MerCruiser 140 Stalls While Accelerating

[Jacalore]

From another thread: Replaced all fuel lines and fittings from tank to engine and from fuel pump to carb. All filters changed (in-line, fuel pump, carb). fuel tank emptied and fresh fuel added.

From AllDodge: Starting to look like we are circling the wagons around the problem and may come up with it before long. Fuel pressure, carb and compression is all there is left

Will check compression and double check timing. Thanks.

(this thread morphed from another, and became mis-titled)

 

[Jacalore]

Re: MerCruiser 140 Stalls While Accelerating

Ordered gauge and tools to complete all necessary tests. From fuel pressure (leaks and blockages) to compression and timing. Hope to have problem pinpointed next week. The cure will be another matter, of course, but you gotta start somewhere. Thanks for all the help and advice. This is all new to me (lifelong sailor) so I appreciate all the help!

 

[alldodge]

Re: MerCruiser 140 Stalls While Accelerating

I'm sure it will work out. Look forward to your findings

 

[Jacalore]

Re: MerCruiser 140 Stalls While Accelerating

Installed clear 3/8" fuel line from inline fuel filter to fuel pump intake. There are large pockets of air present in the line. After the engine warms up, and starts to drop to idle rpm, it quits. Can only start it again after throttle choke and will run for a few seconds at high rpm then die. Air pockets move around but never move thru. Removed inline fuel filter and ran straight from tank to fuel pump, still see large air pockets moving around in the clear fuel line. Do I have a leak in the tank? Or are these air pockets normal? Thanks.

 

[andyspoppa]

Re: MerCruiser 140 Stalls While Accelerating

Hi,
I was suffering these same symptoms and found that my fuel pump was full of crud/rust on my 165. Looked for a fuel pump and got one out of Florida...installed it, primed by turning over engine with coil wire unplugged...hooked the muffs up, connected wire and it started WITHOUT throttle advancing, spraying the carb with starter fluid, or anything except in idle! It starts every time in about 1/3 a revolution of the crank pulley! A cold engine crank without frustration...oh yeah! Just my two cents for what it's worth...

 

[Jacalore]

Re: MerCruiser 140 Stalls While Accelerating

replaced the fuel pump last week... trying to figure out if I'm onto the problem (air pockets in fuel line) or chasing a non-issue?

 

[Jacalore]

1985 MerCruiser 140 Stalls While Accelerating

1985 MerCruiser 140 Stalls While Accelerating

Idles ok, stalls if you give it throttle.

This is what I've done: Replaced all fuel lines and fittings. Changed inline fuel filter and filters in pump and carb. Ran engine from exterior tank with fresh gas, same symptoms. Replaced fuel pump with new (pressure at 6 between pump and carb). Replaced carb with identical part number carb from '86 engine (not rebuilt). New plugs. Compression 135-140 in all cylinders. Timing set.

The only weak link I see now is the carb... but symptoms remained the same with original and replacement. What's left?

 

[alldodge]

Re: MerCruiser 140 Stalls While Accelerating

Ordered gauge and tools to complete all necessary tests. From fuel pressure (leaks and blockages) to compression and timing. Hope to have problem pinpointed next week. The cure will be another matter, of course, but you gotta start somewhere. Thanks for all the help and advice. This is all new to me (lifelong sailor) so I appreciate all the help!

What was the results of the three test listed above?

Installed clear 3/8" fuel line from inline fuel filter to fuel pump intake. There are large pockets of air present in the line. After the engine warms up, and starts to drop to idle rpm, it quits. Can only start it again after throttle choke and will run for a few seconds at high rpm then die. Air pockets move around but never move thru. Removed inline fuel filter and ran straight from tank to fuel pump, still see large air pockets moving around in the clear fuel line. Do I have a leak in the tank? Or are these air pockets normal? Thanks.

The engine is not getting fuel. It's one thing to see air bubbles but another for them not to move and go away after a short time. Can you take a picture of the fuel pump on the engine and what is the part number of the fuel pump you bought?

 

[Jacalore]

Re: MerCruiser 140 Stalls While Accelerating

Compression good, 135 - 140 in all four cylinders. Timing is almost dead on, lagging just a hair at 8 BTDC. Ran the engine from an external tank, same prob: idles mostly ok, stalls if you give it throttle. The fuel pump is a mechanical type - the shop put that on and said the pressure improved from 2 to 6. I thought sure it was a fuel delivery prob, now I'm not so sure.

 

[alldodge]

Re: MerCruiser 140 Stalls While Accelerating

Compression good, 135 - 140 in all four cylinders. Timing is almost dead on, lagging just a hair at 8 BTDC. Ran the engine from an external tank, same prob: idles mostly ok, stalls if you give it throttle. The fuel pump is a mechanical type - the shop put that on and said the pressure improved from 2 to 6. I thought sure it was a fuel delivery prob, now I'm not so sure.

