1981 Ford F100 Revival (Parked for 12 years)

Light Duty

Basically a fleet truck ordered as a meter reading truck, or something like that, which has incredibly tall highway gears and light brakes that would never be asked to haul or tow much weight.

ArdWrknTrk wrote

Light Duty

Basically a fleet truck ordered as a meter reading truck, or something like that, which has incredibly tall highway gears and light brakes that would never be asked to haul or tow much weight.

Thanks for the detailed explanation.  I am now confident that my first truck can haul a truckload of marshmallows with no problem. 🤣

I learned something today.  The frame crossmember reinforcement is not a lift point!  I have jacked up the truck from here before with no issues but last night it buckled and collapsed! So now I am leaving jack stands under the frame so when the tires deflate every day it won't go down too low so I don't need to keep jacking it up. Its a shame too because that part was in good shape and not damaged before I got to it.  From the research I have done so far it is hard to find in good shape.  Does anyone know any aftermarket suppliers for this part?  Or can it be straitened out? How do I find the full part number?  I purchased the part CD from Rock Auto but I haven't figured out how to use it yet.  I did manage to find part of the part number 5C128 but I think the number needs to be longer.

Back to fuel now.  I am trying to see if the fuel pump is defective or another issue.  So I tried to pump fuel from the line before the fuel pump.  I had to pump for a very long time and finally I got some dark looking fluid coming out.  It just seemed way too hard to get the fuel going.  Every specimen bottle I did got a little easier though.  Today I need to purchase some kind of electric fuel pump to drain the tank and to clear the lines at the same time.  The rubber line was very spongy and coming apart.  I need to replace the line from the metal line coming from under the truck to the fuel pump intake. It is funny that it measures metric perfectly. But I capped off with 5/16 to prevent anything getting in there overnight. I also spotted the fuel filter under the air cleaner which I need to replace too.  I need to find some clear fuel filters to put before the fuel pump so I can monitor what is coming out.

Yup, that thing is easily damaged and they are hard to find in good shape due to that.

But "5C128" isn't the part number.  It is the base part number for a "Cross member (frame front lower)", and that number was used by Ford for every Cross member (frame front lower) on every vehicle they've produced anywhere in the world since the late 60's.

A number needs a prefix and a suffix to make it a part number. The prefix will take the form of E1TZ, with the E meaning the decade of the 1980's (D = 70's and F = 90's), the 1 adding to the 1980 making it 1981, the T meaning F-Series truck, and the Z meaning replacement part.  And the suffix will be like A or B or C, and are the iterations on that part.

We have the crossmembers listed on the website on the page at Documentation/Suspension & Steering/Crossmembers.  If you go there and then go to the Text file and then Section 50 Page 6 of your CD I think you'll see they are the same.  The Master Parts Catalog is where I got most of the info on the site.

But, you'll then see that your truck uses Parts List No 3, and in that you need part number E9TZ 5C128-A.  But the E9 means the part was first manufactured in 1989 - well after your truck was made.  So that is a replacement part as your truck's part would have been either E0 or E1.  And if you look at the bottom of the pages of your MPC you'll see March, 1994 and Final Issue.  Ford modified the MPC over time with later parts that fit.  Sometimes they left the original part number and added "r/b" for "replaced by", but in this case they didn't.  (I have earlier versions of the MPC on microfiche.)

Now, if you pull your crossmember off and clean it very well you'll find a number on it.  And it'll not be E1TZ 5C128 - A.  That's because no number on a Ford part is a part number.  

In the late 60's Ford had one of their infamous "Better Ideas" and started placing Engineering or ID numbers on parts.  I have a cross reference book to look up part numbers from ID #'s, but it is the size of the San Francisco phone book and has really small font.

Anyway, school is out.  Recess time.  

Gary Lewis wrote

Yup, that thing is easily damaged and they are hard to find in good shape due to that.

But "5C128" isn't the part number.  It is the base part number for a "Cross member (frame front lower)", and that number was used by Ford for every Cross member (frame front lower) on every vehicle they've produced anywhere in the world since the late 60's.

A number needs a prefix and a suffix to make it a part number. The prefix will take the form of E1TZ, with the E meaning the decade of the 1980's (D = 70's and F = 90's), the 1 adding to the 1980 making it 1981, the T meaning F-Series truck, and the Z meaning replacement part.  And the suffix will be like A or B or C, and are the iterations on that part.

We have the crossmembers listed on the website on the page at Documentation/Suspension & Steering/Crossmembers.  If you go there and then go to the Text file and then Section 50 Page 6 of your CD I think you'll see they are the same.  The Master Parts Catalog is where I got most of the info on the site.

But, you'll then see that your truck uses Parts List No 3, and in that you need part number E9TZ 5C128-A.  But the E9 means the part was first manufactured in 1989 - well after your truck was made.  So that is a replacement part as your truck's part would have been either E0 or E1.  And if you look at the bottom of the pages of your MPC you'll see March, 1994 and Final Issue.  Ford modified the MPC over time with later parts that fit.  Sometimes they left the original part number and added "r/b" for "replaced by", but in this case they didn't.  (I have earlier versions of the MPC on microfiche.)

