why wont truck stay running?

Asked by Dec 28, 2014 at 03:11 PM about the 1976 Ford F-150

Question type: Maintenance & Repair

have a 1976 f150 4wd with a 390. the truck turns over and fires but wont stay running
unless you keep the key turned. as soon as u let off it dies. have changed the cylenoid,
tested the ignition module and still nothing different.

3 Answers


There is the start circuit and then the run circuit, in the primary. It sounds like the start works and when the key springs back to the run position, your resistor wire circuit is at fault. look at the schematic and the tests in the Ford manual. Those manuals have been widely donated to public libraries for reference. The fuse panel, the switch, the wires, are all suspect because of the vehicles age. A schematic and the tests can help you find where it has been altered, corroded or has a worn ir moisture damaged part perhaps. The duraspark boxes have been consolidated to like 3 different low cost replacement modules. in the event you still have an issue after proving out the run circuit. any circuit that exceeds .5 ohm is considered excessive resistance except a run circuit that is designed to reduce voltage to save the coil after start up.

2 of 2 people found this helpful.

An ignition feed harness is supposed to be shielded where it traverses the engine longitudinally to reach the ignition parts. alterations to that harness, or an overheating condition can lead to damage and no or "low" spark.


i have a 1991 f150 v8 doing this as well would it be the same problem Dannyl

Your Answer


Looking for a Used F-150 in your area?

CarGurus has 226,360 nationwide F-150 listings starting at $1,250.


Ford F-150 Experts

  • #1
  • #2
  • #3
View All

Related Models For Sale

Used Ford Mustang
457 Great Deals out of 42,832 listings starting at $1,488
Used Ford F-250
419 listings starting at $2,900

Used Cars For Sale

2018 Ford F-150 For Sale
14 Great Deals out of 134,480 listings starting at $18,092
2017 Ford F-150 For Sale
202 Great Deals out of 17,294 listings starting at $18,000
2016 Ford F-150 For Sale
224 Great Deals out of 7,622 listings starting at $16,997
2015 Ford F-150 For Sale
479 Great Deals out of 11,052 listings starting at $9,000
2014 Ford F-150 For Sale
739 Great Deals out of 14,853 listings starting at $7,000

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.