i would hook a timing light up and see if it is flashing when the hard cranking occurs and/or see if the tach is moving during crank. this can help narrow the problem down to ignition or fuel delivery. I would also check fuel pressure at WOT under load. Have seen pumps make spec pressure at idle no load, but once under load they drop below spec...
not familiar with MEFI4, but is there not some sort of base timing that can be checked/set?
I will reply in blue
Originally Posted by tayto
I do not believe 125 rpm is too slow for cranking or starting. I have "pop" started engines that were turning at much slower speeds.One thing I will try to do, is to borrow a tachmeter from my work and see if the engine is cranking 125 RPM like reported by the gateway. If yes, it is too slow to start, NO? I think a ECU goes from cranking mode to running mode around 400 RPM, is it right?
In the most recent video it sounds as if there is a vacuum leak or as if the IAC is fully opened. It may be the sound of the air cleaner doing it but it just doesn't sound as I'd expect. Also, it doesn't start well even on a "good" start. Nor does it idle well compared to what I'm used to. This may be normal for this craft but it's something I'd note.
Despite this engine having a new IAC, startup in the latest video does sound as if IAC is not working properly. You could use a pair of LEDs to check whether or not the ecm is commanding IAC operation properly. Some tests include watching for IAC activity after engine shutdown, and watching for continuous IAC activity during idle which would indicate the ecm attempting to change the engine's idle speed. LED's should be connected across two wires of the same color and can be connected on the backside of the IAC connector to allow the IAC to remain in the circuit. Connecting the old IAC but leaving it uninstalled so you can view the pintle, then running the engine for a short time before shutting it off would also allow you to see if the ECM is successful when it attempts to operate IAC.
Also, can you open the throttle while the engine is off before starting to check for the smell of gasoline? Have you ever noticed strong fuel smell immediately after startup which could indicate excess fuel during cranking? Those tests may be better indicators of a problem with the injector showing up after the engine is shut off. I'm not sure I'd trust that the test you designed as the best way to capture this intermittent issue.
I would not say that. I would put "incorrect calibration" on a list of potential causes and wait to see what continued testing reveals. Is it possible you have a calibration that should have been updated due to an issue? Is it possible a couple of errant values in your calibration are causing an issue under a specific set of circumstances that are not happening to other folks?Yes, harder to figure. But other people with the same engine on boat forums don't have that problem, so I suppose the programming is not too bad???
Is there any history with this engine that may be relevant? Have you owned it since new? If you wanted the engine to start hard for a test, what would you do the try and make that happen?
yea something doesn't sound right... check to make sure the injectors are plugged into the correct cylinder. not sure if this is a bank/batch fire but I think sequential system so this will matter. have you adjusted the valves? i know they are hydrualic but pretty easy to do it while the engine is running. Before this I think it's time to do a basic compression test and report back.
Hiya, please check and reply with the actual service number of the Mefi4. I can't remember the last 3 suffix of the Mefi 4, but 4A ends in 479 and 4B ends in 052. Here are some screen shots of a Volvo Penta Vortec 350 4A file. I noticed on the hard start that the IAT is higher than the ECT and this is not normal for a boat. I also noticed your cranking pulse width is quite a bit lower due to the IAT or some other factor. ECT and IAT sensors are known to 'glitch'. If one or the other 'glitches' during crank or run, you will have intermittent problems in run or crank, and they are HARD to find unless you actually happen to catch it on the scanner.
One suggestion I will make here and also for other projects is to always buy Delphi sensors. We all used to call Ac-Delco the go-to, somewhere along the line they had a fight with Delphi and now it is a 50-50 or worse chance you will get China crap in an Ac-Delco box. I have switched to only true Delphi stuff anymore.
One other thing to note is if this is a spider-web vortec 350, those poppet valve injectors will NOT pulse if the fuel pressure drops below 50psi. You mentioned having some low fuel pressure issues, so, don't forget about a pump/regulator problem.
Let us know :)
-Carl
the vortec marine intake doesn't use the poppet style injectors AFAIK.
reply below:
Last edited by Turbo_Bimmer; 08-11-2022 at 06:10 AM.
it is a batch system. injectors are in the good place because the fuel rail is rigid and the wire loom doesn't have enough play to connect to the next injector. I didn't adjust the valves since there is no ticking sound. I didn't do a compression test because the engine pulls strong at cruising speed at 4000RPM, so I think the compression must be good...
I bought the boat used in 2018 and it was doing that when I bought it. Previous owner just said, open the throttle while cranking when the problem occurs. Yes it helps. I put some time and money finding this problem once in a while, since the boat is still functionnal. It is just embarassing having a shinny boat cranking for 10 seconds and having a bad fuel smell when people are watching LOL
So I looked at a datalog I took of my Express van at startup I took working on the startup airflow in the tuning. It cranks at 115 rpm. It has the same L31 crank sensor, the same coil, same module and HVS distributor as your marine engine. The crank sensor could trigger at 1 rpm. The PMGR vortec starters are gear reduction units not direct drive units, so they crank slower but with more torque. No problem getting my 11:1 383 cranked over even in 20°F weather. The low idle right at startup is what I was datalogging and adjusting to fix.
https://youtu.be/2Ydppg2TtQU
I would check your fuel pressure regulator for leakage. Even though my Marine intake had a returnless system that had the return capped off on the rail, it still had a diaphram and vacuum line connected to the intake manifold. When I pressurized the rail and tested the injectors for leakage, fuel came trickling out of the regulators vacuum port. Most of the MEFI4 marine engines have a fuel rail pressure sensor. I would look at it and see what the pressure is doing. A cold start with a leaking regulator will not have fuel in the manifold to flood the engine out, while a restart will.
Last edited by Fast355; 08-11-2022 at 07:26 AM.
Wow! your engine starts really fast!
Now I remember, at the end of the season here in Canada, with colder temperature, the engine starts quite well. I did check the FPR with a hand held vacuum pump, and it was holding it well. But I will check like you suggest by pressurizing the fuel rail and look if the vacuum hose is leaking gas.
I also opened the FPR to look for paint particles (Volvo painted the inside of their fuel cells in those years), and the screen was nice and clean.
I didn't see any sensors on my fuel rail, unless it is somewhere else.
does the MAP play a role during cranking, or it is just after the engine is running? From my gateway data, the reading seems OK if I compare to the weather forecast...
Maybe Carl can shed some light because I have not played with a MEFI controller in a decade. My 0411 has a Cranking VE table that has RPM and MAP as a reference. A bad MAP on alot of GM stuff can cause hard starts but usually shows up as more of a rough or rich running immediately after startup.
I bought a genuine Bosch T-Map for my marine intake for about $30. Mercruiser and Volvo Penta mark them up about 500%. I will see if I can find the Bosch part number.
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