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#1 |
Project Heaven in my 67!!!
Join Date: Jan 2009
Location: Bosqueville, TX
Posts: 899
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Mechanical Fuel Pump not pumping
Small Block 350 in Project Heaven, thought fuel pump was bad because it was pumping but so slowly that the carb isnt getting any fuel. Im barely getting any to the inline fuel filter. But, there is pressure in the line as when I take one of the rubber lines off of the filter it blows the pressure off.
Replaced the mechanical fuel pump with a brand new one from the local auto parts store and same problem... I made sure that I got the pushrod onto the fuel pump lever properly, even double checked to make sure I had done the install correctly... Any ideas???? |
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#2 |
Registered User
Join Date: Jul 2011
Location: strausstown pa
Posts: 3,394
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Re: Mechanical Fuel Pump not pumping
you could have some blockage in the fuel line and the pump could be struggleing to pull fuel.
I had this same problem on the kids truck it ended up being the sock filter was clogged and half way up the sending unit reduceing the flow
__________________
81 camaro 355 4/spd 342 posi my first love ![]() 67 swb step 454/4spd ott 373 posi 4/7 drop. 2000 s10 zr2 little blue truck that never gets stuck. '74 heald super bronc vt8. tecumseh powered moon rover. |
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#3 |
Registered User
![]() Join Date: Jan 2008
Location: St.Petersburg,Fl
Posts: 1,267
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Re: Mechanical Fuel Pump not pumping
Could be a bad fuel pump lobe on the cam. Not common, but it can happen.
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#4 |
Project Heaven in my 67!!!
Join Date: Jan 2009
Location: Bosqueville, TX
Posts: 899
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Re: Mechanical Fuel Pump not pumping
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#5 |
Registered User
Join Date: Jul 2009
Location: Space Coast, Fl.
Posts: 1,050
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Re: Mechanical Fuel Pump not pumping
Did the fuel pump push rod slide out? There are two bolt holes on the front pass. side of the block. The top one can be used to lock the pump rod if a longer 3/8" shank bolt is screwed into the threaded hole. Maybe somebody put a bolt that's too long in the hole and it's got the the push rod stuck..... maybe?
__________________
Dad always said, "Son, WISH IN ONE HAND, and ......." -------------------------------------- -------------------------------------- Current toy trucks: '71 GMC 1500 SUPER CUSTOM short/step, orig. dk. blue, 350/700r, ps,pb, A/C '72 Blazer 2wd, ochre & white, 454, tremecTKO 500 5spd. ps, pb, A/C, tilt Last 10yrs of hobby vehicles, had a FEW more in the 50yrs. before these: '66 Plymouth Belvedere City of Miami cop car clone. '70 Nova 406"sb, 13.5-1, solid roller, Brodix, p.glide/t.brake, back halved, 9" Ford, spool 4.88, cage,ladder bar/coilover, 10.5 tire....... SOLD!! '67 C10 short/step side mount spare -- SOLD!! '72 Jimmy 2wd, 350/350, ps, pb, fun driver, lots of bondo & a shiny red paint job..... SOLD!! '69 Nova 350, 4spd, A/C, ps, p.b, ...SOLD!! |
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#6 | |||
Project Heaven in my 67!!!
Join Date: Jan 2009
Location: Bosqueville, TX
Posts: 899
|
Re: Mechanical Fuel Pump not pumping
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Midniteblues -- That is a good idea, I will try that tonight... I also called a buddy of mine that is the manager at the local parts store and told him that I think I got a bad fuel pump off the shelf, he has another one so I am going to take it out again and eliminate that as the issue. Rustybucket -- There is a bolt in the top hole but it isnt long enough to hold the rod... I attempted to use it to hold the rod when I replaced the pump, to no avail... |
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#7 |
Project Heaven in my 67!!!
Join Date: Jan 2009
Location: Bosqueville, TX
Posts: 899
|
Re: Mechanical Fuel Pump not pumping
I thought that to so I removed the pickup line and added a short (4 ft.) piece of 3/8 rubber line into a 5 gallon bucket and still no joy all the time. It is almost like it will pump a little fuel and then lose its prime and then pump a little and then lose its prime...
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#8 |
Registered User
Join Date: Jun 2010
Location: Upland Ca
Posts: 4,143
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Re: Mechanical Fuel Pump not pumping
So, you removed the line from the carb and little or no fuel came out of the line while cranking......before or after the filter?
Posted via Mobile Device
__________________
1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703 |
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#9 |
Registered User
Join Date: Jul 2011
Location: strausstown pa
Posts: 3,394
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Re: Mechanical Fuel Pump not pumping
to completely rule out the lines I would attach a rubber line from your gas can directly too the pump then then another rubber line out the pump too another can and crank and see how much it flows then reconnect each line one at a time and note when the flow stops
__________________
81 camaro 355 4/spd 342 posi my first love ![]() 67 swb step 454/4spd ott 373 posi 4/7 drop. 2000 s10 zr2 little blue truck that never gets stuck. '74 heald super bronc vt8. tecumseh powered moon rover. |
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#10 |
Proprietor of Dale's Corner
![]() Join Date: Nov 2012
Location: Vacaville , CA
Posts: 16,117
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Re: Mechanical Fuel Pump not pumping
You should make sure all the rubber lines before the pump are good. A small crack or pin hole may not leak fuel but can suck air, making fuel delivery spotty at best
__________________
"Some Days Chickens And Some Days Feathers" Dale XNGH ECV Sam Brannan 1004 R.I.P. 67ChevyRedneck R.I.P. Grumpy Old Man |
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#11 |
Registered User
Join Date: Jun 2010
Location: Upland Ca
Posts: 4,143
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Re: Mechanical Fuel Pump not pumping
Sounds like a bad pump, good luck! Just out of curiosity, can you blow through the line, has the rubber hose swelled up?
