Help! '93 Ranger turns over but refuses to start

[AsRustyAsEver]

My 1993 Ford Ranger XLT with the 4.0L Pushrod V6 that I bought from a young lady about 3 -3 1/2 weeks ago has been one of the greatest pains these past two weeks.

I go to start it up, and it turns over, but the engine never "catches". Against better judgement, I used some starting fluid and it sounds like it runs very briefly, but its a very hard running. Almost like something is stifling it. I thought it was a fuel problem then because it seemed to have fine compression and spark. (The engine actually backfired).

I then proceeded to take the bed off and trace the entirety of the fuel line. I checked each segment of the fuel line, and had an assistant blow from the opposing ends to check for clogs, and every single one was fine. I blew through the fuel filter, no clogs. I went and got a new fuel pump. It still refuses to start.

You can smell gasoline in the engine bay so clearly, its getting up there, I would think, but its not getting to the engine?

Anyone else have this problem before? I plan to take it to the shop in the next week or so but Id rather save my money.

Interesting thing to note. I replaced the relays and Im not exactly sure how the fuel pump circuit operates in this vehicle, but I dont hear priming of any sort. Though maybe its too quiet.

I also already replaced the Crankshaft Position Sensor, to no avail.

Any help would be greatly appreciated!

 

[RonD]

Welcome to TRS

Fuel pump should run for 2 seconds EACH TIME key is turned from off to on, so repeat as much as you like to determine if fuel pump is running.
It is not quiet, you can hear it HUMMMMM from inside the cab, turn the radio down

Spraying fuel into the intake IS the RIGHT way to do a 50/50 test
If engine starts and dies then fuel delivery is the problem
If it doesn't start then Spark is the problem, maybe compression

You can continue to spray fuel into the intake to keep it running, it does NOT hurt anything

On the intake manifold, passenger side, is a Schrader Valve, looks like a tires air valve because that is what it is, same kind of valve.
Press in the Center pin and gasoline should squirt out, be careful, there should be 30psi fuel pressure in the system.

 

[AsRustyAsEver]

The fuel pump runs fine, there's nothing wrong with it. It's brand new. I've already checked for spark and compression. It seems like its getting stopped at the fuel injectors because there's plenty of pressure yet the spark plugs are dry.

I think it might be something with the computer, ignition control module, or whatever's part of that circuit. Can anybody make or break that theory? The injectors are fine, I cleaned them by hand w carb cleaner and 12v from my battery. As far as I know, they'll still trip if the voltage is applied across them.

 

[AsRustyAsEver]

Bump

 

[Curious Hound]

Need to make sure the injectors are being told to open. They should have 12v applied all the time. The computer connects them to ground in order to open them. There is a test tool called a mood light that you can use to see if the injectors are getting their signals. I haven't used it. But there are other threads on here that talk about that.

This message composed solely of recycled electrons. Go green!

 

[Curious Hound]

Did you check for proper fuel pressure with a guage?

This message composed solely of recycled electrons. Go green!

 

[RonD]

Only way to test for Spark and Compression is by adding fuel manually to the intake manifold.
If engine starts then you have Spark(at the right time), and Compression(that can vaporize cold fuel)

Any other method is incomplete, or done for other reasons not related to a No Start

Lets say you did do the 50/50 test and engine started but then died when it ran out of fuel
So you have a Fuel delivery problem
If fuel injected then you check for fuel pressure at the injectors
Most fuel injected engines have a test port, Rangers used a Schrader Valve(same as a tires air valve), press the center pin and fuel should squirt out, be careful, it can squirt a long ways, 30psi, if there is just a dribble of fuel then there is no pressure
1997 Rangers, and earlier, use a Fuel Pressure Regulator(FPR) on the engines fuel rail to hold 30psi at the injectors when engine is off.
If FPR valve's spring or valve fails then no fuel pressure.

If you have fuel pressure, then you are down to the fuel injectors themselves, having all fuel injectors clog up or die at the same time would be a long shot, lol.
As ericbphoto said, each injector should have 12volts with Key ON, test either wire on one or two injectors to confirm the 12volts
This 12volts comes from a fuse that also powers the computer and spark system, so if 50/50 test got engine to start then injectors should have 12volts, but test anyway since all 6 get the 12v from one wire.

As ericbphoto said the fuel injectors are Grounded by the computer to open them.
Volt meter can't read grounds fast enough to see it happening, ground for injectors is only a few milliseconds long, so there are Noid Lights, that can be attached to fuel injector wiring that will flash if injectors are getting a Ground pulse.
You only really need to test one injector in a No Start situation.
If there is a running engine with a misfire then you can test each injector with a Noid Light.

Computer not Pulsing the fuel injector ground wires can be the end of the line for testing(if you have spark at the right time), at this point you will need to pull out the computer and open its top cover, have a look at the circuit board for discoloration, possible damage.
Image here of whats under that cover: http://www.auto-diagnostics.info/ford_eec_iv

The 3 Blue Capacitors can leak after 20+ years and that can cause problems, less than $5 to replace them.


One Long Shot............unplug the 3 wire connector on the Throttle Position Sensor(TPS), then try to start engine, if TPS shorts then computer will shut off fuel injector pulses, it is called Clear Flooded Engine mode