Anybody ever hear an EFI act like this before?

[sutor623]

'07 60hp EFI

Had the boat on the trailer and was just letting the jet warm up and it started acting like this a minute or two after starting. Very strange. It has done it before, but always seems to be at idle a few minutes after starting. This is on a cold morning (28 degrees). Note that the engine runs strong, has great compression, and is not setting off any alarms. It runs real strong mid range and WOT and has never shown any other signs of issues that I know of. It also sometimes takes 2-3 times to get it to start.

https://www.youtube.com/watch?v=L2sPIvY1bn8

And this is how it normally sounds:

https://www.youtube.com/watch?v=vMnzBAsZfjk

 

[wrench 3]

Most poor cold start and cold running problems can be caused by a coolant temperature sensor that's giving false readings when cold. The CTS and the manifold temperature sensor have the same resistance scale. So if you check them with the engine cold (having set over night) the resistances of both sensors should be the same.

 

[sutor623]

Thanks wrench that's a great place to start.

 

[sutor623]

Ok, so I followed the manual as far as resistance specs for testing the ECT (temp sensor.) They have very precise temp specs for each OHM. What I noticed was there is a median zone where the sensor is out of spec. It just so happens to be around the same temp the engine is at when it is having these issues, because when the engine first starts in the cold, it idles well, then after a minute it will start to shutter, and about 2 minutes later it will start running great. Then it will run great all day, (we normally only fish a spot an hour tops.)

At 41 degrees its telling the engine the coolant temp is 45.
At 52 degrees its telling the engine the coolant temp is 68.
At 58 degrees its telling the engine the coolant temp is 75.
At 68 degrees its telling the engine the coolant temp is 82.
At 75 degrees its telling the engine the coolant temp is 85.
At 85 degrees its telling the engine the coolant temp is 98.
At 95 degrees its telling the engine the coolant temp is 105.
At 110 degrees its telling the engine the coolant temp is 115.
At 120 it is right on spec, telling the engine its at 120 degrees. And what do you know, it idles perfectly when warmed up...............

What do you think Wrench, does this seem legit to you? If so, you hit the nail on the head man!!

 

[wrench 3]

Twelve degrees would definitely have an effect but its still in a gray aria as far as causing your symptoms. If your readings are correct I'd say that it should be changed but can't promise that it will cure you problem. But then again there are very few absolutes in this business.

 

[sutor623]

Twelve degrees would definitely have an effect but its still in a gray aria as far as causing your symptoms. If your readings are correct I'd say that it should be changed but can't promise that it will cure you problem. But then again there are very few absolutes in this business.

Thanks for the reply Wrench.

Unfortunately I dont think we have found the culprit. I checked my infrared thermometer and it is not calibrated properly.

I used a trusty stick thermometer and put various temps of water in a cup with the sensor and thermometer. The resistance was SPOT ON for all temps.

Where would you go from here? The MAT is hard to get to but I will get the meter on it if you think it is the next culprit. I watched that video and man is that engine running poorly when it is misbehaving...............

 

[wrench 3]

Assuming that you don't have access to a diagnostic tester for the control module, the next step would be to test for normal fuel pressure when it's acting up.

 

[sutor623]

Ok I will get a fuel gauge. Wish I had a DDT but I don't. I am not fond of the Merc dealers around here either.............

Anyways, took it upon myself to pull the MAT sensor and surely enough it stayed at the same resistance as the CTS did. They were both in spec from 36 degrees all the way up to 120 degrees.

 

[sutor623]

MAP sensor was spot on resistance-wise also. At the very least I ruled those all out (hopefully.)

 

[wrench 3]

You'll need a pressure gauge that will go to at least 45 PSI.

 

[sutor623]

Wrench,

Thanks for the continued support.

I bought a nice high pressure fuel gauge today. Goes from 0-100PSI.

Spec for resistance across the fuel pump is 32-41 ohms, per the factory manual. I got an OPEN circuit, complete continuity from + to - post on the fuel pump electrical connector. Even after I ran the engine for 30 minutes and check resistance, still an open circuit.

Spec for fuel pump pressure is 42-44 PSI. I got 60 PSI just after start-up and at idle. At about 1500-2000 RPMs I was at 65 PSI. I could NOT get the engine to falter tonight. 35 degrees outside and she fired up after 2 cranks, warmed up and ran well. Id have loved to see what happens with fuel pressure when the motor starts acting up.

I have also heard, after a hard run, a whirring/whining sound at 1500-2000 rpms. It will be constant until I throttle up. Sometimes when I throttle back down you will still hear it, and sometimes not. I know this can also point to a bad fuel pump.

The engine has never made any odd jerks, stalls or falters at mid rpm or WOT. Only issue I have ever seen is the first video I posted.

 

[wrench 3]

If the fuel pressure is running too high you most likely have a problem with the fuel pressure regulator.

 

[sutor623]

If the fuel pressure is running too high you most likely have a problem with the fuel pressure regulator.

Ok thats what I figured. Do they just have a rubber diaphram and spring in them?
What do you think about the fuel pump being an open circuit? Should I just replace it while Im in there?

 

[wrench 3]

Complete continuity, zero resistance, would be a short circuit. It doesn't make sense to have that and not be blowing the fuse. Did you have the test leads on the correct terminals? The pump probably has an anti-surge diode that would give you a very low reading if the ohm meter was hooked up backwards.
I've never cut one of those regulators open but by the style of the case I believe that you are right.

 

[sutor623]

I know that's what I was wondering, how come the fuse isn't blown?!?! Very strange. I appreciate your guidance in the matter. At least we have a good idea that the motor is running rich because of the insanely high pressure and that's probably the cause of the sputtering, whether the ecu is trying to counter it or the plugs are getting too wet.

I am sure that I was checking the right terminals on the plug (it is the two inner ones) and I tried the meter both ways. Same thing either way.

Obviously I need to get into the vst so I think I will pull the fuel pump and check for resistance directly on the pump itself.

If it truely is an open circuit I will thank my lucky stars that I didn't toast my Ecu, start a fire, or get stranded down river. $57 for an aftermarket pump with 1 yr warranty is cheap insurance IMO.

 

[wrench 3]

Good luck.

 

[sutor623]

Thanks!

I checked it with a better meter today and it had 2.0 ohms on it. This was on the 200 scale. If I went to the 20k scale it would read open.

Anyways, I checked my fuse harness, and the spare fuse was blown!

Its a clue!! And it has got me thinking. I wonder if the fuel pump went at one point in time and whoever fixed it put an aftermarket pump on it that had a higher pressure operating range on it. Going to have to tear into her and see what fuel pump is in there.

Once again she started right up and ran great today. Ugggghhhhhhh

 

[sutor623]

Success!! At least I feel that I can assume that for now.

Fuel filters were both dirty as all get out. The reason why the fuel pressure was building so high is because the inlet screen that feeds the fuel pressure regulator was almost COMPLETELY plugged!! I checked the leads directly on the fuel pump and they were again, 2 ohms. This thing was on its way out. I certainly would have been left out on the water by the looks of it. Check it out:



So I cleaned it!



And in general, the VST was just plain dirty. This is why we change our fuel filters and install racor water separators people!!

 

[wrench 3]

Nice cleaning job!
Let's hope that the fuel injectors are in better shape than the VST.

 

[sutor623]

Thanks!

I'm hoping that the high pressure fuel filter did its job in protecting the injectors.

Is there anyway for me to check the injectors or some way to clean them?

What do you think his debris actually is?