Wierd sound when shut off??

[_chiefjt]

So my weber 38 been great but just today my truck makes a sound when I shit it off. After driving it when I turn it off it sounds like it dies out (rocks the truck back and forth) and then makes a hissing sound. But it starts right up every time, idles good, idles at 2,000 rpms on cold start, haven't hooked up the emissions stuff yet.

 

I want the emissions hooked up on it so I can see if it'll pass smog. The vapor canister isn't hooked up so it builds pressure in the tank. I'm thinking that could be the problem? All I need is that little copper looking port to the carb, to hook up the EGR.

 

Any help, thanks

[Tristin]

That sounds like youre dieseling. There is a high amount of fuel still in the cylinders that hasnt burned off, so even though you turn the car off (removing spark for ignition), its still so hot in there that its igniting the unused fuel. 

[ggzilla]

Lots of engines do that. Not a problem. Just make sure the idle speed is correct (750 rpm)

 

To vent the tank, simply unplug the vent line. It doesn't need to be connected to anything.

After driving it when I turn it off it sounds like it dies out (rocks the truck back and forth) and then makes a hissing sound.

[_chiefjt]

Okay, thanks.

[Tristin]

I wouldnt quite say its not a problem... the engine isnt suppose to do it, but it does happen. I want to say that the 720s had anti-dieseling solenoids which is suppose to minimize that happening. You can also look at leaning out your carb some as well. 

[Sealik]

Some Webers come with anti-dieseling solenoids....not needed

 

Dieseling/run on...........

Timing is too far advanced......3-5 degrees BTDC is recommended

Engine is above normal operating temp

Idle speed is in-correct

[Tristin]

Yep. Some people just basically clutch-stall it when they turn it off instead of just shutting it down normally.

[ggzilla]

Open chamber head. Nothing will fix it short of fuel-cut solenoid.

[Sealik]

Been running the 32/36....38 Webers for years with no idle cut.....no issues.

It will sometimes run on though if idle speed is above 950...hot engine etc.

[wayno]

Yep. Some people just basically clutch-stall it when they turn it off instead of just shutting it down normally.

Yep, this is how I shut mine off, and have been for over 15 years, one gets tired of putting so much effort into trying to fix something that don't really need fixed, just shut off the engine and let out the clutch at the same time, very soon you won't even notice doing it that way. :)

[Kingman]

That's exactly what I do with my Weber. I haven't jetted it properly yet so it likes to diesel sometimes but runs good otherwise. Did it twice after I put it on and I thought "well I know exactly how to fix that problem!"

[ggzilla]

Jetting it wont stop the deiseling

[Mr.Dean_Yates]

I had the same issue...I also had another issue that followed... truck just shut off. Look in the passenger side kick panel under the dash an take the fuel pump relay out. Take it to some one who knows how to solder computer chips and fix all the cracks.

 

This solved both my issues.

 

As far as passing emissions, I've heard you can put some e85 in and you can pass.

[_chiefjt]

yeah, I got it to pass and was running 91 octane. Been running higher octane ever since I put the weber on. 

 

Doesn't diesel anymore.

[Phixius]

Hot spots can cause dieseling and also pinging.  Pitted pistons or carbon build up can cause a hot spot, where theres a point/tip of metal or build up will glow red hot and be your new ignition source. Higher octane is harder to ignite, so you might have stopped the dieseling, but your problem is still there... 

[72240z]

The throttle not returning 100% can also cause it. 

Dieseling can cause damage especially over time. 
Clutch stalling doesnt do any real harm and I know is a long held method but it def wears on some things more. The clutch wear from it is prob negligible but the motor mounts and stuff? Forcing the motor to an abrupt stop just cant be good in my opinion. Even though I know it can be said lots of people do it for years and years and yada yada yada 

I was having to shut my Z down that way It hought because I built the L28 with pretty high comp and with dcoe's you have to advance the timing a good deal. Just Didn't like doing it, went back and tightened up the throttle linkage, return etc.. and its stopped. Much better... 

[_chiefjt]

Thanks for the info. Hopefully we can fix up this Ford Focus so my mom can use that instead of my truck. Then, onto the motor rebuild. But for now I'm keeping up with the maintenance.

 

Gonna get a whole new exhaust system, tranny mount, strut rod and control arm bushings, upper and lower ball joints (which are SHOT), wheel bearings, brake lines. Just replaced the center support so now the rear end is leaking, gotta change that seal this weekend.

 

LOTS of things that PO didn't take care of, Or anybody who owned it in the past didn't take care off. It's all still the OG bushings, lines, mounts and stuff.

[ronnny]

Yep, this is how I shut mine off, and have been for over 15 years, one gets tired of putting so much effort into trying to fix something that don't really need fixed, just shut off the engine and let out the clutch at the same time, very soon you won't even notice doing it that way. :)

 

Not saying this is not a problem that should or could be fixed but i turn mine off this way without thinking anymore.  all 3 that i have/had has done this.  did not take the time to find out why.  will have to remember what people have said in this thread so when i get motivated.