Irritation/Maybe a problem

[Alan_nc]

94 Ranger, 3.0, Auto
Runs pretty good (at the moment)
The problem: Every time you start the truck when it has been sitting and the engine is totally cold you have to start it twice. It starts the first time, runs for maybe 15/30 seconds and dies. Start it again and it smooths out and runs just fine. Isn't there some extra injector or some pot that is supposed to kick in when you start the truck and keep the idle up?
Once the engine has been running for any length of time it starts and runs just fine.

Sure would appreciate any thoughts you have on this problem.

 

[RonD]

I would try this first, cycle key on and count to 3 then turn key off, then turn key on again and try to start cold engine
This Primes the fuel system 2 times, 2 second running of fuel pump two times
Which, if it was down to 0psi would give you 20psi
The fuel system should hold pressure for MONTHS but when older they can leak pressure back to the gas tank so no smell of fuel, so after 6-8 hours pressure could be at 0psi
At start up the one Prime, 10psi, may not be enough pressure to keep engine running, so it stalls and then 2nd prime gets pressure high enough to keep it running

1994 Ranger, Engine running fuel pressure should be 30-35psi, engine off it should hold pressure at 20psi or so, for MONTHS at a time

Second
I would replace the ECT sensor on speculation, its not expensive

All gasoline engines need to be Choked when Cold, from a lawnmower to a V12
With Fuel injection there can be no Choke Plate like a Carb had, there are no Jets to suck extra fuel from

So an ECT(engine coolant temp) sensor was added, no connection to dash board temp gauge which uses a 12volt Sender

The 5volt ECT sensor tells computer engine temp with Key ON, and this tells computer how much Choke is needed based on the temp, colder temp needs more Choke, warmer less Choke

If ECT is telling computer engine is warmer that outside temp then not enough Choke would be applied so engine stalls just after start up, but even a few seconds of run time at 900+ deg of cylinders firing warms up engine enough to stay running at minimum Choke

In Choke mode computer will also set higher idle, 1,000+ RPMs, so if that's not happening then ECT replacement would be first stop
And as engine warms up idle RPMs should start to drop
Idle RPMs are set by the IAC(idle air control) Valve, a solenoid controlled by the computer



Yes, some engines did use a separate Cold Start injector, don't think Ford ever did, and for sure never on a Ranger engine
And most fuel injected engines use an air valve to control idle, Fords is called an IAC Valve

 

[Alan_nc]

Thanks for a very complete answer. I will try the key on/off idea. I'm sure it is possible the fuel system isn't holding pressure. If that doesn't work I will check prices on the ECT sensor.

 

[Alan_nc]

Truck had been sitting for 6/7 hours. Tried the key on/off 3 times. Started right up and ran at a slightly high idle. I'll give it a try tomorrow morning and see if I get the same results.

 

[RonD]

1994 has 2 places it can lose fuel pressure while sitting, assume you don't SMELL gasoline leaking out, lol

On the engine is the FPR(fuel pressure regulator) its a rubber diaphragm with a spring that holds it closed, spring is set for about 43psi
FPR has a vacuum line and the RETURN fuel line attached
The vacuum line helps stabilize pressure at about 35psi when engine is running, i.e. high vacuum/low vacuum = engine load
Any higher pressure and fuel is sent back to the gas tank thru the return line
If FPR starts to leak a bit running wouldn't be effected too much but pressure would drop to 0psi over time when engine/pump was off

The fuel pump in the gas tank has a built-in Check valve, basically a flap that is pushed open when pump is on and then closes when pump is off to prevent back flow of fuel into the tank, this can leak as well, but have to change the whole pump, its not a separate part.

 

[Alan_nc]

Did not work this morning (turning key on/off three times). I need to check the fuel pressure next.