Weird Gas Tank Problem
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Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Weird Gas Tank Problem
OK, just got back from a road trip out West - truck ran great but I found a problem that I hadn't ran into before.
The in-cab fuel tank holds 17 gallons according to the manual. The fuel gage is only approximate, so I've always just figured on 10 miles to the gallon - should have no problem getting 150 mile range.
SO, the engine dies on me at around 100 miles. WTF? I fuel up, but can only install about 10 gallons. I don't think the tank is dented, and I can't imagine 5-7 gallons of water in the tank. What's the deal?
The in-cab fuel tank holds 17 gallons according to the manual. The fuel gage is only approximate, so I've always just figured on 10 miles to the gallon - should have no problem getting 150 mile range.
SO, the engine dies on me at around 100 miles. WTF? I fuel up, but can only install about 10 gallons. I don't think the tank is dented, and I can't imagine 5-7 gallons of water in the tank. What's the deal?
Elder User
Joined: Feb 2004
Posts: 909
Likes: 9
From: San Luis Obispo, CA
If you have an unvented gas cap or the vent hole is plugged, you can have two problems that give this symptom:
o The vacuum created can suck the gas tank walls inward, creating a tank with reduced volume. You will be able to see that the front side of the tank behind your seat is concave.
o On a long run, the tank may be OK, but the vacuum will overcome a weak pump's ability to move the gas, causing you to stall. If you immediately open the gas cap and hear a loud "whoosh" as air rushes in, this is the problem.
On short runs, these problems are not ever noticed. Post back if this helps or not.
o The vacuum created can suck the gas tank walls inward, creating a tank with reduced volume. You will be able to see that the front side of the tank behind your seat is concave.
o On a long run, the tank may be OK, but the vacuum will overcome a weak pump's ability to move the gas, causing you to stall. If you immediately open the gas cap and hear a loud "whoosh" as air rushes in, this is the problem.
On short runs, these problems are not ever noticed. Post back if this helps or not.
Logistics Pro
Joined: Jun 2003
Posts: 3,921
Likes: 272
Originally Posted by acheda
If you have an unvented gas cap or the vent hole is plugged, you can have two problems that give this symptom:
o The vacuum created can suck the gas tank walls inward, creating a tank with reduced volume. You will be able to see that the front side of the tank behind your seat is concave.
o On a long run, the tank may be OK, but the vacuum will overcome a weak pump's ability to move the gas, causing you to stall. If you immediately open the gas cap and hear a loud "whoosh" as air rushes in, this is the problem.
On short runs, these problems are not ever noticed. Post back if this helps or not.
o The vacuum created can suck the gas tank walls inward, creating a tank with reduced volume. You will be able to see that the front side of the tank behind your seat is concave.
o On a long run, the tank may be OK, but the vacuum will overcome a weak pump's ability to move the gas, causing you to stall. If you immediately open the gas cap and hear a loud "whoosh" as air rushes in, this is the problem.
On short runs, these problems are not ever noticed. Post back if this helps or not.
Thread Starter
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Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
I thought of that, but am using a locking gas tank cap, and switched back to the o-riginal, which can't really seal all that tight I don't think. No canisters or anything like that. It's not safe to run out of fuel on the highway in general, but on remote two lane I found that only about half the tank is usable and it will stall out. I thought it might be vapor lock but it never got warm enough for that. Fuel pump is fairly new, but it's a thought. Is there a fuel filter inside these tanks?
Logistics Pro
Joined: Jun 2003
Posts: 3,921
Likes: 272
Originally Posted by Tedster9
I thought of that, but am using a locking gas tank cap, and switched back to the o-riginal, which can't really seal all that tight I don't think. No canisters or anything like that. It's not safe to run out of fuel on the highway in general, but on remote two lane I found that only about half the tank is usable and it will stall out. I thought it might be vapor lock but it never got warm enough for that. Fuel pump is fairly new, but it's a thought. Is there a fuel filter inside these tanks?
It's funny the guy I bought the truck from in Arizona put on a new carb, fuel pump, inline filter, new gas cap, etc. He was obviously chasing a fuel problem. Problem was a clogged vent line. You may have a non-vented cap on a non-vented tank.
Postmaster
Joined: Nov 2001
Posts: 3,351
Likes: 1
From: Escondido, CA
I had an issue kind of like that. I found my pickup tube had corroded through 2 inches from the top and was sucking air in. It isn't too far fetched for the tube to have just flaked off during the road trip.
Laughing Gas
Joined: Aug 2006
Posts: 815
Likes: 4
From: mountaintop, Pa
I agree pull out your sending unit and see if your pickup tube is whole. 7 gallons is a lot of water or a very large dent to be unnoticed.
bob
bob
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Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
Likes: 785
From: Simi Valley, CA
Originally Posted by Tedster9
OK, just got back from a road trip out West - truck ran great but I found a problem that I hadn't ran into before.
The in-cab fuel tank holds 17 gallons according to the manual. The fuel gage is only approximate, so I've always just figured on 10 miles to the gallon - should have no problem getting 150 mile range.
