F-150 starting problems--adivce??

[yooperdave]

hello and thanks in advance to all responses.
problem- f-150 4.6 turns over like a champ, but does not fire. fuel pump works, the injector rail has fuel under pressure, battery is strong. after waiting a couple to a few hours, it will start up, no problem. doesn't happen all the time, but it seems to happen a bit more frequently recently.
could it be the "brain box"? 4 yrs ago, there was a leak in the windshield gasket that allowed water to enter the cab and drain down the interior of the dash, causing the "brain box" to get wet. things at that time would be non-working windows, blinkers, wipers, stuff like that, but it always started. the leak was sealed, and all was fine until this late spring. a service tech at a garage told me that they doubted it was the "box" due to the 4 year absence of issues.
any possible problem would be considered...especially from those that had similar experience's

 

[pastera]

Spark???

Corrosion takes time - pull the connection off the 'brain box' and check for corrosion. The computers are usually well sealed against drip damage but the connectors are a different story

Crank position sensor will cause a no spark also - No idea what year truck but my 89 T-Bird SC will give the same issue if the crank sensor is going

Aaron

 

[Corey]

Any ECU codes or Check Engine Light? (Even if the light used to be on and is now off, codes will be stored) If so, pull those and see what they say - some parts stores will pull the codes for free, though their interpretation is somewhat suspect.

Lack of any codes will tell you something, too - the issue is not affecting a sensor or anything else the computer can 'see'. It might me something like a loose power/ground wire fairly far up in the system.

 

[heat seeker]

I'm with Aaron - corrosion takes time. I'd check the connectors (both sides) that go the the control unit. Also agree with reading the codes stored, if any. That can save you much time and money.

 

[soupy1957]

I had a choice, last November.............I could buy a Chevy or a Ford Truck. I chose the Chevy Silverado Flex Fuel, 1/2 ton.

Based on what I'm reading here...........I'm glad I didn't buy the Ford! No Bail Out or not! (I heard that Ford survived on some personal private loans............wonder who the rich benefactors were?????)


-Soupy1957

 

[joefrompa]

Soupy - What exactly are you talking about. Ford benefitted from the availability of government sponsored liquidity (i.e. commercial paper) during a time when bank loans were hard to come by. But they weren't bailed out, nor did their bondholders receive a re-structuring, nor did they enter into any form of bankruptcy proceedings. They took a bath but emerged a stronger company. Somehow you are inferring you are glad you didn't buy a new ford product that was made during their strongest period in years vs. the truck you bought that was made during the companies weakest period? Bold man.

Yooperdave - There is no reason to expect your computer is faulty; they give broader errors than just an occasional lack of combustion. If you have confirmed fuel is ready, and you know you have a good battery, then here's the deal:

1. You can have a bad sensor, but that usually causes either rough running and/or a check engine light

2. You sound like you have a ~10-12 year old f-150 (4.6, your windshield gasket leaked, and your DME was fixed over 4 years ago). That's the time when tune-up related issues start happening among parts that are breaking down. If you are experiencing this especially during humid/wet times, I'm inclined to think that has something to do with it. I.e. cracked coil park/ignition wire cracking. However, again, I would expect you to have some rough running during this.

2a. Your symptoms most closely mimic a situation in which you aren't geting spark into the cylinder. Pull a plug and check for plug while cranking. Also, you might have a timing issue (again, sensors).

...

Just some initial thoughts. Can you describe the running condition of the car? Did you test the schrader valve on the fuel rail and see fuel SQUIRT out?

When was the last time the spark plugs, fuel filter, air filter, etc. were changed?

 

[heat seeker]

Joe,
All good points!
yooperdave, you might try cranking in a dark place (or at night) and watching under the hood. If there are bad wires, etc, you just might see sparks jumping to ground. My friend's Pontiac was running rough, we opened the hood one night and it was amazing to see all the sparks jumping around. It's a wonder the thing even ran. It's easy, it's free, and just might help.
Back to basics - you need spark, fuel, compression at all the right times, and it will run.

 

[nate379]

What year?

 

[woodsman23]

Lets see my 97 F150 i bought new had 309,xxx miles on it when i traded it in. Go figure, never a problem, one clutch, one alt, one starter and i owned it for over 13 years. It was truly the most dependable truck i ever owned.. Chevy well thats another story...

