1991 Force 90hp starting problem

[tavacska]

Updates:

I rebuilt the fuel pump, but I suspect the pump is not for this engine.
The pump shall be installed on the base with a air hole to pump into the fuel pump, as I watched the youtube videos. To me, it seems that someone has just installed a wrong fuel pump to this motor.

Please confirm, thanks.

 

[Nordin]

Seams like that is a franken engine!
Hard to see in the pics but the model is 908F90C or 906F90C?
The XXXF90C says it is a 1990 year model BUT the power head look like a later 1994 or later cause it has the Mercury style fuel pump.
Your fuel pump is the right one for that power head, but the power head looks like a later 90hp 1994 or later.

 

[tavacska]

The models is 908F90C. My thought is someone has replaced the fuel pump with a wrong one. But as I dig out, it seems there is no tracks showing they are the replaced one.

But about the fuel pump, there are four holes, 1-in, 2-out, 3-air port connected to engine with a hose, 4-another air port in the base of fuel pump.
My concern is the 4th port. The fuel pump was installed with the 4th port open to the air. Is that the correct way?

 

[racerone]

No it is not.

 

[jerryjerry05]

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.

The POP is a backfire, could be sucking air somewhere???
Most times the port covers gaskets get blown out when it backfires,
Spray starting fluid around the intake side (under the bottom carb and under the packs/coils and if this makes a difference in the way it runs> then it's sucking air somewhere.

 

[jerryjerry05]

The pump is from a newer model, they switched to Mercury in the early 90's.
Maybe someone with an older model can post a few pics showing the old pump and the hoses to the pump.
That hole with nothing hooked to it could be the problem with the backfiring??

 

[racerone]

This " POP " is a lean sneeze I think.-----So do you think that occurs in the crankcase ?----In the cylinder ?----In the exhaust manifold ?

 

[tavacska]

Updates:

Now I have figured out something.
1. The "POP" when I first run the motor could come from the mis-adjusted timing and linkage. I have strictly followed the stickers and now the "POP" never showed up.
2. The hard-start is due to the idle mixer. It was set as 1 1/4 to 2 rounds, which are too much for FORCE motor. My Mercury tower of power starts from 1 1/2 and can reach to 2 1/2 without idling rough. I am now setting it to around 1 round on muff and it can start much much better.
3. The rough idling is due to the malfunction of fuel pump. The last owner replaced the fuel pump with a newer model by a wrong way. He or the technician blocked the original base holes with a piece of scrap of aluminum plate and painted it well. Without inspection, it's hard to see that it was redone in that way. The newer fuel pump can work with back hole open to air, but with lower efficiency. Whatever, I have replaced the pump with the correct parts and now it idles perfectly.

Thanks everyone so much for the advices. And now the only thing I need to fix is the power tilt problem of no-holding position. I have some ideas now I will keep this updated.

 

[jerryjerry05]

The first 4/5 posts in this forum have tips/ procedures for your motor.
The T@T is covered in one of these.
99.999% of the time a motor that drifts down in the seals in the bottom of the T@T
VERY IMPORTANT!! there's nothing in the actual pump that needs any help!!
The 2 tiny seals(one shown here) are usually the cause of the leak down.

https://forums.iboats.com/attachments/photo274093-jpg.260057/

 

[tavacska]

The first 4/5 posts in this forum have tips/ procedures for your motor.
The T@T is covered in one of these.
99.999% of the time a motor that drifts down in the seals in the bottom of the T@T
VERY IMPORTANT!! there's nothing in the actual pump that needs any help!!
The 2 tiny seals(one shown here) are usually the cause of the leak down.

https://forums.iboats.com/attachments/photo274093-jpg.260057/

Thanks Jerry for the detailed instruction. With your help, it turns out to be a two-hours job. If I have known what to do, maybe I don't have to take out the valve. It was the tip rubber seal which totally failed.

Thanks everyone's advises, I believe I have nothing to fix on this engine.

It cold starts and run after 2-3 times of the turning key on old fuel. It sounds so gladly, which makes me thinking of another question. Should I replace my current engine with it. This Force engine was bought as back up for my boat engine. My boat engine is 1977 Mercury Inline 1150 with distributor. I did a lot work on it and now it has brand new powerhead, trigger, CD, coil and new wiring. It has everything new except for the lower unit. But I don't like the power trim which takes my boat space and looks messy.

My questions are:
1. Does force runs quiet than mercury. It sounds quiet to me on muff than mercury. My mercury of 1977 is so loud that we can not talk too much even on idling.
2. Does Force drink a lot fuel? My mercury drinks a lot. 10 gallon for 30-40 miles cruising.
3. Are there enough parts in the market? Lower unit will be my concern. I didn't see too much sell in my local craiglist but I did see quite often the sale of tower of power. If there are enough parts, as I was told, the FORCE lasts forever with my mechanic level.

 

[jerryjerry05]

Force is quieter.
10 gal for 35miles = 3.5 mpg.
Thats really not that bad for such an old engine.
The Force will probably get the same.
You have to make sure the props the right one for both motors.
Had 17p on twin 88/85s wanted more speed.
Changed to 19p and got 2-3 mph more.
I also got 15% more fuel usage.
Load, weight distribution, and pitch make the boat more efficient.

The 90 Force will last a long time if taken care of.
The gear box= change/ check the oil often.

 

[topgun3690]

"10 gal for 35miles = 3.5 mpg." That's some high powered ciferin right there! Lol

 

[jerryjerry05]

Jethro Bodeen and his sister Elly-mae helped with my numbers alearnin.
Anytime you need help? BE54789 (be-beachwood)

 

[topgun3690]

Likewise.....BR-549

 

[Redbarron%%]

How can you get a few of those tiny seals? This may be the problem with my hard starting on my Sport Jet 90 hp with the mercury style fuel pump.
I do have an electric priming pump installed and priming makes no difference as it often takes a shot of starting fluid when cold. Warm and it usually starts right up.

 

[jerryjerry05]

What seals?

 

[Redbarron%%]

The seals mentioned in the part about the fuel pump. I assume that they seal between the pump and the crankcase or transfer port?

 

[jerryjerry05]

Pic #2 of the pics you posted, there's a thick paper gasket that fits over the stud and the bottom hole.
#7 in the pic I inserted.