Engine "Run-On" ??
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=166940
Printed Date: 17 Jul 2025 at 6:41am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Engine "Run-On" ??
Posted By: FREEDGUY
Subject: Engine "Run-On" ??
Date Posted: 26 Dec 2019 at 4:23pm
What is the "main" reason for the "run-on/dieseling" of a gas engine?? We run a '68 model year 180 gasser that runs FLAWLESSLY during "work "loads, but come time to turn the key off, tends to want to "carry-on"  . Is this a timing issue or carb issue or the nature of the straight 6 ?? Thanks
Sorry, it's a '69
|
Replies:
Posted By: john(MI)
Date Posted: 26 Dec 2019 at 4:42pm
|
Timing, a little advanced if I remember correctly. ------------- D14, D17, 5020, 612H, CASE 446 |
Posted By: dawntreader74
Date Posted: 26 Dec 2019 at 4:47pm
|
had one doing that' sounds like the time;in is retarded some' may need to be advanced a little bit.. |
Posted By: FREEDGUY
Date Posted: 26 Dec 2019 at 5:02pm
But it starts/runs SOOOOO smooth  , it's just the shut down even after letting her sit and idle for 3 minutes or more?? She LITERALLY just PURRS during operation.
|
Posted By: Ed (Ont)
Date Posted: 26 Dec 2019 at 5:13pm
|
Could be a lot of things. Deposits on pistons or valves could be cause. Timing as already mentioned. Check the advance weights on distributor to make sure they are free. Check spark plugs to make sure they are clean and correct heat range. Time it properly with a light. Check idle speed and set as per manual. Too fast idle may cause that problem. Inline 6 cyl probably around 650 or so. I’m sure some one will give you the exact setting. Sometimes just letting it idle a bit before you shut it off helps. If you can’t find solution put in hi gear. Shut off key and snuff with clutch.
Sorry I see you are already idling it down! Lol.
|
Posted By: injpumpEd
Date Posted: 26 Dec 2019 at 5:26pm
|
Not sure how timing will affect it "dieseling", since the ignition system is shut off. Many carburetors have a solenoid in the main jet which is called an "anti-dieseling solenoid" once key is shut off, the solenoid closes and cuts off fuel from flowing through the nozzle. Carbon deposits can cause it, too hot of plugs may too, but idle speed can very much do it. I'd bet the gas is supposed to idle below 600, possibly even 500. The diesels idle spec is 600. I'm a diesel guy now days, but sure have messed with my share of gas engines lol! ------------- 210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers! |
Posted By: FREEDGUY
Date Posted: 26 Dec 2019 at 5:41pm
Greatly appreciate your input !! New plugs,new wires,new cap, new points, new condensor AND new carb (not rebuit). If memory serves, the good DOCTOR said this particular engine was not too friendly to accessing the timing marks on the crank and he was 100% correct !! It's done this for the 14 years that we've owned it,the only other "ignition" we encountered wasa with a D 15 that would "almost" lock up during the starting procedure ( 2 fast revs, then a sudden stall of momentum, the BANG, it was running).
