wouldn’t start)

-with new ECM: will hardly crank (like it has no power)

-no codes on OBD 1 test.

-checked ignition coil, reading 3 ohms

 

Welcome to the site!

Confused with crank but wouldn't turn over. Assuming you mean the starter rolls the engine over but the engine doesn't light off - cranks but no start?

With all the cranking, do you smell any raw fuel? Does the fuel pump complete its 2-second prime when the key is rolled to On?

Given all the pieces-parts changed, hard to determine what were the original problems and what new problems, if any, have been introduced by either bad-out-of--box parts or incorrect installation, not knowing your level of mechanical abilities.

With the slow crank with the new ECM - suggest to inspect the main battery cable connections, both at the terminals, and the endpoints where the cables go - clean and tight. Not seeing where changing an ECM out would affect the speed of crank, or the battery is just getting run down.

The 4.9L should develop 45-60 psi on the fuel rail, measured at the Schrader valve port. Fuel injectors are controlled by the ECM, and stretching memory a bit, believe by grounding rather than sourcing power - so may have a look at your grounds to ensure clean and snug connections and that +12V is present at the injectors.

My opinion is that if the engine is rolled over for an extended period, should catch at least a whiff of raw gas indicating the fuel injectors are likely doing their thing.

So much for the fuel part, now on to the spark part - the ignition coil reading doesn't sound right. Again, dusting off the wayback memories, recalling the resistance between the primary (+) and (-) terminals should be ~0.4 - 0.7ohms, and from the secondary to the (-) primary terminal on the order of 7-10 kOhms.

With spark and fuel, should be getting some bucking and backfiring, then any remaining timing issues can be looked at.

 

Confused with crank but wouldn't turn over. Assuming you mean the starter rolls the engine over but the engine doesn't light off - cranks but no start? Me too.
FYI- I believe your fuel pump is designed to run full time, you have a bypass system if I remember correctly.
Lets assume you have a crank (engine turns over) and no start.
Clean the battery terminals and the wire connections. Fully charge the battery. Does it now crank at normal speed? If not install jumper cables from another vehicle, does it now crank at normal speed? Once you get the engine to crank at normal speed squirt some starting fluid into throttle body and it should kick off, that is try to start.
If not, check for spark by pulling off one of the spark plug wires and inserting a small insulated handle screw driver into wire end and partially grounding (leave a 1/16" gap to a good ground) and crank-did you see a spark?

My Guess is it will respond to starting fluid (buy this at Autozone of Walmart) and you have a fuel problem. If it responds to starting fluid I would check the fuel pressure and I would think it would start with any pressure above 30 psi.
Your fuel system is a bypass system meaning there is a fuel pressure regulator (fpr)) that sends fuel to the engine and bypasses excess fuel back to the fuel tank. If you have low fuel pressure the fpr may be bad or the fuel pump maybe bad. I have seen vehicles that have been sitting for a long time accumulate water in the gas tank so I would pull the fuel filter and change it if your issue is fuel related.

 

Welcome. What brand replacement parts did you use? If you put the old parts back in, does it return to old state?

 

Sorry for my verbiage. It would crank but no start.

I replaced the ECM because the old one had 2 bad capacitors. The “new” one is refurbished, but I believe that it is doing its job. Because with the old ECM, while checking codes, I would turn the key to ON position but no check engine light would illuminate. With the new ECM, the check engine light illuminated with the key ON.

Distributor cap and rotor replacement didn’t seem to have a difference in behavior before vs after.

I have tried starter fluid, to no avail.

While cranking, the only way I could get consistent rotations from the motor was with jumper cables attached (still wouldn’t START).

I will check the battery cables, as it really sounds like a power supply issue. I would get 1 good rotation out of the motor and then it completely bogs down.

hope this clears some things up. Thank you for all of the input.

-again, old ECM would allow the motor to rotate forever while cranking, but still wouldn’t start.

 

Sounds like you have no spark. Check and see if you have spark.
On vehicles that have been sitting for a while rodent damage is often the issue. Take a look around and see if you see any chewed wiring. Take a look at the crankshaft position sensor and make sure it is connected.

 

Update
I do have spark, only when jumper cables are attached to the battery. The battery is brand new. I did a volt test on the battery, and I am not losing any power between the battery and the starter.

 

You have spark with the jumper cables in place, did it start?

 

Nope. Still no start. Jumper cables are the only way that I can get consistent rotations of the motor. Without them, it acts like the battery (brand new) has no power.

 

If you have spark and fuel (starting fluid) with the engine rotating and you still do not get a start you may have a problem with air flow due to a clogged catalytic converter. Remove the upstream oxygen sensor and attempt to start. Again if the problem is a clogged exhaust then engine should respond very differently than it did with your previous attempts and may start. Try this and report back. Do not leave truck running for more than a couple of minutes with the O2 sensor removed as exhaust gases are very hot and could start a fire. Keep wiring away from exhaust stream.
One symptom of a clogged exhaust is basically one revolution of the engine at normal cranking speed followed by much slower than normal additional revolutions, this may be your problem. Cranking speed with O2 sensor removed will be a little slower but not much different normal.
Use care to not damage the wiring to the O2 sensor.
If you can't get to the upstream O2 sensor you can try removing one spark plug and attempt a start but you have to be really careful not to start a fire, don't do this in a garage and have a fire extinguisher on hand.
Report back with results.