Yamaha 4 Stroke Testing High Pressure Injector Pump, Low Fuel Pressure
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- เผยแพร่เมื่อ 21 ส.ค. 2024
- Testing a Yamaha F115 for suspected fuel injection pump failure. This is one of the most common running issues we encounter with 4 stroke EFI. Motor will run normal at idle and through mid range throttle but falls on its face approaching wide open throttle and the VST pump fails to keep up with demand. Normally the motor won't completely stall, but stalling can occur. We are measuring fuel pressure at the injector rail using our FST Fuel Pressure Test Adapter Kit connected to the Schrader fitting on top of the rail with Hose Extension connected to a standard automotive fuel pressure gauge to test fuel pressure in open water. Fuel Injection and VST (Vapor Separator Tank) Pumps can be notoriously tricky to diagnose in the shop and will often turn normal fuel pressure during testing until the pump is tested with the boat in open water and full demand is placed on the pump to maintain fuel pressure to spec (38 to 40 PSI) at higher volumes demanded by the ECU to turn full RPM's. This motor had normal fuel pressure at all RPM's in the shop, but in the river lost fuel pressure as soon as I went near wide open throttle. Confirmation of either a failing VST High Pressure Pump or an obstructed pump or both. The result is the same: back to the shop for a fuel system tear down.
outboardst.com...
Very timely video. My new to me boat (yamaha f115 2005) has the same issue. Be interested to see what you find when you dig into it.
This is actually taken from an older video we did a couple summers ago. Typically the vapor separator tank will have some combination of water and debris settled into the bottom of the tank and obstructing the pump inlet filter screen as soon as the pump starts creating high vacuum to maintain pressure at the injector rail/injectors. The normal procedure is remove and replace the pump and filter screen assembly, inspect the needle valve and seat, inspect the pump grommet pressed into the top of the VST. Replace any visibly damaged parts. Clean the VST and replace the VST gasket and then I send the injectors out to for testing and cleaning. Normally most 4 stroke EFI systems go back to factory spec/normal running condition after this process is completed. I will try to post a video of a fuel system rebuild as soon as possible.
Very informative as I have a 2004 150 yamaha. Experienced the same issue. Do the low pressure pumps have a bearing on this or is only the high pressure pump. Cleaned out the VST tank and was not a lot of crud in there. Is there a way to bench test the hp pump and the low pressure pumps? I’m handy just no a lot of outboard exp. TIA.
Tyler, great topic again. A look at your gauge set up on the engine would be helpful. Did you do other troubleshooting before taking the boat out on the river other than testing fuel pressure? Also, another useful topic would be your troubleshooting the electrical side of the high pressure fuel pump. I am currently troubleshooting severe performance issues (F150TLRC) with no sound from the high pressure pump at key on/key off and have determined there is no voltage at the electrical connector at the Vapor Separator Tank (VST). Working back through the system I found the main relay (68F8195A) failed with 0 ohms resistance across the relay coil and contact not closing. Have you seen this relay failure? Cause (2004 engine!)? I inspected the VST tank and found it and the strainer clean. The high pressure pump runs and pumps when run on jumper leads.I did not check pressure. Suggestions for further bench testing? A new Yamaha high pressure pump is north of $400! Thank you for these videos. Carry on.
This could be an issue with the key switch itself. Multiple, simultaneous electrical failures on isolated systems usually point to a common source. Easiest way to diagnose is to carry a spare, new Yamaha Key Switch at all times. Disconnect the existing key switch, connect the new switch into the main harness and test. If everything lights up normal, the existing key switch is damaged, replace. I carry one in the truck at all times and go through about 10 key switches a year, and I know of very few Yamaha anything from 2004 or older that is on its original key switch. The 68F8195A relay is notoriously prone to failure but they at least can usually pull it together enough to at least click shut. Relay and 12V supply to VST failing at the same time is rare. Once you've confirmed a good key switch move further down the line. Check battery cables for excess wear and tear. If they are crunchy and look like they've been submerged, disconnect at both ends and ohm out. Once cables are verified, move to the fuse panel and relays. Any fuse or relay failures replace as needed. Check power at key on again. If still nothing at high pressure pump connect, shut off power to the motor and ECU, so no power is available to the ECU. Disconnect the engine harness main connector at the ECU. Check the VST pump connector for short to ground and check across the connector for continuity between the hot and ground terminals (dead short). If the hot terminal is shorted to ground or has continuity with the ground side, there is a problem in the engine harness that needs to be corrected. Given that you said the pump powers up when isolated and bench tested, I would iron out the supply issues in the harnesses further upstream first, and would not replace the VST pump unless it either fails pressure testing during open water testing (after you have verified that the pump is getting good hot and ground) OR the owner says, just do it, and doesn't care about cost.
Additionally, the referenced relay 68F8195A is one of the most failure prone and frequently replaced parts in all of Yamaha's electrical system controls. If its the original 2004 relay, it could and should be on borrowed time.
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Thank you for that in depth reply. The issue was a failed main relay in the Yamaha fuse/relay panel. The VST checked out clean, fuel pressure 38 psi at full load sea trial. Test array: Betooll Fuel Pump test kit on Amazon. About $34. OK for my DIY purposes. I recommend spending the $100 or so on a Yamaha factory service manual: Yamaha OEM service manual LIT-18616-02-51 for my F150TLRC for logical troubleshooting. Section 8 "Electrical Systems" describes system checks in detail, with specs. severe performance issue (engine bogging down, 1200 RPM max) was the failed relay controlling the high pressure fuel pump, and the #4 fuel injector. Had all four professionally cleaned, new seals and filters, and bench tested with report.
Excellent Job Brother. Thse motors love fuel pumps 😂
Thanks, and yes, they do eat some pumps.
Where did you get your extension fuel hose from ?
What was the fault in this engine in video? Would love to learn
This engine had a high pressure fuel pump (fuel injection pump) failure that was intermittent, which is normal in early stage fail on Yamaha. When tested in the shop, the fuel pressure held perfect, once it was tested in open water, and full demand was placed on the pump, it would lose pressure a mid/high rpm and cause the engine to lose rpm either because the pump was failing or because the pump intake was obstructed by debris or both. This normally confirms that a fuel system tear down is in order. Vapor separator, injector rail, injectors all come apart, new gaskets, new filtration, almost always a new injector pump. Injectors are sent for cleaning and testing. Flush or replace all hoses, re install and test.