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1998 Ford F-150 4.6L

edited February 2012 in Repair and Maintenance
Sorry, need to clarify previous post on this....
Truck will not restart after it gets warm. However it wil restart after 45 minutes. Taken to dealer, all systems check out fine,electrical,fuel,charging,antitheft, no codes appear. All lights are bright, radio works fine, and it will crank and crank but will not turnover!!! Again, if I wait 45 mninutes or so it will turnover and run great! I love this old truck it has 150K on it and has been terrific!

The Ford F-150 forums are all over the map!
This is an example of the exchanges on this vehicle I have run across on the webb>>>>>>>>>>>>>>>>>>>>>>>>>>>

(eallanboggs: Thanks for the tips on changing the pump. My truck does not have the COPs, so I will pursue spark, fuel, air for cylinder #8...
Update
The truck finally decided to refusing starting again. I took the following voltage measurements, when the truck would crank, but not start:
- Battery voltage, 12.6V (no load)
- Fuel pump, 10V for 1 sec , then 0V (w/ key on, but not cranking)
- Fuel pump, 9V (w/ engine cranking)
- Inertia switch, 11V for 1 sec, then 0V (w/ key on and inertia switch in normal operating position)
- Inertia switch, 11V for 1 sec, then 6.75V (w/ key on and inertia switch in triggered position)

With Crank position sensor unhooked:
- Fuel pump, 11V for 1 sec, then 0V (w/ key on, but not cranking)
- Fuel pump, 0V (w/ engine cranking)

Note: The fuel pressure remained 0 during these measurements, and the truck would not start.


Then, I installed my battery charger and reinstalled the crank position sensor:
- Battery voltage, 14.6V (no load)
- Fuel pump, 13V for 1 sec, then 0 (w/ key on, but not cranking)
- Fuel pump, 10-11V (w/ engine cranking)
And, the fuel pressure rose to ~30, and the engine cranked & started.

My next steps are to a.) have my new battery load tested, since the fuel pump only had 9V while cranking without the aid of the battery charger, and b.) change the fuel pump, since it works with high enough voltage

Does anyone know the voltage spec. for a fuel pump? Should it work with 9V?
Any other suggestions? )

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
PLEASE help! There has got to be someone out there who has seen this. Your advice is greatly appreciated! Thanks very much! We look forward to your suggesstions. Have a great weekend!
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Comments

  • You could still finish telling the story. How old are your basic "tune up" items? (plugs, wires, filters...) Has your check engine light been on and, if so, the dealer would have pulled error codes, so what are they?

    You can easily narrow down the problem so that you know what to troubleshoot. This problem can happen for many different kinds of reasons so you find out what kind.

    First, this can happen because your engine is getting flooded when you shut it down. This will happen if fuel injectors or the fuel pressure regulator are leaking into the intake after shut down. A quick thing to do next time it won't start is hold the throttle pedal to the floor while you turn the key. This is a flood clearing procedure and if it helps you can guess the problem is too much fuel on restart. Checking the fuel pressure regulator is easy - find it & pull off its vacuum line. If there is fuel in the vacuum line, replace the regulator. Checking the injectors is not so easy & you might use a shop for that (but you don't need a dealer).

    Second, it can happen because ignition components get "heat soaked" and you get no spark. Just pick up a spark tester at any auto parts store and the next time it won't start use it to check for spark.

    Third, it can happen from various fuel system problems that result in insufficient fuel supply (the opposite of #1). When you pick up a spark tester also get a can of starting fluid. The next time it won't start, shoot some starting fluid into the intake and if that gets it to fire - even if just a little bit - then you are probably looking at an issue with the fuel pump or some related component.

    If you report back with what you learn from all of this people can tell you more.

    You should also realize that an intermittent problem like this is often very difficult to track down. You are very unlikely to find any dealership's service dept spending any serious time or attention on the issue. This is when you want a good relationship with an independently owned, local shop.
  • edited February 2012
    Buy a "test spark plug" and a can of starting fluid. When it's in the "no start" mode, connect the test plug to one of the spark plug wires and crank it. Do you have ignition spark?? If no, then you have pretty much found your problem. If yes, spray some starting fluid into the air-cleaner box and crank it. It should start and run momentarily..This tells you the engine is not being supplied with fuel..

    You mentioned an anti-theft system..That's a likely suspect assuming it's more than just an alarm..

    Visit this web-site, www.crownvicnet.org There is a forum specifically devoted to the 4.6L engine and these guys are pretty sharp...
This discussion has been closed.