 

[yooperdave]

the truck runs good when it starts. was fine all this past weekend-no issues. idles and runs smooth, no stumbling or stuttering or unexpected shut downs. just the starting issue; i really don't expect it to be wires or coil issues, as when it starts on humid/rainy days, there are no problems.
i did have a vehicle with poor plug wires, and i do remember the "light show" that was present when i raised the hood after dark!

 

[Czech]

Did I miss the year somewhere? Check what kind of pressure you're getting on the fuel rail, they can be very touchy, say a couple a pounds low and no go, the popettes on the injectors are picky. If pressure a varies, may be a fuel return valve leaking back to the tank or start of a bad pump, or even a filter.

 

[yooperdave]

Did I miss the year somewhere? Check what kind of pressure you're getting on the fuel rail, they can be very touchy, say a couple a pounds low and no go, the popettes on the injectors are picky. If pressure a varies, may be a fuel return valve leaking back to the tank or start of a bad pump, or even a filter.

don't know what pressure its at, but the gas comes out like a geyser...leading me to believe the pressure is not an issue. but i will check it out next weekend (or midweek).

 

[joefrompa]

When the truck doesn't start but then starts right up fine a few hours later, was it cold the whole time or was it hot/warm the first time when it failed?

I have a few guesses here:

1. You have a fuel pressure regulator problem which is causing a drain back of fuel and/or a problem with delivering fuel PRIOR to starting, before the regulator is driven by a more constant level of pressure/vacuum.

2. You have a cam position sensor that is on its way out

3. You have bad grounding that is causing just enough errant volts to occasionally go elsewhere that the spark is not bridging the gap in the combustion chamber from time to time.

The intermittent nature of this, and it driving fine, tells me that you don't have a mechanical issue in terms of delivering fuel or spark, proper throttle response (i.e. throttle sensor, spark plugs, coil packs), etc.

You've either got a part that only functions poorly upon starting, a sensor that is on the fritz but only when starting, or an intermittent electrical problem (such as a bad ground).

My recommendation would be this:

1. Next time it does it, squirt some starter fluid down the intake pathway while it's failing to start. If it coughs to life or start sputtering, my guess is the FPR.

2. Find the primary grounding paths for everything associated with spark delivery/engine grounding, or make some new ones nice, and clean up all grounding locations.

 

[yooperdave]

When the truck doesn't start but then starts right up fine a few hours later, was it cold the whole time or was it hot/warm the first time when it failed?

I have a few guesses here:

1. You have a fuel pressure regulator problem which is causing a drain back of fuel and/or a problem with delivering fuel PRIOR to starting, before the regulator is driven by a more constant level of pressure/vacuum.

2. You have a cam position sensor that is on its way out

3. You have bad grounding that is causing just enough errant volts to occasionally go elsewhere that the spark is not bridging the gap in the combustion chamber from time to time.

The intermittent nature of this, and it driving fine, tells me that you don't have a mechanical issue in terms of delivering fuel or spark, proper throttle response (i.e. throttle sensor, spark plugs, coil packs), etc.

You've either got a part that only functions poorly upon starting, a sensor that is on the fritz but only when starting, or an intermittent electrical problem (such as a bad ground).

My recommendation would be this:

1. Next time it does it, squirt some starter fluid down the intake pathway while it's failing to start. If it coughs to life or start sputtering, my guess is the FPR.

2. Find the primary grounding paths for everything associated with spark delivery/engine grounding, or make some new ones nice, and clean up all grounding locations.

the starting problem has occured with both a cold engine (few days since it ran last) to a just got down running engine (hot; shut off in a parking lot then tried to restart anywhere from 5 min. to an hour)

 

[Czech]

Did I miss the year somewhere? Check what kind of pressure you're getting on the fuel rail, they can be very touchy, say a couple a pounds low and no go, the popettes on the injectors are picky. If pressure a varies, may be a fuel return valve leaking back to the tank or start of a bad pump, or even a filter.

don't know what pressure its at, but the gas comes out like a geyser...leading me to believe the pressure is not an issue. but i will check it out next weekend (or midweek).

Only difference between between 40 psi and 56 psi on the rail is one will run the truck and the other will not. Both will look like geyser if you depress the schrader. Just 2 cents...

 

[blades]

Clogged fuel filter? located under drivers side on frame. fuel pump in tank notorious for intermittent problems sometimes caused by blocked filter in tank, coroded connections, and just plain on its way out.
My 99 f150 4.6v8 stopped dead as I was pulling out of parking place by Grocery store last fall. call a tow as would not restart. tow was going to be a couple hours getting there so did shopping and dawdled around for about 1.5 hr. Thought just for the heck I tried once more before the tow got there, boom fired right up. Not a stitch of a problem until about a month ago stopped running as I was going down the road, middle of timbuktu, naturally. fuel pump shot 176xxx miles first pump.

