help with fuel system problem? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

low 84 · 07-24-2003, 11:19 PM

okay i am having a problem with the fuel system. i can't get gas to the mechanical pump. i know the pump itself and everything after is fine (carb, filter, ect.). we broke the cam in by running a feed line out of a gas can into the pump and everthing worked perfect so its a problem with something else further back.

what i did was go from the factory set up with a return line, to a pump with just and in and out. i cut the old return line back at the dual tank switch valve and plugged it. it also had a charcole canister line that ran up into the engine compartment and whas just not hooked up b/c i have no emmsions stuff anymore, and it wasn't plugged, so i cut that line as well back by the valve and lef it open to vent, b/c thats how it was before.

so why can't i get any fuel to the pump? i tried it with the gas cap off b/c i was thinking mabey vapor lock? i also unplugged the old return line and let it just vent and that didn't work either. my dual tank switch has never worked so i've just always used the passenger side tank which is the one its stuck on, so there should be no problem there. if i suck on the input line to the fuel pump i can get choked up with vapors so i know its not plugged or anything, but i haven't tried actualy sucking it all the way in my mouth.

does anyone have a selector valve diagram, i know i hooked the feed back up to the right spot but it might be good to see a diagram just in case.

can someone help me, i really want to be able to drive this thing around

BigRed · 07-25-2003, 08:37 AM

You need to go pick-up a siphon pump and see if you're actually getting gas to the fuel pump. That would be my first step.

low 84 · 07-25-2003, 08:43 AM

i know i'm not getting gas to the fuel pump, if i run it from a gas can it will start right up and run fine, but when i connect it to the hard line running from the tank i get nothing, i just don't know why

BigRed · 07-25-2003, 11:24 AM

Sorry, missed that obvious statement about the gas can I guess. :p

Somehow, it's not being vented correctly. You may look at how the older trucks are routed with only the in and out fuel pumps and duplicate that. My '75 had one line coming from the tank to the fuel pump (in) and one up to the carb (out). Then, it had one line from the charcoal canister that ran back to the tank (that was disconnected). Pretty simple if I remember right. The trank must have some kind of vent to allow for the flow but I'm not sure.

79BIG10 · 07-25-2003, 03:09 PM

try this Ryan- Turn the ignition on but not to where the engine turns over. It sounds like the sending unit is not working or just has too much air in the line. Turn the switch on and let it fill up the line for a couple minutes. You can also check the supply line by taking it off the fuel pump and into a gas can to verify that the sender is working. If not then you have a bad sending unit or a bad wiring. Also check for any fuses that could have been blown. One more thing to look for is the conenction at the firewall by the column driver side in the engine bay. If you happen to have knocked it loose or out when cleaning the engine bay you may not be getting power to your sender. It looks like a small rubber boot with about 4 wires coming out of it and has the conenction made into the firewall.

low 84 · 07-25-2003, 03:53 PM

thanks for the help guys, now i've got some ideas of what to check, it really sounds liek your right about the sending unit brandon, i will check that connection, and i'm gonna siphon the line that goes to the tank to see if i can actualy get gas to come out of it, lemme see if i can get this thing to life w/o using a gas can, lol.

gldevall · 07-25-2003, 04:44 PM

Ryan, check the fuses first.

low 84 · 07-25-2003, 06:39 PM

okay its workin. i was confused b/c of what someone told me a few weeks ago and i had the lines crossed back at the selector valve. thanks guys

*mike reeh* · 07-25-2003, 09:42 PM

It wasnt something I said was it?

Glad you got it fixed but my suggestion was going to be to blow into the feed line and listen for bubbles..

mike

67_SS396 · 07-26-2003, 12:36 AM

Glad you got it worked out! I'll swing by sometime Sunday and pick up my hoist and maybe we can toy with the tuning some. I'll be in the '67 so you can finally hear how the Hooker's sound. I just need to knock the dust off of it first.

low 84 · 07-26-2003, 12:39 AM

sounds good man. just give me a shout whenever on sunday, i should be here.

07-24-2003, 11:19 PM	#1
low 84 Registered User Join Date: Jan 2002 Location: Houston, TX Posts: 2,144	help with fuel system problem? okay i am having a problem with the fuel system. i can't get gas to the mechanical pump. i know the pump itself and everything after is fine (carb, filter, ect.). we broke the cam in by running a feed line out of a gas can into the pump and everthing worked perfect so its a problem with something else further back. what i did was go from the factory set up with a return line, to a pump with just and in and out. i cut the old return line back at the dual tank switch valve and plugged it. it also had a charcole canister line that ran up into the engine compartment and whas just not hooked up b/c i have no emmsions stuff anymore, and it wasn't plugged, so i cut that line as well back by the valve and lef it open to vent, b/c thats how it was before. so why can't i get any fuel to the pump? i tried it with the gas cap off b/c i was thinking mabey vapor lock? i also unplugged the old return line and let it just vent and that didn't work either. my dual tank switch has never worked so i've just always used the passenger side tank which is the one its stuck on, so there should be no problem there. if i suck on the input line to the fuel pump i can get choked up with vapors so i know its not plugged or anything, but i haven't tried actualy sucking it all the way in my mouth. does anyone have a selector valve diagram, i know i hooked the feed back up to the right spot but it might be good to see a diagram just in case. can someone help me, i really want to be able to drive this thing around __________________ '51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works '05 1500 Crew Cab RIP '84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker '80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's Last edited by low 84; 07-24-2003 at 11:23 PM.

