I have a dieseling problem the engine has.. a new holley 2280, a working choke, working warm air snorkel, new autolite 26 plugs, hei, electric fan, new 195 thermostat, new cap, new rotor, new wires, no egr, base timing at 15 degrees before tdc. The idle is 550 rpm, the head was rebuilt with all new exhaust valves.
It will diesel for 2-3 sec after i turn it off.

Sorry for all the stats but, I'm out of ideas.

Thanks for any help.

_________________
85 d-100 HEI 2BBl
06 Toyota Corrola

I have a Holley 390, sitting on a reworked head, and have had dieseling or back spin problems. Because of a rather aggressive cam, and a low vacuum reading at an in gear idle of 600 rpm, the power valve was activated causing a rich condition. I had to go to a 2.5, it still acts up on occasion, and now I will be installing a 1.0 power valve.

First check float level, and adjust if necessary. A high level will dump excessive fuel and can cause that back spin, or dieseling.

Second if float is level is good, test your power valve to be sure it is not leaking or blown (I just put the large end to my mouth and suck on it- if no air passes it is ok), and follow Holley’s recommendation for power valve selection based on your vacuum reading at in gear idle.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

yum power valve its whats for dinner.

I had a pretty bad dieseling problem, but I did the Sea Foam thing to get rid of carbon deposits. No more dieseling. Just unplugged the PCV and stuck the hose into the can, then let 'er rip. Smoked out the neighborhood!

_________________
If it was easy, everybody would be doing it.

Dieseling and "run on" can also be caused by a vacc leak at the carb, or improper seating of the throttle plates.

FYI,

-D.Idiot

Thanks for the ideas I will check them out and report back.

_________________
85 d-100 HEI 2BBl
06 Toyota Corrola

Your timing is pretty aggressive. I'd back it off to 8* or so and see if that helps.

Running as much advance as possible doesn't necessary give the best fuel economy and/or power. The advance curves need to be set so that the pressure peak in the combustion chamber creates the maximum torque on the crankshaft. Too much or too little advance wastes power and fuel. However, insufficient octane will often cause pinging before reaching the point of best torque.

I had that problem on a '75 Coronet w/ 225ci /6; I built a box w/ solenoid valves that let me connect the EGR to manifold vacuum before I turned the car off - the RPMs would way drop down and then it wouldn't run on anymore. The same box could disable EGR entirely for WOT, but let its vacuum amplifier run normally to prevent pinging at mild throttle.

The box had 3 solenoid valves and a dash mounted 3 position switch for (vacuum amplifier) | (manifold vacuum) | (vent to air) to the vacuum input on the EGR valve. I couldn't measure any difference in mileage w/ EGR vented or connected to the amplifier.

shut it off in gear. the trans load will stall it immediately. ron

I checked the power valve adjustment ...and there is no screw I think. I will reset the base timing to 8* and see how it does
thanks for the help

_________________
85 d-100 HEI 2BBl
06 Toyota Corrola

carlherrnstein: There is no adjustment of a power valve, it must be changed for another that meets ones idle vacuum requirements. Also they are either operational, or the diaphragm is ruptured rendering it useless. See one here.

In order to service a Holley power valve one must remove the float bowl, then the block holding the jets. From the back side of the block, use a one inch wrench to gently remove the valve.

Don’t over tighten the power valve when installing it, be gentle.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

ok, thanks wjajr I thought the power valve was something else I'm not too keen on carburetors but I'm trying to learn.

_________________
85 d-100 HEI 2BBl
06 Toyota Corrola

I reset the timing to 8* and it helped a bit now it only diesel when the engine it warm...
I have the plugs gaped to .045"or .050" I can't remember could that be too far?
Also the carburetor gets hot to touch I wonder if the fuel is boiling making it run richer than normal and causing it to diesel.

any ideas?

_________________
85 d-100 HEI 2BBl
06 Toyota Corrola

Yes......running too hot with too much timing and fuel boiling can cause it to diesel especially on a stock low compression motor. As the compression is increased it helps to minimize run on.

Click on the red link below my name and take a look at the heat deflector under my carb.
It really helps allot.......the carb stays much cooler, never hot.
Having a electric fan to cool everything down after the engine is shut off helps allot too!
SL6Dan's fuel line mod is also great improvement.

Restarts after heat soak is immediate!

I run .045 gap on the plugs.

Running hot is great for best mileage but it easy to get too hot under the hood on the hotter 100 plus degree days.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG