1980 F-100 Fuel Problems

smarti01 · 02-06-2006, 02:03 PM

I have a fuel problem... the gas is not getting from the tank to the fuel pump. It is a mechanical pump on the motor and seems to be working OK, but if I pull the gas lines off they are totally dry and are not pulling from the tank. The truck was last used about 2 months ago then sat since, there was no problem last time I used it. There is gas in the tank.

Any suggestions?

mrjohnwayne · 02-06-2006, 03:58 PM

I would suspect either a hole in the line, or it is clogged somewhere between the tank and the pump.

shopratles · 02-06-2006, 05:36 PM

If there is a rubber diaphram in the pump (which I believe there is), my quess is it is now shot. Fuel pumps are cheap, go ahead and replace it.

Good luck.

smarti01 · 02-08-2006, 03:16 AM

Thanks for the info. There is a leak in the tank so I need to change it anyway and that will be a good time to check all of the lines and the pump.

chevyguy · 02-09-2006, 09:10 PM

1.Have you tried to prime the pump? 2.How do you know the pump is working properly if no fuel is moving? 3.have you checked the fuel filter on the frame rail for clogging? I need more info to really halp you out here.

mslwpk · 04-01-2006, 07:36 PM

I have an 80 F100 did the same thing.. We had to chang to a electric pump and we also had to drop the tank and clean it out and replace the float and sock.Good luck!

chevyguy · 04-02-2006, 10:28 AM

Sounds like pin the tail on the problem to me. I would disconnect the fuel line at the filter , check the filter. If it passes then push some compressed air back thru the lines into the tank. If it is clogged you will know without pulling the whole tank out for nothing. Just my 2 cents here.

390FE · 04-06-2006, 07:11 AM

Another trick. I learned this but you have to be real careful and need a 2nd set of eyes. I have only done this once with a mechanical fuel pump motor.

take the hose off the fuel pump and then have your buddy watch it. Go to the tank filler and while trying to cover the openiong as best as possible shoot some air from a compressor into the tank (If your not careful and put too much pressure in the tank you will pop it). if you see gas come out the line than everything up to the pump is ok.

BornToRide · 04-06-2006, 02:43 PM

make sure to check all the lines so none have a hole or are clogged if not you may be needing to look into a new fuel pump.

smarti01 · 04-26-2006, 02:25 PM

Well, I figured it out.

I crawled under the truck to check the fuel line from the tank and to my surprise it fell off in my hand. The line had rusted through at the tank. I dropped the tank and found it had at least 10 holes in it as well.

I'm off to the parts store for a new tank and fuel line tonight.

Thanks everyone for your replies!

Scott

02-06-2006, 02:03 PM	#1
smarti01 Junior Member Join Date: Feb 2006 Location: North Carolina Posts: 6	1980 F-100 Fuel Problems I have a fuel problem... the gas is not getting from the tank to the fuel pump. It is a mechanical pump on the motor and seems to be working OK, but if I pull the gas lines off they are totally dry and are not pulling from the tank. The truck was last used about 2 months ago then sat since, there was no problem last time I used it. There is gas in the tank. Any suggestions?

02-06-2006, 03:58 PM	#2
mrjohnwayne Moderator Join Date: Apr 2005 Location: Texas Posts: 3,104	I would suspect either a hole in the line, or it is clogged somewhere between the tank and the pump. __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

02-08-2006, 03:16 AM	#4
smarti01 Junior Member Join Date: Feb 2006 Location: North Carolina Posts: 6	Thanks Thanks for the info. There is a leak in the tank so I need to change it anyway and that will be a good time to check all of the lines and the pump.

02-09-2006, 09:10 PM	#5
chevyguy Senior Member Join Date: Sep 2005 Location: ALABAMA Posts: 3,160	1.Have you tried to prime the pump? 2.How do you know the pump is working properly if no fuel is moving? 3.have you checked the fuel filter on the frame rail for clogging? I need more info to really halp you out here. __________________ When i die, i dont want to walk gracefully thu the pearly gates and turn in a unused body. i want to go sliding thru sideways and turn in a body that has been completely used up.

04-02-2006, 10:28 AM	#7
chevyguy Senior Member Join Date: Sep 2005 Location: ALABAMA Posts: 3,160	Sounds like pin the tail on the problem to me. I would disconnect the fuel line at the filter , check the filter. If it passes then push some compressed air back thru the lines into the tank. If it is clogged you will know without pulling the whole tank out for nothing. Just my 2 cents here. __________________ When i die, i dont want to walk gracefully thu the pearly gates and turn in a unused body. i want to go sliding thru sideways and turn in a body that has been completely used up.

02-06-2006, 05:36 PM	#3
shopratles Senior Member Join Date: Dec 2005 Location: Texas Posts: 172	If there is a rubber diaphram in the pump (which I believe there is), my quess is it is now shot. Fuel pumps are cheap, go ahead and replace it. Good luck.

04-01-2006, 07:36 PM	#6
mslwpk Full Member Join Date: Mar 2006 Posts: 25	I have an 80 F100 did the same thing.. We had to chang to a electric pump and we also had to drop the tank and clean it out and replace the float and sock.Good luck!

04-06-2006, 07:11 AM	#8
390FE Senior Member Join Date: Sep 2005 Location: S. NH Posts: 336	Another trick. I learned this but you have to be real careful and need a 2nd set of eyes. I have only done this once with a mechanical fuel pump motor. take the hose off the fuel pump and then have your buddy watch it. Go to the tank filler and while trying to cover the openiong as best as possible shoot some air from a compressor into the tank (If your not careful and put too much pressure in the tank you will pop it). if you see gas come out the line than everything up to the pump is ok.

04-06-2006, 02:43 PM	#9
BornToRide Senior Member Join Date: Mar 2006 Location: Canada Posts: 86	make sure to check all the lines so none have a hole or are clogged if not you may be needing to look into a new fuel pump.

04-26-2006, 02:25 PM	#10
smarti01 Junior Member Join Date: Feb 2006 Location: North Carolina Posts: 6	Well, I figured it out. I crawled under the truck to check the fuel line from the tank and to my surprise it fell off in my hand. The line had rusted through at the tank. I dropped the tank and found it had at least 10 holes in it as well. I'm off to the parts store for a new tank and fuel line tonight. Thanks everyone for your replies! Scott

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