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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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Vz175 HPDI will only fire while cranking after changing throttle

Customer Question

vz175 HPDI will only fire while cranking after changing throttle body, and under cowl fuel filters. As soon as key is moved to run position engine dies.
Submitted: 6 months ago.
Category: Boat
Expert:  Charles replied 6 months ago.
Hello, my name is***** see that your question has been here for a bit and thought I would assist you with this. I do have a few questions back for you. When you turn the key to run, does it sound like the engine runs out of fuel or loses spark?When it was on the YDS, did you check the fuel pressure when it was trying to run?Why did you need to replace the throttle body?
Customer: replied 6 months ago.
seems like it loses spark, dies immediatelywhen i hold the key in the start position and its firing, the fuel pressures climb up to where they're supposed to be 50 / 700 or soA water pressure gauge line ruptured and sprayed saltwater under the cowl. the throttle body linkages got rusty and hard to move. I cleaned it everything up and replaced the throttle body with a used one from ebay that works and looks a lot nicer. I lubed / freed up the old one to keep as a spare. None of the electronics look corroded from the salt water. I rinsed everything with salt terminator, low pressure water from a hose, let dry well and applied CRC 6-56.I replaced the medium pressure canister filter, water separator filter, and spark plugs just as PM. The boat is new to me. Before I changed everything out, it would idle but gradually increase rpm. I attributed that to the stuck throttle body. I only did that once before I tore everything down.Previous owner had used it and it ran fine two weeks before I idled it and found the throttle body stuck. I trust his story as he's a good friend of mine. Fuel is pretty new and was topped off after last trip.
Expert:  Charles replied 6 months ago.
Did you take apart any of the wiring connections to see if they were corroded on the inside?
Customer: replied 6 months ago.
Everything i took apart looked good, including inside the fuse and relay boxes. I disconnected most of the wiring harness plugs on the port side of the engine and they all looked good, air sensor, tps etc. There was some corrosion on the main starter lead (heavy gauge) which i cleaned up and reconnected. Also the exposed iron and bolts on the ignition coils had some corrosion which i cleaned up but didn't look bad enough to affect continuity. Some of the small diameter hose clamps on the port side (oil / vacuum lines) were pretty corroded I replaced them.
Expert:  Charles replied 6 months ago.
Did the water get near the ECU at all? Did you look at those plugs as well?Does the main harness plug for the key switch not lay on the right side down in the lower pan?
Customer: replied 6 months ago.
The main harness plug is low on the starboard side I didn't take it apart. I'm not sure where the ECU is, I can look at a drawing and check those.
Expert:  Charles replied 6 months ago.
The ECU is the main computer on the engine. It is on the back of the engine. Has plugs at the top and the bottom. If the lower pans filled with water when that hose broke, it would be wise to check all connections that are down low. It sounds like when you take the key from start, you are losing voltage to the run circuit going to the ECU. That is why I am saying to check all the plugs.
Customer: replied 6 months ago.
All the ECU plugs look like the gaskets worked, no corrosion on any of the pins.
Expert:  Charles replied 6 months ago.
Thats great. How did you test the key switch?
Customer: replied 6 months ago.
I used a volt meter on the key switch behind the console panel at the waterproof connector. The Y/R wire had 12v when in run and 0 in off.
Expert:  Charles replied 6 months ago.
When the motor dies, do you also lose the gauges?
Customer: replied 6 months ago.
no, everything stays powered up
Expert:  Charles replied 6 months ago.
Have you checked the spark on the engine with a timing light to see if it is losing it when you go from start to run?
Customer: replied 6 months ago.
I haven't, I can check that.
Expert:  Charles replied 6 months ago.

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