Starts with first turn of key, but immediately dies -- help!

[colding]

Hey guys, looking for some advice. Two weeks ago, took the family out for some fishing and crabbing. Motor started right up. I drove it at cruising speed for about 20 miles with a few stops in between. On the last stop, the engine would fire, but only run a few seconds before dying. Had my son try to keep pumping the bulb while running, but it would still die after 10-30 seconds each. Started looking at all my fuel lines and connecting to make sure I had no leaks. None found. Pulled the cover off the motor and notice once of the carbs had a leak around the gasket of the float bowl. We we able to get back to the landing (about 7 miles away when issues started) by running wide open for the 10-30 seconds it would run without dying completely. Luckily the battery held out for the 50 or so times I had to restart.

Get it home and immediately order carb kits for all 4 carbs. Everything arrives in a few days. Putting carbs back together I notice another problem. Most of the plastic float bowls are warped and won't seal properly. So, I promptly order 4 new float bowls. They arrive in time for the next weekend. Get all the carbs back on and confirm there is no longer a leak around the float bowls or anywhere else on the carbs.

Now, the issue is not fixed. Not only that, it seems worse than before. It will no longer stay running for more than a second at a time. It fire right up every time I turn the key, but dies almost immediately. I go buy an auxiliary tank with new primer bulb and fuel lines and hook that up in place of my built-in tank/fuel-water separator/bulb fuel lines just to rule out any issues there. Still the same issue. The bulb stays primed the entire time I'm trying to start. There is definitely fuel/oil getting to the carbs. The bowls are full of fuel when I remove them from the motor.

My best guess now is the fuel pump. But a new fuel pump for my motor is almost $400. I don't mind buying it, but I definitely don't want to if it's not the issue. I guess my questions are these:

1) How can I test the fuel/oil pump? I was thinking I could remove the output hose on top of the pump and try to start it and see if fuel shoots through it. But, even if it does, I don't know how much force it should be pushing through it.

2) If it's not the fuel pump, where else should I be looking?

BTW, this is a 2005 Johnson 90HP Saltwater series. Model #J90PLSOA. I've had the boat for almost a year and had it out almost every weekend since I bought it with no issues until now. Looking for any insight you might have. Trout season is here.

 

[Tim Frank]

Re: Starts with first turn of key, but immediately dies -- help!

Now, the issue is not fixed. Not only that, it seems worse than before. It will no longer stay running for more than a second at a time. It fire right up every time I turn the key, but dies almost immediately. I go buy an auxiliary tank with new primer bulb and fuel lines and hook that up in place of my built-in tank/fuel-water separator/bulb fuel lines just to rule out any issues there. Still the same issue. The bulb stays primed the entire time I'm trying to start. There is definitely fuel/oil getting to the carbs. The bowls are full of fuel when I remove them from the motor.

My best guess now is the fuel pump. But a new fuel pump for my motor is almost $400. I don't mind buying it, but I definitely don't want to if it's not the issue. I guess my questions are these:

1) How can I test the fuel/oil pump? I was thinking I could remove the output hose on top of the pump and try to start it and see if fuel shoots through it. But, even if it does, I don't know how much force it should be pushing through it.

2) If it's not the fuel pump, where else should I be looking?

BTW, this is a 2005 Johnson 90HP Saltwater series. Model #J90PLSOA. I've had the boat for almost a year and had it out almost every weekend since I bought it with no issues until now. Looking for any insight you might have. Trout season is here.

Before you spend $400- on a fuel pump....or throw any more parts at it....just hoping they might stick, spend $40- on an OEM service manual....that will remove most of the guesswork.
The troubleshooting sections are well laid out, and specific to your motor.

 

[colding]

Re: Starts with first turn of key, but immediately dies -- help!

I have ordered it, but it won't be here until later next week. And it was not $40. Cheapest I found it for was $65.

Was hoping for some things to try this weekend.

 

[Tim Frank]

Re: Starts with first turn of key, but immediately dies -- help!

1) How can I test the fuel/oil pump? I was thinking I could remove the output hose on top of the pump and try to start it and see if fuel shoots through it. But, even if it does, I don't know how much force it should be pushing through it.

2) If it's not the fuel pump, where else should I be looking?

1) I have two OEM service manuals and the procedure for testing the fuel pump is the same. You doubtless have a VRO so it may be different.
To do a proper test you would need a fuel pressure gauge ....full scale reading LT 10 PSI....5 PSI would be better. You would need to tee it into the the fuel line between the fuel pump and the carbs. At 600 RPM fuel pressure would need to be ~ 1 PSI. At 2500 RPM ~ 1.5 PSI, at 4500 RPM ~ 2.5 PSI.

Have you drained all the fuel lines and refilled with fresh fuel?

 

[Joe Reeves]

Re: Starts with first turn of key, but immediately dies -- help!

