Engine

Tiny
DODGENWW
  • MEMBER
  • 1981 FORD F-250
  • 4.9L
  • 6 CYL
  • 4WD
  • MANUAL
  • 180,000 MILES
Ok I just rebuilt this engine and now it won't start can spray starting fluid in the carb and it spits and spudders like it's trying but it's not wat could be the problem I'm thinking it's the timing but everything is lined up the way it says
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Thursday, January 7th, 2016 AT 12:52 PM

15 Replies

Tiny
WRENCHTECH
  • EXPERT
All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.

Every engine requires spark, fuel and compression to run. That's what we have to look for.

These are the basics that need to be tested and will give us the info required to isolate a cause.

1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.

2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.

3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.

4) If all of these things check good, then you would need to do a complete compression test.

Once you have determined which of these functions has dropped out,
you will know which system is having the problem.
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Thursday, January 7th, 2016 AT 1:05 PM
Tiny
DODGENWW
  • MEMBER
Ok I did check all of them and they all checked out and did a compression test on all cylinders
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Thursday, January 7th, 2016 AT 1:09 PM
Tiny
WRENCHTECH
  • EXPERT
Well, if that was the case, it would be running.
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Thursday, January 7th, 2016 AT 1:15 PM
Tiny
DODGENWW
  • MEMBER
Ok there are no injectors in this engine and I did notice yesterday that it's not keeping fuel pressure wen key is off
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Friday, January 8th, 2016 AT 4:54 AM
Tiny
WRENCHTECH
  • EXPERT
If this is a carburated engine, then you can look down the throat of the carb and open the throttle, looking for a squirt of gas when you do that. If you have a squirt, then fuel is OK. Check the spark and compression on all cylinders.
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Friday, January 8th, 2016 AT 6:17 AM
Tiny
DODGENWW
  • MEMBER
The compression was at 90 on all cylinders
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Friday, January 8th, 2016 AT 6:21 AM
Tiny
DODGENWW
  • MEMBER
And I have spark on all of them also
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Friday, January 8th, 2016 AT 6:42 AM
Tiny
WRENCHTECH
  • EXPERT
90 PSI is too low. You may have the valve timing off.
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Friday, January 8th, 2016 AT 6:43 AM
Tiny
DODGENWW
  • MEMBER
Ok wats that mean
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Friday, January 8th, 2016 AT 6:45 AM
Tiny
WRENCHTECH
  • EXPERT
It could mean any number of things since you just rebuilt the engine. It could be rings, cylinder walls, valves, timing, etc.

Try squirting a little oil into the cylinder and test the compression again.
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Friday, January 8th, 2016 AT 6:48 AM
Tiny
DODGENWW
  • MEMBER
Ok
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Friday, January 8th, 2016 AT 7:08 AM
Tiny
DODGENWW
  • MEMBER
Ok I'm more worried bout getting it started than the compression of it so wat else it could be
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Monday, January 11th, 2016 AT 5:01 PM
Tiny
DODGENWW
  • MEMBER
Or wat would the distributor position be
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Monday, January 11th, 2016 AT 5:02 PM
Tiny
WRENCHTECH
  • EXPERT
You can't ignore compression. That's the reason it won't start.
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Monday, January 11th, 2016 AT 5:05 PM
Tiny
DODGENWW
  • MEMBER
No it's not cause it had lower compression than that wen it ran
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Monday, January 11th, 2016 AT 5:23 PM

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