Z24 Dieseling (Running on)

[NicktheMillwright]

Good afternoon

 

Title is pretty self explanatory, here's what I've tried:

 

- Adjusted timing

Resulted in a better running motor and better startup, but problem is persistent

 

- Changed spark plugs

Previous owner had the wrong plugs in the motor. Improvements in engine operation but hasn't helped the issue

 

- Ran a liter of water through the carb to clean it. (Weber 32/36)

 

-Adjusted idle position

 

Nothing here is helping my issue. I haven't tried changing the carb jet, I have however cleaned the hell out or the entire system

 

I'm out of ideals.

[powderfinger]

What is your idle RPM once the engine is warm?

[NicktheMillwright]

2 minutes ago, powderfinger said:

What is your idle RPM once the engine is warm?

Hard to tell, truck doesn't have a tachometer

[datzenmike]

Weber. Does it have an electric idle cut solenoid???? Someone will say, but depending on the Weber you may be able to retro fit the idle cut solenoid option. The idle cut solenoid when on with the ignition allows fuel down into the idle circuit. When the idnition is shut off so is the fuel and the engine stalls normally.

 

 

If not equipped, the simplest thing to do is when shutting the engine down, stop and hold brake on, put in 4th or 5th, let clutch up to load the engine down and hold there, turn off ignition. Engine will immediately stall but make sure you wait till totally stopped before releasing the clutch fully. Won't harm anything and a few tries and you will do this effortlessly every time.

 

 

 

Other causes of run on or dieseling could be...

 

Choke not shutting off, causing a rich condition.

Idle speed too high and not affected by the idle cut solenoid if you have one.

Carburetor is flooding, causing an over rich condition. Might be caused by too high fuel pressure.

 

[NicktheMillwright]

19 minutes ago, datzenmike said:

Weber. Does it have an electric idle cut solenoid????

 

 

If not equipped, the simplest thing to do is when shutting the engine down, stop and hold brake on, put in 4th or 5th, let clutch up to load the engine down and hold there, turn off ignition. Engine will immediately stall but make sure you wait till totally stopped before releasing the clutch fully. Won't harm anything and a few tries and you will do this effortlessly every time.

 

 

 

Choke not shutting off, causing a rich condition.

Idle speed too high and not affected by the idle cut solenoid if you have one.

Carburetor is flooding, causing an over rich condition. Might be caused by too high fuel pressure.

 

1. There is no idle cut solenoid on my carb from what I can see

 

2. I've been killing my engine in exactly this fashion since owning the truck. Worked so far but im not happy with it.

 

3a. This motor starts like shit when stone cold. I have to give it a bit of gas to get going.

 

3b. May be the idle speed but when it's running when warm it idles fairly low. If I had to guess in the 1000 range. I'll have to get a tachometer soon.

 

3c. Previous owner did replace the fuel pump, not sure if it's over-pressurizing the system. Could a inline regulator be used to resolve this?

[datzenmike]

See if you can retro fit an idle cut. I just don't know much about Webers.

 

 

 https://www.ebay.com/itm/362524140346

 

[powderfinger]

19 hours ago, NicktheMillwright said:

3b. May be the idle speed but when it's running when warm it idles fairly low. If I had to guess in the 1000 range. I'll have to get a tachometer soon.

 

With my weber it doesn't take much more than 1000RPM idle to make the truck diesel when shutting off. I used to bump the idle speed up on my weber in the warm weather months to be able to handle the load of the AC. If I shut the truck off without the AC running it would occasionally diesel.

[banzai510(hainz)]

try running SUPER in this and see what happens.

 

Most Webers sold are the manual versions and use the smaller idle jet.

Maybe even the newer elelctric ones are the smaller idle jet meaning it will NOT accept the idle cutoff selinoid.

 

the 32/36 DGEV-IC is the carb one has the selinoid.  as the threaded block has bigger hole to screw in for the selinoid.

 

If this has been since you had the truck you pretty much live with it.  The Stock carbs had the selinoid and most people have this issue when changing to a Weber w/o the cutoff. 

If motor still cold? does it still do this. Or in winter time?  ONly way to cheat this is maybe run a coller thermo stat to cool the head more but in Summer time it still might not help.

On my 521 I had this issue alot cause of running a L20head on a L16. then one day I swapped a distributor(L20 with Pertronix ignition) and it stopped doing it. I dont know really why but it worked. Before I swapped jets ect cooler stat and soem of it helped untill one has a 85deg day and dont matter. One time I ran a 38/38 with a cutoff and still would diesel. I assume it just pulled the gas thru the 2nd barrel I dont know.

Edited May 3, 2022 by banzai510(hainz)

[datzenmike]

3 minutes ago, banzai510(hainz) said:

try running SUPER in this and see what happens.

 

Most Webers sold are the manual versions and use the smaller idle jet.

Maybe even the newer elelctric ones are the smaller idle jet meaning it will NOT accept the idle cutoff selinoid.

 

the 32/36 DGEV-IC is the carb one has the selinoid.  as the threaded block has bigger hole to screw in for the selinoid.

 

 

 

 

 

Good info I wasn't sure.

 

Again easier to just use the clutch to stall the engine. Perhaps checking that the idle is around 700 will help.

