No Spark from Distributor Cap, Has Spark from Coil

Ajgasper

New User
I have a MF 135 with a Perkins 3cyl gas engine (AG3.152). It started running rough. I rebuilt the carb, replaced filters, sediment bowl and gas lines, and cleaned the tank. Compression testing was 85, 99, and 100 PSI on 1, 2, and 3 cylinders respectively. Still ran rough, and eventually became harder and harder to start until now not starting. I finally checked for spark and there was none.

I get spark from the coil, but nothing out the distributor cap. I've replaced the condenser, points, rotor, coil, and distributor cap 3 times and plug wires and ignition twice. I've moved the dwell 180 degrees in both directions to try and get a spark with no results. I've also swapped the distributor with no results.

Does anyone have any ideas of what to try next?

Thanks
 
I suggest buying an inline spark tester ($8 at and auto parts store). You will see the spark much
clearer while having both hands free.
A WAG is bad condensers (not unusual to find bad ones right out of boxs) or you forgot to install
rotery button.
one of these
 
I've been using an inline tester for spark. Bought one several years ago for an 8N, and for small engines on chainsaws and mowers. Definitely a lot easier/better to use than holding the wire if you can't see the spark :lol: .

I've had the distributor cap off and on so many times I'm starting to wear out screw heads. So one or more times I may have forgotten to replace the rotor button, but not each time.

I've tried three different condensers, two of them new. I can get some more to try. However, I may be wrong here, if the condenser was bad, would it not affect the spark from the coil, and not from the distributor cap. I'm getting spark from the coil.

Right now I'm I'm trying to figure out how to hook the inline tester up to test through the distributor to the rotor button. I think I figured out a way to test the rotor button by holding the coil wire to the spring on top of the rotor button, and then holding the inline tester to the probe on the rotor that makes contact within the distributer cap. Probably going to need my wife for that one, but if all else fails I'll use her finger to see how high she jumps if I get juice.

Thanks
 

Some review and clarification please as we aren't there to see what you are seeing, as you have worked on this. These may seem self-explanatory, or stupid, but sometimes there can be a clue.

You say you get spark out of the coil. How are you checking that? Are you holding the distributor end of the coil wire close to the engine block? Are you using your spark checker between the coil wire and block or in line to the distributor? What type of spark checker do you have (adjustable or non adjustable gap)? How far will the spark jump and what color is it?

Likewise what is your procedure/set up for checking for spark from the distributor posts to the spark plugs? Are the wires solid core or carbon core, resistor type?

The rotor button's spring contact, on the top of the button, should be in contact with the center, coil wire, post in the distributor cap. There should be a small gap between the solid end of the button and the plug wire terminals inside the cap, that the spark has to jump. If the solid end of the button were to contact the plug terminals it would lead to broken rotors and caps.

Is there a chance the new caps and rotors are the wrong ones? Are the new parts identical to the old ones it had been running with prior to the no start condition? Sometimes cross references are wrong. Are you using every other hole in a 6-cylinder cap or are you getting the true 3-cylinder caps? If a 6-cylinder cap could you be in the wrong set of holes? What are the brand(s) and part numbers of the new parts you are using?

Dwell angle, normally measured with a dwell meter when running, relates to how long the points stay closed between openings. I doubt you turned the dwell 180 degrees. Do you mean you turned the timing 180 degrees? Please explain. Have you physically checked #1 at TDC on its compression stroke to see that the rotor position matches?

Have you turned the engine over with the distributor cap off, and watched to see that the rotor turns as the engine turns? You say you changed distributors, but if something happened to the cam or gears it might not be turning properly.

Just some thoughts and things to look at.
 

No problem.

I'm checking the spark both ways out of the coil by using the spark checker between the coil wire and block, and in line to the distributor; using a non adjustable gap (by hand). The spark jump seems to be an 1/8th or 1/16th inch jump (maybe less). The color appears blue closest to the tester, and yellow at the block.

I remove the spark plug wire and inserted one end of the tester on the plug, and the other end into to spark plug wire. The wires are solid core copper made in the USA, and don't believe they're resistor type?

I believe the rotor button's spring contact, on the top of the button is in contact with the center, coil wire, post in the distributor cap; but don't know if there is a way to test/check. The same with the small gap between the solid end of the button and the plug wire terminals inside the cap.

The new caps and rotors seem to be identical to the old ones. I've measured using a straight rule as best I could, and they seem the same. Definitely a 3-cylinder cap.

I bought a second set of parts from the Brillman Company close to my home. The parts were:

3 Cylinder Perkins Distributor Cap B4003-058
Delco Remy (D-205) Distributor Condenser B4002-012
Autolight/Prestolite Distributor Contact Points B4001-012
Delco Remy (D419R) Distributer Rotor B4004-013

I don't know right now what the previous new parts were.

Definitely the dwell. May not have been a full 180 degrees, but close. I'll check the TDC for the compression stroke again. It's been a while since I double checked. I take the valve cover off to check the #4 valve being opened/closed as the manual says since I have a hard time seeing into the inspection hole whether I'm at TDC or TDC-1.

Yes, I turned the engine over with the distributor cap off, and watched the rotor turn as the engine turned.

Thanks, this is helpful.
 
(quoted from post at 10:09:47 08/26/20)
No problem.

I'm checking the spark both ways out of the coil by using the spark checker between the coil wire and block, and in line to the distributor; using a non adjustable gap (by hand). The spark jump seems to be an 1/8th or 1/16th inch jump (maybe less). The color appears blue closest to the tester, and yellow at the block.

I remove the spark plug wire and inserted one end of the tester on the plug, and the other end into to spark plug wire. The wires are solid core copper made in the USA, and don't believe they're resistor type?

