Wisconsin VH4D STARTS. RUNS, STALLS, STARTS, RUNS, STALLS

[Yamahog.pop]

I have a Melroe Bobcat M-700, era about 1967, It has a VH4D (S/N: 4558985, Spec 311711) Not the original motor. (if anyone could tell me the date of the motor that would be great) bought it about 4 - 5 yrs ago, was kinda a mess, cleaned it up, redid all wiring, new coil, plugs, wires, seem to run well, but 2 winters ago it decided it was only going to start hard & run short times, acted like not getting fuel. Last summer replaced mechanical fuel pump with electric, got it to start and run, still not steady, rebuilt carb, no improvement, replaced carb, installed fuel line filters, same issue, could occasionally get to stay running bit longer when choked (before new carb, now makes no diff). Did seem to note that she seemed happier with a full tank as apposed to 1/2 tank, but couldn't swear by it. To date: I have pumped all fuel out of the tank, replaced the fuel cap, replaced & re-gapped plugs, new coil, (but did note new coil gets warmer than old one), fresh gas, new fuel line from tank, The unit has Electronic ignition (Pentex I assume), far as I can tell, still acts like someone shut off the gas or flipped a switch, but have a glass filter in line, can see it is full, (by the way, this is the 3rd fuel pump I have tried, all low pressure).

These items I have not replaced: the plug wires, nor the coil to dist wire, Cap/Rotor, Pentex ignition, The unit is positive ground, thus I had the old coil reversed, put on new coil, ran for while, began start stop pattern. (I did reverse the wires on the coil in case it was a polarity issue, same OH same OH!) The unit starts almost immediately after stalling, under 5 seconds, 10 at most, usually without choking. So if it is the ignition module, wouldn't it fail and need to cool down before any future success, or start hard? The only other thing I have just now considered is the air filter possibly plugging, not sure how, is older with oil bath, sorta? But wouldn't that cause choking like running, seems to run clear, no smoke, is a bit hesitant to rev, but once she has her wind, watch out! There is a relay and some sort of wiring/condenser (???) mounted on the engine, I believe these go to the onboard generator, but the unit has an external alternator, I did hook them up, mainly because they were there. It ran with the wiring as I had redone it, and ran good, now this, am stumped. I thinking it might be related to the Electronic ignition, but how do you tell if one is going bad, and would they restart almost immediately? I would think if it was the ignition, it wouldn't be willing to restart so fast.

AT times it's like someone turned off a switch or stopped the fuel: do these things have low oil sensors that might be killing it? (Oil level is good.) Thing uses an idiot light for the oil warning. The other thing that occurs is that maybe (and I felt this way with the old carb) the needle valve was not letting in fuel fast enough, but shouldn't this have been resolved with a new carb, and there are two filters on the fuel line, should be clean. this could explain the ease of restart, since the pump keeps pumping after the stall, which would refill the carb, all lines from the tank to the pump, and pump to carb are new. I am using a lower pressure fuel pump, everything I could find motioned that way. (to drain the tank, I used the electric pump, pumped until dry, not a hiccup)

It does not slow or slug down, simply acts like out of gas or ignition switch was turned off. What do Pentexes act like if/when they go bad?

Any other ideas, I am open for suggestions. I don't work on this every day, but have a couple of projects I need it for, would like to get finished sooner than later. I have included some pics of the unit, anyone see anything that stands out? Could this be related to a bad, failing, or corroded ignition switch? (did have wasps build in the gauge/ignition box, but got that cleared out and sealed) but why restart so easily? Am grasping at straws, literally!

Thanks for your time!!

 

[Rob Gunn]

I had a old Bobcat years ago with the similar V4 Wisconsin engine. It would do the same as what you are describing. I found that as the engine warmed up the plate inside the distributor where the points are mounted to would find a way to ground out. I removed that plate and ground off a good 1/8" off the perimeter to achieve clearance between the plate and the inside of the distributor. Also went with all new points, condenser, cap. My next step would have been to go with new electronic ignition but never had to go that step.
Let us know what you find as the fix...

 

[Tinkerer]

Welcome to HEF, Yamahog !
Get a neon spark plug test light and determine if it is in fact an electronic problem.

 

[56wrench]

Maybe the electronic ignition does not like the positive ground. Just change to a negative ground. My old VG4D has neg ground and was built in the 50’s

 

[Arny L]

Did you try checking for vacum leak around intake manifold. Spray some brake clean when its running around the ports, see if you can keep it running.

 

[Yamahog.pop]

Did you try checking for vacum leak around intake manifold. Spray some brake clean when its running around the ports, see if you can keep it running.

