Mechanical Fuel Pump Question
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5th Wheeling
Joined: Aug 2020
Posts: 43
Likes: 11
Mechanical Fuel Pump Question
Newbie question. Just finished up some work on my engine and I am looking to start it for the first time. Its a 240 and has the mechanical fuel pump. Id like to do a compression check before I do this. My question is, will the mechanical fuel pump continuously pump fuel to the engine while I do this? Is there a way/need to stop the gas flow while I do the compression check? I just picture flooding the engine with fuel when there is no spark and cant see that being good.
Appreciate the help.
Also, any other tips and tricks are always welcome. Ive torqued everything, checked connections, and feel im close. Is there a way to prime the engine with oil or anything Important I should be doing?
Appreciate the help.
Also, any other tips and tricks are always welcome. Ive torqued everything, checked connections, and feel im close. Is there a way to prime the engine with oil or anything Important I should be doing?
Tuned
Joined: May 2009
Posts: 301
Likes: 40
From: East Tennessee
Yes it will be pumping. Just disconnect the supply hose between the fuel line and the fuel pump (down by the left engine perch near the inner fender). If it’s been sitting a while you’ll want to replace that rubber anyway (as well as the short piece under the cab at the drivers door).
Real common with those old mechanical pumps for the diaphragm to rupture and then you start getting gas in the oil. If you have to replace your fuel pump, get a Carter pump (NAPA sells them). The Chinese knock offs are garbage. I had one from Advance Auto that flooded my carb due to excessive pressure. Back it went and the Carter from NAPA is perfect.
Real common with those old mechanical pumps for the diaphragm to rupture and then you start getting gas in the oil. If you have to replace your fuel pump, get a Carter pump (NAPA sells them). The Chinese knock offs are garbage. I had one from Advance Auto that flooded my carb due to excessive pressure. Back it went and the Carter from NAPA is perfect.
Tuned
Joined: May 2015
Posts: 413
Likes: 52
To do a compression check you need to pull all the plugs. Without plugs you won't get any appreciable flow on the intake stroke so no fuel will flood the engine - unless your float is stuck. You can also hold the choke open if you are still concerned.
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5th Wheeling
Joined: Aug 2020
Posts: 43
Likes: 11
Good idea Chirkware, I will be relacing those fuel lines so best to just do the compression test then. Fuel pump seems like a easy cheap change for some reassurance, but looking at summit, they seem to have a few different options from Carter. three without the filter and one with a filter housing. Is there any difference? I do prefer to have a filter, I cleaned the tank out but better to be safe then sorry. I suppose if I am changing the rubber lines, it wouldnt be much to add an inline filter, or would both be better?
Without filter
M60387
M6399
M6807
With filter
M60092
Gpatrick, this is good info. Its a new carb so hopefully nothing is stuck. And with a manual choke, its easy to set it open. Will most likely do it while changing the lines though.
Without filter
M60387
M6399
M6807
With filter
M60092
Gpatrick, this is good info. Its a new carb so hopefully nothing is stuck. And with a manual choke, its easy to set it open. Will most likely do it while changing the lines though.
FTE Legend
Joined: Nov 2015
Posts: 30,876
Likes: 4,116
From: Angier, NC
There is no need to stop fuel to the pump as the fuel will not (should not) get pass the needle & seat of the carb.
I also know you are to hold the throttle wide open but when there is only you I dont.
As long as the readings are close to each other and not really low you are good.
Just make sure you pull the coil wire from the dist. and put it to ground and do the test you are good.
Dave ----
I also know you are to hold the throttle wide open but when there is only you I dont.
As long as the readings are close to each other and not really low you are good.
Just make sure you pull the coil wire from the dist. and put it to ground and do the test you are good.
Dave ----
Tuned
Joined: Mar 2011
Posts: 361
Likes: 7
From: Bliss NY
Disconnect and plug the fuel line in between the fuel pump and the gas tank, gas will pour out as your doing this so be careful. You need the spark plugs out and the carb wide open, put a brick on the gas pedal or a screwdriver down the carb opening the throttle plates. Make sure battery is fully charged. Have fun!
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