I believe the rotor button's spring contact, on the top of the button is in contact with the center, coil wire, post in the distributor cap; but don't know if there is a way to test/check. The same with the small gap between the solid end of the button and the plug wire terminals inside the cap.

The new caps and rotors seem to be identical to the old ones. I've measured using a straight rule as best I could, and they seem the same. Definitely a 3-cylinder cap.

I bought a second set of parts from the Brillman Company close to my home. The parts were:

3 Cylinder Perkins Distributor Cap B4003-058
Delco Remy (D-205) Distributor Condenser B4002-012
Autolight/Prestolite Distributor Contact Points B4001-012
Delco Remy (D419R) Distributer Rotor B4004-013

I don't know right now what the previous new parts were.

Definitely the dwell. May not have been a full 180 degrees, but close. I'll check the TDC for the compression stroke again. It's been a while since I double checked. I take the valve cover off to check the #4 valve being opened/closed as the manual says since I have a hard time seeing into the inspection hole whether I'm at TDC or TDC-1.

Yes, I turned the engine over with the distributor cap off, and watched the rotor turn as the engine turned.

Thanks, this is helpful.

As far as I know, simply put, the dwell is a function of point gap and number of lobes on the distributor cam. A 3 cylinder would have 3 lobes the peaks 120 degrees apart. Actual dwell (time the points are closed will be less than 120 degrees when you factor in the degrees of that 120 when the points are open. If you turned the distributor, you were turning the timing not the dwell.

I don't understand how you turned the dwell, you will need to explain how you turned the dwell for me.
 
Also your spark is way weak. I would expect to see 1/2" to 3/4" of a good crisp blue/white spark between the coil wire and block.

What is the voltage at the input terminal of your coil?

More confirmation items.

6 or 12 volt?
Positive or negative ground?
Coil type; is it designed/built for use in a 12 volt system, no resistor required? You said it is new.
Do you have a ballast resistor in the wire coming from the ignition switch?
 
Thank you, it's running.

When you said the spark needed to to a half to three quarters inches, I remembered reading something on the forum about wiring. I started replacing wiring and found a wire to/from the ignition switch had shorted out/melted at some connectors. I replaced all wiring, and tried to check the spark from the coil with the inline light, and almost hit the ground. It also turns out the new distributor had a crack with the spark jumping to my hand holding the light. I got another coil off an MF 50 that I have, and it tried to start. I adjusted the dwell a little and it's running. I need to reset the timing, dwell, and carburetor tomorrow with some instruments.

From what I can figure out the previous owner must have put quick disconnects on wiring under the dash that probably were loose and vibrated causing some sparking. I believe that's the original problem. On the coil someone somewhere along the line probably dropped the box cracking it.

Anyway it's running much better than when I started having problems thinking it was a fuel problem. I need to learn to use those meters that measure electricity.

Again, thank you very much.
 
Jim.ME,

To answer your questions. On the dwell, I loosened the bolt that secures the distributor, and then twisted the distributor so the points contacted (or opened) at different locations. As you stated, a function of the point gap. While cranking the engine I slowly twisted the distributor in an attempt to have the points make contact at different degrees in an attempt to get the rotor to make contact with the distributor plug lugs. This was an experiment to try and confirm or eliminate if it was an alignment issue. On a Perkins AG3.152 if you disconnect the the points wire from the coil you can twist the distributor around 360 degrees. Not sure if this makes any sense, but I was trying to find anything that changed operations by changing any one particular component.

Not sure what the voltage was at the input terminal. I need to buy and learn to use a volt meter, or whatever they're called. It certainly would have dramatically reduced the amount of time it took to work through all this.

The MF 135 is 12 volt with a negative ground.

I used both coil types. The original had an external ballast resister. The new coil had an internal resister, that I connected directly from the ignition switch. The coil from the MF 50 is using and external ballast resister between the ignition switch and coil. When I go to Advanced Auto to exchange the coil they sold me I'll get another with an internal resister.

Hope the answers make sense. I appreciate your help. I was very beneficial.
 

Sorry, but you have terms mixed up. You changed the timing by turning the distributor; not the dwell. Turning the distributor changes where the points open and close in relation to the position of the pistons in relation to TDC of the compression stroke. The actual gap between the point contacts remains the same when you turn the distributor. You have to loosen the contact point set's mounting screws and move the contact point held by the mounting screw inside the distributor to change the point gap (which changes the dwell angle). When you installed the new points you should have set/adjusted the gap between the two contacts of the point set -- that gap controls the dwell angle. The book calls for that gap to be set at 0.021". Set the point gap properly and you don't need to be concerned with the dwell angle on your tractor. Most people don't have dwell meters to check that with, and the angle isn't often published anymore either.

You need to set the timing on your engine with a timing light hooked to #1 plug wire. Having the timing way off can cause hard or no start and can do damage to your engine.

Do you have Massey Ferguson service manual # 1448813 M1 ? (The M1, or other suffix, may or may not be included on the newer printings of the manual.) If not you need to get a copy to have the proper info for your tractor. You should also have an Operator's/Owner's manual. There is an on line copy of one you can download at this link:

https://www.manualslib.com/manual/984086/Massey-Ferguson-Mf-135.html

To view the on line parts book for your tractor, go to: https://apb.agcocorp.com/ . In the GUEST USER area at the lower right, click on VIEW BOOKS. That will take you to the search page. Enter 135 in the bar for a model search. Check the Massey Ferguson box in the manufacturer's list and click the exact match box. Clicking those boxes will reduce the models you have to look through to find yours. You should see 135 tractors (Parts book # 651199) as a choice in the list. Click on that and you should have your parts book to look at. HTH

mvphoto60844.jpg
 

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