1971 Ford F-100 Warm engine cranking

Tiny
JBLJOHN
  • MEMBER
  • 1971 FORD F-100
  • V8
  • 2WD
  • MANUAL
  • 87,500 MILES
1971 Ford F-100 with 302 V-8 and 87,500 miles (bought new by my father in law in 1971).

When engine is cold the truck cranks immediately.

After driving and engine is warm and the engine is shut off for 15 - 20 minutes, the engine may or may not restart. When it will not start, I can crank by holding accelerator petal to the floor and cranking as if the vehicle is flooded, but there is no smell of gas.

Car has been to the shop twice and I'm advised this is not a carburator problem

Help Please!
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Sunday, June 20th, 2010 AT 11:11 AM

13 Replies

Tiny
RASMATAZ
  • MEMBER
Hi jbljohn, Welcome to 2carpros and TY for the donation

Car has been to the shop twice and I'm advised this is not a carburator problem

Do this open the choke plate -pull the throttle back do you see gas squirting into the throttle bore? Also is this a conventional or electronic ignition system-let me know asap
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Monday, June 21st, 2010 AT 3:17 AM
Tiny
JBLJOHN
  • MEMBER
Conventional (points, condenser) ignition. Fuel to carburator OK.
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Monday, June 21st, 2010 AT 5:52 PM
Tiny
RASMATAZ
  • MEMBER
Inspect the contact point gap if in specs use a dwell meter and adjust the angle and readjust the ignition timing
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Monday, June 21st, 2010 AT 7:51 PM
Tiny
JBLJOHN
  • MEMBER
Gaps within specs and timing already adjusted.

If this was the problem, wouldn't engine be difficult to start when "cold" also?

Next idea please.
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Tuesday, June 22nd, 2010 AT 6:40 AM
Tiny
RASMATAZ
  • MEMBER
When it will not start, I can crank by holding accelerator petal to the floor and cranking as if the vehicle is flooded, but there is no smell of gas.

Ans. Doing this will clear a flooded engine even if the choke is closed you should smell gas-Check the fuel pressure to rule the fuel pump and for clogged fuel lines. Also check the the float needle valve if its opening to include the inline fuel filter

Check the resistance wire from coil to the ignition switch and also the ignition switch itself Or do this run a wire from the battery positive post to the coil positive terminal and see what happens.
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Tuesday, June 22nd, 2010 AT 2:09 PM
Tiny
JBLJOHN
  • MEMBER
New automatic choke installed previously to address this problem - did not solve problem.

What am I looking for when I connect positive from battery to positive on the coil?
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Tuesday, June 22nd, 2010 AT 2:44 PM
Tiny
RASMATAZ
  • MEMBER
Doing this will bypass the ignition switch-try this and see if it will fire up without waiting if it works could be the wire or the switch itself
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Tuesday, June 22nd, 2010 AT 2:47 PM
Tiny
JBLJOHN
  • MEMBER
Just to be clear. My problem is that after driving (engine hot) the engine will not start after sitting 15-20 minutes. The engine will always turn over, it just will not start.

Can it be an ignition problem if the engine always turns over?
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Tuesday, June 22nd, 2010 AT 4:39 PM
Tiny
RASMATAZ
  • MEMBER
Don't wait for nothing-turn key on and check for power at the coil positive this will confirm if your ignition switch is failing-you sure its not vapor locking
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Tuesday, June 22nd, 2010 AT 4:42 PM
Tiny
RASMATAZ
  • MEMBER
I use to have the same year/model w/a 302 on it came out to be the ignition switch
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Tuesday, June 22nd, 2010 AT 4:43 PM
Tiny
RASMATAZ
  • MEMBER
Test the coil could be heating up when it cools down it fires right back up
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Tuesday, June 22nd, 2010 AT 4:46 PM
Tiny
JBLJOHN
  • MEMBER
I have been told by a mechanic that it is not vapor locking. Is there a test for vapor locks?
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Tuesday, June 22nd, 2010 AT 5:32 PM
Tiny
RASMATAZ
  • MEMBER
Your mechanic should be able to do this test-also I need some results on the coil-this vehicle configuration is so simple not like the computerized vehicles in today's technology-You need to do everything I've suggested so I can knock this problem out
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Tuesday, June 22nd, 2010 AT 5:37 PM

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