1990 90HP Force Outboard starting issues

[Tonykilla85]

Good information, it sounds like the first way to go is checking the reeds. I did notice a backfire or (one cylinder firing) when the top plug was out so i'm assuming the middle reed is good. Due to the fact I do not have spark on the bottom cylinder. Think i'm going to hold up until I get new coil pack in the mail and check the bottom cylinder before tearing her down again. Getting closer one step at a time! I will post back with results of the reed tests and the carbs if the reeds are ok.
Thanks again!

 

[Tonykilla85]

Got her RUNNING!!!!
It is not the coil pack it was a bad cdi box.
The top two cylinders were firing with not starting.
I switched the #2 plug wire to the #3 cylinder and she fired right up and idled!!!
I have a new cdi box coming now. Hope to be on the water sometime next week!
Thanks for all the help! This form is awesome. Learned a lot and saved a lot of money! :laugh:

Until next time Tony K.

 

[Jiggz]

Great!

 

[Tonykilla85]

Well like I said I did end up getting the boat started when switching the 2nd coil wire to the 3rd plug. I thought it was the coil pack!
Ended up getting a used "claimed it to be working" coil pack. "Did not work"
Checked the cdi boxes 1 working great the other noting...
Again I ordered a "claimed to be good" used CDI box. "Did not work"
I thought it might be the trigger assembly so I switched out the one on the boat with an extra one I received as a spare when I bought the boat.
The spark went from being on the 1st and 2nd cylinder to only the 2nd.
I again ordered a used trigger assembly part "claimed to be good" and i'm back to firing only on the 1st and 2nd cylinder.
The only other thing I can think it could be is the stator/ or a bad used part? Any advise in checking the electrical components with a multimeter or any advice in general would be appreciated.

Thanks Tony

 

[Jiggz]

I recommend just switching components around and see if the problem follows. Then you know for sure which component needs replacing.

 

[Tonykilla85]

Would the stator effect this at all? Or would it olny be something with the coil, cdi box, or trigger assembly?

 

[Jiggz]

No Title

First I want to make sure we are on the same page on the type of ignition system on your motor. The 1990-90HP's came in two versions of ignition system, the Prestolite and the other is Thunderbolt. The T-bolt has a switchbox while the Prestolite has the CD modules (2 of them). In your case, I believe you have the Prestolite although you are referring to the CD modules (CDM) as CDI boxes. For if you have the T-bolt you should have been referring to the Switchbox (one only). Here's an ignition system diagram for a Prestolite and T-bolt systems.


Here's some troubleshooting steps for a Prestolite system. Note the stator has a pair of wires (yel/grn) that goes to the rectifier for charging the battery. And then there is also the two pairs of wires for the ignition system (yel/brn or blk/yel). Each pair of wires goes to each CD modules. The module serving #1 and #2 is referred to as #1 module and the other is #2 module. Don't confuse the cylinder numbers served for ID'ing modules. If you have sparks on #1 and #2 plugs, then it tells you #1 CDM is working perfect. If you do not have spark on #3 it could mean there is problem on at least four items. First will be the ignition coil, but you already eliminated this by swapping it around with a known working coil from either #1 or #2.

The second could be the CDM. There is a spare ckt on #2 CDM (since each CDM has two separate ckts as shown on #1 CDM) because you only have 3 cylinders. You can try using this to find out if the current ckt you are on is faulty. If problem persists, try swapping the CDM's (and only the CDM's while the stator and trigger wires stays and so with the coil wires) but make sure you only move the CDM's and not the other wires that connects to it, otherwise it could cause backfires and damage to the engine. If problem persists while #1 and #2 continues to have sparks (after the CDM swapped, meaning the both CDM's are working perfectly), then the other two things left is the stator or the trigger wires.

And the stator is the third item that could go wrong. Note the wires and colors are the same for each ckt serving the CDM's. It is very unlikely one ckt could go bad while the other stays working. However, you can also swap the wires from the stator between the CDM's just to eliminate the stator as source of the problem.

And the last thing that could go wrong is the trigger. Before going on with the trigger I need a verification you have the Prestolite system or T-bolt system.

 

[Tonykilla85]

Yes Jiggz I do have the Prestolite ignition system... I believe the CD #2 box is bad based on what I have done so far, I will swap the stator wires just to make sure of this... I'm assuming the trigger wires can be swapped the same to eliminate the possibility of a bad trigger?

 

[Jiggz]

The trigger wires are not readily swappable like the stator wires. The T wires are timed with each cylinder and swapping will put the motor out of timing resulting in backfires. Instead, what you need is to do voltage output readings or make ohm resistance comparison with known working trigger wires. Voltage reading requires a DVA adapter since the voltage is highly transient (a spike rather than continuous output). Resistance comparison readings will also indicate if there is problem with the wires or the trigger. Just make sure you disconnect at least one of the wires (or both) to read resistance on known working pair of trigger wires and then compare readings from a suspected problematic pair of trigger wires.

If resistance difference is more than 10% then the trigger wires or the trigger itself could be the problem. Before jumping to conclusion, check each wire individually especially on terminal board connections or any other connections for tightness and cleanliness. The trigger voltage output is really low, any resistance due to dirty, scaled or loose connection can make it non functional.

