Hard to start/choke question mercruiser 4.3 1987

[HasseEd]

I cant get my choke closed when I push the throttle all the way open and back again. It always stay open. The is no wires connected and cant see any anything that will engage the choke. Is the anything missing on my carb ?
I have to pump the throttle at least 10-15 times before i try start. The carb was rebuild by former owner.

Have a look at the picture, is there something missing here ? which carb do I have?

/H

 

[Another retired guy]

Re: Hard to start/choke question mercruiser 4.3 1987

I have a 1988 4.3 with a Rochester carb which has a thermostatic spring operating the choke. The spring is mounted on the manifold and connected to the choke with a small rod. There are no other controls- it operates automatically. I also had some cold start problems and traced it to the rod jamming against the spring casing. It doesn't take much to stop these things working!
The second picture looks the same as my set-up and I see the casing for the spring bolted to the manifold. Try removing and disassembling this device to see what's going on inside. It operates purely on manifold temperature and opens/closes as temp varies. There is no "stop" when it's open and moving the throttle to full and back doesn't reset anything.
Another possible cause could be the vacuum cylinder ( pulls the choke plate open once the engine fires ) is stuck in the " open" position.

 

[Don S]

Re: Hard to start/choke question mercruiser 4.3 1987

If you open the throttle slightly, can you push the choke plate closed by hand?

 

[HasseEd]

Re: Hard to start/choke question mercruiser 4.3 1987

I have a 1988 4.3 with a Rochester carb which has a thermostatic spring operating the choke. The spring is mounted on the manifold and connected to the choke with a small rod. There are no other controls- it operates automatically. I also had some cold start problems and traced it to the rod jamming against the spring casing. It doesn't take much to stop these things working!
The second picture looks the same as my set-up and I see the casing for the spring bolted to the manifold. Try removing and this device to see what's going on inside. It operates purely on manifold temperature and opens/closes as temp varies. There is no "stop" when it's open and moving the throttle to full and back doesn't reset anything.
Another possible cause could be the vacuum cylinder ( pulls the choke plate open once the engine fires ) is stuck in the " open" position.

Thanks !
The only thing thats keeping the choke in open position is the springloaded thermostatic spring. I will have to disassemble and take it apart and see how it?s working.
/H

 

[Don S]

Re: Hard to start/choke question mercruiser 4.3 1987

If the picture of your choke coil is with a cold engine, either the choke coil is damaged, or it's the wrong one.

 

[Don S]

Re: Hard to start/choke question mercruiser 4.3 1987

I looked in the manual, and the parts lookup, ans it looks like you do indead have the wrong choke stove.
You should have one like this. Merc PN 72625

 

[Another retired guy]

Re: Hard to start/choke question mercruiser 4.3 1987

The fix may be simpler than that! Assuming your carb is the same as mine it looks as though the coil has been mounted "backwards".
I just went to check mine and the rod coming from the spring is closer to the vacuum unit. So looking at your picture the rod should be on the right side. If it is backwards then the rod is not long enough to operate the choke and is holding it open under tension.
Worth a try!

 

[Don S]

Re: Hard to start/choke question mercruiser 4.3 1987

You can't turn them around, it only has a single screw. Besides, the problem is the coil rod need to be at the bottom of the choke stove when cold to close the choke plate. Then when the coil gets hot it pushes UP to open the choke plate.

 

[Another retired guy]

Re: Hard to start/choke question mercruiser 4.3 1987

Agree re the single screw but maybe during the prior carb rebuild the thing was reassembled incorrectly. ?
If you rotate the unit 180 degrees wouldn't the coil still operate the same way? ie the rod will still be at the bottom but further away from the choke plate connector.

 

[HasseEd]

Re: Hard to start/choke question mercruiser 4.3 1987

The picture is taken with a cold engine. Feels like something got wrong when rebuilding the carb...
Had a better picture that shows choke coil. I will take i apart tomorow !
/H

 

[Another retired guy]

Re: Hard to start/choke question mercruiser 4.3 1987

Ah, I see from that new picture that there are some subtle differences between your coil and mine. I don't see how yours could be reversed so best bet is that something has gone wrong inside the casing
But first check that the rod isn't rubbing against the metal casing - it looks to be very close to the edge.

 

[HasseEd]

Re: Hard to start/choke question mercruiser 4.3 1987

I looked in the manual, and the parts lookup, ans it looks like you do indead have the wrong choke stove.
You should have one like this. Merc PN 72625

View attachment 156962

I think I found the problem ! Someone have turned the casing in the wrong direction on choke coil and forced the choke into an open position. If you look at my picture of the choke coil there is place for the knee of the rod thats on the wrong side.
I will try tomorrow and see if it?s working.
Thanks guys !

 

[Don S]

Re: Hard to start/choke question mercruiser 4.3 1987

Not sure how you can turn it around, there is only one mounting screw hole.

 

[Another retired guy]

Re: Hard to start/choke question mercruiser 4.3 1987

The metal casing clips onto the coil base. Looks like someone has jammed it on the wrong way around. I don't see how the rod can be attached to the coil. Probably isn't!!

 

[HasseEd]

Re: Hard to start/choke question mercruiser 4.3 1987

Took two pictures after I took it apart. Mayby the rod doesen`t fit when the turning the matel casing. I think my coil looks like the new one ? I try to see if it fits today.
/H

 

[Another retired guy]

Re: Hard to start/choke question mercruiser 4.3 1987

The coil looks to be ok. Just insert the bottom end of the rod into the loop at the bottom of the coil. If everything is adjusted correctly the choke plate should now be closed under light tension.

 

[Don S]

Re: Hard to start/choke question mercruiser 4.3 1987

You can try it, but that spring looks like it's distorted (Gap between last coil) and my not move enough when it gets hot, to open the choke. Just something to be aware of.

 

[HasseEd]

Re: Hard to start/choke question mercruiser 4.3 1987

I think it works now !
Took some new pictures.
First pict: choke coil without metal casing
Second: Cold engine(not running )
Third: Cold engine (running)
Fourth: Warm engine( not running)

It starts much better now when engine is cold. But still got some problem to start it when varm. If I try to start it after 15-30 minutes, I must pump the throttle 15-20 times to get it started. Mayby I must check if timing is ok.

/H

 

[Another retired guy]

Re: Hard to start/choke question mercruiser 4.3 1987

Looks as though choke is working ok now, but did you check what position the plate was in after cooling down for 15-30 minutes?
Also did you have this warm-start problem before?
As Don S posted the spring is deformed so may not be working as designed thus placing the choke plate in the wrong position for that particular temperature?
Have you checked that the carb fuel pump is actually pumping gas - 15 to 20 pumps on a warm engine is a lot of gas!

 

[HasseEd]

Re: Hard to start/choke question mercruiser 4.3 1987

Looks as though choke is working ok now, but did you check what position the plate was in after cooling down for 15-30 minutes?
Also did you have this warm-start problem before?
As Don S posted the spring is deformed so may not be working as designed thus placing the choke plate in the wrong position for that particular temperature?

After 15-30 minutes the choke plate was in position open because the engine temp was still over 130 F.
We have warm and nice weather here in Sweden now

I will check tomorrow if choke plate will close when engine is cold.
Yes, I had warm-start problem before.


/H