__________________
1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703 |
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#12 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,622
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Re: Mechanical Fuel Pump not pumping
Ignore that filter. My old truck did the same. Never looked like any fuel in it. Truck just kept on running on and on.
If it's running good leave it alone. |
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#13 |
Project Heaven in my 67!!!
Join Date: Jan 2009
Location: Bosqueville, TX
Posts: 899
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Re: Mechanical Fuel Pump not pumping
At this point I am trying to get the motor running after it sat for quite a while. So I am having to work to eliminate all the issues just to get it running again.
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#14 |
Proprietor of Dale's Corner
![]() Join Date: Nov 2012
Location: Vacaville , CA
Posts: 16,117
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Re: Mechanical Fuel Pump not pumping
If the float is stuck in the up position (which I have had happen) just tap on the top of the carb to get it to fall. I repeat tap not bang lol
__________________
"Some Days Chickens And Some Days Feathers" Dale XNGH ECV Sam Brannan 1004 R.I.P. 67ChevyRedneck R.I.P. Grumpy Old Man |
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#15 |
Registered User
Join Date: Nov 2011
Location: Kirkland, WA
Posts: 343
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Re: Mechanical Fuel Pump not pumping
I have this problem now. New plastic tank, new sending unit with screen, new mechanical pump and the truck ran before rebuild. Tried bypassing the new tank by running a short hose to a gallon of gas. Nothing. Installed another new mechanical pump. Still nothing. Sucked gas up the lines to be sure they were not obstructed and getting fuel, they were. Removed second new pump and checked that the push rod was free and moving up and down, it was. Held the rod with a 3/8 bolt in the top hole, reinstalled pump still nothing. Bought a electric pump fuel tonight but I think I need to change my cam. I am hoping that the push rod is getting stuck and after I get the truck running it will be lubricated enough to function. Hoping!
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#16 |
Senior Member
![]() Join Date: Aug 2008
Location: Cedar Park, Texas
Posts: 7,500
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Re: Mechanical Fuel Pump not pumping
I had a similar problem issue with my build "Ruby". I had installed a nw manual fuel pump, rebuilt the Q jet and had the truck running. Dad and I tore the truck apart for paint and 2 yrs later when I re assembled everything, the pump wouldn't pump. I installed a new pump and everything worked fine, The first pump had about 30 minutes of run time on it!
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#17 |
Registered User
Join Date: Nov 2011
Location: Kirkland, WA
Posts: 343
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Re: Mechanical Fuel Pump not pumping
Well, it appears that a mechanical needs to be primed. I did not know this and swear I never have done it before. However, after 2 new mechanical pumps I bought a electric pump and plumbed it in series. Meaning that I have it pumping to and through the mechanical pump. It pulled from the poly tank, through 2 filters the mechanical pump and loaded the floats of the Edelbrock 1406 and my engine fired. Because I need to adjust my lifters and have my covers off, I did not start the engine and hooked up my under hood starter. While cranking the engine I noticed my fuel pressure gauge jump up to 7-8 lbs WITHOUT the electric pump! I let it rest a while and did some other tasks, came back and the pressure gauge dropped to 0, so I squeezed the remote starter trigger and the engine cranked, and the fuel pressure gauge jumped right back up to 7+ lbs!!!! Why would a mechanical pump need to be primed? Also, as I had sucked gas up through the line from 2 different sources to check for flow the mechanical pump did not build pressure. Anyone have any input?? This was very frustrating!! Guy
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#18 | |
Registered User
Join Date: Oct 2007
Location: Vancouver, BC, Canada
Posts: 3
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Re: Mechanical Fuel Pump not pumping
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#19 |
Registered User
Join Date: Jan 2009
Location: Colorado Springs, CO
Posts: 357
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Re: Mechanical Fuel Pump not pumping
If there's no fuel in the line after sitting or when you run it out of gas, you have to prime the carb. The bowls have no fuel in them. The starter cranking will not be enough to prime the fuel pump but when you start the truck up by pouring a little gas in the top of the carb, it will prime the whole system quickly.
I have been doing this a lot recently after the engine rebuild, replacing old lines and such. ![]()
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Dan Smith Colorado Springs, CO 71 GMC Custom Camper "Longhorn" 454, TH400 73 Chevy Camper Special (Yes, it's badged a camper special) Flat Bed Motorhome conversion 454, standard tranny "DON'T TREAD ON ME !!!" My Project: http://www.picturetrail.com/sfx/album/view/20829244 , http://www.picturetrail.com/sfx/album/view/24654442 |
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#20 |
Registered User
Join Date: Oct 2007
Location: Vancouver, BC, Canada
Posts: 3
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Re: Mechanical Fuel Pump not pumping
Thanks hilandr, I have tried that about fifteen times, starts for about five seconds still no sign of fuel making it out of the pump, new line from pump to carb, disconnect at the bottom of tank and fuel pours out freely, I have purchased a second new pump and will try that right now, maybe its a faulty pump.
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