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crankcase vaccum for fuel pump

R

redbarchetta

Member
Dec 2, 2007
350
19
18
blackhills, wy
I have a 98 mxz 670 and am not getting fuel to carbs, I took the fuel pump out and manually put vaccum on the pump and it will pump fuel. Can anybody tell me what the vaccum should be out of crankcase and why it may be low I have 110lbs of compression!! All help would greatly be appreciated thanks!!!
 

byeatts

Well-known member
Premium Member
Nov 29, 2007
3,402
1,215
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I have a 98 mxz 670 and am not getting fuel to carbs, I took the fuel pump out and manually put vaccum on the pump and it will pump fuel. Can anybody tell me what the vaccum should be out of crankcase and why it may be low I have 110lbs of compression!! All help would greatly be appreciated thanks!!!

Diaphragm can become wore /weak
 
R

redbarchetta

Member
Dec 2, 2007
350
19
18
blackhills, wy
Make sure the signal/pulse line to the pump is sealed and does not have a crack in it. Maybe a crank seal is out too.
Are you talking about the line that runs from crankcase to pump? If so that is in good shape!! I was thinking crankcase seal as well but no way to check with machine not running!!! I could check it with carb cleaner if it was running right?
 
T

tukernater

Well-known member
Nov 4, 2009
897
266
63
54
BC
Are you talking about the line that runs from crankcase to pump? If so that is in good shape!! I was thinking crankcase seal as well but no way to check with machine not running!!! I could check it with carb cleaner if it was running right?
Just cover each carb, pull over a few time and if one cards got no suction or very low suction that's the side the seal will be shot.
 
Last edited:
S
Jan 4, 2017
2
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1
97 Mxz 583 fuel issue

I have a 97 Mxz 583. It was running when I stopped to get lunch. Went to go start it again....no go. Has good spark and and a freshly rebuilt fuel pump and fuel pick up. But I still don't have any fuel to the carbs. Advice please?
 
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