An interesting idea, but I think if it were a manifold leak, wouldn't it be hard to start, at least on my old car engines a vacuum leak always resulted in hard starting. this starts right up, no choke needed unless cold. But it might explain the hesitation, won't start with throttle opened up, but will start on idle, then wants to buck when initially throttling up? once she has been rev'd, no hesitation, until she stalls. Could that be related to a ailing electronic ignition? will try and find a spark tester.

 

[Yamahog.pop]

Welcome to HEF, Yamahog !
Get a neon spark plug test light and determine if it is in fact an electronic problem.

that sounds like a good idea, at least to rule out spark issues. But has anyone ever had experience with an electronic ignition going bad, how do they act? the part where it seems to start and run without hard starting, stall, then start right back up again has me baffled, keeps making me look at the fuel issue? or something turning off power? intermittant power disconnect?

 

[Yamahog.pop]

Maybe the electronic ignition does not like the positive ground. Just change to a negative ground. My old VG4D has neg ground and was built in the 50’s

It was already set to positive ground when I got it, and had the electronic ignition already installed, not unless being positive ground caused the ignition premature failure, again, what does a failing electronic ignition act like? hate to spend $$$ if it is not the issue. But I am wondering about the ignition switch, it seemed that the fuel pump may have stopped just before it stalled, then restarted, had wasps get in behind the ignition switch, maybe they caused something I did not see when I inspected and cleaned that area. Lots of straws, just not finding the short one.

 

[Tinkerer]

A loose or broken wire will cause those issues. Could even be a defective ignition switch.

 

[Yamahog.pop]

Been a long summer! I pulled it apart, removed the seat, lifted the cage, removed floor plates and got access to the fuel tank, replaced gas line, added a filter before the pump, one I could see the fuel flow, followed wiring, no breaks, replaced a relay attached to some old engine wiring, (do not know what that wiring does) but I cannot see that it connects with engine running. I did notice at one point the ammeter gauge did not register any action, and shortly after had a dead battery. set battery on charger, and tested, good, took alt and had bench tested, good. replaced ignition switch, but when I went to try to start, system went dead. if key was off, had 12 volts at switch, if on, zero at switch, after some following and testing, found the amp meter gauge was bad, Thought this may have been a contributor to the problem? replaced ammeter gauge, and switch, fired it up, ran, accelerated, ran 15 minutes straight, no hesitation, no dying, it was like it was saying, " where's the work, lets go!". Thought OK! had it resolved. It ran without a hitch, that was about 3 weeks ago, been buried in other projects. Finally got back to it yesterday and today, put everything back together, floor plates, seat assembly, cage, all set to go, started it up, went right back to stalling after 30 - 40 seconds, will restart right off, no choke, spins well, sprk on the plugs right up to the end, getting gas, ammeter shows good charging, I am out of ideas! Cannot figure out what changed just by reassembling the cage seat, and floor plates. they have nothing to do with anything that I can see. the wiring completely goes another direction. local bobcat won't look at it, too old for them. plus getting it there when it won't run adds problems. This is not a hobby, am 2 summers behind on projects I need this for, do not know what else to do.

 

[Arny L]

Maybe you should start from scatch again. Spark and fuel. An inline spark tester would allow you to physically see if your losing spark, at the moment it stalls. As far as fuel, have a can of brake clean with a nozzle ready and pointed into carb or intake manifold, so you can squirt some as it dies. Either test should give you some idea. I thought I noticed your first metal fuel filter looks backwards, the word IN is facing carb. Could just be picture angle too.

 

[56wrench]

Maybe when you put it all back together something is grounding out from vibration

 

[Yamahog.pop]

Maybe you should start from scatch again. Spark and fuel. An inline spark tester would allow you to physically see if your losing spark, at the moment it stalls. As far as fuel, have a can of brake clean with a nozzle ready and pointed into carb or intake manifold, so you can squirt some as it dies. Either test should give you some idea. I thought I noticed your first metal fuel filter looks backwards, the word IN is facing carb. Could just be picture angle too.

Did recheck spark, has spark up to end, is getting fuel, best as I can tell, I am inclined to suspect the electronic ignition, but don't know enough about them, thing is it ran perfectly until I reassembled the floor plating, reattached the seat assembly, and the cage housing (driver protection cage) of which non have any connection with the engine. This is not a spark or fuel issue, it shows spark until the end, however a spark tester does not shows the level of spark being sent, if the spark levels drop after 30 or 40 seconds, it may not be enough to not fire the plugs, but it does show spark going to the cylinders, I tested on 2 diff cylinders and had spark showing right up to dead stop on both cylinders. I think this takes testing equipment I do not have access to, from my conclusion, either the carb is not letting in fuel, which it does seem to quit pumping (both filters are clear view, can see gas flow) there is bubbling or visable movement in both when starting, but seems to get still, although if I feel the pump, it is still pumping, and when the engin stalls, the filters show fuel is being sent to the carb (it is a new carb replaced last summer) if this is a float issue, then it is on two carbs in a row, how likely is that?

