150 hpdi stalling

[Shinola2014]

2003 hpdi 150hp will only run for 5-10 seconds. My mechanic has diagnosed to the following point. When the key is on, the VST pump runs until pressure after VST (~40psi?) is reached then shuts off. He then cranks the motor, it runs for a few seconds, but pressure and voltage to the VST cut off within seconds, and then the motor dies once the pressure drops (or fuel is used) at he high pressure pump.

Any ideas? The only conclusion that could be reached was that the issue was with the injector control driver.... ~$1400!

I'm going to need a second opinion.

This is a new account, but I've been on before and found this board the most knowledgeable and helpful place on the net for hpdi's. Don't fail me now.

Merry Christmas.
Shinola

 

[chapin123]

Hi, have you checked the low pressure fuel pumps. They tend to go and there are two on engine. Also check all fuel filters and replace especially VST filter and Racor .

 

[99yam40]

the motor dies once the pressure drops (or fuel is used) at he high pressure pump.

Any ideas? The only conclusion that could be reached was that the issue was with the injector control driver.... ~$1400!

Shinola

If there is no pressure coming from low pressure pump after running for a short time,
I do not see how he could think it would be an injector driver.
Find a better Yamaha tech

 

[Shinola2014]

Been thru the fuel system a year back, all new filters. Also, replaced both low pressure pumps. I think they are good if the sight glass never loses fuel correct?

 

[Shinola2014]

Prior to the 5-10 second running issue, there was a different problem. They may be related so I'll describe that one too. A few months back, when up on a plane, the gauges would start acting funny (tach would go backwards past zero, voltage would diver) and a few seconds later, the engine would die. Now I can't get it to run long enough to make this re-occur.

Another symptom, which to me seems unrelated, but I can't tell at this point, is the oil sender pump is getting no voltage.

I've checked the grounds and replaced an old battery (oldest of 2).

 

[Shinola2014]

Just consulted with another mechanic, seems to be a bit more experienced with Yamaha's. He does however think the injector driver assembly could be the fault. The logic is this:

The VST pump has power at the top, red wire is 12V, blue wire is ECM controlled ground. When you go thru Key on, the ECM powers the VST pump for some number of seconds (10 or 20) to build pressure for the crank then shuts off. When the motor is running, the 12V should be on continuously. If the 12V goes away from the VST pump, and the pressure drops, he suspects that a faulty injector driver is pulling down the voltage of the entire system, dropping the VST pump and the HP pump consumes enough fuel to drop the VST pressure and shut off the motor. If the pressure goes away, but the 12V does not, the VST pump is bad, perhaps it is seizing or there is a pressure leak at the top of the pump.

The first mechanic mentioned that the voltage and pressure went away just prior to the stall, but I'm going to repeat the test.

 

[99yam40]

my thoughts are that if the VST is full of gas the high pressure pump should keep it running for longer than 5 -10 seconds at idle.
And I have read that even the lower pressure pump will allow it to idle just not run at higher RPM.

I would monitor all pressures and voltage to see what is going on

 

[Shinola2014]

Just repeated the test the original mechanic performed. Reading VST voltage across blue/red pair I get 12V at cranking for about a second. Nothing really at key on though. After that, the voltage goes away and the motor runs maybe up to 20 seconds. I can't monitor pressure continuously yet (still assembling a gauge) but with a tire pressure gauge, I get 50 psi every time I have checked it.

If I jump blue to block ground, the VST continues to run getting a constant 12V+ and the motor runs at idle, haven't tried higher RPM yet.

Second mechanic is coming out for a check and is going to try to isolate the cause of dropping 12V. He thinks it is the ECM or the injector driver. I hope he's wrong on both counts. Could this be a faulty ground somewhere in the system? I know they are hard to find, but I'd rather search a month than drop a grand+ on new electronics.

 

[Shinola2014]

Have now tested and verified the problem is most likely the injector driver. While running, the voltage drops from VST pump. according to Yamaha tech, the injector driver operates the VST pump thru a gated ground. The injector driver pulses the pump on and off, many times a second. I'm not sure what the purpos of such a system would be since there is a return from the HP pump back to the VST. Is it just to extend the pump life?

This may not be the best long term solution, but I grounded the blue terminal of the VST pump to block ground and water tested today. Motor ran like a top, never ran better.

But I'm still having dash gauge issues, will start a new thread.