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1994 40hp tiller/man. start/4 cyl. - Will start and run in idle but dies when in gear and throttled?

R

rjustinyoung

New member
I was fishing yesterday and everything was running fine until we went to leave and i couldn't get above an idle in gear without the engine dying! It has a priming bulb on the motor next to the kill switch and after pulling the inline fuel filter and the checking all the fuel lines I tried to pump the priming bulb and I could get a bit faster than an idle but the throttle was wide open. I have had no problems with it at all until now. any one have any ideas?
 
Determine which of the 4 cylinders are not firing by unplugging one spark plug at a time. Use insulated plug wire pliers or insulated gloves. If the RPM does not drop...that one is not firing.
 
guyjg said:
Determine which of the 4 cylinders are not firing by unplugging one spark plug at a time. Use insulated plug wire pliers or insulated gloves. If the RPM does not drop...that one is not firing.
Click to expand...



When I pull 1 and 2 the engine stays running, but when I pull 3 or 4 it dies.
 
It will run normal hooked up to the water hose, but i guess under a load, its not firing on all 4 cyl. Im gonna replace the spark plugs and test it out. Thanks for the help.
 
OK, I have replaced all 4 spark plugs, added some sea foam and fresh gas. Gonna put her in the water tomorrow and test with a load. I noticed a small leak of water around the top cylinder spark plug, I tightened it up but it still leaks and that can't be good. wish me luck.
 
I hooked it up again and i definitely have water coming out of the top two spark plug holes. Im hoping this is the head gasket. How hard is that to get to and change out?
 
I got the plate off with one bolt head casualty. I've never seen behind one of those plates. Once I get that one bolt out of the housing I'll replace the gasket. Before I took off the plate I removed the top two spark plugs and pulled the crank on the motor and it fired up and ran a good idle on just cylinder 3 & 4. I'm guessing that because it fires 1-3-2-4 this is possible. Should it also then fire and run on just 1 & 2?
 
OK, I did a compression test and got 115, 115, 115, 110 on 1-2-3-4. Not sure what it is supposed to be? I also tested for spark and am not getting any on wires 1 and 2. about to clean up all electrical connections and retest. What would cause this? Selector switch? I have read some older posts about this engine not firing on 1&2 at idle.
 
It runs on all 4 at idle.-Not sure where your information came from ?----The big 4 cylinder inline 4 does only run on the top 2 cylinders at idle.
 
10-4. I cleaned all connections and made sure everything was tight and still no fire on top two wires. is there anything I can do to find out if it is the selector switch or the coils without taking it in to a shop?
 
I would definitely get a service manual and a dva tester and follow the instructions on how to trouble shoot it correctly. You will drive yourself crazy trying to figure it out on your own. Racerone mentioned it only runs on two cylinders at idle. I don't know the answer, but the service manual will help you understand your engine and how it is supposed to work. I am personally "guessing the easiest thing" is your fuel line is bad or has loose leaky connections, but what do I know.
 
Only the big 100 / 115 / 125 HP inline 4 cylinder motors run on the top 2 cylinders at idle.---All 4 cylinders have spark at idle on those.---The bottom 2 cylinders do not get enough fuel to run.-Only a wee bit for cooling and lubrication.
 
I swapped the coils around and I am still only getting spark on 3 and 4. No Spark on the top two cylinders. So it is not the coils or wires. I guess Im gonna take it to the shop and see if they can pinpoint where Im loosing the voltage at. I just hate to buy a switch box and it be a stator or some other issue.
 
It is really easy to test the stator and trigger with a simple ohms test. To test the switchbox, you will need a DVA tester, but if you eliminate the stator and trigger being the problem, then it would most likely be the switchbox. Do a simple ohms test with the stator and trigger installed. Test across the red and red/ white wire. Test across the blue and blue white wire. both should have resistance which a manual or the above link will specify. Next test across the purple white and black wires coming from the trigger, also outlined in the cdi test link above. If these all test out ok, then it is your switchbox. It has to be one of these components if you are getting some spark. I am not gutsy enough to say which one at this stage.
 
from CDI

NO SPARK ON 2 CYLINDERS:
1. Check resistance and DVA of trigger:
WIRE Read To OEM Ohms CDI Ohms DVA
Purple (Violet) White 700-900 800-1000 4V or more
Brown White/Black 700-900 800-1000 4V or more
2. Swap the stator’s Red and Blue wire with the Red/White and Blue/White wires to see if the no fire problem follows one side of the
stator. If it does, the stator is bad. If the problem remains on the same 2 cylinders, the power pack or trigger is probably at fault.
3. FOR CRANKING TEST ONLY- Swap the trigger Purple wire with the Brown wire, and White wire with the White/Black (Black) wire.
NOTE Some OEM triggers used a Black wire instead of a White/Black wire.
 
ok, on the stator there is a blu/wht not connected, 2 yel to the terminal block, wht/grn &grn/wht to stator adaptor and blk to ground. From stator adaptor it is blu & blu/wht to switch box. I swapped the blu & blu/wht and still no fire on the top two. So, test the trigger to rule it out and then it is or isn't the switch box? my stator is red.
 
I am trying to get my hands on a DVA tester. In theory, if I swapped the stator wires and no fire on top two, swapped the trigger wires and no fire on top two, and swapped the coils around and no fire on the top two, then it has to be the switch box correct? If the fire would have followed the stator wires, then it would have been the stator, and if the fire had followed the trigger wires, then it would have been the trigger. Since it stayed on the bottom two cylinders it has to be the switch box?
 
You are on the right track here, you really need that DVA adapter to confirm everything. You can get them pretty inexpensively on ebay without having to buy the entire DVA tester. There are instructions on how to make your own as well, but I just spent the $30 and got one already made. The DVA adapter allows your regular multimeter to read the voltage spikes, which is what you are looking for. It buffers out all the erratic readings and gives you a stable reading to match your specs.
 
http://www.selocmarine.com/content/manuals/1416/pdf/14164w204.pdf

This is the wiring diagram that matches my motor. I checked the resistance on the trigger and the stator and they are in the range listed. I went to look for a DVA adaptor, but no luck, just looked up how to make one and found them on Ebay. If I can't find a buddy that has one, Ill get one. Thanks for all the help. If any of you are ever around Boerne Texas, look me up, I owe y'all a good'ol Texas Ribeye.
 
Good work so far, it looks like you have it narrowed down to the stator adapter or the switchbox, the DVA adapter will help you finish this up and only buy the part you need.
 
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