1991 Force 90hp starting problem

[tavacska]

These days I am working on my back up engine.
1991 Force 90 HP, 3 cylinder

The top piston position is at 0 deg correct.
The full throttle is set at 28 deg with help of timing light.
The idle mixture is set 1 1/4 turn from touch position.
Idle speed is set as the mark is right below the touch point.

When I try to start it, it can first run for 3-4 sec and then there is a huge pop sound and the engine stops. It dies every time like that.

What could be the reason of that? The used motor comes with a mess of the wiring even with the 2nd coil connected to the first cylinder. I double checked the wiring from trigger - CD - coil, with the wiring diagram on the engine.

The engine sounds like back fire. Please advise how to diagnose this problem.

Thanks.

FYI, the compression is super good for all the 3 cylinders.

 

[Nordin]

Which ignition system does it have Prestolite or Mercury Thunderbolt?
You are saying "Idle speed is set as the mark is right below the touch point"????
Idle speed screw is at the tower shaft and you adjust it by screw it in or out and it rests at the engine block.
I think you mean the throttle pick up point set.
You adjust that by pull off the throttle rod and then adjust the roller that is excentric so the mark at the throttle cam just intersect the roller at the cam mark.
BTW check the magnets under the flywheel. They are glued and tend to loose by age.

 

[jerryjerry05]

Sounds like your sucking air someplace, maybe one of the port cover gaskets?
Maybe the fuel pump diaphragm is bad or a gasket somewhere is sucking air??

 

[tavacska]

This is the ignition, it seems not the Thunderbolt?
"Idle speed is set as the mark is right below the touch point" - I mean, I set the cam just touch at the stopper with the mark on the stopper. Then I adjust the idle screw to advance the timing and the mark is just below the stopper. This was learned from the tutorial in this forum.

 

[tavacska]

I jumped the engage trigger, to make sure that it can be cranked even if it is engaged in full throttle. This is to set the timing for 28 deg at full throttle.

But accident happened. I forgot to put it in neutral, and cranked it started. It started so violently and I shut it down just in time. No bad results happened. And I know that it can run good in some speed.

So have to figure out what's wrong with that starting.

The air tight is difficult to diagnose for me. I will leave it there and want to make sure there are no other causes.

 

[Nordin]

Look at the sticker in the top of this forum by FrankA to set the timing and throttle pick up point.
There is also a You tube video by FrankA how to do it.
I think your setting of the idle and the throttle pick up point is out of adjustment.

 

[racerone]

Check flywheel key.

 

[tavacska]

Check flywheel key.

What is a flywheel key?

 

[jerryjerry05]

The flywheel is mounted on the top of the crankshaft, it's indexed using a small piece of metal(key) it makes the ignition fire at the right time.
If? the key breaks/shears the spark might not work or sparks at the wrong time.

 

[Redbarron%%]

Make sure the timing is correct for all cylinders. #1 at ~0 #2 at 1/3 of the way clockwise and #3 at 2/3 clockwise. If the leads are swapped the thing is not going to run and will kick back.
Move your induction timing clamp to each in turn.
Also you could have a bad trigger.
Also it looks like the impulse line from the crankcase is crimped.

 

[jerryjerry05]

IF???? it started at wide open???
Then move the throttle back and start it at a slower speed.
Make sure the muffs are on or the lower unit is DEEEEP in a bucket.
4-5" over the cavitation plate.
If the timing was at 28d. I'd not worry about it.

 

[tavacska]

Thanks everyone for the good points.

I followed the sticker again. I don't know what make the difference. But the motor starts normally now.
The main changes include:
1. release and re-tight the throttle arm. Make sure they close or open together.
2. Re-do the timing light and make sure it's on 28 deg full throttle. That's a minor adjustment, only 2 turn of the screw.
3. Re-check the cam position, and no adjustment needed.
4. Re-adjust the idle speed screw, which I believe it should be at almost the same position.
5. Re-adjust all idle mix to 1 1/4 turn.

