Mercruiser only starts with starting fluid

[BrennanB]

I’ve had an annoying problem this summer with my tige 22i it has a Mercruiser 350.

it doesn’t matter if it hasn’t been started or if it’s warmed up it will not even bump over once without starting fluid. Give it a spray of starting fluid and it idles flawless, has a little stutter at lower rpm’s but runs great after 2500rpms.

Fuel pressure goes to 4 after one key cycle then 39 after 2-3 more cycles. I’ve replaced the low pressure pump, fuel/water separator, it’s went through 3 full tanks of gas, the fuel pressure regulator screen was spotless and vent hose is dry, high pressure pump sounds good.

what could it be?

[Vettedrmr]

How does it run between idle and 2500 rpm?

Edit to ask more questions: Have you performed a fuel pressure bleed down check? It should hold pressure fairly well. I had a need to test mine today ('08 22ve), and it bled down from 48 to 45 psi in 10 minutes.

Have you looked at the plugs? You might find one (or more) that are sooty and rich running. If so, you might have an injector that's leaking.

[BrennanB]

Thanks for the reply!

it has a bit of sputter between 1500-2500 roughly.

I did do a bleed check and it lost about 1 psi/minute, ai says it’s not that bad lol.

for the spark plugs, whoever got ahold of them last over tightened them way too much, so trying not to open that can of worms yet.

[Vettedrmr]

Seems to me like a 1 psi/minute leakdown could be pointing to injectors that need servicing or replacing (I'd replace them, they're what, 20 years old?). Option 2 would be a weak ignition coil. I like that option less because I think it wouldn't smooth out at higher rpms. Leaky injectors tend to clean up as you demand more power from the engine, just because the leak is overcome by the fuel demand.

HTH, and have a good one,
Mike

[BrennanB]

Ok. I’ll order some and see what happens, I’ll let you know.

if it’s just a couple injectors, wouldn’t it atleast sound like it’s getting some fuel and trying to turn over?

[BrennanB]

Also, this may change things I totally forgot. It sat for two years. I drained as much of the bad gas as a could. Then filled it up with premium and added octane booster. It started by itself like 1-2 times and after that but never did again.

[Vettedrmr]

Ok. I’ll order some and see what happens, I’ll let you know.

if it’s just a couple injectors, wouldn’t it atleast sound like it’s getting some fuel and trying to turn over?

The opposite. I'm thinking the engine is trying to start flooded; the starter fluid forces a combustion event, which gets air into the engine, and off you go.

[BrennanB]

It’s fixed! It was the cap and rotor (same spark plug wires though), put a new one on and fires up perfectly.

but it seems the sputtering is a different problem.

when we first took it out it was like it was in limp mode for the first 10 minutes, but then it got out of it and was fine all day. But at perfect surfing speed it starts to sputter, back fire (through intake it sounds like) over and over again, and cant keep a steady rpm. When you give it more throttle it’s steady and runs great (could still be backfiring just not as bad, couldn’t really tell because the motor noise covers the sound.)

[Vettedrmr]

A backfire through the intake indicates the timing is a bit too advanced. There's a clamp on the base of the distributor; loosen that clamp and twist the distributor clockwise just a tad. Clamp it back down and see what happens. The reason it's happening, IMO, is that the computer isn't really programmed for surfing conditions (high load, low rpm), and it's advancing the timing too much. That's why when you speed up, the symptoms get better or disappear. You're getting into the operating range the computer was programmed for.

[BrennanB]

That makes sense. But it’s never done that until this season. Could it have came out of time for some reason?

[Vettedrmr]

I think the time has come for you to break out the penetrating oil and pull the plugs. Especially with the cap/rotor issues, you could have plugs that are partially fouled and misfiring occasionally.

[BrennanB]

That’s what I was afraid of hahaha. I’ll say a little prayer before each one. They were replaced two years ago but I tried to take them out before this summer and they were wrenched in there from whatever shop it was at before I got it.

[Vettedrmr]

Soak them overnight with a really good penetrant, like PB Blaster. 2nd, "rock" the plugs: if they won't loosen, try torquing them in the tightening direction. You're just trying to crack the metallic crystals loose. It's worked for me many times. Patience is your friend.

[BrennanB]

Preciate the advice, I’ve heard this mercruiser is notorious for them breaking off.

[Vettedrmr]

As I think about it, here's another tip. This one requires 2 people. One person on the ratchet, applying a firm amount of pressure to loosen the plug (this assumes everything is soaked overnight); the other takes a long tapered round punch and puts it on the socket, as deep into the plug well as they can reach, and repeatedly tap it with a hammer. They're not trying to punch a hole in anything, but instead sending a really short duration shock wave through the metal. Again, trying to crack those crystal bondings loose. The persistent torque will get them to move, and once they move, rock them back and forth, until it loosens up.

Oh, and when you put in new plugs, USE ANTISIEZE!!

HTH, and have a good one,
Mike