|
Ed (Ont) wrote:Posted By: wide
Date Posted: 26 Dec 2019 at 9:45pm
|
Idle too high? |
Posted By: tbran
Date Posted: 26 Dec 2019 at 10:13pm
|
gas engines 'dieseling' as stated , has nothing to do with ignition system - unless your key is bad - when you turn the key off it stops firing. Now, when the plugs stop firing the engine is still running probably 600 rpm approx. Air and fuel is still being pushed into the engine - IF the engine has high compression and is hot , any bit of carbon, spark plug debris, or other item that remains a hot spot will act as a spark plug and ignite the fuel. (if the timing is WAY out it could cause the plugs to overheat - the engine usually will self destruct if it is run long term like this - unless you just worked on the timing this is very unlikely) The remedy will lie in plug replacement to a colder plug if that is the culprit , adding anti carbon additives like seafoam or other products for a long time - not jus a one shot deal - or you can do what I do with my gas high compression engines that do this - back the screw out of the idle stop to the point where when the throttle is jammed tight shut -it kills the engine even with the key on.. shutting off the fuel ( as mentioned some carbs - as in the deere and massey line- had anti diesel electric $olenoid$ in the main fuel jet to shut off the fuel) will stop the run on. An engine will not run w/o fuel. If you do have one that does - apply for a patent, quick - and run for president... ------------- When told "it's not the money,it's the principle", remember, it's always the money.. |
Posted By: SteveM C/IL
Date Posted: 26 Dec 2019 at 11:07pm
| My 45 will try to do it if just a hair too much idle speed,but it doesn't sound nice at all! Good way to break ring lands and if severe enough, crack cranks. Slow the idle down. A 6 ought idle at 450 rpm pretty easy,maybe less. |
Posted By: PaulB
Date Posted: 27 Dec 2019 at 5:46am
|
Incorrect timing will most likely cause you to have the carburetor idle speed and mixture set incorrectly, getting everything set correctly should allow the engine to stop when allowed to idle for a couple minutes before turning the key off. Poor quality gas can also be part of the problem. ------------- If it was fun to pull in LOW gear, I could have a John Deere. Real pullers don't have speed limits. If you can't make it GO... make it SHINY |
Posted By: jaybmiller
Date Posted: 27 Dec 2019 at 6:33am
|
Without coil power to spark the plugs, the only way I know for it to run is hard carbon deposits in the cylinders. They act like little, intense glow plugs .the 'fire in the hole' needed for the big bang. Two ways to remove... 1- pull the head and scrape them off, 2- chemically. I've heard that if you drip water into the intake at just the right rate, it'll 'steam clean' the carbon out. has to be fast idle and lots of water, almost to stalling it. Whatever method you decide on do it NOW before the engine handgrenades !! ------------- 3 D-14s,A-C forklift, B-112 Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
Posted By: john(MI)
Date Posted: 27 Dec 2019 at 7:05am
|
Back in the 70's it was almost normal for cars and trucks to diesel. And that was new and with the ignition turned off. It was always said to be caused by the timing being advanced. Although, it didn't matter what you did, they would still diesel. If I remember correctly(Questionable) it was about the same time they made the switch to unleaded gas! ------------- D14, D17, 5020, 612H, CASE 446 |
Posted By: Tbone95
Date Posted: 27 Dec 2019 at 7:50am
| john is right. I remember TV ads for stuff that addressed "engine run on". Personally, I had a 1980 F 150 straight 6 that was a champion at it for a while! Messed with timing and carb settings and even changed out carbs and finally a vacuum leak somewhere knocked the rest of it out. |
Posted By: TimCNY
Date Posted: 27 Dec 2019 at 8:02am
|
OK laugh away but I shut off the fuel at the sediment bowl and let it run out of gas then shut off lol. Never diesels! [<:o)] ------------- I need more than 200 characters for my "signature." I'd love to see that changed to 250! |
Posted By: Dave H
Date Posted: 27 Dec 2019 at 8:17am
Ding ding, winner winner chicken dinner.
|
Posted By: jaybmiller
Date Posted: 27 Dec 2019 at 9:48am
|
probably take 5-10 minutes to stop ? In that time, engine cools down and carbon stops glowing so dieselling can't occour ?? ------------- 3 D-14s,A-C forklift, B-112 Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
Posted By: TimCNY
Date Posted: 27 Dec 2019 at 11:00am
|
Rarely more than a full minute and a half, at slow idle. Otherwise no, sometimes at half throttle and always less than a minute that way, at least by my reckoning but honestly I don't pay attention, the only thing I DO pay attention to is turning the key off once it stops. It just works for me and I don't like having gas in the bowl if it's just going to be sitting for extended periods. Doesn't hurt, just turn gas on, turn the key and sometimes (most times?) it fires up and never even hear it crank. At most, ever, a full revolution before firing. Argue with that lol! Works for me, not gonna change it. ------------- I need more than 200 characters for my "signature." I'd love to see that changed to 250! |
Posted By: FREEDGUY
Date Posted: 27 Dec 2019 at 5:09pm
I appreciate all of the replies, sadly 2 of the posters don't realize where the shut off valve is on a 180  . Might look into the the chemical additives for carbon build-up. No, the timing has never been tweaked since we've owned her; 11 years. She idles at 510 rpm BTW.