So, now it can start and idle easily. But I didn't let it run for long, because there is no water flow into the motor.
1. The water pump is rebuilt one year ago.
2. I install a hollow screw on top of motor, which did spray out water before. But it never did last weekend.
3. I am using muffs, which is good on my Mercury 1150, but seems to be mis-matched in this lower unit. Is it the muffs that leak water and prevent water into the pump?
4. I re-opened the water pump and everything looked perfect to me.
5. I used clamp to tighten the muffs, but still no water came out from top.
6. I noticed the water pump is pretty higher than the water intake. But I don't have a deep big water bucket to test it.

How do I deal with it?

 

[jerryjerry05]

Buy muffs and duct tape them in place.
Needs to be dry,dry,,dry.
Then turn the hose up as far as it goes.
Bucket: needs to have the water 4-5 inches over the cavitation plate.
These pumps aren't self priming and needs to be under water to start.

 

[tavacska]

Buy muffs and duct tape them in place.
Needs to be dry,dry,,dry.
Then turn the hose up as far as it goes.
Bucket: needs to have the water 4-5 inches over the cavitation plate.
These pumps aren't self priming and needs to be under water to start.

Thanks Jerry, I think your ways work, although I didn't do the tape and use the clamps instead.
The muffs need to be tight and water pressure needs to be high to push water to the pump.

Now for updates:
The motor runs very good, unless there needs minor adjustment on the idle speed and idle mix.

I didn't expect the mix is so sensitive that 1/4 turn more turn will be hard to start. Now it is set as 1 turn from seat. And the motor idles but some time RPM increases for a while and then back to the normal.
I think I still needs to play a while on the mix to make it stable before installing on the boat.

 

[jerryjerry05]

The adjustments need to be done on a warm motor, in the water and in gear.
Some motors, no matter what you do just don't idle as good as you think they should.
The 85: the factory sent out a bulletin stating the 85 needs to have the air screw set at 1 turn out and left there.
All of the 85's I owned (4) had the air screw set at 1 1/8th turn out.

TEST: starting fluid, start motor, spray SF around the intake side of the motor, including the 3 port covers under the coils (4 for a 120/125)under the bottom carb and everywhere you can reach(except in the carbs)
One TINY cough, backfire, stutter can blow one of these gaskets and you'll be sucking air and the motor won't run right.

 

[tavacska]

The adjustments need to be done on a warm motor, in the water and in gear.
Some motors, no matter what you do just don't idle as good as you think they should.
The 85: the factory sent out a bulletin stating the 85 needs to have the air screw set at 1 turn out and left there.
All of the 85's I owned (4) had the air screw set at 1 1/8th turn out.

TEST: starting fluid, start motor, spray SF around the intake side of the motor, including the 3 port covers under the coils (4 for a 120/125)under the bottom carb and everywhere you can reach(except in the carbs)
One TINY cough, backfire, stutter can blow one of these gaskets and you'll be sucking air and the motor won't run right.

That's awesome tip, thanks. Will test it out very soon.

 

[tavacska]

Updates:

The unstable idling problem has been identified. It's fuel pump problem.
The fuel pump doesn't work or barely work. After idling good for a while, the idle speed rises up and then finally bogs down. If I keep pressing the bulb while it's running, it idles perfectly as long as I want it.

But here is another problem showing up:
The power tilt works fine when rising or lowering the motor. But it won't hold for a minute then the motor falls down. I checked the fluid level and it's ok. I can't find the manual release screw and I didn't find any leaking in the power tilt system. Shall I open the cylinder and replace the seals? But before that, is there anything else I shall check?

 

[topgun3690]

Take a look at the stickies at the top of this forum.....Force and Chrysler FAQ....there is info on T & T troubleshooting tips. Helps to isolate where the problem is.....lots of times it's the check valves in the valve body that cause a leak down problem. FYI

 

[jerryjerry05]

In the Force forum: look for these posts. Should be in the first posts in this forum.
Remember there's NOTHING inside the pump that you can fix!!!
Don't try to adjust or look inside the pump, chances are you'll be replacing the pump.
The valves for up and down need replacing, see directions.

Force 3-wire Tilt and Trim system with shock absorber system "test & repair" procedures. by pnwboat & Jiggz Read all the posts. Links Verified

Force Tilt & Trim Relief Valve Repair by jerryjerry05 Links Verified

 

[tavacska]

Big thanks. Exactly what I need!