new carb dieseling

[ryan.johnson]

Just installed a 1406 on a performance eps 2701 intake after numerous problems.
I put in the off road needles and seats and adjusted the floats on the carb before I installed it and am running a holley fuel pressure regulator around 5 psi peak.

I'm idling around 850 park 650 drive and timing is about 8-9 btdc - unless my distributor is off a tooth as I just changed the esc system out for a hei.

starts pretty slowly and the distributor is disconnected from vacuum and carb plugged- not sure if its normal but the ported side was whistling before i plugged it.

I've tried adjusting the mixture screws and that brought the idle down some, as well as the idle screw on the throttle arm.

its still dieseling something terrible, throwing fuel out once it stops turning over, and it sounds a little uneven.

will it sound different with a different carb on it? What can cause this dieseling issue?

thanks for the help.

 

[350runner]

Did you rebuild the carb, or is it new? Try making out the throttle screw more.

Sent from the dust in front of you!

 

[Thunder]

Normally dieseling is caused by a timing issue. Changing distributor to hei you might need to change your plug gap. Advance your timing a few degrees, see if that helps. Check your distributor and be sure you are not that one tooth off. You can move your plug wires back one hole, counter clockwise, and not have to pull distributor.

 

[ryan.johnson]

throttle screw is almost all the way out and the mixture screws are pretty far in, its a new 1406 with off road needles and seats.

advancing the timing to around 12 doesnt seem to make much of a difference. Do I need to go further?

also, whats a good idle range for park/drive?

 

[350runner]

I've found dieseling to be caused by to much opening off the throttle blades

Sent from the dust in front of you!

 

[bucket]

Where is the fuel coming from when it diesels? Bowl vent?

Get a vacuum gauge and set the idle mixture screws for highest vacuum. Speaking of that, it sounds like you may have a vacuum leak.

And also, there's really no such thing as having the dizzy off a tooth on an older engine with adjustable timing. You just rotate the housing to make up for it. If the timing lights says it's advanced * degrees, then it's advanced * degrees.

 

[Swims350]

You want 600rpm in gear and 800 in park idle too high idle is a big cause of this problem

 

[350runner]

How snug are the carb to intake bolts? May want to tighten them.

Sent from the dust in front of you!

 

[bmfp407]

i had a similar issuer and it ended up being a intake leak

 

[Swims350]

the main things that cause this...

idle too high

dist./timing advanced too far

and too low octane fuel or so they say.

any type of leak like vac. from carb to intake, or intake, or cracked or missing vac. lines, causes idle to raise and thus diesel.

best thing is a tach and if you don't have one then maybe try to pick up a dwell/tach meter setup, not sure where to get one or how much they are.

set your idle speed down to 800 in park, hok up the vac. gauge and tune the idle mixture screws on the front in until it starts to stumble which is clockwise, then out, which is counter clockwise until you reach the max rpm on that screw, then do the other,, then try to turn the first one out more to get more vac. or maybe in if going out fails, then repeat for the other screw.

reset idle speed to 800 and you're done.

if it's an all stock setup nothing really changed other then the carb, try to set it back to factory timing specs. then do all the carb stuff.

 

[chengny]

When you say this:

starts pretty slowly

Do you mean that the engine rotates slowly and with difficulty when cranking it over on the starter?

Do you ever get a kick back when the engine is hot?

If either of these is true, you are too far advanced on ignition timing. I see in post #4 that you are advancing the timing - that's the wrong way.

Ignore the timing marks for now. Retard the timing until you get a normal cranking speed when starting and the diesel effect goes away when you shut down.


Then start bringing the timing back in the advance direction - in small increments. Test drive after each advance. Keep doing this until you get a ping under a heavy load (or until you get kickback while starting).

 

[ryan.johnson]

Okay, dieseling has stopped. I pulled the timing back to what sounds right and checked it, around 8 degrees. I then tightened down the carb a bit more and loosened up the throttle linkage- which might have had too much tension and was cracking the throttle open.

Here's the last thing: I'm adjusting the tv cable for the 700r4. when I open up the throttle all the way should the choke open fully?

Right now if I have someone hold down the gas peddle i still have to bump the throttle arm to make it click all the way open.

 

[chengny]

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The TV cable should not be thought of as an automatic downshift cable. It controls line pressures, shift points, shift feel, part throttle downshifts, and detent downshifts. The function of the cable is similar to the combined functions of a vacuum modulator and detent downshift cable. The TV cable operates throttle lever and bracket assembly, Figs. 1 and 2.

1. Stop engine.

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2. Depress readjust tab, Fig. 3, and move slider through fitting, away from lever assembly, until slider stops against fitting. Release readjust tab.

3. Open throttle lever to full throttle stop position to automatically adjust cable, then release throttle lever and check cable for sticking or binding. Do not use accelerator pedal to rotate the throttle lever, rotate it by hand at the carburetor.

4. Road test vehicle. If delayed or only full throttle shifts still occur, proceed as follows:

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a. Remove oil pan and inspect throttle lever and bracket assembly, Fig. 4.

b. Check TV exhaust valve lifter rod for distortion, or binding in control valve assembly or spacer plate.

c. Make sure TV exhaust check ball moves up and down in conjunction with lifter.

d. Make sure lifter spring holds lifter rod up against control valve assembly.

e. Make sure TV plunger is not stuck.

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f. Inspect transmission for correct throttle lever to cable link, Fig. 5.

 

[deanobigred]

oh boy I cant wait, I have this problem and I have a manual choke 1406 carb, my question is if I have no idea of the history should I rebuild first ? as long as the choke is shut it runs (sounds) good when I push on the gas

 

[1987 GMC Jimmy]

When you push on the gas...? I'd say that if it looks bad, or if you know that the vehicle has sat for a long time, rebuild it. If it looks relatively new, or at least kept up, and you don't know if it's sat for a long time, what I'd do is I'd test the accelerator pump by actuating the throttle and looking into the primaries of the carb. You should get two healthy squirts of gas. Those squirts should also be proportional to the amount of throttle you give it. If you give it just a hair of throttle, you should get a drop out of both sides. If it's sloppy, odds are the accelerator pump diaphragm is failing, but if it's inconclusive, I'd work my way up the carb tuning totem pole. I attached a PDF of the owners manual for your carb that has tuning instructions in it. I would do the easy stuff with idle mixture and curb idle speed first to see if that cures everything. I use a vacuum gauge for that, but as you'll see, Edelbrock assumes you have a tachometer in the car, which I don't. That's what I'd try first unless you find a major fuel delivery problem in the aforementioned acc. pump test.

http://edelbrock.com/automotive/misc/tech-center/install/1000/1404_manual.pdf