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Thread is now too long to read everything you've done. Have you ruled out a bad boost pump? These pumps are diaphragm pumps and perhaps one (or both) has a torn diaphragm.
Also, have you attach a length of clear hose between the fuel line on the tank side and where the fuel filter was to see if you are getting any air bubbles in the fuel feed line?
At the instruction of Andy at SIM, I unbolted the boost pumps from the block and squeezed and held the fuel bulb, for like 30 seconds. The bulb stayed firm, and there was no fuel coming out of the small holes in the back of the boost pumps that would indicate fuel coming through the diaphrams.
I have not used clear line to look for bubbles on the low pressure end of this, but I am also thinking that any air bubbles that got into the VST would be at the top of the VST chamber, and not at the bottom where the VST pump intake is located. Basically, I don't think the VST pump can suck air as long as there is an inch of fuel in the bottom of that chamber.
I am also thinking that holding that fuel bulb in a firm grip would tell me if there were a leak between it and the VST. That's how I found the leak at the fuel filter.
At the instruction of Andy at SIM, I unbolted the boost pumps from the block and squeezed and held the fuel bulb, for like 30 seconds. The bulb stayed firm, and there was no fuel coming out of the small holes in the back of the boost pumps that would indicate fuel coming through the diaphrams.
I have not used clear line to look for bubbles on the low pressure end of this, but I am also thinking that any air bubbles that got into the VST would be at the top of the VST chamber, and not at the bottom where the VST pump intake is located. Basically, I don't think the VST pump can suck air as long as there is an inch of fuel in the bottom of that chamber.
I am also thinking that holding that fuel bulb in a firm grip would tell me if there were a leak between it and the VST. That's how I found the leak at the fuel filter.
I'm not thinking between the VST and the diaphragm lift pumps but between the boat fuel tank and the diaphragm lift pumps. Is the RPM drop gradual or sudden?
Squeezing and holding the fuel bulb pressurizes everything between it and the boost pumps. That is soft, gray, low pressure yamaha fuel line there. Any leak would be very apparant. We don't see any, and the bulb holds firm. If there were a leak between the bulb and the boost pumps, I would expect the bulb to slowly go flat and have to be squeezed again. That is not happening. The bulb stays firm. We cannot find any fuel leaks in those lines. The bulb is right past the Racor in the bilge. The Racor has all new lines on it. But, thinking about it, if there were a fuel or air leak BEFORE the bulb, this test would not find it. I will take a look at that.
Drop is sudden. Motor starts and idles well. It's about a mile or so out to open water up this canal we have been launching in, so the motor has plenty of time to warm up, stabilize, etc. It seems to be running well. When I get to open water, and slowly advance the throttle ( If I hammer it, the Contender swamps the engine with water) it accelerates fine up to, usually, around 5,000 RPM, which it holds for maybe ten seconds or so. Then it starts running ragged, and the RPM drops to around 3,000. It is erratic at 3,000, bouncing around, say 2800-3400, but this number varies. The throttle is still at WOT at this point.
Then I bring the throttle back until the engine smooths out at something less than the 3,000, where it seems to run okay although a little ragged still.
If I advance the throttle full again, it will not run back up over whatever max it declined to. It will not, for example, go back up to 5000 RPM a second time.
The running ragged part gets my attention. Every engine that was starving for fuel that I have ever seen just bogs down at the point where the fuel supply cant keep up with the demand. The running ragged part sounds like it has a bad coil or plug wire that fails when it gets hot. It should be interesting to see if running the engine without the cowling and the air silencer on makes any difference.
We hit four stores on the island yesterday looking for one of those spark gap things....that you put between the plug and the coil and view the spark in a clear window.... lets you know the coil is putting out. I don't know the name exactly. But we couldn't find one. We also were looking for the pieces to construct a fuel pressure gauge. We need something that threads onto the Shraeder valve, not a tire pressure thing you press to it. Nope. couldn't find that, either.
We CAN measure resistance with a VOM. Could we make up new spark plug wires with automotive spark plug wire?
You probably could make a plug wire from auto parts. The boot just threads on to the wire as I recall. I would test the coils with a meter to see if one is out of spec. You could always resort to pulling plug wires when its running ragged to see if it makes any difference. You might isolate a problem.
Did you know there is a Bird Rock just outside the entrance to Leeward-Going-Through here? It's a local navigational landmark. I got quite a few photos of it.
Bullshipper...
The filter I removed goes between the fuel line coming in to the motor, and the VST filter. It was obviously intended by Yamaha to be a "better-than-nothing" filter and fuel/water seperator. The filter element filterd down to 28 microns..
Okay, I installed a bigger, better filter in the boat. It filters down to ten microns. The fuel that gets through that then goes to the VST, where there is a screen, also ten microns. From the VST the fuel has already been filtered twice to ten microns, and then goes through a third filter, which is a screen to catch anything that gets out of the VST pump. THEN it goes to the HP pumps, THEN to the fuel rails, and THEN to the injectors.
The 28 micron filter was not contributing anything to this process. IT would do more good if I installed in in the bilge of the boat, before the Racor.
But since it was causing problems, leaking fuel, etc. I just took it out. It wasn't going to find any 28 micron sized gravel in the 10 micron sand that came though the Racor... Never.
Ok, but the 10 micron will plug a lot past that the screen with more open arealimiting flot to the engine.