07-25-2003, 08:37 AM	#2
BigRed Registered User Join Date: Jun 2002 Location: DFW, TX Posts: 1,680	You need to go pick-up a siphon pump and see if you're actually getting gas to the fuel pump. That would be my first step. __________________ Scott Shelbourne

07-25-2003, 08:43 AM	#3
low 84 Registered User Join Date: Jan 2002 Location: Houston, TX Posts: 2,144	i know i'm not getting gas to the fuel pump, if i run it from a gas can it will start right up and run fine, but when i connect it to the hard line running from the tank i get nothing, i just don't know why __________________ '51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works '05 1500 Crew Cab RIP '84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker '80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's

07-25-2003, 11:24 AM	#4
BigRed Registered User Join Date: Jun 2002 Location: DFW, TX Posts: 1,680	Sorry, missed that obvious statement about the gas can I guess. :p Somehow, it's not being vented correctly. You may look at how the older trucks are routed with only the in and out fuel pumps and duplicate that. My '75 had one line coming from the tank to the fuel pump (in) and one up to the carb (out). Then, it had one line from the charcoal canister that ran back to the tank (that was disconnected). Pretty simple if I remember right. The trank must have some kind of vent to allow for the flow but I'm not sure. __________________ Scott Shelbourne

07-25-2003, 03:09 PM	#5
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,775	try this Ryan- Turn the ignition on but not to where the engine turns over. It sounds like the sending unit is not working or just has too much air in the line. Turn the switch on and let it fill up the line for a couple minutes. You can also check the supply line by taking it off the fuel pump and into a gas can to verify that the sender is working. If not then you have a bad sending unit or a bad wiring. Also check for any fuses that could have been blown. One more thing to look for is the conenction at the firewall by the column driver side in the engine bay. If you happen to have knocked it loose or out when cleaning the engine bay you may not be getting power to your sender. It looks like a small rubber boot with about 4 wires coming out of it and has the conenction made into the firewall. __________________ 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

07-25-2003, 03:53 PM	#6
low 84 Registered User Join Date: Jan 2002 Location: Houston, TX Posts: 2,144	thanks for the help guys, now i've got some ideas of what to check, it really sounds liek your right about the sending unit brandon, i will check that connection, and i'm gonna siphon the line that goes to the tank to see if i can actualy get gas to come out of it, lemme see if i can get this thing to life w/o using a gas can, lol. __________________ '51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works '05 1500 Crew Cab RIP '84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker '80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's

07-25-2003, 04:44 PM	#7
gldevall Registered User Join Date: Mar 2003 Location: Walker, LA Posts: 2,925	Ryan, check the fuses first. __________________ Gary -1986 SWB: lowered 4/6, SOLD!!! -Best 1/4 mile: 14.51 @ 91.01 MPH -2001 Pewter Tahoe, billet grill, Corsa Sport Cat-back, K&N FIPK SOLD!!! -2004 Z-71 Extended cab with a flowmaster, BDS 6.5", 3" BL, 35x12.5x18 Trail Grapplers on Pro-Comp 18x9 wheels

07-25-2003, 06:39 PM	#8
low 84 Registered User Join Date: Jan 2002 Location: Houston, TX Posts: 2,144	okay its workin. i was confused b/c of what someone told me a few weeks ago and i had the lines crossed back at the selector valve. thanks guys __________________ '51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works '05 1500 Crew Cab RIP '84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker '80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's

07-25-2003, 09:42 PM	#9
mike reeh 5 day ban, learn to behave. Join Date: Nov 2002 Location: san diego, ca Posts: 684	It wasnt something I said was it? Glad you got it fixed but my suggestion was going to be to blow into the feed line and listen for bubbles.. mike

07-26-2003, 12:36 AM	#10
67_SS396 Registered User Join Date: Mar 2000 Location: Blue Ridge, Tx Posts: 1,172	Glad you got it worked out! I'll swing by sometime Sunday and pick up my hoist and maybe we can toy with the tuning some. I'll be in the '67 so you can finally hear how the Hooker's sound. I just need to knock the dust off of it first. __________________ Fawker Fab three seater rock crawler buggy 498 BBC/SM465/203/205 doubler, propane, 5.13's, 42" PB Rockers '66 C10 - The new hot rod '77 3+3 Dually - 12 valve 4wd conversion tow rig project '28 Ford 2 door sedan street rod RevLimit Offroad "Hang on beer, we can do this."

07-26-2003, 12:39 AM	#11
low 84 Registered User Join Date: Jan 2002 Location: Houston, TX Posts: 2,144	sounds good man. just give me a shout whenever on sunday, i should be here. __________________ '51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works '05 1500 Crew Cab RIP '84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker '80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's



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