Fuel pump issues |
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AlfaDon ![]() Senior Member ![]() Joined: September-18-2011 Location: San Leandro, Ca Status: Offline Points: 392 |
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Hi
As many of you know I’ve been chasing a problem with my engine falling on its face about 2500rpm. I’ve replaced just about everything fuel related and now I’m back looking at the fuel pump as the problem started when I switched from an electric pump to a mechanical one. The mechanical pump I have is a Carter M60839. After chasing other fuel related problems I came across a thread where others have had multiple failures with the same pump. Has there been a consensus about a reliable replacement? I wonder if it’s possible to buy an automotive pump and install a vent or us the top of the carter on a new body. Thanks |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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That's really a 60389
![]() For troubleshooting purposes I'd try a cheap automotive pump for something like a 84 F-250 with a 351. Just consider it a 25 dollar troubleshooting tool ![]() It looks a lot different but will bolt up and work to tell you if you have a fuel pump issue or rule it out I have one hanging around just for that purpose. You'll have a little replumbing to do, but it's only temporary. The Carter's usually are bad due to a leaking diaphragm sending fuel up the sight tube and dumping that fuel in the carburetor so it's a visible indication along with a lousy running engine. Just to say it again, temporary for troubleshooting |
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AlfaDon ![]() Senior Member ![]() Joined: September-18-2011 Location: San Leandro, Ca Status: Offline Points: 392 |
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Thanks Keno.
So after the troubleshooting what’s the next option? It seems that there was discussion about the Airtex maybe being a little better but they’re not available as of a discussion I had with a parts guy today. Is it possible to take a nice billet one and add the vent tube? Most of the ones I’m looking at have the hole in the casting. |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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People have done what you're talking about
Who knows, after the troubleshooting you may not need a new fuel pump ![]() |
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AlfaDon ![]() Senior Member ![]() Joined: September-18-2011 Location: San Leandro, Ca Status: Offline Points: 392 |
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So I took the fuel pump apart and there’s no sign of deterioration of the diaphragm. I guess the check valves are still suspect. It was holding a little pressure when I took it apart, which was interesting.
The symptoms of what it’s doing are as I accelerate slowly the power just drops about 2500rpm. I’ve got an O2 sensor on it and at the time the power drops the 02 sensor reads lean, so I’m pretty sure it’s a fuel issue. I’ve checked the tank tube and screen. The tank is immaculate. I removed the anti siphon check valve. When I’m idling the fuel pressure gauge will show 2 psi, and when I’m underway it drops to zero. It’s a pretty new Quick fuel 650 com carb I’m at a loss |
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63 Skier ![]() Grand Poobah ![]() ![]() Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4232 |
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When I bought my boat, it had a known stumble at close to full throttle that the seller made me aware of. It ran Ok at skiing speeds but a bit more throttle and would stumble, would recover with less throttle. A good mechanic I know tried the obvious and was stumped for a while, but on a water test figured out my fuel hose was collapsing. I wasn't there so no idea if he saw the actual spot or assumed it was the problem. Anyway, ran new fuel lines and the problem was gone, has never come back.
Just saying it might be worth investigating. You could run a short length of new fuel line to a jug of gas and see if the problem is the same. Maybe you already did that, I didn't go back and read your prior troubleshooting. |
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'63 American Skier - '98 Sport Nautique
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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I had one with check valve issues that did pretty much the same thing. Wouldn't go over 2500 rpm, and low on pressure. it was an old style that could be rebuilt and i replaced all 3 check valves and things were good again. |
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AlfaDon ![]() Senior Member ![]() Joined: September-18-2011 Location: San Leandro, Ca Status: Offline Points: 392 |
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Dang Keno. You sure have been through lots of fuel pumps.
Today while waiting for a different fuel pump to arrive, I reinstalled the old Carter and started messing with the carb. I went from a 71 primary jet to a 73, and changed the power valve from a 65 to an 80 and what do you know, the problem seems mostly to have been resolved. I’m still not convinced that the fuel pump is doing its job because I was watching the pressure gauge and the pressure was all over the place. I can’t tell if the liquid filled gauge is part of the erratic readings or not. Tomorrow I’m going to try the 71 jets again and use a 75 power valve. It was definitely running a little rich. Thanks for your help and I’ll report back after the fuel pump change. |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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Lots of boats, friends with boats, friends of friends etc whose boats I seem to work on and that irresistible urge to have spare parts hanging around ![]() |
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phatsat67 ![]() Grand Poobah ![]() Joined: March-13-2006 Location: Indiana Status: Offline Points: 6148 |
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Don, on that QF Carb where did you put your fuel pump vent line? One of those ports is plugged and it will eventually cause the fuel pump to not keep up with flow if the vent tube is on the plugged port.
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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Zach I think I need some help here I can't find these ports you speak of on a Quick Fuel I can find a timed spark port on the side of the primary metering block and I can find another timed spark port and a manifold vacuum port in the baseplate under the primary fuel bowl and then there's a PCV connection at the back of the baseplate but nothing else, so where are you hooking this tube to? A picture would be good I also pulled my tube from my Holley that had a specific spot for the overflow tube and plugged it and took the boat for a ride to see what happened to the fuel pump. Just like Gilligan and company, it was a 3 hour tour but unlike them nothing broke down. My wife did enjoy the ride though ![]() It ran just fine with the overflow tube from the pump plugged |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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Here's a link to some Quick Fuel instructions with the ports I mentioned
![]() I'd imagine a timed spark port would work link |
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MourningWood ![]() Gold Member ![]() Joined: June-13-2014 Location: NorCal Status: Offline Points: 886 |
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One option is a pro rebuild. I have sent pumps to: www.then-now-auto.com Have had great results over last 15 years. All come back bench tested and set to deliver the requested/required pressure. Very quick turnaround. Guaranteed. |
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1994 Ski Nautique "Riot"
1964 Dunphy X-55 "One 'N Dun" 'I measured twice, cut three times, and it's still too short!" |
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AlfaDon ![]() Senior Member ![]() Joined: September-18-2011 Location: San Leandro, Ca Status: Offline Points: 392 |
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Lots of interesting information.
My vent tube is going to the timed spark port in the metering block. It’s not obstructed, But when I tested a different pump there wasn’t any vacuum at the pump end of the vent tube either. I would imagine it makes sense to use one of the two ports below the butterflies. I looked at the warranty info for the Carter M60389 and it’s one year. I sent the receipt to carter and we’ll see what they say. I also found out that Carter and Airtex are not manufactured at the same facility. |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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You really don't care if there's a vacuum on the overflow line. Look at all the flame arrestors that have the little line for the overflow tube to dump into the flame arrestor. At idle speed there's squat for vacuum at the timed spark port(s) and as you increase speed the vacuum gets better to a certain point then starts dropping off and at full throttle it's the same as manifold vacuum. The 2 timed spark ports sense the same vacuum above the throttle plates. You can find plenty of reading on timed and manifold vacuum sensing The manifold vacuum port is vacuum sensed after the throttle plates ( the same vacuum you want to read with a vacuum gauge to diagnose your engine. At idle you have high vacuum and as speed and load increase the vacuum drops off to pretty much zero at full throttle. Hooking your line where you have it hooked up although unorthodox, accomplishes what you want it to do I think and that's to give a place for the fuel being pushed out of the tube when the diaphragm ruptures to dump into the carburetor above the throttle plates and stall the engine or at least make it run really crappy. Or you could get a flame arrestor with the tube built into it ![]() Somebody on here just recently got a warrantied replacement from Carter with Carter telling him there were some issues with some of their pumps. I don't think they even cared to get the old one back. |
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JoeinNY ![]() Grand Poobah ![]() ![]() Joined: October-19-2005 Location: United States Status: Offline Points: 5693 |
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Well if you have your fuel pump vent connected to a vacuum port, timed or not that likely is why you are not getting proper fuel pressure. The pump is basically operating at a pressure differential to the backside of that diaphragm. A good healthy vacuum in that area would cause the pump to put out about 0 psi of fuel pressure relative to atmosphere. That vent tube should should dump above the throttle plates, never below. edit - not only above the throttle plates but above the venturis - so the back side of the fuel pump diaphragm sees the same pressure as the fuel in the fuel bowls - People with old school turbo set ups would add a nipple to that side of the diaphragm there and run a hose to the pressurized box around the carb to increase the pressure of the fuel the pump put out as the boost pressure went up other wise they would have the same issues you are causing yourself. |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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I figure if you asked them about rebuilding a new cheapo like they sell now they'd laugh at you but it could be worth a phone call. The actuating arm pin is held in differently than the old ones making disassembly and reassembly a whole lot harder ![]() Here's a link to a good video by Then and Now of rebuilding the older Carter pumps. This one is for a 460 Ford but it's the same thing except for the operating arm . link He mentions that they're painted on the inside, but not all of the marine Carter's are painted inside |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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The timed spark port is sensing above the throttle plates |
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JoeinNY ![]() Grand Poobah ![]() ![]() Joined: October-19-2005 Location: United States Status: Offline Points: 5693 |
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I am slow - I went up to edit - needs to be not only above the plates but also above the venturis - or more commonly open to atmosphere. 4.5 to 6 psi is about 9 to 12 inches of mercury vacuum |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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I saw the edit
![]() I figure if he disconnects the hose from the port and takes the boat for a ride, he can see if the problem he has goes away or is still there. All the Holleys with the overflow connection do have the dump port above the venturi's like Joe mentions. And as I think about it, I agree with Joe |
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AlfaDon ![]() Senior Member ![]() Joined: September-18-2011 Location: San Leandro, Ca Status: Offline Points: 392 |
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Check out the brain on Joe!!
I just got off the phone with Quick Fuel and they described my problem exactly. At the port on the metering block there is no vacuum at idle or wide open, but there is vacuum mid throttle. Which is enough to disrupt fuel pressure. The tech suggested a bulkhead hose barb fitting into the top of the spark arrestor where excess fuel will get dumped directly into the throat of the carb. The engine will flood out and die. On another note, I’ve got a 25’ roll of the clear fuel resistant hose for the overflow. If you want a piece, just let me know And I’ll send it to you. |
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JoeinNY ![]() Grand Poobah ![]() ![]() Joined: October-19-2005 Location: United States Status: Offline Points: 5693 |
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I was doubting me but as I went up and read the symptoms and I am coming back around to the timed port on the vent hose being a likely root cause... falling on its face at 2500 on smooth running - would be at about where that thing would see the most vacuum on a timed port and with enough time to empty the bowls that would fill up at idle. Plus no problems with an electrical pump vs mechanical on the same setup - electrical pumps you boost reference the regulator not the backside of the diaphragm - and putting a vacuum on the electric pump weep point would't cause any pressure issues. |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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So all you have to do now is unplug the hose from your timed spark port and see how it runs.
![]() Then you'll have some more info. |
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phatsat67 ![]() Grand Poobah ![]() Joined: March-13-2006 Location: Indiana Status: Offline Points: 6148 |
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It’ll run like it’s supposed to. I’ve seen several boats in the shop with the same symptoms and same solution. Most recently Brad Harpers Sanger. Ran great. Swapped on quick fuel with vent tube to the spark port and no fuel at midrange.
Pump needs open airflow to the vent or it wouldn’t have one. Auto pumps are open to the atmosphere for that reason. No need to pump fuel into the carb if they fail. Busy today sorry for the late reply. |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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So maybe you can explain how the AC dual diaphragm pumps work since the leak line between the 2 diaphragms went to a small unvented glass bowl and the area above the upper diaphragm vented to absolutely nowhere. (or in other words...........no vent) And your explanation earlier didn't doesn't jive with what you're saying now ![]() So where did you hook the vent tube to on the Quick Fuel ? There's no port for hooking the hose to
Or maybe you can explain why I could drive around for 3 hours yesterday with the vent line plugged . it was a Carter pump. |
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MrMcD ![]() Grand Poobah ![]() ![]() Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3594 |
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I worked with Carter in the 90's while Federal-Mogul owned them but still needed to look this up to verify what I thought about the vents. I looked and I guess I have now tossed the old catalogs from Carter. That is to bad because some of those old Cats offered a lot of information and details.
"Marine pumps have a double diaphragm. When the first one breaks, it will leak fuel into the cavity where the small hose port is and send it to the carburetor instead of the bilge. Also, the anti-siphon valve in the tank pickup will prevent fuel from free-flowing. Both the small hose and the anti-siphon valve are required by law." |
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phatsat67 ![]() Grand Poobah ![]() Joined: March-13-2006 Location: Indiana Status: Offline Points: 6148 |
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Yours drove ok which doesn’t jive with other stuff I’ve seen plugged in incorrectly. I’ve seen several not work properly. It jives perfectly with what I said earlier. Vent line plugged to a carb port (not a vent line port) will make a pressure differential like Joe said.
I never researched much to see what exactly those ports did. No vacuum on them at idle. Pull the line to atmosphere and I’ll all but guarantee your pressure issue will be gone. |
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AlfaDon ![]() Senior Member ![]() Joined: September-18-2011 Location: San Leandro, Ca Status: Offline Points: 392 |
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I installed an automotive pump and without the vacuum on it, it ran great.
Now to put the Carter back on and test it without vacuum. I just ordered a bulkhead barbed fitting to install in the spark arrestor. I also spent 52 cents on a rubber cap for the carp. I’ll report back tomorrow |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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So, now you know why there's no vacuum on them at idle if you read the whole thread but you haven't exactly answered the question of where you hooked the overflow line to. Explain where the vent line port is on a Quick Fuel, pictures would be great ![]() The "vent line" just plain old plugged so there's no vent path at all let's the pump operate just fine but doesn't satisfy marine requirements. The hole on an automotive pump like Don put on for testing is there to let you know the diaphragm is leaking and it's not a vent to let the pump operate properly You seem to forget that After Joe mentioned it, I agreed with him about where the line should go (above the venturis) One thing we're all agreeing on is that with the line vented to atmospheric pressure (above the venturis) the pump should work right. unless it happens to be broken ![]() |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10667 |
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I guess you can't find that non existent fitting Zach thinks is on the carburetor to hook the line to ![]() Out of curiosity, why did you hook it there to begin with? |
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