dt225 dies out How to test fuel pump

[baldbob]

Guys
The engine will run fine fast or slow for awhile but then acts lick its staved of fuel and dies out. The bulb isnt flat or especially soft but after I pump the fuel bulb a few times I'm back in business for a little while. I tried replacing the fuel/water separator with no affect. New marine gas, no water in fuel. I'm thinging the fuel pumps are going bad. Its there an easy way to test them?

[seaox230c]

You can test the output of the high pressure pump but you need some stuff. A pressure gauge that reads at least 50 pounds psi full travel...you don't want one that reads more than 100 or its tough to read at the lower numbers.. about 10-15 feet of 1/4 fuel hose a 1/4 brass t and some small hose clamps..slide the oil tank out of the way and find the line from the pressure regulator to the fuel rail. Insert the T in the path of that line and clamp. the last fitting on the T is connected to the rest of the long fuel line that goes to the gauge . I made mine long enough to reach the steering wheel so I could monitor it myself while in motion. You might need some assorted fittings to connect the gauge to the hose. clamp everything well because that line is pressurized to 40 psi. Normal operating pressure is 36-39 psi all the time the engine is on. 2 mechanical low pressure pumps feed the line to the hp pump. These usually go bad before the electrical pump..the check valves break inside these units. You have to split the pumps to see this and the check valves are not part of the rebild kit. If the hp pump goes bad you will probably see 0-5 psi on the gauge and the engine will die instantly..if the lp pumps are bad you will have less than 35 but more than 5. Its tough to diagnose the low pressure pumps as bad...usually if you die at idle .Don't buy a used lp pump the check valves are probably bad

[baldbob]

Thanks for the info. I replaced both the LP pumps about 6 years ago. The motor is a 2003. Maybe the LP pumps are only good for 6-7 years. Seems a little short to me but it would be consistent.

[seaox230c]

If it runs rough or poorly for a few min before it dies most likely lp issue. If it just runs good and dies suddenly then hp issue. Buy 1 or both of the rebuild kits they are cheap enough and open them up......mark the orientation between all the segments....if the check valves are intact....rebuild it. They are small clear plastic discs. Tough to see but if you find bits of clear plastic in pump body then bad..mine went after about 10 but they might have been bad for a while. Don't lose the small o rings from behind the body

[Solarman]

Id like to think the lp fuel pumps would last longer too. Six to 7 years isn't good. You can take the pumps apart carefully, and not have to rebuild them if you don't damage the diaphragms. Also wouldn't hurt to have a kit for backup if one did tear.

If the old lp pumps were bad in the past, did the check valves break apart, or diaphragms just tear? I'm guessing check valves broke apart. So...

If fuel is the issue (it sounds that way), and you replaced the lp pumps in the past, did you remove the float and needle valve seat in the VST when you replaced them, at that time? And clean the in-line filter at bottom of VST to hp pump? If you did clean the VST, did you remove the needle seat (possible restrictive blockage from old lp pumps), and did you reset the float level per manual?

And yes, the problem could still be related to lp pumps? When you remove each pump, also check that small hole where it is mounted for possible blockage. That hole provides the negative, and positive pressure to keep those lp pumps working properly.

Post backwhen able, good luck.

[baldbob]

Last time I replaced the LP pumps and the little fuel filter by them. The motor runs fine then dies out at various times. No rhythm or reason. I pump the fuel ball several times and I'm off and running again for 10-20 minutes. I have new LP pumps in hand. Do you think I should do the HP pump as well? I got about $190 in the new LP pumps. I check what a new HP pump is. Thoughts

[artdf175]

When you say you pump the Bulls several times and you are off and running indicates it is more of s fuel line problem
If you have a small portable fuel tank or borrow one
Take and try running off this first
Sounds like either a fuel line blockage or the air vent to your tank is plugged
Rule that out first

[Solarman]

Have you had any problems with bad fuel, or trash in any filters?
If no trash, then check output of low and high pressure fuel pumps.
It could be a problem with low pressure pump not supplying enough fuel for high pressure pump. Or possibly the regulator is not maintaining proper pressure?
If you had trash, you may still have trash restricting fuel flow into VST at the float needle valve.

Let us know what you find, good luck.

[Valvguy]

Sure would love to know what the fix was. My DT-140 is doing the Exact Same Thing. I already rebuilt the mechanical fuel pump without fixing the problem.

[Kunselmr]

I had a similar problem with my DF40. It took me years to figure it out. I believe this problem can happen to almost any outboard. The engine runs fine even at WOT but becomes fuel starved after the fuel runs out in the VST. I confirmed this with a fuel pressure gauge after the low pressure pump. I ruled out everything before the fuel pump so logically I replaced the low pressure fuel pump. Problem still persisted. I gave up for a long time until one day I took the oil fill cap off shortly after running and a decent amount of pressure released. I found that the breather tube was kinked under a cover. The pressure that builds in the case especially at wot prevents the diaphragm in the pump from operating. Check the breather tube/PCV valve.