|
Posted By: Dave H (NE)
Date Posted: 27 Dec 2019 at 5:33pm
|
idle speed should be 400 to 450 rpm from ac service book |
Posted By: FREEDGUY
Date Posted: 27 Dec 2019 at 5:47pm
Thanks for that, I will make an adjustment
|
Posted By: SteveM C/IL
Date Posted: 27 Dec 2019 at 9:18pm
| You need to put a big ole plow on it and WORK it. That will fix your carbon issue. |
Posted By: wekracer
Date Posted: 28 Dec 2019 at 6:33am
|
We have an 89 Chevy tandem dump truck with a 427 gas engine. With 15 tons in the bed it weighs 54,000. It is the worst for dieseling that I have ever seen. It will diesel for what seems like 30 seconds. We have a mechanic up the road that does the maintenance on it. It runs good and sounds good. Even if you let it cool 10-15 minutes it will still do it. We just put it in gear and turn the key of and gently let the clutch out. |
Posted By: TimCNY
Date Posted: 28 Dec 2019 at 7:27am
Well shoot, I had threads mixed up. You're partly right, I just forgot this thread was regarding a 180. My apologies. ------------- I need more than 200 characters for my "signature." I'd love to see that changed to 250! |
Posted By: FREEDGUY
Date Posted: 28 Dec 2019 at 4:49pm
LOL!! , sadly dad sent the White 508 down the road 13 years ago
 . Granted the 180 unballusted wouldn't pull the old 5/16 . It's the planting/auger(8x51) and summer "bush hog" mowing tractor  |
Posted By: FREEDGUY
Date Posted: 28 Dec 2019 at 4:53pm
You have NO reason for an apology, any input is "normally" good input
 . Have a great new year !!! BTW, the shut off location/access on a 180 leaves ALOT to be desired |
Posted By: captaindana
Date Posted: 28 Dec 2019 at 7:30pm
|
We also had a new 180G in 1970 and ran it for 5000 hours before trading it in for a larger workhorse. It too dieseled as stated above during every shutdown until we, like wekracer , simple stalled it gently only by shutting off the key and pulling back on the lift arm hydraulic control lever. Worked for me. Dana ------------- Blue Skies and Tail Winds Dana |
Posted By: Adam Stratton
Date Posted: 28 Dec 2019 at 9:13pm
| Have a nearly identical setup acts the same way. Never been a big deal but then i got in a hurry in a rainstorm... Drove it in the shed, killed it in gear and jumped out to get the combine in out of the rain. It dieseled backward before i even got the door slammed. Instead, the door caught the support pole of the shed and got turned into an ugly accordian! Glad it was the door instead of me, but was a strong reminder of how a little thing and a big hurry can cause problems. |
Posted By: Steve in NJ
Date Posted: 28 Dec 2019 at 10:03pm
|
Back in the early 70's, cars and trucks used to "run on" for 10-20 seconds or so due to the higher compression ratio's and the introduction of unleaded fuel. GM added a shut down solenoid up at the Carburetor to correct the run-on problem. This solenoid was activated by the key switch. When you turn the key on, 12V's was sent to the solenoid which activated the solenoid to push out its plunger and open the throttle blades just a tick to start the engine. When shutting the engine off, the plunger would pop back in (12V's gone) and close the throttle blades completely shut. This cut the air off which stopped the engine from running on. These solenoids were pretty easy to install and would work pretty much on any engine. The reason the engine ran on is because of the throttle blades being held open by the idle screw, allowing air to rush in past the throttle blades and pull fuel vapor from the idle circuit to keep the engine running for those 20 seconds or so. I've used these solenoids on everything from stock cars and trucks to hotrods. They always worked. I believed they were called "aniti-diesel solenoids" or "Idle Stop Solenoid". They were also used on air conditioned cars that when the A/C was turned on, the solenoid would kick the throttle up a tick to compensate for the load put on the engine when the A/C was activated. The engine running a little hotter than normal would also make the engine run on. Might want to try one of those... HTH Steve@B&B ------------- 39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife |
Posted By: DaveKamp
Date Posted: 29 Dec 2019 at 12:00am
|
The reason the engine continues to run, is autoignition. Autoignition is when a combustible mixture is above the given temperature and pressure at which it will ignite all by itself. Autoignition is the concept behind a Diesel engine- compression raises pressure and temperature high enough, so that when fuel is injected in fine mist, it autoignites. Autoignition occurs in spark-ignited engines as a result of either a hot spot in the engine, excessive compression, or an exceptionally volatile fuel (like... very high in light fractions, and substantially less heavies). The very first thing I would do, is back off the ignition timing by about two degrees, and verify that the centrifugal spark advance mechanism is properly operating. If this has no effect, I would remove the plugs, and replace with the next lower heat range, and try again. A 'colder' plug has an electrode insulator design that more rapidly transmits heat from the center electrode to the cylinder head. IF the center electrode is getting too hot, it will serve as the hot surface ignition point. If the GROUND electrode is getting too hot, then you've got a different scenario... the plug threads are not conducting heat fast enough to the head. Wire brush them, and reinstall with no anti-seize or other compounds that would impede heat flow. ------------- Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest. |
Posted By: CTuckerNWIL
Date Posted: 30 Dec 2019 at 7:21am
|
Ran a can of Sea Foam thru the gas tank, working(like plowing or some kind of tillage work) the engine while you do it. It will help clean out the carbon build up that acts as a glow plug. ------------- http://www.ae-ta.com" rel="nofollow - http://www.ae-ta.com Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF |
Posted By: FREEDGUY
Date Posted: 30 Dec 2019 at 6:13pm
I am a HUGE believer in the SEA FOAM !! I have ran several 16 ounce cans through her in the past 3 years. I have a feeling it just doesn't get "worked" hard enough
. Even pulling the 4x30 JD Conser-Till planter with both dry fertilizer boxes heaped is childs play with it . Thanks again to all that replied !! |
Posted By: Brian Jasper co. Ia
Date Posted: 31 Dec 2019 at 12:05am
|
There are several reasons for dieseling, glowing bits of carbon, stopping the engine with the throttle above idle, and LATE timing. How can late timing be the cause because when you turn off the engine you're turning off the spark? The reason is LATE timing causes the engine to be less efficient. It requires the throttle to be opened farther than intended giving the engine more fuel/air to burn just to maintain idle speed. This also generates more combustion chamber heat. More fuel/air in the presence of more heat makes for ideal conditions for dieseling. By advancing your base timing, you improve engine efficiency by giving less fuel and air more time to burn. Because of the smaller requirements to idle, the throttle plate(s) are not open as far, and the combustion chamber is not as hot, so the conditions for dieseling are not ideal. Indirectly, timing most definitely has an effect. ------------- "Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford |
Posted By: SteveM C/IL
Date Posted: 31 Dec 2019 at 10:03am
| Sooo.....did you ever drop the idle speed and what was the result. Do we have to wait til spring for an answer? |
Posted By: FREEDGUY
Date Posted: 31 Dec 2019 at 4:08pm
|
Won't get out to the farm for another week,NO,haven't had a chance to drop the idle,and am seriously looking into borrowing/renting a timing light to see what's going on. Just out of curiosity, what's the "service manual" spec for the timing on a '69 2800 gasser and at what rpm?? Seems like Doc stated an rpm but I have not been able to find the post. The 180 is in hibernation as far as "work" until April,BTW . HAPPY NEW YEAR !!!