Can you post your result when you swapped the CDM's? Did the problem persists with #1 and #2 continuing to normally fire (when connected with the #2 CDM?). Meaning #3 is still not firing despite the CDM swap.

 

[Tonykilla85]

Good information, I think i'm going to do a little troubleshooting tonight, it will be the only chance I have due to us heading on vacation Friday am.
I know the coil works, when I switch the #3 coil to the CDM box supplying the #1 & #2 coil it fires.
I will first do the resistance check on the trigger assembly to make sure everything is clean and no insulators cut ect.
If everything checks out there I will move on to swapping the stator wires, just to make sure there are no issues with her.
If I still do not have and spark on the #3 cylinder I will replace the #2 CDM module with the used part I have.
If nothing changes after that I am thinking I will be returning the used CDM module I brought and buying a new one or 2 just to make sure there are no further issues in the future. Thanks again for all the help Jiggs. One day soon i'm going to know everything about the top end of a force outboard! Lol

 

[Tonykilla85]

Well the trigger seemed fine. It had the same continuity on both the working cylinders and the non working cylinders.
I swapped the stator wires around and didn't get any cylinder to fire correctly? I'm assuming that the stator is OK??
When disconnecting the #3 coil pack from the back of the #3 CDM and reconnecting it I sometimes get a single blip of spark on the timing light? Weird stuff...
I'm think I need to get a new CDM, what do you think Jiggz? Another question for you, are the CDM #1 & #3 interchangeable? Thanks Tony

 

[Jiggz]

Tony, I asked earlier what were the results when you swapped the CDM's and never got a clear response. Remember, there are only two CDM's. Each has two separate circuits in it. The CDM supplying #1 and #2 cylinder is referred to as #1 CDM (see diagram) and both circuits are in used. The CDM supplying #3 cylinder is referred to as #2 CDM and only uses one of its two circuits, i.e. for #3 cylinder while the other is not connected and is a spare. YOU NEED TO DO THE SWAP AND POST RESULTS. DO NOT MOVE ANYTHING ELSE JUST THE CDMS.

Now for you latest troubleshooting, when you swapped the stator wires and did not get any spark in any of the 3 cylinders, it tells me there is more than one problem with your ignition system. First, one set of stator wires is not working. Second, #2 CDM is most likely not working either. You could have eliminated the second problem, i.e. #2 CDM had you done the swap I had requested you to do earlier. So now, you will need to put back the stator wires in their original configuration and then do the CDM swap mentioned above. Post your results.Additionally, do a ohm resistance comparison reading on the two sets of stator wires. If there is a big disparity on the resistance, you could end up removing the flywheel to investigate further. Post result. While doing this check the integrity of the connections and the wires in question.

As for the trigger wires, having comparable resistance indicates the trigger should be good. Do not buy anything yet until you verify which component is actually faulty, unless you have $$$ burning in your pocket.

 

[Tonykilla85]

I apologize Jiggz,
The #3 coil pack/ cylinder fires when it is attached to the #1 CDM module.
I swapped out the #2 CDM box with the used box I bought and it does the same thing my box did.

 

[Jiggz]

Understood #3 coil is working which we already agreed earlier. But the way you tested #3 coil doesn't test #2 CDM. And when you swapped #2 CDM with a used one (and not knowing the used one is a known working unit) it does not really test #2 CDM. The main reason for swapping components is to do a process of elimination by using KNOWN working components. And with this, we know #1 CDM is working and should have been the one used for the swap to do an elimination.

Anyways, do the CDM swap and if #3 cylinder continues to have no spark but #1 and #2 have sparks just leave the CDMs at their swapped positions. Next move is then swap the stator wires. If #3 cylinder now have sparks and #1 and #2 don't, then you know the stator has problem on one of its circuits. Replace the stator wires to their original configuration and troubleshoot the stator wires for the now #2 CDM (which was #1 before the swap).

 

[Tonykilla85]

I ran a resistance check on the stator and the working side (wires #1 & #2) are reading 726 while (wires #3 & #4) are reading 0. I think I need buy a new stator then check if the #2 CD box has spark.

 

[Jiggz]

You can go ahead and buy the stator, personally though, I would remove the flywheel (which by the way you will be required to do anyways if you replace the stator) and inspect the wires from the stator coils connection. It is not unusual these wires get severed either by falling magnets or improperly placed or secured wires which rubs or get caught with the flywheel. I believe when you said reading was "0", you actually meant infinity or open indicated usually by the number zero followed by a period and the capital letter L or "0.L" which means there is no resistance or continuity between the two wires.

If you find any of the wires, severed, you can solder them together just make sure you insulate it there after with electrical tape and shrink tubes. And then test again.

If you do not find any broken wires, it could be that the stator coil has burnt up (with burnt marks) and opened. Hence, no repair except to replace.

 

[Tonykilla85]

Well I replaced the stator and the spark issue is corrected on the #3 cylinder, but now i'm having an issue with no spark on the #2 cylinder. This doesn't make any sense to me??? Everything is wired according to the prestolite wiring diagram. It seems to me the 2 cd boxes and the 3 coils are working. Maybe a bad trigger, or stator? Or should I be looking into something else. (the flywheel has been on & off this motor) It's looking like shes coming off again! lol

 

[ErSa]

GREAT work guys. Interesting reading.

 

[jerryjerry05]

OLD!!! post