1950 wd misses when warmed up.
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Category: Allis Chalmers
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Topic: 1950 wd misses when warmed up.
Posted By: Gulfsuper
Subject: 1950 wd misses when warmed up.
Date Posted: 17 Dec 2017 at 5:00pm
| Hey everybody, I need some help with a 1950 Wd. When it warms up it begins to misfire badly and if you shut it off it will not start until it cools of again. It has the six volt system with a distibutor. I have replaced the coil, plugs, wires, points, codensor, cap and rotor. Also ran a wire directly from battery to coil no change. This is a tractor I pickup about a year ago and has been rode hard, it came from a local apple orchard and put in many years of service. I am doing a preservation rather than a restoration to show the hard work she has done over the years. Any suggestion are greatly appreciated. |
Replies:
Posted By: DrAllis
Date Posted: 17 Dec 2017 at 5:14pm
| Spray some WD-40 or other penetrating oil around the intake manifold where is seats against the head while it is hot and acting up and see what happens. |
Posted By: LeonR2013
Date Posted: 17 Dec 2017 at 5:16pm
| Believe I'd do a redo on the coil and condenser. Also check the compression hot and cold. See if the head gasket is blown between two cylinders or more. Start with the simple stuff first. Has it been converted to 12V? Check your volt-a-drop. |
Posted By: DougS
Date Posted: 17 Dec 2017 at 6:28pm
| Could be a sticky valve too. That would show up during a hot engine compression test. |
Posted By: Gulfsuper
Date Posted: 17 Dec 2017 at 6:40pm
| Thanks for the suggestion, still a 6 volt system. It may have had a mag originally, it still has the mag kill switch that is disconnected, a toggle switch was added. What will happen with the wd40? |
Posted By: Gulfsuper
Date Posted: 17 Dec 2017 at 6:49pm
| I just replaced the coil last week and no change. When I got the tractor it had a carb problem and flooded badly. I had the carb rebuilt and did a complete tune up and service so I replaced all the electrical components at the same time and don't know if it was a previous problem. I have also replaced the generator and totally rewired the tractor, these were done after discovering the missing problem |
Posted By: Gulfsuper
Date Posted: 17 Dec 2017 at 6:54pm
| What would be an acceptable range for compression? |
Posted By: DougS
Date Posted: 17 Dec 2017 at 7:21pm
| If you have a bad cylinder or two you’ll know. The compression will be well below the good cylinders. |
Posted By: lentsch
Date Posted: 17 Dec 2017 at 7:27pm
|
Compression would depend on how worn the engine is. I would check for a difference in one or more cylinders. For example- 3 cylinders at 85 and 1 at 35 indicating a problem with that cylinder. What happens if you choke it or put a load on it when it misses? ------------- WD,D15,190XT,7000,8010x2,7060,8070 |
Posted By: Gulfsuper
Date Posted: 17 Dec 2017 at 10:02pm
| Haven't tried to choke it,but the more the load the worse the miss. |
Posted By: lentsch
Date Posted: 17 Dec 2017 at 10:55pm
|
The fact that it doesn't start when warm leads me to think it may be an ignition problem-maybe coil? Had one do that once. Could you put the old coil back on and try that? I assume you have checked the fuel system thoroughly-especially when it's warm and won't start? ------------- WD,D15,190XT,7000,8010x2,7060,8070 |
Posted By: dawntreader74
Date Posted: 17 Dec 2017 at 11:25pm
| the plug gap may be open to much try' 28 gap if open to much it's not good when hot' |
Posted By: Brian G. NY
Date Posted: 18 Dec 2017 at 8:54am
| I would take the good Doctor's advice! |
Posted By: Stan IL&TN
Date Posted: 18 Dec 2017 at 8:56am
The engine will smooth out and speed up. The intake manifold may be leaking or cracked as it heats up and thus sucking in more air and less fuel. If there is a leak it will suck in the WD40 and burn it. ------------- 1957 WD45 dad's first AC 1968 one-seventy 1956 F40 Ferguson |
Gulfsuper wrote:Posted By: Sugarmaker
Date Posted: 18 Dec 2017 at 4:32pm
