Fuel starvation issue
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Boat Maintenance
Forum Discription: Discuss maintenance of your Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=39852
Printed Date: November-16-2024 at 11:36am
Topic: Fuel starvation issue
Posted By: Skicenturion86
Subject: Fuel starvation issue
Date Posted: September-04-2016 at 9:54pm
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1986 Ski Centurion Pleasure Craft V8 The boat starts fine and drives fine at idle. Once we get above 25 for more than a minute the fuel stops being delivered to the motor and the motor stalls. We have replaced: Fuel pickup in the tank Fuel line from tank to fuel/water separator The fuel/water separator Hoses to mechanical fuel pump The mechanical fuel pump (Metal tube from fuel pump to hoses not replaced) Hoses and fuel filter Brand new carburetor We can't figure out how the system is being starved of fuel only at high speeds basically everything has been replaced in the fuel system. What are we missing? Any ideas? https://youtu.be/BhVMH2X32sU" rel="nofollow - Video of what is happening |
Replies:
Posted By: tryathlete
Date Posted: September-04-2016 at 11:23pm
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Could be a clogged vent. If you crack open the fuel filler cap when it starts to stall and it keeps running--bingo. Other possibility is a clogged anti-siphon valve assuming it's equipped with one. You've gone through a lot of parts to get to this point and that makes my two guesses a lot easier to make. Best of luck--we all hope it's fixed ASAP. |
Posted By: Skicenturion86
Date Posted: September-05-2016 at 12:13am
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We were also trouble shooting with two separate fuel tanks to verify it wasn't the fuel tank or vent issue. The issue still happened with a open fuel tank. What does a anti siphon valve do? Haven't replaced that yet. Could it be an issue past the fuel filter? Carburetor issue? Or past the fuel pump, fuel water separator issue? |
Posted By: tryathlete
Date Posted: September-05-2016 at 1:45am
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The anti-siphon valve was a mandated device to prevent fuel from being drawn out of the tank if the boat fuel line broke and the tank level was above the engine pump. Here's more detail; It is only necessary if the fuel tank is above the level of the fuel lines. Have you ever siphoned fuel from a tank? If so, do you remember that the end of the fuel line had to be positioned below the level of the fuel? If you raised the fuel line above the level of the fuel tank then the fuel in the line will simply flow back to the tank. Then, if you lowered the fuel line no fuel would flow out because there was no fuel in the line. To start the siphoning again you would have to suck fuel in the line and keep the line below the level of the fuel in the tank. Let's assume that you have a fuel tank on a boat that is above the level of the engine. The fuel line runs from the tank downhill to the engine. The line is full of fuel because it has been supplying fuel to the engine. If the fuel line were to break at the engine, the fuel in the line would then siphon the fuel from the tank and dump it on the engine. The engine is hot. A fire might start. The fuel that is continuing to be siphoned from the tank will continue to supply fuel to the fire. Not good. An anti-siphon valve is a device that requires some amount of negative pressure (suction) to open it and let fuel flow. The engine driven pump, or an electric pump, has sufficient suction to open the valve and let fuel flow. The amount of suction resulting from siphoning does not. So, the valve will let fuel flow if the engine pump is drawing fuel but if the line broke and a siphon tried to start, the valve will close and stop the siphoning. Sometimes (quite often???) the siphon valves go bad and even the engine pump cannot draw enough fuel through the damn thing to keep the engine running properly. |
Posted By: tryathlete
Date Posted: September-05-2016 at 1:52am
| If you used two separate fuel tanks, that kind of rules out the anti-siphon valve. Hmmmmm. Maybe the mechanism that drives the mechanical pump is not engaging properly? I look forward to seeing the solution to this mystery. I'm going to watch that video again. |
Posted By: tryathlete
Date Posted: September-05-2016 at 2:03am
| Maybe the pump is not generating enough vacuum. It's supposed to generate 6" of HG. You're only reading the output. If it cannot draw fuel it won't matter what the output pressure is. |
Posted By: TedR
Date Posted: September-05-2016 at 10:46am
We had kinda of the same issue with the engine cutting out at just about 2500RPM replaced the holly, check for clogged fuel vent, checked fuel pick up,new fuel filter, DUI Distributor (with some eventfulness installing  ), but it might have come down to a slight kink in a fuel line that i had not noticed between the filter/water separator and pump. It sounds like you have check everything though... Best of luck sir.
