Engine will not start

Tiny
MATMO
  • MEMBER
  • 1991 FORD F-250
  • V8
  • 2WD
  • AUTOMATIC
  • 159,000 MILES
The 7.5L engine in my F250, with dual tanks, will not start. I have been troubleshooting it now for a couple of weeks and just can't seem to find anything wrong, and have now run out of ideas. I will provide a list of everything that have tried and the results.

- The engine cranks over nice and hard, so I know the battery and starter are good.
- Both fuel pumps are working, as you can hear them come on when the key is turned on.
- Verified that the fuel pressure is 40 psi at the schrader valve on the fuel rail for both pumps.
- Replaced the fuel pressure regulator, and verified fuel is flowing from the hole when it was off.
- Ignition module tested good at Auto Zone.
- Verified injector solenoid winding resistance on all injectors, they read between 14.9-15.3 ohms, this is cold. Can not test hot as the engine will not start.
- Pulled the connector from all injectors and verified 12 vdc present on the positive wire of each with the key on.
- Verified firing pulses as each injector was plugged in one at a time. No injector caused the pulses to stop. I used your "how to test an injector" article.
- Verified spark at the end of each plug wire.
- Verified that the inertia switch is not tripped.

Spark plugs, wires, rotor, distributor cap, fuel filter, air filter & O2 sensor were all replaced about 6 months ago, and have less then 5000 miles on them.

Thanks for any help you can provide.
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Sunday, July 11th, 2010 AT 2:59 PM

10 Replies

Tiny
DOCFIXIT
  • EXPERT
Hi
Try this remove air snorkel open throttle spray CARB cleaner into crank does it fire?
Let me know
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Tuesday, July 13th, 2010 AT 12:44 PM
Tiny
MATMO
  • MEMBER
I did not try this with carb cleaner, but I did try it with starting fluid. It would not start with that either. It was after that, that I started looking into the injectors and verifying if I had spark.
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Tuesday, July 13th, 2010 AT 7:32 PM
Tiny
DOCFIXIT
  • EXPERT
The spark you get at plugs is it 1/4 to 1/2 in. And blue/white?
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Wednesday, July 14th, 2010 AT 3:17 PM
Tiny
MATMO
  • MEMBER
To check the spark I pulled the wire off of each plug, inserted and extra plug that I have, grounded the plug, and then turned over the engine. The spark only goes across the small gap of the plug, it was white in color. So, no it was not 1/4 to 1/2 inch long. Do you have a different method of doing this? Please let me know and I will test it in that manner.
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Wednesday, July 14th, 2010 AT 3:29 PM
Tiny
DOCFIXIT
  • EXPERT
Your method is O.K. So need three things for engine to run fuel, spark and compression. So the question have you checked compression? Did thie problem come sudenly? Any warning signs?
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Friday, July 16th, 2010 AT 11:39 AM
Tiny
MATMO
  • MEMBER
Actually I just got the gauge and adapter from Auto Zone to test this. I should be able to perform the test sometime this weekend. I was also reading more material on your site and found a page that mentioned that a blocked exhaust could cause this problem as well. As I am sure that the catalytic converter is the factory original It would not surprise me if this was a problem.

The no start condition just came on suddenly. I have had an issue since the last time I was at lake last year. I accidentally got the muffler under water and it has been hard to start ever since. I usually have to hold the pedal to the floor and then start it, to rev the engine up, otherwise it will start and then die. I will post back once I have checked these two items.
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Friday, July 16th, 2010 AT 3:21 PM
Tiny
DOCFIXIT
  • EXPERT
If muffler was under water likely got to CAT and fractured it. This will cause exhaust restriction and hard start
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Saturday, July 17th, 2010 AT 3:42 PM
Tiny
ROCKINTATER
  • MEMBER
Have you checked the MAP sensor? Or if you live in California you would have a MAF sensor. Let me know I have a non runner doing about the same
Mine will start and idle for half a minute then die like its running out of fuel, then not want to start again for a few hours
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Monday, November 12th, 2018 AT 5:14 PM
Tiny
ROCKINTATER
  • MEMBER
Also I have a running 7.5l, I believe I will swap the sensors to see if this is the problem, if not I will swap the fuel pressure regulators and try that
Cross your fingers
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Monday, November 12th, 2018 AT 5:16 PM
Tiny
KEN
  • ADMIN
These trucks had problems with the ignition module cutting out then needing to cool before they will run again. Here is a guide to help as well with instructions below to help you replace the module:

https://www.2carpros.com/articles/car-cranks-but-wont-start

REMOVAL

1. Remove two screws retaining TFI/heatsink assembly to lefthand fender apron.
2. Disconnect harness connector, then remove two screws retaining TFI module to heatsink. Remove TFI module.

INSTALLATION

1. Coat metal base plate of TFI ignition module with 1/32 inch thick layer of silicone grease.
2. Install module on heatsink, then torque two retaining screws to specification.
3. Install TFI/heatsink assembly to left hand fender apron using two retaining screws.
4. Connect harness connector.

Please let us know what you find. We are interested to see what it is.

Cheers, Ken
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Thursday, November 15th, 2018 AT 5:34 PM

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