1989 2455 OMC 5.8L 351 Holley sucking sound?-gctid363831

[Guest]

hey guys,

Well it's another year... and same problem. i thought the tech at the marina was going to fix my boat this winter, but he got canned...causwe he sucked.... Anyway... My 2455 has a OMC 351 5.8L with a holley 4 barrel.... When I start her up, she cranks right up... I engage the neutral throttle and she idles up great.... until I get to about 1800 RPM...at that point if I have the engine hatch open, I can hear the Carb making a sucking sound. the more throttle I give her, the more intense the sucking sound, and then eventually at 1800 rpms, she will start backfiring, and if I keep increasing, will eventually backfire and die.... i don't understand what it is... i am about to change the fuel pump... With the engine off, I can go back there and work the throttle lever on the carb and I can see fuel shooting in on the forward side of the carb out of 2 jets...... Anyone go any ideas?? I have changed the filter 3 times, I have cleaned the inline screen.... It appears to be the original fuel pump, so i figure either way it needs to be changed... HELP! I need to get her fixed this week...the in-laws are coming to town, and i need to get them out of the house....

[boatworkfl]

hadeswraith wrote:
hey guys,

Well it's another year... and same problem. i thought the tech at the marina was going to fix my boat this winter, but he got canned...causwe he sucked.... Anyway... My 2455 has a OMC 351 5.8L with a holley 4 barrel.... When I start her up, she cranks right up... I engage the neutral throttle and she idles up great.... until I get to about 1800 RPM...at that point if I have the engine hatch open, I can hear the Carb making a sucking sound. the more throttle I give her, the more intense the sucking sound, and then eventually at 1800 rpms, she will start backfiring, and if I keep increasing, will eventually backfire and die.... i don't understand what it is... i am about to change the fuel pump... With the engine off, I can go back there and work the throttle lever on the carb and I can see fuel shooting in on the forward side of the carb out of 2 jets...... Anyone go any ideas?? I have changed the filter 3 times, I have cleaned the inline screen.... It appears to be the original fuel pump, so i figure either way it needs to be changed... HELP! I need to get her fixed this week...the in-laws are coming to town, and i need to get them out of the house....

Check your timming, and then air spark arrester for cleaning.

[Guest]

I see your boat is a 1989 so you still have points, when is the last time you did a complete tune-up? Do you have fresh fuel in the boat? That sucking sound is the carb doing it's job, pulling air into the motor and adding fuel on it's way thru.

[2850Bounty]

After thoroughly checking all else; fuel pump pressure, float bowl level, BASE advance, set point dwell (not point gap), check for good hot spark, etc,......... here's what may be a long shot, but perhaps worth looking into.

Ignition timing that is not advancing may cause a sound similar to what you are describing when there's not enough spark lead to increase power and RPM. It will hold back RPM and enhance the vacuum sound as the throttle plates open and attempt to deliver more fuel/air than what the engine is capable of per that RPM. You may get this sucking sound that you mention.

The engine requires progressive spark lead (in addition to BASE) in order to reach and produce higher RPM power.

Put a timing light on #1 spark plug lead.

Fire the engine up, and begin strobing your timing marks.

Write down what the Initial or BASE advance is.

Set to OEM specs if not correct.

Increase RPM to 1,000 and then further in segments of 500 rpm each, and write down the corresponding advance degrees.

Post these numbers here in your thread.

Example Only:

650-700 rpm 8*

1,000 rpm still 8* but wanting to advance

1,500 rpm 13*

2,000 rpm 17*

2,500 rpm 21*

3,000 rpm 25*

Like said, this may be a long shot, but this is a good thing to check anyway.

Camshaft indexing would be another long shot, although I'm not a big believer that timing chains can jump a tooth without offering very obvious other tell tale signs.

However, a camshaft that is not indexed correctly, will also cause a tremedous loss of power.

It will also throw ignition timing off by whatever the effect is to the crankshaft angle.

One tooth off on the SBC is approximately 16.3* @ crankshaft, and 8.18* @ cam.

One tooth off on the 5.8L Ford, is approximately 17.14* @ crankshaft, and 8.57* @ cam.

[johnrupp]

Sounds like you have a problem with points and or timing. Replace the points, set dwell and then timing.

[CaptUgly]

1800 rpm under load or in neutral? If you've changed the filters 3 times are they dirty? Bad gas? Gas isn't what it used to be! Was it treated for the winter? Anti-siphon valve sticking? Vacume leak when 4 barrel kicks in? I'd consider runnning carb cleaner & maybe an octain boost!

I hope my rating doesn't go down!