|
Posted By: Dave H (NE)
Date Posted: 31 Dec 2019 at 6:12pm
|
26 @ 2200 rpm for G2800 |
Posted By: LeonR2013
Date Posted: 31 Dec 2019 at 6:37pm
| Check the dist shafts for wear, or even the governor weight for excess play. It seems like an awful long time for it to run for all these years though. Has someone overhauled it and made a hot rod out of it? Sounds like it has an awful lot of power. Put it on a dyno and see how many HP it is making. Just a thought. Leon |
Posted By: Acdiesel
Date Posted: 01 Jan 2020 at 11:38am
|
maybe not your case but, customer had a d17 ser.4 that ran on after key was turned off, found issue to be with a bad wire off the alternator causing the cold side of the ignition switch to stay hot and still getting spark, if you forced the throttle lever it would idle low enough that the alternator wasn't putting out and the engine would shut off. (There wasn't the typical dieseling sound in this case) Dan ------------- D19 Diesel,D17 Diesel SER.3 2-D14, 2-D15 SER.II WF/NF D15 SER.2 DIESEL D12 SER.I, D10 Ser.II 2-720'S D21 Ser. II Gmc,caterpillar I'm a pharmacist (farm assist) with a PHD (post hole digger) |
Posted By: FREEDGUY
Date Posted: 01 Jan 2020 at 4:07pm
Funny you should bring this up,
. The guy we bought it from(jockey) claimed it had been O/H'd within 200 hours of us buying it( it was sooooo rough looking I told dad to BAIL) so dad jumped. 2 years after we ran it it went in to a local independent for a main clutch and after assembly he put it on a dyno and said she puts out 74 HP . I took compression readings after brought home and all 6 cylinders were 135-138 PSI. Uses NO oil and minimum blow-by. Seeing oil seepage off of the front cover though . |
Posted By: wayne IA
Date Posted: 07 Jan 2020 at 11:55pm
| As ACdiesel mentioned, usually most ignition systems have a diode in them to prevent back feeding from the alternator. If the diode fails to a short, or is removed it will back feed on the ignition side and keep running like if the key is on. Local repair shop makes plugs with a diode in them to replace the defective diode. If the engine is slowed to a low enough rpm, then the alternator can get to where it won't make the small amount of power to keep the ignition alive and the engine will stop normally with the key. |
Posted By: DrAllis
Date Posted: 08 Jan 2020 at 8:16am
| I don't have my service manual in front of me, but compression should be 170 psi for a standard 180 with 265 cube gas engine. HP can never be more than 64 HP Nebraska Test rating unless it has a larger carb on it, more RPM than stock or more cubic inches. |
Posted By: FREEDGUY
Date Posted: 08 Jan 2020 at 6:11pm
To my knowledge, it's the original 2800 engine, we installed a NOS carb that crossed with the original AGCO part # last summer, have NO clue how the independent came up with his HP rating -he runs an MW dyno if it's a factor- and high idle is 2100 'ish ? I/we try not to approach higher than 2000. Like I said, she's a planter/auger/brushhog "princess", no heavy tillage at all. In fact,the calcium was drained when it was first bought due to HORRIBLE tire tread/rusted rims . It's not even set up with factory wheel weights. Thanks for the information, like I said, when I saw it at the sellers property, I BEGGED dad to let her set
. Amazingly, after "somewhat" minimal major repairs( the double split to repair an input/output shaft with bearings was costly), a very reliable tractor, just the run-on issue. |
Posted By: DrAllis
Date Posted: 08 Jan 2020 at 6:59pm
| One-Eighty's and One-Ninety's are a G-2500/265 cube engine. They are identical except for carb size and 2,000 RPM rated speed versus 2,200 RPM rated speed. The One-Ninety XT gas is a G-2800/301 cube engine with an even larger carburetor. |
Posted By: FREEDGUY
Date Posted: 08 Jan 2020 at 7:47pm
| My mistake, it's a 2500. Still unsure about the HP reading from the "local" mechanic? Even he was impressed. |