1990 Ford F-250 intermittent starting problem

Tiny
VERNY'S FORD
  • MEMBER
  • 1990 FORD F-250
  • V8
  • 4WD
  • AUTOMATIC
  • 115,000 MILES
My 5.0L engine cranks normally when attempting to start but frequently just doesn't fire. It requires multiple attempts before it fires and then runs great until I shut it off and need to restart. It is getting most frustrating. Thanks Bill Swanson
Wednesday, October 29th, 2008 AT 12:50 PM

9 Replies

Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
You first need to determine if you are losing spark or fuel, or both.
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Wednesday, October 29th, 2008 AT 7:04 PM
Tiny
VERNY'S FORD
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  • 5 POSTS
With the help of my timimg light, I determined that there is a spark while the engine is cranking but not starting.
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Friday, October 31st, 2008 AT 4:17 PM
Tiny
JAMES W.
  • MECHANIC
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Bill, To make sure I have this right. When you hold the key in the "start" position the motor runs. When you release the key to "run" position, it dies? Please advise, Jim. If it doesn't try to run in either position, and you have spark, then we have to look at fuel pressure and injector pulse. Fords of this era are notorious for bad fuel pumps.
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Friday, October 31st, 2008 AT 5:05 PM
Tiny
VERNY'S FORD
  • MEMBER
  • 5 POSTS
No, when I turn the switch to start, it cranks but does not run. After a few attempts it starts and runs fine until the next time I shut it off. Then I usually go through the same routine of turning the switch to start several times before it will run. It runs just great until the next time I need to start it. It never just dies.
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Saturday, November 1st, 2008 AT 11:56 AM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
OK, now I understand. What we need to do is determine what is missing on key start, SPARK or FUEL.
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Saturday, November 1st, 2008 AT 1:44 PM
Tiny
VERNY'S FORD
  • MEMBER
  • 5 POSTS
Yesterday I established, with the help of my timing light, that while the engine is cranking but not starting, there is indeed a spark. Consequently, the problem appears to be in the fuel delivery.
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Sunday, November 2nd, 2008 AT 6:47 PM
Tiny
JAMES W.
  • MECHANIC
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Ford trucks are notorious for bad fuel pumps. Keep me posted, jim
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Sunday, November 2nd, 2008 AT 7:36 PM
Tiny
VERNY'S FORD
  • MEMBER
  • 5 POSTS
Hello, Jim. You mentioned that Fords are notorious for fuel pumps. I can hear the pump run and stop when I turn the ignition on. Is there another device along the way that can keep fuel from the injectors? Bill
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Monday, November 3rd, 2008 AT 11:29 AM
Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
The fuel pump will run for a few seconds when ingition is turned to key "on". This is to pressurize the fuel rail before start. The crank shaft position sensor has to be ok or you wouldn't have spark or fuel. The next part in line is the computer itself. If you can hook to a scanner or other diagnostic unit, you should be able to check computer output to the fuel pump relay. I think this is where you'll find your problem.
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Monday, November 3rd, 2008 AT 8:07 PM

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