[Guest]

I'll take a wild shot at it.

I'm guessing that you've got a blockage of some kind in the fuel system that feeds the secondaries (the two air passages on the back side of the carburator. The sucking sound sounds like the secondary butterflies opening, which is pretty normal (it's probably more obvious with the cowl off). If your carb is like most automotive Holleys, you've got a secondary float bowl on the rear of the carburator. If the secondaries aren't getting fuel, the engine will go lean as the secondaries open and probably act just as you're describing.

My though is that you're either not getting fuel into that bowl, or you've got some blocked jets. I'd check for a stuck float valve first, and if that doesn't fix things, check for blocked jets, fuel passages, filters, etc. I believe some of the holleys have dual fuel lines with filters for each of the bowls. while some just have a crossover tube to feed the second bowl.

Good Luck

Carl

[Guest]

I was thinking the exact same thing... and another engine buddy told me the same thing... It only has a single line so maybe I just need to have the carb cleaned.... I have another mechanic coming to look at it this week, and I have created a Word Document with all of you guys "possible solutions"... I will let you know who wins the big prize.

Thanks,

[2850Bounty]

hadeswraith wrote:
........... 1.... When I start her up, she cranks right up... I engage the neutral throttle and she idles up great.... until I get to about 1800 RPM...at that point if I have the engine hatch open, I can hear the Carb making a sucking sound. the more throttle I give her, the more intense the sucking sound, and then eventually at 1800 rpms, she will start backfiring, and if I keep increasing, will eventually backfire and die....

2.... With the engine off, I can go back there and work the throttle lever on the carb and I can see fuel shooting in on the forward side of the carb out of 2 jets...... Anyone go any ideas?? I have changed the filter 3 times, I have cleaned the inline screen....

3... It appears to be the original fuel pump, so i figure either way it needs to be changed...

1.... I understand what Carl is saying, but I highly doubt that you are near opening the secodary throttle plates @ 1,800 rpm... or even slightly above that.

What is it doing while under load???? Same thing????

2.... What you're seeing is the accellerator pump nozzles squirting fuel as the throttle plates open..... and as they should.

3... There are certain items of which are not a bad idea to change..... this can be one of them.

[Guest]

Yes Bounty,

Under load it does the exact same thing.. I can idle a long down the lake, but as soon as I give it throttle and increase to 1800 rpm, it starts sucking and back fireing...

I am gonna wait and see what the mechanic says this week, but if he appears to be just "part changing" I will go ahead and change the fuel pump.. Question: are these fuel pumps all or nothing?...is it possible I am getting flow, but just not enough flow?

[2850Bounty]

First of all, ask for diagnostics, and ask for a price for diagnostics that will identify the problem.

If he is a "parts changer", this may prevent a portion of that.

Meanwhile, throw your timing light on it and do the simple check that I suggested! It won't take you more than 15 minutes.

.

[Guest]

Guys,

I went down to the boat this evening thinking that I would just poke around and see what I could see... i was gonna look at the card, but then noticed that the DISTRIBUTOR was loose... not the cap, but the whole distributor. it was spinning freely where it connects to the block... Now I am not an Gas Engine guy, but something tells me it shouldn't be loose. Upon inspection, there is a cross headed bolt with a clamp that is suppose to hold the Distributor in place.... there is also a Mark (made with a chisel) on the Distributor body..... I can't figure out what the "mark" is suppose to line up with....But, hope I have found the problem.....unless that crappy mechanic I had working on it the first time left it loose when he replaced the points.... Can someone help me understand what this "mark" might be indicating?... What would this affect if it was out of adjustment? Would it be the cause of the sucking sound I am hearing in my carb?? I am half way excited I stumbled onto this, but I am also concerned that it was just an oversight from the tech who replaced the points.... PLEASE TELL ME YOUR THOUGHTS....

[2850Bounty]

Get out your OEM specs, look up your timing specification, and set your BASE advance timing!

Then check the progressive!

Lock the distributor down when you're finished.

.

[boatworkfl]

I used to love that sound on my cars when young.

[johnrupp]

Bingo, you found the problem. With the distributor loose your timing is all over the place hence the backfiring. The chisel mark was probably put there as a mark when someone had the distributor out. Is there also a chisel mark on the bracket or block? A picture would be helpful.

The sucking sound you hear is totally normal. You just don't notice it over the normal noise of the engine.

I would do the following,

Snug down distributor.

Remove cap and check dwell angle. Should be 29%.

Reinstall cap and see if engine will start.

If it does set timing at 10% BTDC at idle.

Tighten bracket holding distributor.