Ignition, Fuel Pump or other...?

[rangerpilot]

I have a 99 Ranger 4.0 V6 4x4 that is having trouble starting on cold mornings. I have done a little research but I am lost at how many problems can have similar symptoms.

So far, all I have tried to to replace the fuel pump relay. Now I don't hear the pump coming on when I turn the key on. My plans today are to...

1) Replace fuel filter...in case there is some water in the line that may have frozen preventing fuel from getting through.

2) Check fuel pressure with a loaned tool from AutoZone

3) Spray intake with starter fluid and see if it fires.

Based on the outcome, I have a fuel pump ready to be installed if needed but I am afraid it could be something else (pressure regulator, injector, etc.). Assuming the truck fires with the starter fluid, what should really be my next step.

The truck will crank all day until the battery dies...so far it only has trouble starting on cold mornings. Hopefully this afternoon, my tests will prove solid results so I know where to go next.

Of course, ideas are requested and welcome!

 

[RonD]

Is it a 4.0l OHV or SOHC?

The '99 won't have a fuel pressure regulator, it uses a Pulse damper on the fuel rail and no return line.
The Returnless system fuel pressure should be 65psi
The Pulse damper does have a vacuum line in case of a leak, you can pull that and check it for gas smell, it should not have a gas smell

Fuel pump should come on for 2 seconds when key is turned on, if that is not happening then that would be the place to start.
Check the Fuel Pump Power Fuse, it has it's own fuse, 20amp, that is the power the relay passes when it is closed by the computer for those 2 seconds.
Make sure fuel pump relay is all the way in it's socket.
Have someone turn on the key while you have your hand on the relay to feel if it "clicks", there is a relay right next to it, the EEC relay, that will click when key is turned on, so listening for the click doesn't tell you if the Fuel pump Relay is the one that is "clicking".

There is a fuel pump shut off switch called an inertia switch, it cuts power to fuel pump if there is an accident, usually located under the glove box by the passengers feet or in the passenger kick panel, it has 1 wire in and 1 wire out, it should have 12v power on both terminals for 2 seconds when key is turned on, assuming relay is working, it has a small reset button on the top if it is not passing power.

This is the 12v power flow for the fuel pump:
Battery--------fuse------relay------inertia switch--------fuel pump

Yes, if it fires when starting fluid is used then fuel supply would be the problem.
If it doesn't then check EEC relay, it supplies power to coil, injectors, and Fuel pump relay, not fuel pump, just the relay.

Hard starting in cold weather could be a dirty MAF sensor, it detects air flow AND air temperature, colder air is denser so needs a richer fuel/air mix.
ECT sensor, which rarely fails, is used by the computer to detect engine temperature, it is the "choke" for EFI engines, if it is not telling computer that the engine is cold then fuel mix will be too lean, engine should start through, it would just run rough and stall until warmed up.

 

[rangerpilot]

Thanks for all the suggestions. Here is where I am so far.

The engine fires with starter fluid so thankfully it is getting a spark. The fuel filter (while dirty) was not the problem as I expected. I could not get the pressure gauge to read any pressure at all so either I am doing it wrong or the line is dead since I just changed the filter and the pump may be inoperative.

I have since removed the truck bed and gained access to the fuel tank but ran out of time. For those later referencing this forum...it is a T55 bit for the 6 bolts on the truck bed. Much easier than trying to drop the tank.

As for the inertia switch. I didn't check it but I hear it click on and off (distinct sound coming from the right side of the vehicle where that switch is located). So hopefully I won't regret not looking at this cause I ruled it out early in the process.

I did also think about the MAF but haven't checked it. I will do this before swapping the pump so that I don't waste $100 bucks on a pump for it not to work.

I do believe it is the pump though case I don't hear it come on when I turn the key. I will post back final results.

 

[RonD]

I would have just pulled the fuel filter again and turned on the key to see if fuel pumped out.



General rule about fuel filters is that engine will idle fine but will lack power at higher speeds as filter gets clogged and can't pass fuel fast enough.

 

[rangerpilot]

I would have just pulled the fuel filter again and turned on the key to see if fuel pumped out.

Dang, that is an excellent idea.

 

[zekew64]

The inertia switch SHOULD NOT click on and off. I'm willing to bet that the switch is bad, and when it clicks, it's killing the power to the pump.

Also, follow the wiring and check your grounds. A bad ground can cause a pump to not pump fuel the way it is supposed to. Just because you might hear it when you turn the key on doesn't mean it's working when you turn the ignition switch to "Start" or to "Run."

I'd also check the wiring at the ignition switch and make sure it's okay, as well.