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Fuel pump questions 1967 2.5

T

txgalzdah

Regular Contributor
"1967 MC-1, 2.5L 4 cyl, 120hp. Low pressure, 5psi, mechanical fuel pump. Going through my check lists and came across some questions on mechanical fuel pump.
Purchased a replacement fuel pump. Being a marine pump it has the connector for the draft side of the diaphragm. From previous posts I understand that clear motorcycle fuel line can be used.
My question is how long should this sighting tube be? What is a good method of plugging the open end so the coasties won't pinch me? Does this arrangement cause any back pressure on the diaphragm?
Regards,
TxGalz Dah"
 
"Hook a clear line you can pur

"Hook a clear line you can purchase at home depot or lowes,

It is designed to go the choke housing of the carb so any gas will flow right into the carb.

You could drill and tap a 1/8 npt hole into the choke horn area and put a barbed fitting in and hook the hose up like it should be

It just has to be below the flame arrestor."
 
"You need a "fuel rated&#3

"You need a "fuel rated" hose or you'll be making more problems. I prefer TYGON, usually available from a small engine shop, locally. If bonafided, it will be translucent yellow tubing with TYGON clearly visible on it. I'd be leary of the BigBox as you never really know what they are selling.

The best method is the 1/8" NPT fitting method described by Kghost. Ideal location is a direct shot into the venturi, below the choke plate and above the throttle plate. Holley provides a fitting that dumps any fuel from this hose into the flame arrestor, above the choke; may be "approved" but isn't optimal."
 
"i think he has the old style

"i think he has the old style with a sight glass there was no clear hose from the carb to the fuel pump.

If the diaphragm went the sight tube filled with gas , as we all know so the fuel didin't dump into the bilge.

If i am correct you can use all the old fittings, from the old pump. The original setup lasted so i see no reason why the new pump won't last also.

My only obssevation, is the pump you bought does it give between 4-6 psi and no more then 7. Your old pump was giving what? Why the replacement?"
 
"Wow, lots o info here. I wil

"Wow, lots o info here. I will check into the Tygon. Yes, there is a hole in the butterfly plate under the carb. I can use that penetration. Sounds right when you put all the pieces together. I have to say that the POS we dragged home in '08 had a great deal of shade tree modifications to it. Especially the fuel system.
Chieflen, don't read anything into my reply but facts be facts. I replaced the fuel pump becasue the unit on the motor was 43 years old, had a glass sight glass was full of something I didn't recognize and smeelled like something other than fuel. Took a good bit of Napa Orange to get the smell off my hands.
Yes, the fuel pump is rated for 4-6 psi. This info I got from the OEM manuals. We started the motor last SEP and baby she purrs like a kitten. I remember at the end of the day my face hurt from smiling so much. Now that's a good kind of hurtin. Thanks again for the help up.
Regards,
TxGalz Dah"
 
"Good luck i won't bother

"Good luck i won't bother you again, i had the 120 in my boat when i got it, know it inside and out had it apart twice.

Hope all goes well for you !"
 
"I would NOT use the vacuum ad

"I would NOT use the vacuum adapter pipe plug, except as the last resort. You're much better having the 'fuel dump' point at atmospheric pressure."
 
"PLease check out the picture.

"PLease check out the picture.. I've seen the plugs in the TOP section of the carb.. I do not recommend the bottom plug either.. as you dont want it to SUCK the Gas into the Carb.

notice.. GREEN Circle - Good
RED Circle - BAD..


376384.jpg
carb
 
"Mako/Brian,
After looki

"Mako/Brian,
After looking at the picture and reading the posts I must whole heartedly agree. If the diaphragm fails the engine will run for a period of time with the fuel in the bowl but sucking fuel from a failed pump would not be good.
As I posted the motor had may mods made to it. I am interested in getting the rebuild back to right and tight. Just to starboard of the carb on the valve cover is a pipe connection which I assume is to keep a vacuum on the upper drive train. This connection is currently in the upper/green port. Would it be acceptable to put the valve cover (pcv?) hose to the vacuum port and the fuel dump to the upper port?
From what little I know of motors I thought the plug on the butterfly plate was there to connect a test vacuum guage when checking carb vacuum. Am I off base here?
Regards,
TxGalz Dah"
 
"Chieflen,
My writing is

"Chieflen,
My writing is sometimes brash when I start throwing facts. As my friends constantly remind me. If you have
2_cents.gif
worth then I am glad to hear it. No problem here mate.
happy.gif


Best Regards,
TxGalz Dah"
 
"The PCV is a NON vaccuum conn

"The PCV is a NON vaccuum connection and the flame arrestor should have a tube connection on it for the pcv line. The fitting in the valve cover is only a port and not a chack type valve as in automotive.

It simplies lets the crankcase vent thru the valve cover to the flame arrestor only!



376424.jpg
"
 
"Tx:

The plug on the thrott

"Tx:

The plug on the throttle plate is for vacuum check, or for auto aps, for vacuumm accessories.

Kghost's description of the Vent hose connection is spot on. FYI, these are not PCV systems, but much older styled vent systemm. Same idea just done a lot simpler (usually good in marine enviros)."
 
"OK, yall. Thank you for the p

"OK, yall. Thank you for the photogs. I can make this happen. Now if the weather will just co-operate.
Regards,
TxGalz Dah"
 
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