dieseling: aka (Engine Run-on)
Thread Starter
|
New User
Joined: Jun 2004
Posts: 3
Likes: 0
dieseling
hey guys, i recently bought a 79 f250 that has a 351w in it and im trying to get everything running right on it . when i got it , it would diesel badly when i shut the engine off after it was up to temp. i adjusted the timing clockwise and it got alot better. i did this rough timing by ear and when i hooked up my timing light, vacuum removed and plugged, its wayy off the marks. if i move it back to read on the light the dieseling returns. is there something else i may need to try or just keep the timing set like it is....the power and fuel economy seem ok like it is for this motor..it has new plugs and cap/rotor...thanks
Junior User
Joined: Mar 2003
Posts: 56
Likes: 0
dieseling can also be caused by an air leak check all your vacuum lines and caps. You can try spraying carb cleaner around the base of the carb and any other sources of vacuum while the engine is running and listen for a change in idle speed.
Thread Starter
|
New User
Joined: Jun 2004
Posts: 3
Likes: 0
i see i got moved to this page...yes its a 351w...not original engine in the truck came outta a 76 torino i think i was told...well anyways...i'll check for vacuum leaks and such its has the d4ae carb?...or something like that.....
Posting Guru
Joined: Dec 2002
Posts: 2,003
Likes: 2
From: chicago burbs
get a balancer that hasn't spun, better yet a new one. they get dangerous when the outer ring comes loose. there are aftermarket balancers that aren't much more than a rebuilt stock one. all of the above mentioned things to check for can cause run-on, too high of idle speed, advanced igniton timing and vacuum leaks.
Trending Topics
Elder User
Joined: Sep 2003
Posts: 908
Likes: 4
Dieseling can only happen when raw gas is in the intake after shut down. It almost always implies too much idle, or a bad anti-diesel dashpot on the carb. Makes no difference what 351 you have, or even a Chevy or Mopar.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 6 Best Deals Available on New Fords & Lincolns Right Now
Brett Foote
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Verdad Gallardo
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Senior User
Joined: Jun 2004
Posts: 155
Likes: 1
It happens to all my engines. Especially when they get older. I like big cams and stuff, so I have to have the idle screws open a little more to get them to idle. Then when you shut er off, they diesel a little. Bone stock you can usually get rid of this, but modified with aftermarket carbs it's a lot harder.
Cargo Master
Joined: May 2003
Posts: 2,561
Likes: 1
From: Earth
What type of ignition system are you running? I was installing my new MSD goodies on my '71 400 in my '53 today and I was thumbing through the "trouble shooting" section of the manual and they mentioned something to the effect of voltage leakage or something can often cause run-on when you shut an engine off. They gave a tip on what to do and it was simple enough to cure too. I can get my directions out and look it up again if you think your digital ignition may be the problem. Let me know.
Thread
Thread Starter
Forum
Replies
Last Post
Ken Claydon
1987 - 1996 F150 & Larger F-Series Trucks
4
Apr 13, 2020 10:42 PM
och
6.0L Power Stroke Diesel
5
Sep 2, 2012 09:30 AM
