Question about 1999 Ford Explorer

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I have a 1999 ford explorer 4.0 SOHC here we go this is driving me crazy it is hard starting when cold turn on key cranks fine no problems. will not start. if you turn key off and on 4 to 6 times will then start most times fuel pressure at check is right at 65psi when at idle. when it wont start you cane go to pressure check valve push it and no gas comes out have replace fuel filter and fuel silonoid still same if i park it faceing down hill alot of times it will start right off help whats the problem here . it just seems strange the fuel pump would be bad when the pressure check is in good range and no problems after it starts.

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  • ksalmons62 Nov 08, 2010

    ok here is an update just to be sure not a sensor problem while changeing thermostate went ahead and changed both water sensors solved temp problem seems to idle and run better as well now for the starting problem fuel solenoid as was told the name is by dealer only place that shouwed it is located on the fuel rail drivers side has a small single hose connection on it that runs over under the air breather. thought about relay may be problem so i replaced it as well . will find out about cold start later tonight but new action i found . when engine is at warm operating temp sometimes you turn it off and when you go to start it back up acts like vaporlock . if you go to the scrader valve push it you get what seems like fuel but alot alot of just air as well found this intresting let the pressure off hit the key and it started right up so just for spite sake changed filler cap . found two bad ground straps bad body to frame have replaced one will do other tommorrow when it comes in. as for cold start when it does it there is no fuel at the scrader pressure test valve. Thats why i cycle the key on an off to pump gas up through the system but don't always here the pump kick on.and this is from inside the explorer witch makes me lean towards fuel pump excpet for the fact once you get it to start it runs like theres nothing wrong.

  • ksalmons62 Nov 09, 2010

    From what i've noticed on over view look there are no missing heat sheilds. the inertia switch on my explorer isn't located in the cargo they put in on passanger side upper right floor board. Now if memory serves me right since i've owned this explorer the switch has kicked off twice on me once in the winter and once in the summer had to rest it no idea why no impact.won't be able to check out ingition switch till next week end when i will have enough time to do it right .unless it goes all the way down so with the time i have during the week ill see about the inertia switch being 11 years old would be a good idea to change it anyway.and am planning to check into the fuel return part of the system just to make sure all is in good working order just to play it safe . Also just wanted to thank you for the suggestions some i thought about and others you have gave have given me some very good places to look .

  • ksalmons62 Dec 21, 2010

    Well its still not starting normal but wired getting used to it .Have replaced electric part of ignition switch no change the funny part is for about two weeks it started like nothing was wronge then started doing its thing again . now haveing idle trouble at first start but am almost certain that this is air sensor troubles do to the fact once its warmed ou its fine when its cold it will miss some idle high then low have some codes going to check but just not sure if its mass air-flow or oxy sensors. have to wait until after xmas kinda of drained at moment.Also theres a person at work haveing the same problem getting intresting .



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Hello, well at least you know the end cause is there is no fuel at the check valve. Can't really explain cold start part, except the Brain needs a signal from the Water temperature sensor to put it in a "Cold cycle" start with higher idle and richer fuel mix. This sensor is not the one that runs the dash indicator. It also would not kill all the fuel pressure. Most likely a separate problem which can be fixed with a new sensor.

When you mentioned fuel solenoid, were you referring to the Relay in the Black box full of Relays?
A relay would explain the hit or miss fuel pump action. Check the Relay plug sockets for Corrosion. A bad Ignition switch could also fail to power the Relay. Having to turn the Ignition switch 4 to 6 times to get the fuel pump to work can mean the Run terminal inside the Ignition switch is worn. The Start terminal in the Ignition switch would power the fuel pump only while the Starter is cranking.

As for parking downhill, a bad fuel pressure Modulator would allow all the fuel to siphon back to the tank overnight, leaving you with a dry start in the morning. With a working fuel pump this pressure is restored in seconds, but with your problems it can explain why you benefit from downhill Parking.

You are correct about strange actions. Seems you have 4 or 5 things that could be wrong with nothing being definite. The Ignition switch is cheap to try, no expense to look for corrosion in the Relay plugin. A Relay for the fuel pump if it is not the Solenoid you were indicating. If no pressure again at pressure check valve, disconnect tank side of pressure Modulator and see if it has pressure (Indicating a faulty modulator). The Temp sensor for the Cold start cycle.

Would like an update for what you found.

Posted on Nov 08, 2010


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  • fordexpert Nov 08, 2010

    Glad you are making progress. What about Ignition switch to make fuel pump work? For no apparent reason the Inertia switch could be a bad connection to fuel pump. The magnetic ball inside is connecting the power to the pump. Inertia switch is in rear cargo access panel.

    Haven't a clue for Vapor lock in November. Bad gas with low volatility? Missing heat shield?

  • treetom Dec 13, 2010

    I am having that exact same condition with my Explorer as well. New fuel filter and relay, pressure is good and now that it is cold, having big trouble getting it to start. Thought to it could be the ignition switch or fuel pump. Most say it is the pump, so I bought one. Motorcraft PFS-422, but now I found that there are 3 different types of pumps for the years of this body style. One with a metal retaining ring, one with bolts and the 2000 and up uses a plastic ring and can only have the pump assembly replaced as a unit. Hope to have the tank off and apart sometime soon. I will post results.

  • treetom Dec 16, 2010

    Fuel pump has been changed. My advice is get a metal fuel line removal tool and take the spare tire down before you start. With the spare in place it would be near impossible to work due to a lack of space/access. Will let you know if the problem is gone completely in a few days.

  • fordexpert Dec 22, 2010

    This is Fordexpert, we had a comment about the idle air control valve pending for results and effect of cleaning it. If you have a Vacuum gauge you mentioned a small single hose going from under the Air Cleaner to a fuel solenoid(?) in your message 1 month ago. Do a vacuum check on this line as you know you found air in the system at the schrader valve earlier.