If the fuel pressure is at 6 psi the engine should have no problem running. The reason I wanted the pic is to see the setup because something is missing in this puzzle, need to see what's going on. You have good compression, spark, air so it should run. Only think left if everything else is up to spec is the carb. Float settings, accelerator pump and jets.

 

[Jacalore]

Re: MerCruiser 140 Stalls While Accelerating

The carb was replaced with another, same part number (not rebuilt) but no change - same symptoms, so I hesitated to go there... but I've come full circle, not much else left now... I know all these specs by testing myself except for the fuel pump and pressure between pump and carb, the shop made that test.

 

[alldodge]

Re: MerCruiser 140 Stalls While Accelerating

Agree, I'm out of options without being able to see or my hands on

 

[Jacalore]

Re: MerCruiser 140 Stalls While Accelerating

Here's the photo you asked for... see anything?

 

[Bondo]

Re: 1985 MerCruiser 140 Stalls While Accelerating

Re: 1985 MerCruiser 140 Stalls While Accelerating

Idles ok, stalls if you give it throttle.

This is what I've done: Replaced all fuel lines and fittings. Changed inline fuel filter and filters in pump and carb. Ran engine from exterior tank with fresh gas, same symptoms. Replaced fuel pump with new (pressure at 6 between pump and carb). Replaced carb with identical part number carb from '86 engine (not rebuilt). New plugs. Compression 135-140 in all cylinders. Timing set.

The only weak link I see now is the carb... but symptoms remained the same with original and replacement. What's left?

Ayuh,... The Symptoms says Accelerator pump in the carb,...

 

[alldodge]

Re: MerCruiser 140 Stalls While Accelerating

Thanks for the pic I was pretty sure you had the old style pump. I see nothing out, that causes me concern. Should use clear tubing for secondary diaphram pump line, but this is not the current issue. The connection where the diaphram line goes to the carb is not a vacuum line correct? Other then that if this was mine, I would start with putting a pressure gauge on the fuel pump line and verify the pressure. Since I didn't put the pump on, I would take the fuel pump filter cover off and verify the filter and internal diaphram are positioned correctly

 

[slothman]

Re: MerCruiser 140 Stalls While Accelerating

It seems like you are getting fuel. If the fuel pump is new and you swapped out the carb. My next guess would be weak spark. Check the coil, cap, rotor, plugs, etc.

 

[Jacalore]

Re: MerCruiser 140 Stalls While Accelerating

New plugs today, thought they would have an effect since originals looked pretty worn out and black at the firing end. But no...

Let me back up a bit, in case something jumps out at you: I bought the boat a couple months ago (been messin' with it ever since!). PrevOwner said last summer he rebuilt the carb, put in a new head gasket and changed over to electronic ignition. Problem he had is the problem I have - no acceleration. PO said all the boat needed was a carb rebuild because he neglected to put a new float, and now when the "bowl empties, it doesn't get refilled" and stalls. Boat has sat since. Figured I could handle this, got a good price... and ... here I am.

 

[Bondo]

Re: MerCruiser 140 Stalls While Accelerating

New plugs today, thought they would have an effect since originals looked pretty worn out and black at the firing end. But no...

Let me back up a bit, in case something jumps out at you: I bought the boat a couple months ago (been messin' with it ever since!). PrevOwner said last summer he rebuilt the carb, put in a new head gasket and changed over to electronic ignition. Problem he had is the problem I have - no acceleration. PO said all the boat needed was a carb rebuild because he neglected to put a new float, and now when the "bowl empties, it doesn't get refilled" and stalls. Boat has sat since. Figured I could handle this, got a good price... and ... here I am.

Ayuh,.... So ya bought a boat with a known carb problem,....

Ya replaced everything but the carb, 'n it didn't improve,...

Ya swapped on another old carb, 'n no improvement,....

Ya say Everything is dead on, but the carb,.... 'n ya put in new spark plugs,...

I'd try another Carb,....

 

[alldodge]

Re: MerCruiser 140 Stalls While Accelerating

New plugs today, thought they would have an effect since originals looked pretty worn out and black at the firing end. But no...

Let me back up a bit, in case something jumps out at you: I bought the boat a couple months ago (been messin' with it ever since!). PrevOwner said last summer he rebuilt the carb, put in a new head gasket and changed over to electronic ignition. Problem he had is the problem I have - no acceleration. PO said all the boat needed was a carb rebuild because he neglected to put a new float, and now when the "bowl empties, it doesn't get refilled" and stalls. Boat has sat since. Figured I could handle this, got a good price... and ... here I am.

You have the same issue as previously mentioned, a fuel suppy issue. If you had a spark issue it wouldn't run

 

[Jacalore]

Re: MerCruiser 140 Stalls While Accelerating

Ayuh...

Ayuh,.... So ya bought a boat with a known carb problem,....

Ya replaced everything but the carb, 'n it didn't improve,...

Ya swapped on another old carb, 'n no improvement,....

Ya say Everything is dead on, but the carb,.... 'n ya put in new spark plugs,...

I'd try another Carb,....