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Posted By: 8122pbrainard
Date Posted: September-05-2016 at 11:13am
How are you determining the fuel flow stopping? ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Skicenturion86 wrote:Posted By: tryathlete
Date Posted: September-05-2016 at 11:50am
| Pete--gotta see the video. They've used a sight glass inline fitting and it shows fuel being replaced by air. |
Posted By: KENO
Date Posted: September-05-2016 at 1:54pm
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After the engine quits, what do you have to do to get it running again? What's that gauge hooked to? Looks like it's reading engine vacuum, I'd hook it up to the fuel pump discharge and get some readings. Sounds like you had the issue, then replaced stuff and have the same issue still? Was the fuel pump a brand new one ? What brand ? I had an issue like this and it was the fuel pump. You could go slow all day long but give it some gas get to about 2500 rpm and same as you about a minute or so later it would die. It wasn't a diaphragm issue but a valving issue(inside the fuel pump). Some of the discharge was going back to the suction and starving the carburetor at higher RPM. Checking fuel pressure told me a lot. Cleaned the valves and it worked correctly again. Sounds like you already tried a separate tank but I'd hook it up again with a fuel pressure gauge on the pump discharge and see what you get KenO |
Posted By: 8122pbrainard
Date Posted: September-05-2016 at 6:51pm
Peter, Thanks, I hadn't watched the video!  It's not a sight glass but rather one of those inline fuel filters designed to go on the suction side of the pump rather than the high pressure side to the carb. Dan, Ken's got some good suggestions. Try them and report back. BTW, I do hope that filter is just in there temporarily and you are planning on replacing the high pressure line from the pump to the carb with a USCG method. They have some pretty strict rules so people don't drive around in potential bombs like yours. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Skicenturion86
Date Posted: September-05-2016 at 7:26pm
That's how the boat was setup for decades 8122pbrainard. We will look into how to properly setup the fuel line. Do you know how its supposed to be setup? Video out there maybe? We will do some tests and get back to you guys. Thanks for the help so far. |
Posted By: 8122pbrainard
Date Posted: September-05-2016 at 9:17pm
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Dan, Here's an old thread by Ken where he links some info on the fuel line. Ken's one of the sites respected "gearheads" who's advice is worth noting. He's into engines so much that he even R&R's starters to see how fast he can do it!!  
------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: KENO
Date Posted: September-05-2016 at 9:30pm
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Ha Ha , Thanks, You one funny guy Pete Just wanted to show him (jtryon) that it wasn't a hard job to do. The site did get his problem resolved Keeps my wife chuckling at some of the things I do too. There are only certain things I know anything about and some topics I won't go near at all. KenO |
Posted By: Skicenturion86
Date Posted: September-05-2016 at 11:29pm
To get the boat started again we just spray starting spray inside the carb that is enough for the fuel pump to do its thing and get the fuel back to the engine. As far as brand of pump we have no idea. its mechanical and has a lever that a cam inside just continually pumps. It has an in and out line plus a third line that goes to the top of the carb. I believe thats a USCG thing too. how would I connect a fuel pressure gauge? thanks alot we are stumped by alot of this. |
Posted By: KENO
Date Posted: September-06-2016 at 12:21am
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The gauge in your video is also a fuel pressure gauge. Use a tee fitting that fits in your fuel line (probably 3/8 inch) and fits your tubing on the gage (probably 1/4 inch) and put it where the filter is now and you can read the fuel pressure while it's running. 5 to 7 psi should be about right. I had one that put out a couple pounds and very little volume due to internal valve leakage in the pump and it acted just like yours. (At higher speeds the carburetor used more gas than the pump could supply.) If you hook your temporary tank to the suction when doing this test, that should take any questions about the suction side out of the picture |
Posted By: KENO
Date Posted: September-06-2016 at 4:20pm
  For today's fun I figured I'd hook up a gauge and check the fuel pressure on a Carter marine fuel pump that works just fine.. One picture is the Tee fitting used to hook it to the fuel line. The other is the gauge steady as a rock at 6.5 psi (Pay no attention to the finely manicured thumbnail) No matter what the RPM it was steady at 6.5 psi If you hook it to the suction side, it rapidly fluctuates between 0 and 5 in Hg vacuum while the pump is operating. KenO |
Posted By: GottaSki
Date Posted: September-06-2016 at 4:53pm
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Tell us more about this 'replaced' fuel pickup at the tank. Have you taken the pickup's tube and fittings entirely apart? ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: Hollywood
Date Posted: September-06-2016 at 6:58pm
| can you please just run it off a fresh can of fuel plumbed straight into the pump? |
Posted By: Skicenturion86
Date Posted: September-07-2016 at 12:53am
That's the plan but can't work on it for another two weeks.. will update soon as I get back home and test this stuff out. Thanks to all for the ideas. |
