98 405 Port Engine Will Not Start

[Midnightsun]

This is not your problem but there is a bad kink in the fuel supply line leading to the filter that should be corrected.
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[Serendipity]

Yes I had already noticed that myself.

Thanks again

[Serendipity]

I agree with everyone's comments and the upper and lower risers were replaced 10 months before I purchased the boat. Boats are nothing like the engines I grew up around. I really thought these engines would be a cake walk for me but so far, they are different in a lot of ways.
Thanks for the insights gentlemen

[Serendipity]

Okay I am working on the boat tonight. I have swapped out the relays and the port engine will still not start, just spins over. I swapped all 3 atmos fuses although they did not appear blown.

Starboard engine starts fine on the port engine relays and fuses which were 15/10/15.

My 10E Koehler Generator has a facet electronic fuel pump located right in the front.
Why can't my engine fuel pumps be this easy to locate?

Speaking of fuel pumps for the engines. Where are they located and are they mechanically driven or electric?

[Serendipity]

Brain Fart

So I retired from being a automotive service and parts about 7 years after 25 plus years.

Apparently I forgot everything I learned on tracing problems done.. SMH

So I traced the fuel lines from the tank to the water separator, then underneath the engine to a black rectangular housing. This has a long skinny tube inside it and I presume this is the electric fuel pump.

I am by all means going to check the fuel pressure first. But I am thinking I might just need to keep one of these fuel pumps on hand.

So any ideal what model or part number I need to get for these 7.4 mpi 454's? And where to get them?

Thanks gentlemen

[Viper]

Look at my previous posts, I explained the location in one of them. It's in a rectangular black box on the port side of the engine beside the oil pan next to the forward engine mount. You'll see fuel and raw water lines going in and out of it and should have a blue drain plug on the bottom of it. Contains an electric pump, regulator and cooler. Not always easy to get at.

[Viper]

Did you listen to the starboard engine for the fuel pump cycling when you key ON? If it does and you don't get the same thing on the port side when you key it ON, then the pump is likely your problem if swapping the relays didn't work. You should take a voltage reading at the pump plug to ensure you're actually getting 12 volts there with the key ON in case it's the ignition switch or wiring.

[Serendipity]

Sending beer money up I just realized it had been a few months.

We might as well have a beer and ya have a great 4th of July.

So I can hear both fuel pumps cycle on. I know, I said damn I was so sure it was going to be a fuel pump.

I am still going to purchase a fuel pressure tester tomorrow. I will test everything fuel related and go from there. Then I am going to retighten my ignition switches on the top panel, no cockpit controls.

I am going to clean up around the engines while I have the couch moved and the hatches up.
Yes, the kinked fuel line will get replaced and clamps that need replacing as well.
I am not sure where to go from here, the engine still spins over but want start.

I will update again after I check the ignition switches and fuel pressure.

Ya have an awesome 4th of July Gentlemen

[Serendipity]

Here is an update for the port engine not starting.

So I checked the fuel pressure as shown with a new fuel pressure or fuel injection gauge.

Fuel pressure jumps to 20 when the key is cycled on. Fuel pump is easily heard cycling.

It reads 42-44 when turning over the engine. Which is normal based on what I am reading online.

Voltage is good at the pump. I am tightening the ignition switches right after I submit this to ya just as a precaution. I even have a new ignition switch on the boat I might just replace the port engine switch with, although it is only 2 years old.

It appears there was a service bulletin for this issue back in the day that was MCSB 98-04 I believe it was, but I could not locate it online due to dead links.

Mercruiser never was able to come up with a solution based on the other posts I read. Sometimes a fuel regulator would solve the problem and sometimes it was a vapor lock, sometimes a primer bulb inside the line running to the water separator. Odd because I thought vapor locks only happened on carbs from fuel sitting the bowl.

So Viper and guys, I guess the next step is to swap sensors and ecm's on the engines to see if it will start.

With new spark plug wires, dist cap etc on both engines, I have ruled those out in my mind, but I can revisit after checking everything else.

What would be your thoughts at this point ?

[Viper]

Sounds like you've eliminated the fuel system which is a good start. Having said that, have you confirmed that the injectors are actually firing? If you can't hear them while cranking, pull a couple of plugs after cranking for a while. They should be wet with fuel. Or with your fuel pressure gauge hooked up, build pressure, then disconnect the fuel pump harness, crank again, and see if the pressure drops to zero with a few revolutions.

It won't be vapor lock unless you're trying to start it in an engine compartment that's already above 180*F or supplying fuel that's over 110*F. Those specs lower with increased vacuum due to restrictions such as elbows, line kinks, anti-siphon valves, selector valves, routing, hose length and diameter, accessories, additional filters, etc. but the temp specs give you a starting point.

Vapour lock can happen in carbed and EFI apps. Your fuel filter is mounted low because it's cooler there, and they also surrounded the filter in a casing which is missing according to your pics.

You have the advantage of a second engine that's working so use that but don't be temped to swap several things at once to save time. Swap only one thing at a time, then test. That way you'll know which part was faulty. Though it's rare, EMCs do fail. Careful how you handle it, they don't like static, and don't bend any pins when pulling and installing the harness plug. Disconnect the batteries first.

Have you confirmed that you're actually getting spark? When you replaced the ignition components, was the inside of the distributor clean? Swap the ignition module and see if that solves the issue. They can be pricey so test first.