Truck cranks but wont start

[Low]

Hey yall, I'm new to wrenching and need some help.
Working on my 1991 ranger xlt 4.0 v6 4x4.
I just replaced my clutch, flywheel, clutch master/ slave cylinder.
Put it all together and it started right up and drove great! That was yesterday. Today, I started it and it started right up. I put it in reverse and backed out of driveway, then put it in 1st and I wasn't giving it enough gas and it died. Now it won't start at all.. Cranks and cranks but nothing "engages".
I thought maybe I flooded it, waited half an hour and it still won't start. Did that 3 times this morning and nothing..
Did my spark plugs die?
Iam new to all of this and any advice is greatly appreciated!

 

[RonD]

Welcome to TRS

Check around the upper bell housing to make sure no wires got pinched between engine and trans when reinstalling, it happens quite often

First thing to do any time you have a "crank but no start" is the 50/50 test
Pull off the large air tube from upper intake, you can leave it off, just make sure fan can't hit it
Spray fuel: gasoline, quick start(ether), carb cleaner, ect..............., into the engine
Try to start
If it starts and dies, then you have spark and compression, but no fuel delivery
If it doesn't start then you have no spark or compression
50/50, instant results on what to check next, no guessing


Just for a heads up and not your current issue
1991 4.0l has a left and right O2 sensor, the plugs for these are next to each other at the back of the engine bay
Either O2 will plug in to either connector, O2s use universal connectors
Once engine is running and warmed up, if it runs poorly and you get both lean and rich codes at the same time these plugs are reversed

 

[Low]

Hey, i can't tell you how much I appreciate the quick advice on how to tackle this. This forum is incredible. My friend is otw with carb cleaner! I'll let yall know how it goes.

 

[Low]

So if there's no fuel delivery, where would that lead me?

 

[RonD]

Watch the CEL(check engine light)
If should come on with key on, that means the Computer(PCM) powered up
CEL should go OFF when cranking engine, that means PCM is getting a timing pulse to start fuel injectors

When you turn the key on you should HEAR a "click", from engine bay, then a HUMMMM from behind the cab, HUMMM only lasts 2 seconds, but should happen EVERY TIME you turn the key from off to on
That HUMMM is the fuel pump inside the gas tank

Fuel pumps do just fail one day, usually not while driving, just fail to start next time you need it, lol
So there is no "warning sign"
There is a fuel pump fuse and fuel pump relay, both in the engine bay fuse box
The "click" with key on is the PCM relay and also the fuel pump relay, both activate, fuel pump relay deactivates after 2 seconds, it's a safety thing, it activates again after engine is started, above 400RPMs

In the cab, passenger side, behind glove box on the firewall, is the Inertia switch
Looks like this: https://www.explorerforum.com/forums/data/xfmg/thumbnail/13/13002-27fcde25b1dced57966868966193aed3.jpg?1583516289

Green wire is 12volts FROM the relay, pink wire is 12volts OUT to fuel pump
You can put a test light or volt meter on either wire and then turn on the key, should see 12volts for 2 seconds
Might see 5 to 8volts after, thats from a monitor circuit, no AMPs just volts so not fuel pump power

Inertia switch has a red button on the top, inside the switch is a heavy weight, in a sudden stop(accident) or roll over, the weight would shift and that would break the contacts inside cutting power to fuel pump, and red button would Pop Up
You can push the red button down again to get power back to fuel pump, but once these are "tripped" one time they can't be fully reset, so slamming a door or going off a curb could trip it again
Wrecking yards are NOT a good place to get a replacement, lol

 

[Low]

Hey, thank you for replying. You a very knowledgeable, I appreciate your sharing. It's been a blast so far figuring it all out.

 

[Astro_fusion]

Most of the time with these 4.0s a random no start scenario is more than one thing unplugged or your crank position sensor. There are much better ways to tell if you're getting fuel like depressing the schrader valve on the fuel rail, especially if it was running great before. Pulling things off and spraying carb cleaner into your motor is ill advice.

 

[bobbywalter]

Most of the time with these 4.0s a random no start scenario is more than one thing unplugged or your crank position sensor. There are much better ways to tell if you're getting fuel like depressing the schrader valve on the fuel rail, especially if it was running great before. Pulling things off and spraying carb cleaner into your motor is ill advice.

I don't agree..
.starting fluid is classic and instant.


Shrader valve confirms psi at rail....not injector events.


And not spark.

With this system and the laymen with few tools, this information for effort is priceless.

I guess explaining not to give it more then a whiff at a time could be prudent.


But as directed here. I see it as perfect.

Save for carb cleaner or brake cleaner is sometimes not flammable enough which could lead to overdose..... The fire hazard is present either way..... stabbing the shrader valve has bit me in the ass several times

 

[RonD]

Yes, the 50/50 test of spraying fuel into a gasoline engine has been around since 1880's and the FIRST gasoline engines

A test used for 140 years probably means it has its uses

Even more so on fuel injected engines, with a carb you could look in and SEE gas squirting out if accelerator pump was working, not so with EFI

And as said above fuel pressure certainly doesn't mean gasoline is getting INTO the engine, just that its "near" the engine, lol