Now, the issue is not fixed. Not only that, it seems worse than before. It will no longer stay running for more than a second at a time. It fire right up every time I turn the key, but dies almost immediately. I go buy an auxiliary tank with new primer bulb and fuel lines and hook that up in place of my built-in tank/fuel-water separator/bulb fuel lines just to rule out any issues there. Still the same issue. The bulb stays primed the entire time I'm trying to start. There is definitely fuel/oil getting to the carbs. The bowls are full of fuel when I remove them from the 2005 90hp Johnson motor.

If the problem was fuel, the engine should continue to run until those carburetors were out of fuel. Start trouble shooting with the basics rather than to assume the cause or start throwing parts at it.

But before getting into the basics..... a common problem is that the ignition switch develops a intermitent shorting problem that allows a small amount of voltage to travel down the black/yellow wire (kill circuit) to the powerpack. This will in time destroy the powerpack. To test the ignition switch, simply disconnect that black/yellow wire from the ignition switch. If this cures the problem, replace the ignition switch. If it does not cure the problem, read on.

1 - Check the compression. What are the psi reading of each cylinder.

2 - Check the spark. The spark (with the spark plugs removed) should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?..... Note that the gap of 7/16" is important!

If possible, check the spark when this problem takes place.... the reason being as follows. The stator under the flywheel is a two fold component. There are a series of small coils lining the sides of the stator that pertain to and are the beginning of the battery charging system. There are two larger coils within that stator that pertain to and are the beginning of the ignition system which provide approximately 300 AC volts to the powerpack to energize the pack.

These two larger coils are subject to breaking down, melting down, due to the extreme heat generated in that area. When this happens, when cool, the stator may function normally, but as it becomes heated, it breaks down and encounters a voltage drop to the powerpack. This results is a situation where the spark is weak, erratic, and eventually non existent.

This may not be your problem BUT these two areas are at the top of the list of the trouble shooting chart regardless of what the final found cause might be.... Example, a failed head gasket could force a small spray of water into a cylinder that would destroy a piston BUT at the same time would result in a overheating problem. Assuming the water pump is at fault and replacing it would be a waste of time and money, whereas a simple compression test would reveal the problem immediately.

The VRO.... Find the hose leading from the VRO to the crankcase (pressure/function hose). Disconnect the hose, then pump the fuel primer bulb up hard. If fuel/oil flows out of the pump side of that hose, the VRO requires rebuilding. Crank the engine over momentarily to make sure you get a healthy pulse out of the crankcase side of that hose fitting. The pulse is actually a healthy blast caused by the downward force of the related piston. With that hose reconnected, disconnect the hose of the VRO that leads to the carburetors, then temporarily connect a longer hose to lead away from the engine to a container of some sort. Crank the engine over to see if the VRO actually shoots fuel out of that hose as it should.

Since you had the primer bulb being pumped when this problem surfaced (acting as a manual fuel pump) and no improvement occurred, that eliminates the VRO as a problem UNLESS a VRO diphragm has failed and is letting fuel flow thru it directly into the crankcase (flooding) as suggested above (the pulse/function hose check).

Let us know what you find.

 

[colding]

Re: Starts with first turn of key, but immediately dies -- help!

Thanks for the advice. I'll be starting on it first thing tomorrow morning and I'll let you know what I find.

 

[colding]

Re: Starts with first turn of key, but immediately dies -- help!

This is what I've found so far:

1) Disconnected the yellow/black wire at the ignition. Problem still persists.
2) Checked spark with two different meters. Both show consistent blue/white spark on all 4 cylinders.
3) Visually inspected all electrical connections.
4) Had do way to check the PSI coming out of the OMS pump to the carbs, but it definitely pulsed out when the ignition was turned over. It did seem like it was not much pressure, but I have no other source to compare it to.
5) Took the fuel and air portion of the OMS pump apart, leaving the oiling portion undisturbed. Found that there are two small tears in one of the diaphrams, approximately 1/4" in length each.

Could this be causing the issue? You can hardly see the tears until you put a little strain on the diaphram. I'm about to order the pump repair kit, which is $145, and it includes both new diaphrams.

Anything else I should look at? My OEM service manual should be here tomorrow according to tracking details on my package.

 

[Joe Reeves]

Re: Starts with first turn of key, but immediately dies -- help!

Two tears in one of the VRO diaphragms? Yes, that'll do it. Unless you developed two problems at the same time, Rebuilding that VRO should put you back in business.

 

[colding]

Re: Starts with first turn of key, but immediately dies -- help!

Just an update. I finally broke down and brought it to a real marine mechanic who said he'd only charge me $65 for the diagnosis after rebuilding the fuel pump failed to fix the issue. It's amazing how having the right tools for the job makes all the difference. After only a few minutes of his testing, he determined it was the timing sensor. Replaced the $70 part and now she's purring like a kitten again. I doubt I would have ever found the root cause on my own.