SO, the engine dies on me at around 100 miles. WTF? I fuel up, but can only install about 10 gallons. I don't think the tank is dented, and I can't imagine 5-7 gallons of water in the tank. What's the deal?
The in-cab fuel tank holds 17 gallons according to the manual. The fuel gage is only approximate, so I've always just figured on 10 miles to the gallon - should have no problem getting 150 mile range.
SO, the engine dies on me at around 100 miles. WTF? I fuel up, but can only install about 10 gallons. I don't think the tank is dented, and I can't imagine 5-7 gallons of water in the tank. What's the deal?
FYI: The complete sending unit is still available. As long as you are removing the sending unit, replace the float also. They are made from two pieces of copper soldered together, solder breaks down, gas seeps in, float begins sinking to tank bottom.
D1AZ-9A011-A .. Fuel Pump Filter Screen
C0AZ-9202-A .. Fuel Tank Sender Float
C1TF-9276-A .. Fuel Tank Sender Gasket
D7TZ-9275-G .. Fuel Tank Sender Assy (comes with float, gasket and filter)
C4RZ-9030-C .. Locking Gas Cap~Vented Anti-Surge (Motorcraft FC-91)
B6TZ-9030-A .. Non Locking Gas Cap~Vented, Anti-Surge (Motorcraft FC-23)
Last edited by NumberDummy; Apr 13, 2007 at 06:10 AM.
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Fleet Owner
Joined: Jun 1999
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From: Creedmoor, North Carolina
Gentlemen PLEASE, I must challenge your statement that the vacuum is great enough to collapse the tank and it rebound. I don't think it is possible. Those tanks are pretty rigid.
I won't disagree that a vacuum could stop the flow of gas but I have a real problem with the tank collapsing.
John
I won't disagree that a vacuum could stop the flow of gas but I have a real problem with the tank collapsing.
John
Logistics Pro
Joined: Jun 2003
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Originally Posted by jowilker
Gentlemen PLEASE, I must challenge your statement that the vacuum is great enough to collapse the tank and it rebound. I don't think it is possible. Those tanks are pretty rigid.
I won't disagree that a vacuum could stop the flow of gas but I have a real problem with the tank collapsing.
John
I won't disagree that a vacuum could stop the flow of gas but I have a real problem with the tank collapsing.
John
I agree, John. I didn't catch that part.
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Post Fiend
Joined: Apr 2002
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From: Waterloo, Iowa
Originally Posted by NumberDummy
The plastic mesh filter screen on the pickup tube is prolly clogged. All Ford trucks (and cars) from 1961 till the pumps went electric in the 1980's have these filters. They just slide on. The correct gas cap for your truck is the vented type.
Fleet Owner
Joined: Jun 1999
Posts: 24,552
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From: Creedmoor, North Carolina
Originally Posted by Tedster9
Do I have to remove the tank to get access to this filter screen? How do I get to the pickup tube?
John
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
I should have added that since this truck is 43 years old and the gas today is full of impurities, removing the tank, and sending it out to be cleaned isn't a bad idea. It's prolly full of scale, dead bugs, and mebbe Jimmy Hoffa's in there too. Heck, they've looked for him everywhere else..so who knows.
Elder User
Joined: Feb 2004
Posts: 909
Likes: 9
From: San Luis Obispo, CA
I started it, so let me say that it is unlikely that a Ford behind-the-seat tank would collapse as it is heavily ribbed. The reason Fords tanks are heavily ribbed is that tanks did occasionally collapse in the past. I try to make my answers general as I know a lot of people with many different vehicles are reading our FTE posts. I have never seen this happen on a Ford, but I heard of this occurrance and have personally seen one collapsed tank - sorry I do not remember what it was on. Lets assume it was a GM product.
P.S.: If the collapse is slight there will be a rebound, but once there is permanent distortion, the tank stays in its new shape and has less capacity. If one notices a sucking sound as the cap is removed that is the sure sign of a vent problem. I have been at the side of the road with this symptom - once the vacuum was broken, I could immediately drive on. I kept the cap loose for the rest of the trip.
P.S.: If the collapse is slight there will be a rebound, but once there is permanent distortion, the tank stays in its new shape and has less capacity. If one notices a sucking sound as the cap is removed that is the sure sign of a vent problem. I have been at the side of the road with this symptom - once the vacuum was broken, I could immediately drive on. I kept the cap loose for the rest of the trip.
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Post Fiend
Joined: Apr 2002
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From: Waterloo, Iowa
Originally Posted by jowilker
Just flip the seat back forward, the access is on the top of the tank.
John
John
I do recall the original owner said he removed the tank for cleaning as the truck sat in a barn for quite a few years with fuel in the tank that had turned to sludge. He said he sealed it with with one of those slosh-around from a can products, can't rememember what it's called.
Part of this may be because I finally got the truck running so well - complete rebuild engine, new carburetor, pertronix. BTW, it looks like my figure for 10 miles to the gallon isn't too far off the mark - A rough estimate of fuel mileage shows 11.73 miles to the gallon (highway) fully loaded. Sound about right?