DF70 Idles great, but will not rev up.

[beeze455]

Here is what is happening: https://www.youtube.com/watch?v=Kj_d3FxsaXU

We just bought this motor. We where told the motor ran fine, but obviously it does not and im not sure the owner ever had it running.

Thing idles great and will idle for hours. It hits a certain rpm and just starts surging like in the video.

This engine has 16 hours on it and I have a parts engine with 268.

SDS listed on current code of injector or harness problem, but the other ecu shows no codes when hooked up.

New plugs, swapped injectors, fresh gas, When surging like this fuel PSI is 30. Just took off VST and it is very clean. If I clamp the return line on the fuel rail, it will just die. Compression is 180 in all cylinders.

Thanks for the help!

[Moonlighter]

Does it do the same thing when it is in gear on the water?

[beeze455]

Have not had it in the water yet. I assume it will do the same thing.

Is 30 PSI high enough? Why does my motor stall when I clamp the return line?

[Moonlighter]

These engines have a neutral throttle limit switch that prevents them being revved past about 3000rpm when they are not in gear. The ecu limits fuel supply, restricts spark and advance.

That video sounds to me very similar to what happens when it hits this limiter. They surge and fart, much like a race car that is driving down pit lane with the pit lane limiter on.

Simple solution: dont rev it up in neutral, no need to do that.

[beeze455]

They do have that. I start it with it connected and once running I unplug the plunger. SDS also shows it off, so I know that is not it.

[Moonlighter]

Well, it would have helped to know that!

That said, disconneting the sensor may well leave the ecu missing the signal that the motor is in gear -Im not sure about that but it seems likely. Do you have the Suzuki service manual for this motor?

Really, why not tell the full story up front, starting with the model year of the motor, and why you started doing all this work in the first place, before (apparently) even having this motor on a boat and water testing it?

[beeze455]

The full story like I said above is we bought the motor and it does not run right. The person we bought it from did not have a harness, battery and was not home when I picked up. the price was right and we expected issues. I mounted the motor and noticed this surging issue.

The SDS program shows when the neutral switch is on or not. The switch needs to be on to start and off to rev.

Yes, I have the service manual.

Ill be working on it today.

[beeze455]

The evinrude that we are trying to get running is a 98 and the suzuki parts is also.

I find it interesting that the suzuki VST tank is different than the evinrude. The suk has a pressur regulator in the bottom off it and the line one the bottom is a different location.

[beeze455]

Put ii in the water just to make sure and does the same thing. Does it at 3700RPM. Ran fine at 3400 RPM,

[beeze455]

It does seem to crank kinda slow. Heard if the ECM sees below 12v that it may limit the RPMS to 4k. I added another battery and going to let them both charge until I see a static level of 13. Static level is 12.5 right now.

[beeze455]

I put the other battery on and it did the same thing. I let it keep charging, swapped ECU, Swapped MAP sensor and swapped the coil packs. It is alive and running good. I am thinking the motor is not charging the batteries, so gotta fix that.

[Samuel Kaymen]

I have a 2000 DF70 that idles perfectly, however it will not run smoothly when I throttle it up. When I cut back on throttle it smooths out again. Any suggestions would be greatly appreciated.

[odellyt]

I'm having the same troubles. Can't get it above 3500 rpm. Did you resolve it? was it not charging?