Fuel pumps - The 1947 - Present Chevrolet & GMC Truck Message Board Network

scotto0609 · 07-11-2006, 10:31 PM

Ok, found out why po put electric fuel pump on truck. Put new mechanical pump on and wouldn't pull fuel. It is the same line that the electric is pulling from,any ideas? thanx

79BIG10 · 07-12-2006, 12:34 AM

Sounds like the sending unit. Take a bucket and turn the hose down into it. Take the key and turn on but not try to turn over. This will get the ignition turned on and see if the sending unit is working. If not check the fuses for a easy fix.

scotto0609 · 07-12-2006, 06:30 AM

Sorry dont think i gave enough info on last post. The truck is an 85 k30 crew cab big block dually. It is a carbed motor that the po retro fitted an electric in line pump (toyota?). My ? was why the new mechanical pump wouldnt work, the rod was there in engine block. Do cams wear out wear the fuel pump eccentric is? Thanks for the reply 79big10 !

bigblock73 · 07-12-2006, 07:08 AM

I would start by putting a new fuel pump rod in the truck...they are cheap...and who knows if you even have the right one in there now, or if it is worn or damaged. You could also check your lines around or near the pump, perhaps something is up there.

79BIG10 · 07-13-2006, 12:22 AM

Jeff has some good points to start diagnosing. Check the fuel pump rod to make sure it's the right one. One thing is to place some oil on the rod and it helps hold it in place while you insert the fuel pump arm. Also you can place a bolt through the front of the engine to hold it as well.

Turbo85GMC · 07-13-2006, 08:08 AM

Do you know if the cam has ever been changed? I've seen cam's advertised that say they don't have a lobe for a mechanical fuel pump. The PO could have ordered/installed one of those by mistake.

79BIG10 · 07-14-2006, 06:15 PM

Never thought about that but that's a good point.

07-11-2006, 10:31 PM	#1
scotto0609 Junior Member Join Date: Nov 2005 Location: new york Posts: 226	Fuel pumps Ok, found out why po put electric fuel pump on truck. Put new mechanical pump on and wouldn't pull fuel. It is the same line that the electric is pulling from,any ideas? thanx

07-12-2006, 12:34 AM	#2
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,774	Re: Fuel pumps Sounds like the sending unit. Take a bucket and turn the hose down into it. Take the key and turn on but not try to turn over. This will get the ignition turned on and see if the sending unit is working. If not check the fuses for a easy fix. __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson

07-12-2006, 06:30 AM	#3
scotto0609 Junior Member Join Date: Nov 2005 Location: new york Posts: 226	Re: Fuel pumps Sorry dont think i gave enough info on last post. The truck is an 85 k30 crew cab big block dually. It is a carbed motor that the po retro fitted an electric in line pump (toyota?). My ? was why the new mechanical pump wouldnt work, the rod was there in engine block. Do cams wear out wear the fuel pump eccentric is? Thanks for the reply 79big10 !

07-12-2006, 07:08 AM	#4
bigblock73 yeller Join Date: Oct 2001 Location: Twin Cities Posts: 13,824	Re: Fuel pumps I would start by putting a new fuel pump rod in the truck...they are cheap...and who knows if you even have the right one in there now, or if it is worn or damaged. You could also check your lines around or near the pump, perhaps something is up there. __________________ Jeff 73-87.com 73-87.com Facebook page 73-87 cab corner 6x9 speaker brackets for sale 67-72 cab corner speaker brackets for sale 47-54 cab corner speaker brackets for sale

07-13-2006, 12:22 AM	#5
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,774	Re: Fuel pumps Jeff has some good points to start diagnosing. Check the fuel pump rod to make sure it's the right one. One thing is to place some oil on the rod and it helps hold it in place while you insert the fuel pump arm. Also you can place a bolt through the front of the engine to hold it as well. __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson

07-13-2006, 08:08 AM	#6
Turbo85GMC Registered User Join Date: Apr 2005 Location: Medford, MA Posts: 307	Re: Fuel pumps Do you know if the cam has ever been changed? I've seen cam's advertised that say they don't have a lobe for a mechanical fuel pump. The PO could have ordered/installed one of those by mistake. __________________ '85 GMC 1500 "Friends don't let friends drive stock!"

07-14-2006, 06:15 PM	#7
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,774	Re: Fuel pumps Never thought about that but that's a good point. __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson



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