Posted By: Skicenturion86
Date Posted: September-28-2016 at 12:24am
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So we timed the motor and tuned the carburetor so the motor is starting like a dream. It Idles so nice, runs great except for a ticking noise at high rpm here's a youtube link to that video... https://youtu.be/KIEbR_1KnI4" rel="nofollow - https://youtu.be/KIEbR_1KnI4 Any ideas on this ticking? at the :20 sec mark when the motor opens up you'll hear the ticking I'm referring to... We ran the motor directly from a can of fuel and still had the same fuel disappearing issue. So it's nothing in the fuel system from the tank to the pump... Only thing I can think of is the fuel pump itself is the issue.. So I think we will try yet another fuel pump. Any last suggestions for us before we do this... |
Posted By: KENO
Date Posted: September-28-2016 at 9:53am
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So, how's your fuel pressure? Did you check it? Was it a new pump you put on? |
Posted By: Hollywood
Date Posted: September-28-2016 at 11:03am
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Let's worry about the tick later. I can't see where the fuel can is hooked to in your video. Is it straight to the fuel pump or does it have to go through any sort of water separator/filter? Still no fuel pressure gauge? Take off the lines from the pump to the carb. Stab a wire through them to make sure they are clean and clear. Plumb the gas can straight to the fuel pump with a line that you've also stabbed through to ensure it's clean and clear. Now we know there are no restrictions anywhere. If the engine runs out of gas again it sure would point to the pump. |
Posted By: Duane in Indy
Date Posted: September-28-2016 at 11:50am
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Take that glass fuel filter off and plumb in the TEE and Gauge like KenO showed you on Sept 06 post. See what your fuel pump is actually doing. Then unhook the gauge and TEE and run the line into a SAFE catch can and measure the flow rate (using additional hose to get the catch can outside of the boat). It appears in the second video that you replaced the fuel filter?? You need to throw it away while you are at it. Assume you have checked the float levels?? edit: while your at it, throw the starting fluid away also ------------- Keep it as original as YOU want it 1978 Mustang (modified) |
Posted By: 8122pbrainard
Date Posted: September-28-2016 at 2:03pm
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Dan, I suggest reading this complete thread from the start. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Skicenturion86
Date Posted: September-28-2016 at 7:46pm
| We replaced the pump, it's new, but the next step is checking pressure.i suppose we could have two bad pumps but this seems way odd. I was hesitant to check pressure since I can see the fuel pressure goes away visually so why bother checking it. It must be the pump. But we got the tee and some extra hose and will check the pressure soon as I return back home. Off to work for another week... thanks to those that are helpful. |
Posted By: 8122pbrainard
Date Posted: September-29-2016 at 12:55am
"goes away" Do you mean when you see air in that clear filter? I always thought air could be pressurized too! ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Skicenturion86
Date Posted: October-01-2016 at 11:56am
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So looks like we are pushing 7.0 and 8.5 at speed on the fuel pump. My brother ended up adjusting the needle and seat. https://www.quickfueltechnology.com/tech-info/carburetors/carb-class/carb-class-needle-and-seat-fuel-pressure" rel="nofollow - ...needle and seat? Not sure what that is but he said the pressure was fine and adjusted the needle and seat and the boat ran for 15 minutes above 30 MPH. First time since we rebuilt it. So that was the problem... Now the clicking sound... Any ideas? https://youtu.be/KIEbR_1KnI4" rel="nofollow - Clicking sound... |
Posted By: 8122pbrainard
Date Posted: October-01-2016 at 12:03pm
Bad links! ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Skicenturion86
Date Posted: October-01-2016 at 12:04pm
| fixed.... |
Posted By: Duane in Indy
Date Posted: October-01-2016 at 1:01pm
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[QUOTE=Duane in Indy] Assume you have checked the float levels?? ie: adjusted the needle and seat Now hope you pitched the glass filter as posted above by several ------------- Keep it as original as YOU want it 1978 Mustang (modified) |
Posted By: 8122pbrainard
Date Posted: October-01-2016 at 1:02pm
Had to say what the click is. Could be a lifter ticking or even sounds like a alternator bearing tick. Does it tick under load on the water? ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: KENO
Date Posted: October-01-2016 at 3:37pm
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I think the video shows it under load on the water. I also think I'd be checking the timing since it doesn't happen till heavy load and higher rpm's. What's the timing at idle? How about at 3000 rpm? How about at 4000 rpm? Does it make the noise when it's in neutral being revved up with no load? KenO |
Posted By: 8122pbrainard
Date Posted: October-01-2016 at 4:13pm
Dan, On the water under load or not. I didn't see much movement in the video so I didn't think it was taken uder load? One other thought on the tick. Check your exhaust manifolds for a exhaust leak. The typical spot is between the block where they are bolted and the main water jacketed manifold body. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |