Mechanical fuel pump question |
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fanofccfan
Platinum Member Joined: December-13-2009 Location: North Bend NE Status: Offline Points: 1722 |
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Posted: July-09-2019 at 10:52am |
A friend has a 1950's Chris Craft With fuel issues. I removed the fuel pump and submerged the inlet in a cup full of gas and manually pumped the lever and gas came out the outlet. The motor runs with ether (i know thats unsafe and not a good idea but it is his boat and he was in charge of that). All lines appear to be unobstructed. We blew in the tank fill and gas came out the supply line. After reinstalling the pump and cranking the motor the glass bowl would not fill with gas. My question is why does it pump gas while pumping it with my fingers but not when run by the lobe? Also, can mechanical pumps get weak or do they either pump or not pump? Would a stuck float not allow the pump to do its job?
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2004 196 LE Ski 1969 Marauder 19 1978 Ski
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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Unhook the line at the carburetor and aim it into a container and see if it pumps while cranking the engine.
Not knowing what your pump looks like, diaphragms can get weak and the check valves in the pump can leak or stick too. Is the pushrod or eccentric in the engine making the pump arm move. If you crank it with the suction hose removed from the pump and your finger over the suction port, do you feel suction? This 50's stuff is Pete's territory |
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fanofccfan
Platinum Member Joined: December-13-2009 Location: North Bend NE Status: Offline Points: 1722 |
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The line fitting at the carb was very tight and I didnt feel like breaking it so i did not take that off. I should have done that though.
I couldnt tell if the pump arm was moving from the eccentric lobe. the lobe itself was moving. The boat ran great ,last year so i assume its pump related or a float stuck. |
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2004 196 LE Ski 1969 Marauder 19 1978 Ski
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Bill, Ken's got some great advice here. First choice would be the diaphragm. If the pump has never been rebuilt or it's bee 20 years, then it's time. It ran great last year but over winter the diaphragm certainly could have gone bad especially if he ran any ethanol. The originals were not designed for the ethanol. The pump is very rebuildable. Then there's the eccentric on the cam as well as the pump arm itself. Look for wear on both. Hopefully your friend hasn't been running modern oils without the ZDDP. I've seen some pretty bad Hercules cams with lobes that are almost round!! It pumps with the hand/manual arm because it moves the diaphragm farther and not off the eccentric arm |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Bill,
Here's the Then and Now website. They have the kits but also rebuild pumps. |
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fanofccfan
Platinum Member Joined: December-13-2009 Location: North Bend NE Status: Offline Points: 1722 |
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He ordered a kit today. We did talk about oil and zinc levels but he did not recall what the brand or weight was. So what i think I hear you both saying is the pumps can get weak, Its not necessarily they either work correctly or they don't work at all? That would make some sense in this case.
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2004 196 LE Ski 1969 Marauder 19 1978 Ski
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Bill,
When your friend gets to the point of screwing the two halves of the body together with the new diaphragm between them there is one procedure he needs to be aware of. The arm needs to be compressed so it partially stretches the diaphragm and then the screws are tightened. The pre stretch greatly extends the life of the rubber diaphragm Without the pre stretch, the rubber is stretched with every stroke. |
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fanofccfan
Platinum Member Joined: December-13-2009 Location: North Bend NE Status: Offline Points: 1722 |
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Thanks Pete. I will send that info along. Partial compression of arm? Or full?
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2004 196 LE Ski 1969 Marauder 19 1978 Ski
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Bill,
Just partial. I'd say so it stretches the diaphragm about 1/4 inch from flat. |
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fanofccfan
Platinum Member Joined: December-13-2009 Location: North Bend NE Status: Offline Points: 1722 |
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Gotcha Thanks again.
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2004 196 LE Ski 1969 Marauder 19 1978 Ski
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fanofccfan
Platinum Member Joined: December-13-2009 Location: North Bend NE Status: Offline Points: 1722 |
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To update this thread the fuel pump kit was successful. The old diaphragm appeared to be in perfect working order but certainly was not. Put it back together and the old girl fired up beautifully!
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2004 196 LE Ski 1969 Marauder 19 1978 Ski
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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What model and year Chris is it? |
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fanofccfan
Platinum Member Joined: December-13-2009 Location: North Bend NE Status: Offline Points: 1722 |
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Model year 53 but built in 51. 22’ CC Custom Sedan. CC Marine straight 6 ML engine. I uploaded pictures here a while back. I can’t find the thread though.
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2004 196 LE Ski 1969 Marauder 19 1978 Ski
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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I think this might be the thread you're looking for in the link below Bill link |
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fanofccfan
Platinum Member Joined: December-13-2009 Location: North Bend NE Status: Offline Points: 1722 |
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Bingo! Thanks Ken!
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2004 196 LE Ski 1969 Marauder 19 1978 Ski
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Beautiful sedan. The ML is a beast!!!
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1987don
Newbie Joined: July-08-2014 Location: derry nh Status: Offline Points: 11 |
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Mechanical fuel pumps rarely die
Gas lines do from ethanol Replace the rubber gas lines and the vacuum will stop and you will get fuel Maybe the fix but it’s cheap and easy troubleshoot Mine would start then die under load I tried everything Old timer at parts store told me to change the file line and it worked |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Don, We are discussing a 50's pump on a Hercules. How far back do you go? Tell us more. The rubber diaphragms in the 40's, 50's, 60's and even 70's were NOT alcohol resistant. |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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Did you bother reading the whole thread? His issue was fixed with a new fuel pump Looking at your old posts, you seem to think that replacing the fuel line is the cure all for every fuel issue out there. It's a good suggestion but it sure ain't the problem every time |
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1987don
Newbie Joined: July-08-2014 Location: derry nh Status: Offline Points: 11 |
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Keno
Point taken I should look deeper I found it simple cheap after I spent ton of money digging Old timer turned me on to it Gotcha though While I have you Any suggestions for sluggish acceleration only when puliiing skier ? Happened rather suddenly last week? Thx |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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Does it accelerate smoothly, no skipping or hesitation, no funny noises............just slow?
Maybe as a start, check the timing at idle around 10 degrees BTDC and watch it advance as the engine speed increases. Should end up in the 30 range at around 4000 rpm's with the stock Prestolite distributor Since Pete dug up your old thread from 2014, maybe somebody stole your ACME prop |
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1987don
Newbie Joined: July-08-2014 Location: derry nh Status: Offline Points: 11 |
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Runs smoothly through all rpm ranges
BUT Only topping out at 4000 Could that be a timing issue? I never expected that Been reading about carbs a litttle Do you know anything about accelerator pump adjustment ? |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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Hi Don
If it's not bogging or hesitating, the accelerator pump is most likely not an issue. Check the thread in the link below from a couple of years ago It gives an easy way to check that your secondaries are opening on the carburetor. Just need a zip tie. As it mentions in the thread, they don't open all the way on a 351 with a 600 cfm carburetor, but you can check that the zip tie moved on the shaft to verify that they're at least opening some Also as mentioned the boat lost a few hundred RPM, lost some acceleration and lost a few MPH. It's worth sacrificing a zip tie to find out link |
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KENO
Grand Poobah Joined: June-06-2004 Location: United States Status: Offline Points: 10662 |
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One other thing, the secondaries only open with a load on the engine, so the zip tie check needs to be done while driving the boat. Accelerate to full throttle, come back down in speed, pop open the engine box and check that the zip tie moved or didn't move
Revving the engine in neutral won't make the secondaries move at all, you need that load on the engine for them to operate. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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I still think it's the fuel pump.
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