My99 F350 v10 pulled a similar stunt about 2 years ago. I do not run this one all that much. 75 mile round trip pick up a load in the middle. Pulled in at home shut her down. unload go to restart no can do- fuel pump 97000 miles at the time.

 

[joefrompa]

The problems you guys are describing (clogged fuel filter, bad fuel pump) would cause both running issues and would not be intermittent in nature causing a no start condition (for example: a truck will on a lower PSI of fuel pressure than needed....it won't run well, and it won't run consistently, but it'll cough).

The problem appears to be distinctly related to the car being off. Since it can happen even when the car was just run, I'm going with electrical and maybe the FPR in the background (since it's vacuum actuated, it can give problems when its not getting normal vacuum).

I'm guessing you have a problem delivering spark during starting. My guess is:

1. Starter
2. Ignition wires
3. Bad grounding causing intermittent stray voltage drain during start activities alone (i'm leaning towards this, as it's the most likely to cause weird and intermittent problems during ONLY starting and without causing a Check Engine Light (CEL) of some sort)

 

[Renaissance]

I would suspect the crankshaft position sensor. As they age, they sometimes generate a weaker signal. For a car with a dying CPS, it's possible to run (once started) perfectly fine, but starting becomes hit or miss. Sometimes the car will refuse to start while cranking, but will readily fire if push started at a decent speed. I'm not familiar with your exact vehicle, but if your instrument cluster is powered while cranking, check for tach activity. That's one way to check if the PCM knows the engine is turning. Another is to listen for the hum of the fuel pump while cranking. Most cars will not run the pump on a bad crank signal.

Also, bad coolant temperature sensors and intake air temperature sensors have been known to cause flaky starts.

 

[Czech]

The suspense is killing me, keep us posted on the outcome please. All great advice as far as I'm concerned, but I can't wait to see who gets to say I told you so! In a nice I heat by burning stuff kind of way of course.

 

[blades]

Fuel pump out will not cause a code to be generated nor will a clogged fuel filter cause a code. This I can say for sure on my 99's. When the F150 shut down I just happened to have had my reader with me, first thing I did was plug it in. zip, nada. On the F350 it caught sputtered died that was it ,just crank after, no codes there either. Bad vacuum will blow codes not always directly related ( it is not going to mention vacuum) more like right or left bank running lean. ( been there also). On the 4.6l v8 there is a vacuum line from the back center of the intake manifold travels over along the firewall and then to the pcv valve, it rots out right at the pcv and the intake manifold. This is sneaky as it has a foam cover over the formed rubber hose ends. 50% of this line is hard plastic tube. To generate a code on my year trucks require a 40% failure. In the case of the plugs wire and coils this would require 1/2 the cylinders to not fire, resulting in o2 codes, before that happens the ecu will shut down the injectors to keep from loading the cats with raw fuel ( experienced this also). 4.6l v8 is a bit of a hybrid as it still has plug wires and a separate coil for each plug but the coils are assembled in packs of 2 so you have 2 paks of 2 mounted on the front of the engine on either side. Wires criss cross from each pak to either side of engine resulting a couple of them being 6ft long.

 

[blades]

Ford did have trouble with CPS units although this was more notable on the 7.3,6.0,6.4 diesel units, common note was to keep a spare in the glove box along with a 11mm wrench to change it out.

 

[blades]

I have heard of others having problems with the terminal box(cpu) under the dash behind the fuse box relating to bad connections due to moisture in one form or another, no personal experience on that. I do have a bad solder connection on the odometer connections causing it to wink in and out generally at start up.

 

[yooperdave]

well, the mystery is solved. brought the truck in for a fuel tank strap re-call, then the dang thing wouldn't restart at the dealership after the new tank straps were installed!

yep, it was the fuel pump.

good thing it happened there, and not out in the woods right?

bad thing that it happened at the dealership, and i have to pay the dealers labor rate! they didn't have one in stock at their parts room, so they said it would be a few days before the order came in...why don't you put an aftermarket pump on???? well, we can do that...it'll be done tomorrow morning.
hello, is my truck ready? yes, but we also replaced a brake line........

but it's done now, and thanks for all the suggestions/advice on the problem!