I agree with you not having another one, and that its more logical to proceed without it JUST during the trouble shoot process, but to me it sound like
The motor sits
runs good for a moment or too with a lot of full going to the filter area that is cleanest, untill that clogs up again, limiting flow and rpms.
So the only way I can know trouble shoot the delivery is to
clean the injectors to make sure they are clean
have new filters in the motors and in the racor to assure that I am not making life impossible on the suction or pressure sides of the pump.
Then if it doesnt run, then I check fuel pressure- AND FLOW through the system.
Marine spark plug harnesses come with Alum wire, cars come with copper.
Copper lasts less time in salt, but works in a pinch.
A common hacksaw blade is 21/1000" of an inch, if you cant find a guage, approximate gap with that.
You just look at the spark on the plug, holding it with insulated pliers and a glove- if its blue the coil, wire and plug are fine. If is orange, then remove the plug connector jacket and see if the spark coming off of that is blue or orange going to ground- cranking the engine, not running it.
But if your battery is low, the coil output will never be blue.
i just this morning checked the resistance to all of the plug caps, the primary and secondary ignition coils. These would have gotten a fair bit of splash when the water control valve failed and corroded through;
All within spec.
Checked out batt connections, etc. at same time. Haven't suspected batteries, even though they are five years old. They work fine. Run the bilge on auto, never go dead, etc. And the connections are good. One batt will start the motor. I run it with the switch on the "Both" position. Plenty batt.
Will probably go out shortly and try to do the 'squirt-inflammables-into-the-air-intakes' trick if the weather behaves as forecast for early afternoon.
thanks, but I just cancelled that. We need glossy smooth water to even try this. And it's picked up to a slight chop over the past thirty minutes, despite the forecast.
There is NO way to keep that motor dry on this Contender. The cowling is the only thing that keeps the ocean off the ECM etc. The seawater gets about an inch or so above the cowling gasket when I first advance the throttle, and the following wave does about the same thing when I come off plane. I can probably finesse it if it's flat calm, keeping the trim just right, etc. but If I take the cowling off to do this test, with any waves at all, there is a 90% chance of seawater getting onto the motor. And probably a 50-75% chance of splash into the air intakes. So that's scrubbed, again. And no flat calm days are in the two week forecast.
Right now my thinking is running like this:
If I can find a small cat with twins for the right price, I will just buy it outright and import it. I will continue to work to fix the HPDI, and then sell it and the Contender for enough to cover my costs in getting the small cat down here.
The coils test ok... I was hoping for a questionable one.
Good luck with the water test. If or when the engine quits producing 5000rpms.. I would do everything you do when you put the boat on the trailer. Trim the engine all the way up for a few minutes, shut the batteries off, take the key out of the ignition..etc. Wait a little while.. maybe do some fishing. Then try another speed run and see if the rpms change any. Just a suggestion.
If your range rover is fuel injected then it probably has the same test point with scrhrader valve.
The fuel press test gage when threaded on the test point, it depresses the schrader valve.
Also you can use any fuel press gage and remove the schrader valve just like a tire.
Don't mix it with tire schrader valves because it is fuel resistant. http://www.summitracing.com/parts/SUN-CP7838/
__________________ FL Upper Keys,33 foot World Cat w controlled upper bridge,Yam F250 w mech shift and throttles
See what yamaha says about running the engine without silencer at more than about 3000 rpms. May do some damage. This testing of rpm dropping to about 3000 from 5000 sounds like fuel starvation of some kind. Maybe even a line sucking air at a high fuel demand.
it's not a matter of being able to USE any fuel pressure guage with it, it's a question of FINDING any fuel pressure guage here. I would be willing to sacrifice a tire pressure guage, if I could find a cheap one with a threaded attachment. Cheapest one I saw that threaded onto a valve was $ 88. That's a lot for something to use once that will be destroyed by gasoline eventually.
If I end up ordering a guage, I need to find out first what I need to do to check the HP fuel pumps. A 100 psi guage won't do the job there.
I am thinking about the air leak thing, though.
How would air get into the HP pumps as long as there is any fuel at all in the bottom of the VST? That electric pump sucks it right off the bottom of that VST canister. That would have to be totally dry for air to get to the injectors.
I don't think the air leak is downstream of the VST, that's at 50 psi and a fuel leak there would be very obvious under that pressure.
The filter creates back pressure against the suck of the pump, bringing air in through the hose clamps anywhere up stream. A ball that won't stay firm is sometimes sympomatic of this.
But are you sure your injectors are clean? Did I miss the part where you verified that?
Like you would trace for a fuel leak, trace for air leaking "in" from one end to another to the injectors including condition of components where fuel goes through them. Something else anyway during the process of elimination.
Spray each cylinder individually while under load and it will pinpoint the problem cylinder if it is one. I know you say when you start and stop water washes over the cowling, so maybe start get going, and then take the cowling off, do your test and put it back on. i think you have to do this step to rule out a lot of things. first any ignition related problem. second may pinpoint what cylinder is going dead, or if all of them are starving for fuel. but this is just the way i would go about it.
__________________ Aristocraft boats. building quality boats since 1946.
Stamas Tarpon 290 Yanmar 6lp
One way that may not do you any good on the island. I'd suggest ordering 6 brand new ones, send the other to be tested and cleaned. You'll have six spares for the next go around.