 

[Yamahog.pop]

Maybe when you put it all back together something is grounding out from vibration

I considered that, but the parts I reconnected don't come near wiring, not in any way I can see. and they are solid bolted, in fact got new bolts to make sure all was secure, guess it hates the new bolts? if this was a grounding issue, why would it start right asway, stall after 30-40 seconds, and restart right away, almost as fast as you can hit the key? Thing is it was getting spark before I discovered the bad ammeter, not unless it is burning out ammeter gauges? but the gauges appears to work?

 

[Yamahog.pop]

I found someone local who knows Wisconsin engines, will post his findings to this so you all know.

 

[Rob Gunn]

If im understanding your scenario correctly it's still dying after it warms up? I would try a new coil, Iv had some coils work when cool but then warm up and fail.

 

[Vetech63]

On those engines the throttle link position is imperative to how well the engine runs under a load. The governor lever has multiple position holes for the link and you have to be in the right position for a specific engine load. Has this been checked?

 

[Arny L]

Did recheck spark, has spark up to end, is getting fuel, best as I can tell, I am inclined to suspect the electronic ignition, but don't know enough about them, thing is it ran perfectly until I reassembled the floor plating, reattached the seat assembly, and the cage housing (driver protection cage) of which non have any connection with the engine. This is not a spark or fuel issue, it shows spark until the end, however a spark tester does not shows the level of spark being sent, if the spark levels drop after 30 or 40 seconds, it may not be enough to not fire the plugs, but it does show spark going to the cylinders, I tested on 2 diff cylinders and had spark showing right up to dead stop on both cylinders. I think this takes testing equipment I do not have access to, from my conclusion, either the carb is not letting in fuel, which it does seem to quit pumping (both filters are clear view, can see gas flow) there is bubbling or visable movement in both when starting, but seems to get still, although if I feel the pump, it is still pumping, and when the engin stalls, the filters show fuel is being sent to the carb (it is a new carb replaced last summer) if this is a float issue, then it is on two carbs in a row, how likely is that?

Did recheck spark, has spark up to end, is getting fuel, best as I can tell, I am inclined to suspect the electronic ignition, but don't know enough about them, thing is it ran perfectly until I reassembled the floor plating, reattached the seat assembly, and the cage housing (driver protection cage) of which non have any connection with the engine. This is not a spark or fuel issue, it shows spark until the end, however a spark tester does not shows the level of spark being sent, if the spark levels drop after 30 or 40 seconds, it may not be enough to not fire the plugs, but it does show spark going to the cylinders, I tested on 2 diff cylinders and had spark showing right up to dead stop on both cylinders. I think this takes testing equipment I do not have access to, from my conclusion, either the carb is not letting in fuel, which it does seem to quit pumping (both filters are clear view, can see gas flow) there is bubbling or visable movement in both when starting, but seems to get still, although if I feel the pump, it is still pumping, and when the engin stalls, the filters show fuel is being sent to the carb (it is a new carb replaced last summer) if this is a float issue, then it is on two carbs in a row, how likely is that?

Actually the spark tester I have does show the kv amount. Right down to small engine, hence SE. So you can adjust gap until you reach your coils output. Yours should easily produce 15 to 20 kilovolts I would think.

 

[Yamahog.pop]

I finally located someone local who knew wisconsin engines to look at it. the issue was that the engine was not orig,(we suspect it may have come off a bailer and was older than the M700) and had some kind of rectifier, the rectifier was causing a voltage drop that was not enough to stop spark, but caused the voltage to lower below what the fuel pump required to run correctly. this drain only occurred while it was running, and voltage would return to normal when the engine stalled, but ignition continued to fire to the end. This all started when the mechanical pump began failing, I put on an electrical pump, which eliminated the priming issue of the old mechanical pump, worked well for several months, then started dying at shorter and shorter intervals. always felt it was a fuel issue, and was, just not due to an expected cause. When we turned on the key, the electric pump filled the carb, then as the voltage dropped, the pump got less and less able to pump fuel, until it was not pumping anything, it was still running, but not fast enough to move fuel, when the engine stalled the voltage would return to normal and the fuel pump would fill the carb up even b4 I hit the starter, which left for a very confusing situation. I don't feel too bad, it took the mechanic 3 days to finally figure it all out. Thanks everyone for your input and ideas. hopefully this may help someone else down the road with a similar problem. It also explains why when the battery was fully charged (like having been on a charger) it would initially run longer which is what happened when I retested it after getting every tested. Explains a lot.

 

[Arny L]

Epic, what is the rectifier used for? Show a machine some love, and it bites ya. Good you got it remedied.