|
Well you may have one or more issues. I am sure not a expert. But I do know that these will run when a lot of things are out of whack. (that's a technical term too):) I think I would check for spark and gas both, when it wont start next time. Regards, Chris ------------- D17 1958 (NFE), WD45 1954 (NFE), WD 1952 (NFE), WD 1950 (WFE), Allis F-40 forklift, Allis CA, Allis D14, Ford Jubilee, Many IH Cub Cadets, 32 Ford Dump, 65 Comet. |
Posted By: Steve in NJ
Date Posted: 18 Dec 2017 at 6:24pm
|
Sounds like a vacuum leak or a valve hangin' up when it gets warmed up... ------------- 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: Gulfsuper
Date Posted: 18 Dec 2017 at 6:28pm
| Thanks for all the great info and suggestions. It has good voltage and spark at the points when it won't start. The cap rotor and points all look like they are burning clean, no residue or odd looking burn marks. I am pretty sure it is not fuel related, when it starts to miss it seams like your turning the ignition switch on and off. It will almost completely die and then backfire. I could try the old coil again but the new one made no difference. I am going to get a compression gauge and check the cylinders, like I said this tractor is well used. I am going to try a new set of points and codensor. Any suggestions on reliable manufacturer? What exactly does the codensor do? |
Posted By: DougS
Date Posted: 18 Dec 2017 at 7:10pm
| I'd do a compression test before I replaced anything. A coil can be heat sensitive, but I'd not think a condenser would be so much. |
Posted By: Gerald J.
Date Posted: 18 Dec 2017 at 7:21pm
|
The condenser makes a resonant circuit with the coil primary so the current interrupted by the points oscillates and that is what makes a fat blue spark. In air that blue spark should be more than 3/8 long. In the process the condenser keeps the points from arcing and wearing asymmetrically as the condenser keeps to voltage down while the circuit is oscillating. Some condensers are temperature sensitive and some can't handle the voltage and they get shorted by the high voltage. They tend to recover poorly but I have heard of them recovering when cooled for a while, like 15 or 20 minutes. Gerald J. |
Posted By: steve(ill)
Date Posted: 18 Dec 2017 at 7:22pm
|
Thanks for all the great info and suggestions. It has good voltage and spark at the points when it won't start. Pull out a couple plugs and make sure they are sparking.... but it does not sound electrical if you have good spark. ------------- Like them all, but love the "B"s. |
Posted By: Gulfsuper
Date Posted: 18 Dec 2017 at 7:32pm
| I'll try and do a compression check tomorrow, if they are close when it is cold I'll check it again when it is warm and starts missing. It doesn't smoke or burn oil, the plugs are clean and look like they are burning clean. Thanks for the condenser explication, I never was sure how it worked |
Posted By: TimNearFortWorth
Date Posted: 19 Dec 2017 at 6:22am
| A good dose of Seafoam in the engine may help on sticky valves; get her warmed up, add Seafoam (full can . . . .) and get her good and warm. Drop oil/filter and let her drain good before adding new oil. Change filter again after running new oil after 1-2 hours as Seafoam can "break down" old deposits that can restrict screen on pickup. Good idea to keep an eye on oil pressure while doing this. |
Posted By: cpg
Date Posted: 19 Dec 2017 at 8:15am
|
Just to throw it out there a few years ago I put new points and condenser in my B (wouldn't even start anymore with the old ones) and with the new tune up it ran great for the first probably 30 minutes of run time and progressively got worse and worse to where I could barely get it to fire anymore. Returned the points and condenser and got another new set and put it in and that was 3 years ago. It is a crap shoot sometimes with the quality of these replacement points and condensers and even coils depending on where you got it so just because you just replaced it don't totally rule it out in your mind if you don't find any other issues. |