Suzuki DF140 Bogging Down at 2500 RPMs

W

Westie

New member
Hi there - hoping for some advice on an engine issue

I have twin 2007 Suzuki DF140s and today the starboard engine shut down at about 3000 rpm as I left the marina. It started fine and idled without issue before we left the slip.

Once it shut down, we pumped the ball and it was collapsed. It wouldn't start at neutral so I rev'ed it a little and started at high RPM. The RPMs were not holding firm so we returned to the slip.

At the slip, we found that it started fine and idled well but couldn't hold consistent RPMs above 2500. It was bogging but not shutting down.

The engine has about 700 hrs. I had replaced the low pressure fuel filter at 400 hr and changed the fuel/water separator recently. Also, the port engine ran perfect so I'm ruling out bad gas.

Everything ran great 10 days ago and the boat is used regularly.

Right now, I'm thinking high pressure fuel filter but that shouldn't need to be changed until 1000 hours.

Any thoughts?
 
Primer bulb new or old and vertical?

All fuel hoses including ones in rigging hoses new or old?

tank vents clear?

Does it have high pressure pump filter?

VST clogged?
 
Thanks for the questions. Responses:

Primer bulb new or old and vertical?
- Old and vertical

All fuel hoses including ones in rigging hoses new or old?
- Old

tank vents clear?
- Yes

Does it have high pressure pump filter?
- Yes with 700 hr. PM says change at 1000

VST clogged?
- Not sure how to check.
 
Wouldn't the collapsed primer bulb indicate a problem on the tank side? It may be as simple as a clogged screen on the fuel pickup in the tank. It is free to check - unhook the hose from everything beyond the tank and blow through it. If it is plugged, that should dislodge enough to make it run until the screen can be removed and cleaned properly.

It could also be any filters on the tank side of the bulb. If the bulb is flat then the motor fuel system is trying real hard to draw fuel from the upstream side, so the pumps, filters and vapor tank are at least trying to function.

Good luck - I hope it is an easy fix.
 
On our shakedown cruise our big new Suzuki ran fine but the new 9.9 sucked the bulb flat and died. Something was installed wrong before the bulb or was defective. I am installing a larger filter/water separator and will replumb the small engine parts, hopefully that will sort it out and since the big motor runs fine and there is a new line from the tank to the filter I know that is not the problem.

If the bulb is sucked flat it seems that the Suzuki 140 problem is before the bulb. Do both run separate lines and filters all the way from the tank? If rhey share any part of the system and one motor runs good then it is good in the shared section.
 
I haven't delt with outboards in decades. I have been sorting out diesel fuel systems and know their problems well, am I missing something on outboard systems with primer bulbs?
Thanks.
 
Checked with my buddy and he said the bulb wasn't "collapsed" or "deflated". I don't think the issue is before the bulb.

Also, he pumped it while at high RPM, the engine was running rough and pumping the bulb didn't change anything.

Im thinking its a clog in the VST
 
I would make sure to change the filters out. Not too expensive to change them out. Also make sure to change the fuel separator. If you have any water in the system it becomes less efficient at separating when near capacity. You may have taken in some water from a source such as a marina. Change all three, water/fuel separator/both filters.
 
I had a similar issue once. I checked all the usual suspects before having to be towed back in. It turned out to be a crimped fuel line after the last service was done. I straightened out the line and the problem was solved.
 
Had same problem. I pulled the input end of the fuel bulb loose and connected it to a remote 6 gal fuel tank from my dinghy. Pumped the bulb and all ran well. That isolated everything but the fuel feed from the tank. New filter and hose was in good shape. Screen on tank pickup tube was clogged with a piece of plastic.
 
Fuel hoses have an inner hose and can separate or kink at sharp bends like going from rigging tube to the under cowling fuel system

Checking the fuel rail pressure will help

I dont have a factory service manual to look at the fuel system

VST is vapor separator tank can accumulate debris and in Yamaha motors, there is high pressure pump inside the VST with a screen filter at the pump bottom. The pump pressurizes the fuel rail to the injectors
. Check rail pressure would be helpful
 
Thanks all!

I ordered new filters and will pull out next weekend for maintenance.

Any input on replacing the H/P Filter?

I read someone say they used a special tool but I don't see what they are referring too.

Anyone do this work themselves, that could offer advice?
 
BrentB - I will! I am so thankful for this resource!

Pulling the boat out Thursday. I plan to change all filters, spark plugs, inspect all hoses, and valves.

Ordered 3 day delivery from Browns Point. I hate having her unavailable!
 
Guys - I replaced the fuel filters (low and high) and the fuel water separator. No change.

I dont hear any leaks.

I really dont think its bad gas. The fuel water separator was fine and the other engine is running perfect. I filled the tanks up at the same time/same pump.

I can see the check valve on the pick up and it looks fine. I dont know how to inspect further.

Any suggestions?
 
I wooed inspect ASV

ASV is unscrewed from the fuel pickup elbow fitting and hose removed from other end

ASV can fail

Takes a few minutes to remove
 
Yep, I agree but spring and ball can corrode or clog with debris , slowing down fuel

Another approach is connect the portable gas tank to motor bypassing the tank to determine which side the issue is.

If have external fuel filter head,, easy to replace fuel filter and O ring and check the filter head is not clogged or blocked

Sharp bends in fuel hose can slow or stop gas

Several possibilities

Post the answer!
 
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