[Thomas Perkins]

I have a Weber 32/36 K646 with the idle cut off solenoid and it runs perfect.I tried using the Red line one and it wouldn't work.They have came out with another,don't know if it work's.I tried my Weber without a idle cut off solenoid and it would not stay idled.The red line didn't work,still have it.So I bought a Empi 43-5350 Idle Cut-Off Solenoid from Ebay,it didn't come with a jet or a O ring,I bought some O rings from Harbor freight and took the jet off the Redline cut off solenoid and it works perfect.The jet on the idle cut off is a big one.Size is .155 and it is 5.94.On my old wiring,i have the connector with a bunch of wires,the blue wire goes to the choke,red wire goes to the idle cut off solenoid.You will have to get your dremlin tool and grind the piece by the hole to make solenoid fit in hole or you will strip the threads out.To test the solenoid,while it is running,just disconnect the wire and engine will die.Mine idles at 850 rpm.To start in the morning,just push gas pedal to floor  and release to lock cam in.Turn key and it starts ride up and the idle will go to 2000 rpm's and tap on gas pedal and it will go to 1100 rpm's and wait a minute and tap on gas again and it will go to 850 rpm's.When I get off work,say 12 hours later.I just turn key with no pushing gas pedal and it starts right up.You can adjust your fast idle speed.But you have no tac,so I just won't explain how to do it.I know the Weber like the back of my hand,Here is the site I bought my solenoid.https://www.ebay.com/itm/112735834481?epid=2100936924&hash=item1a3f945171:g:YtkAAOSwcwlf64NF also a good place to buy Weber parts is.https://www.carburetion.com/diags/3236DGAVDiaginfo.asp and another good site is...https://www.carburetion.com/diags/3236DGAVDiaginfo.asp.... I BOUGHT FROM BOTH...Also take off the big brass nut next to the fuel inlet line and put some Teflon tape on it or it will leak,Weber does not do it.Also have a new EGR valve.

Edited May 4, 2022 by Thomas Perkins

[NicktheMillwright]

14 hours ago, Thomas Perkins said:

I have a Weber 32/36 K646 with the idle cut off solenoid and it runs perfect.I tried using the Red line one and it wouldn't work.They have came out with another,don't know if it work's.I tried my Weber without a idle cut off solenoid and it would not stay idled.The red line didn't work,still have it.So I bought a Empi 43-5350 Idle Cut-Off Solenoid from Ebay,it didn't come with a jet or a O ring,I bought some O rings from Harbor freight and took the jet off the Redline cut off solenoid and it works perfect.The jet on the idle cut off is a big one.Size is .155 and it is 5.94.On my old wiring,i have the connector with a bunch of wires,the blue wire goes to the choke,red wire goes to the idle cut off solenoid.You will have to get your dremlin tool and grind the piece by the hole to make solenoid fit in hole or you will strip the threads out.To test the solenoid,while it is running,just disconnect the wire and engine will die.Mine idles at 850 rpm.To start in the morning,just push gas pedal to floor  and release to lock cam in.Turn key and it starts ride up and the idle will go to 2000 rpm's and tap on gas pedal and it will go to 1100 rpm's and wait a minute and tap on gas again and it will go to 850 rpm's.When I get off work,say 12 hours later.I just turn key with no pushing gas pedal and it starts right up.You can adjust your fast idle speed.But you have no tac,so I just won't explain how to do it.I know the Weber like the back of my hand,Here is the site I bought my solenoid.https://www.ebay.com/itm/112735834481?epid=2100936924&hash=item1a3f945171:g:YtkAAOSwcwlf64NF also a good place to buy Weber parts is.https://www.carburetion.com/diags/3236DGAVDiaginfo.asp and another good site is...https://www.carburetion.com/diags/3236DGAVDiaginfo.asp.... I BOUGHT FROM BOTH...Also take off the big brass nut next to the fuel inlet line and put some Teflon tape on it or it will leak,Weber does not do it.Also have a new EGR valve.

 

So heres what I'm going to do;

 

Firstly I've bought a pressure testing kit for the fuel pump as I'm unsure A, the brand of this pump and B, what the pressure is. Previous owner replaced it and in not convinced its running the 2-3 psi the weber requires. Replacing it accordingly if required or adding a regulator, whichever I feel.

 

Secondly, I've purchased both the Redline and Empi solenoids. If my 32/36 DVEG doesn't work with the redline one, I'll modify the Empi like Thomas has suggested. I have a different Weber from what I can tell, so it may work.

 

This way I can potentially eliminate the main culprit first before installing the surefire fix/preventative measure.

[datzenmike]

Cheaper to replace the fuel filter. Pressure tester might show low pressure which could be pump but could be pump struggling with a clogged filter. If pressure is fine then the tester was a waste and it's the carburetor with float  set too low, the inlet screen is plugged or the jet is plugged.

 

Did you check the fuel level in the float bowl? If full then NOT the pump. Again costs nothing to check this. 

[NicktheMillwright]

Ok so I have solved the issue thanks to our resident Weber guru, Thomas Perkins.

 

I took your advice, bought both solenoids and pulled the Jet and retaining O-ring off the weber and put it on the Empi. Works like a charm, I didn't have to adjust the Carb much, maybe a 1/8th turn in the idle mixture, and the truck shuts off perfectly. No more killing it with the assistance of the clutch.

 

Thank you all