Engine is dieseling

[Stillwater35]

https://m.youtube.com/watch?v=Q5hGjeL47d4

Every time I turn my blueprint 306 complete engine off, it sputters and the run backwards for a second or two. I have no idea what’s causing this or how to resolve. It sounds horrible.

Any help? I’ve emailed blueprint

[GoDadGo]

On carbureted engines fuel will get sucked into the engine until the engine quits spinning.
If the idle mixture is rich and the engine idle RPM is pretty high it may want to run off after the ignition is shut off.
Basically the fuel keeps dripping as the engine turns over and it detonates without the spark plugs kicking off the process.
If your engine is Fuel Injected, then that is outside of my wheel house, but a F.I. set up may also be running a tad fat leaving un-burned fuel in the intake too.
I'M NOT A PROFESSIONAL MECHANIC; however, I do often stay at Holiday Inns (Express Type) when traveling on business.

Good Luck From The Dark Dart Side!

[Stillwater35]

Too rich. Pulled the plugs. It’s a carbureted blueprint 306

107904

107905

[NAZ]

Too lean may cause dieseling but too rich would tend to lessen the condition. Lean is hot, rich is cool. In the olden days of emissions controls carb engines were run very lean which can cause hot carbon in the combustion chamber to ignite the fuel charge after the key was shut off. To cure this the OEMs used an electrically powered idle solenoid that when powered off would allow the throttle blades to close down, eliminating the run-on condition. As a Ford technician in the progressive tree huger People's Republik of Kalifornia, cars had to be very lean to pass the draconian smog laws of the early 70's and I worked on a lot of warranty issues troubleshooting run-on conditions. EFI instantly eliminated this problem as it does not feed fuel when the ignition is off. Carbs continue feeding fuel independent of ignition power.

BTW, reading plugs is not as easy as most would like to believe. If you want to detect a AFR issue at idle you have to start with a clean plug and idle the engine long enough to color the plug. If that plug has run on the highway at all you will not get an accurate indication of idle and vice versa.

[GoDadGo]

BTW, reading plugs is not as easy as most would like to believe. If you want to detect a AFR issue at idle you have to start with a clean plug and idle the engine long enough to color the plug. If that plug has run on the highway at all you will not get an accurate indication of idle and vice versa.

NAZ,
This is a huge help to me so thanks!
I never could do an adequate job as it was always a guessing game when an engine was running pretty well.

Stillwater,
Here's an article that may shed some additional light on the subject.
http://www.badasscars.com/index.cfm/page/ptype=product/product_id=94/prd94.htm

[Railroad]

I could not tell if your electric fan was spinning down during your problem. I have heard that the spinning fan motor can generate enough current to keep the ignition activated. One of the solutions is to put a diode in the wiring to the fan. I am sure someone can put some wordier explanation up, if you need it.

[GoDadGo]

I could not tell if your electric fan was spinning down during your problem. I have heard that the spinning fan motor can generate enough current to keep the ignition activated. One of the solutions is to a diode in the wiring to the fan. I am sure someone can put some wordier explanation up, if you need it.

The Dynamo Effect?

[sethmark]

Frequently, dieseling is caused by having the enrichment screw open to far leaving the butterfly open slightly when your foot is off the gas. Basically your idle is turned up too high. Turn the air bleed screw to lower your idle speed a quarter of a turn and see if it helps.

[Stillwater35]

Thanks to everyone. Lots t try tomorrow. 1 more week until I’m inspected and legal

[BluePrintEngines]

Wanted to check in after we emailed. did the carb adjustments prove effective?

Johnny

[Stillwater35]

Yeah - and Johnny is the man for replying over the weekend to get me settled in. Thanks man.

[BluePrintEngines]

Yeah - and Johnny is the man for replying over the weekend to get me settled in. Thanks man.

Anytime!