    I am thinking new ignition switch is getting all the juice to electrics. I believe the PCM relay sends a signal to the Fuel relay and uses the Fuel relay to complete a loop. Some WD40 in the terminal sockets might help. I don't have wiring diagram in front of me, going by memory.

  • ksalmons62 Dec 23, 2010

    OK here goes not completely sure on this but i replaced the solenoid after i finally found it and i don't think i've had the air in the fuel line since don't have vacum guage buut may no where i can get one will get and check . Also just fior the sake of it replaced relay did not notice any type of problem there all lucks like new witch was nice to see.but still have same problem cleared up for two weeks and then went back to the same thing it was doing before i have to admit at this point im lost.I am going to have to replace oxy sensors as idle is now becomeing a problem but only at start up after it warms up its fine .

  • fordexpert Dec 23, 2010

    Fordexpert here. Rec'd latest comment. At first new water sensors helped when engine was cold. Now cold engine is running rough again? About the only thing that goes away after a cold start is the load on the Alternator. Wonder if you can link WHEN the Alternator is recharging the cold battery to WHEN the engine is running rough? If volts are off it can affect everything. I do not have the specs for the O2 sensors to test if one is bad.

  • ksalmons62 Dec 24, 2010

    At first i never had a rough idle problem when it was first started this has just happened in the past week or so going out to code here in a little while to se what comes up before even when it got where it was hard to start any and all codes come up saying lean on banks both sides.Now of coarse its going to show miss fire and a few others due to the way it idles when cold.Only problem i had before was haveing to switch the ignition switch on and off 4 to 8 times to get enough fuel to the system to start once started ran fine with fuel pressure at 65psi.also am going to check ildle selonoid and mass air .for vacum leaks from where they have been cleaned.

  • treetom Dec 29, 2010

    No troubles with my 99 after putting in a new fuel pump assembly. I to had ruff idle at start up at times, spitting and coughing and such. All gone now. Can find the Autocraft assembly on Amazon for about $130.


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Sounds like the idle air control valve to me, you might just need to clean it with some throttle cleanner but you'll need a new gasket that only cost 3bucks or just get a new one, I just went through this cold start junk myself...

Posted on Dec 21, 2010

  • Mark Cannistraci
    Mark Cannistraci Dec 30, 2010

    I don't think the Idle Air Control is the problem because that component doesn't have anything to do with the fuel system. The observation of no fuel pressure at cold start-up is a sure sign of impending failure of your fuel pump. Change it now before it leaves you broken down on the side of the highway calling for a very expensive tow truck!
    What I think is happening is this (and it comes from real life experience, mine!):
    Here's what's happening... Throughout your the years of service your car has given you, all moving parts have been wearing out. From water pumps to alternators and every other moving part, they have all been designed to eventually wear out and fail. This is happening to your fuel pump's electric motor. On one end of the electric motor is something called a Commutator. The Commutator is a series of electrical connectors. In this case, pairs of Poles. A pair of Poles consist of 1 ( )Positive Pole

  • ksalmons62 Jan 10, 2011

    i have decided to replace the fuel pump for what good it will do now . reason is i have a new noise that makes me now to where im waiting for one of the rods to come threw the oil pan .lol yes i said lol at this point all i can do looking at other autos now but am going to still work on explorer not giving up yet .just need something to drive while i do so i like the explorer and until now have no complaints 7 years and no trouble till now .except for what it would take to change timming chain and gear its a joke.i've done my share of changeing them but sohc engine is a nightmare but when it runs it runs but a hard engine to work on.if i am able to get another auto then i will post my findings on the problems oh almost forgot codes all say lean .lean bank 1 and 2 and lean on all cylinders but cylinder1 strange and most off all i want to thank eveyone for there help with these problems of mine .


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Remember, if money is tight and times are hard, find your nearest Wrecking Yard! Auto-dismantlers like Pick n Pull can be a great money saving option. If you go to a yard where you have to remove the parts, these are great places to learn and break things. That way you don't have to learn costly lessons the expensive way! If the yard you visit pulls the parts for you, chances are they will also guarantee the part for like 30 - 90 days. If it's the wrong part or it doesn't work, they'll exchange it for you and get you the one that fits and works! This is still a lot cheaper than buying it off the shelf or special ordering and having to wait for it to be shipped. Last thing: Since you're decided to replace the fuel pump, do yourself a favor and go buy a new fuel filter!!! This is CRITICAL when changing a fuel pump! The reason I say this is because the fuel filter is the most overlooked and under-changed filter on every car ever made! And with electric fuel pumps (most of which are of the In-Tank style), you can never be sure what caused it to fail. If it's dirt that killed it, then the dirt is in your tank and fuel system right now! That means the fuel filter has also failed. It may have holes in the filter element letting dirt flow into and through the pump, destroying it from the inside or the fuel filter may be clogged after so many years of being ignored. This causes Back-Pressure to build and make the fuel pump work harder than it was designed to work, thus causing it to wear out and fail. So change the filter. Regardless of where you get the pump, if it fails and you take it back to exchange it, one question will be asked: "Did you replace the fuel filter when you installed this pump?" Answer "No" and you'll be buying another pump! Trust me, I've had to enforce that policy and people are not happy when they hear that even though I show them where in the box that notice is and have them read it before I pull another pump off the shelf along with a new fuel filter. Oh and NEVER try "Testing" a new pump out of the tank! The pump is designed to use the fuel as it's coolant and it's only Lubrication!!! A 2-second test can fry an electric pumps seals.
Anyway, keep us updated and Good Wrenching!

Posted on Jan 10, 2011

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