Bogging and wild tach question

[metsfan3197843]

left the dock today and after motoring through the no wake zone and letting the temps come up and stabilize I dropped the hammer to get up on step. As I was ramping up I noticed the tach going crazy and then the engine bogged down and I shut it off but it would have died on its own. I assumed water in the fuel as I’ve sucked out about 6 gallons recently and I didn’t try to restart because getting the water out of the rail was a real PITA. I limped in on my kicker and went home and pulled the filter. I was shocked to find not a single drop of water. Bled out the rail and zero water there also. So my questions are can the crazy tach cause any engine issues and if not any thoughts on the issue? I know I need to check fuel pressure and I have the gauge to do that but need to be on the water not the hose to see what it does under load. I Read the ECM and no codes. I reprimed the fuel system and she started right up and ran fine on the hose of course. Maybe need to do cap/plugs and wires?

thanks for any help

 

[Bondo]

Ayuh,..... Disconnect the tach, 'n try it,.....

 

[maddog2112]

Just curious Bondo, would the tach cause the engine to bog down ??

 

[Bondo]

Ayuh,..... If it's groundin' out internally, it Can,....

 

[metsfan3197843]

So I’d just need to unwire at the tach then correct?

 

[Bondo]

So I’d just need to unwire at the tach then correct?

Ayuh,.... Take the gray wire off the (-) tiny terminal on the coil,......

 

[metsfan3197843]

Doesn’t appear to be an option for me. Mine is a plug

so I did a little fuel pressure testing on the trailer today. Fuel pressure is swinging around 15 psi at idle. Gets worse when you goose the throttle. Pulled vac lines off regulator with no change. Key on engine off 43 psi while pump cycles and when it kicks off settles and holds solid at 37. Something is not right but not sure where to go from here....

Thoughts?

edit. I did disconnect the tach at the gauge so I’m ruling that out I guess

 

[metsfan3197843]

Anyone have any suggestions on ruling out the regulator or the pump? Figure they are the most likely cause of my fluctuations in pressure

 

[metsfan3197843]

Rechecked today with another fuel psi gauge. 35 psi steady at idle and 43 with vacuum line to regulator removed. Now I’m really not sure where to go from here....

 

[QBhoy]

Hi
after having well documented issues on here with the same engine, i might be perhaps as gallas enough to maybe dare say I’ve seen the most of them perhaps.
Aside from the usual IAC, tps sensor, shift interupt switch (which some maybe doubt) and anything less than an excellent battery on these...without doubt the most common thing that doesn’t cause even an alarm or beep on the dash..and dies things like this and more is the diz cap failure issue. It can do this at any given time and short things enough to even cause other sensors to play up along the line. Somewhere between that and the fuel pressure regulator and or crank sensor can do this at any given time. But also fool you into looking elsewhere for an issue and even behave well for a while thinking you’ve cracked it. But no. Take heid

 

[metsfan3197843]

lol so that’s basically everything....I’m 90 percent sure it’s fuel system related. Just waiting on Alaska weather to let me launch again with fuel gauge installed

 

[metsfan3197843]

Update ran today with fuel gauge on the rail. Pressure good until 3000 RPM then steadily drops to nothing. Had an auxiliary tank along and tried that next to rule out the pick up and anti siphon valve. Same issue. Running out of fuel. High pressure pump making some noise when it’s losing pressure but hard to tell if it’s sucking air or running out of fuel??? Looking for advice please

 

[metsfan3197843]

What role does the low pressure pump play? If it failed what would the expected issues be?