Now, if you pull your crossmember off and clean it very well you'll find a number on it.  And it'll not be E1TZ 5C128 - A.  That's because no number on a Ford part is a part number.  

In the late 60's Ford had one of their infamous "Better Ideas" and started placing Engineering or ID numbers on parts.  I have a cross reference book to look up part numbers from ID #'s, but it is the size of the San Francisco phone book and has really small font.

Anyway, school is out.  Recess time.  

Thanks Gary!  That was the details I needed.  I wondered how their part numbers worked.  Now I just need to find the part.  Is it really needed?  I saw one thread where someone said if it is not connected to your sway bar you don't need it and can pull it off.  But I can see how it can help protect the undercarriage.

You need to replace all the fuel hoses as they will all be soft and spongy.  On Dad's truck I wadded one line up into a ball and it stayed there as the hose was that sticky.  It allowed air in while running, and that killed the vacuum of the fuel pump, and it leaked fuel out when stopped.

There's a hose from the tank to the hard line, one from the hard line to the fuel pump.  But if you have dual tanks there will be a hose from both of the hard lines to a switching valve on the frame below the driver, and then a hose from the valve back to the hard line going to the pump.

As for the tank, I wouldn't mess with getting a pump and cleaning out the tank.  I tried that and never, ever got rid of the rust sediment.  It continually plugged filters.  Just buy a new tank.  They are about $100 and will give you a lot of peace of mind.

I ran the '82 Explorer for years w/o that part - because I damaged it in towing.  And the guy that bought the truck is still running it w/o that part.  So I'd say it isn't necessary.  But I'd start looking for one anyway 'cause it is nice to have it.

Gary Lewis wrote

You need to replace all the fuel hoses as they will all be soft and spongy.  On Dad's truck I wadded one line up into a ball and it stayed there as the hose was that sticky.  It allowed air in while running, and that killed the vacuum of the fuel pump, and it leaked fuel out when stopped.

There's a hose from the tank to the hard line, one from the hard line to the fuel pump.  But if you have dual tanks there will be a hose from both of the hard lines to a switching valve on the frame below the driver, and then a hose from the valve back to the hard line going to the pump.

As for the tank, I wouldn't mess with getting a pump and cleaning out the tank.  I tried that and never, ever got rid of the rust sediment.  It continually plugged filters.  Just buy a new tank.  They are about $100 and will give you a lot of peace of mind.

Interesting you mention air in the lines.  I couldn't get a solid stream of fuel in the clear hose of my vacuum pump.  There was always air bubbles in the line.  Can you tell by the picture if I have the 16.5 or 19 gallon tank?  Mine looks more like the 19 gallon from what I can tell.  It is very long and slender. I guess I probably will need a new pickup and sending unit too.

Gary Lewis wrote

I ran the '82 Explorer for years w/o that part - because I damaged it in towing.  And the guy that bought the truck is still running it w/o that part.  So I'd say it isn't necessary.  But I'd start looking for one anyway 'cause it is nice to have it.

Thanks, I will pull it off for now.  It is bugging me looking at what I did.

Only Shortbeds and Flareside get the 16 gal tank.
Any 133" WB truck is 19 gallon front and rear.

Yes, a porous fuel line admits air and causes all sorts of problems.

As for the fuel tank, I don't know if you've said what your wheelbase is.  But according to this from our page at Documentation/Fuel Systems/Fuel System Part Numbers/Fuel Tanks a 1981 F100 shortbed got a 16 1/2 and the long bed got the 19 gallon tank.

ArdWrknTrk wrote

Only Shortbeds and Flareside get the 16 gal tank.
Any 133" WB truck is 19 gallon front and rear.

Beat me to it.  And with far fewer words.  

ArdWrknTrk wrote

Only Shortbeds and Flareside get the 16 gal tank.
Any 133" WB truck is 19 gallon front and rear.

Thanks! Mine is a long bed.  What does WB mean?

Gary Lewis wrote

Yes, a porous fuel line admits air and causes all sorts of problems.

As for the fuel tank, I don't know if you've said what your wheelbase is.  But according to this from our page at Documentation/Fuel Systems/Fuel System Part Numbers/Fuel Tanks a 1981 F100 shortbed got a 16 1/2 and the long bed got the 19 gallon tank.

Thanks, AutoZone has the 19 gallon in stock.

WB is wheel base.

On the tank, make SURE that it is the one with the smaller opening for the sender.  In '85 the opening went to 4" from 2 1/2".  And yes, while you are at it you may need to add a new sender.

Gary Lewis wrote

WB is wheel base.

On the tank, make SURE that it is the one with the smaller opening for the sender.  In '85 the opening went to 4" from 2 1/2".  And yes, while you are at it you may need to add a new sender.

Thank you again. I added a sending unit to the cart.  Hopefully it matches it. Is all the fuel line I need going to be 5/16th?  What about the filler neck or vent valve?  Any other parts I should get?

I think all of the fuel line is the same size.  I bought several feet of new hose that's rated for ethanol and used it everywhere.

The fuel filler hose is probably fine, but the vent valve's hose should be inspected.  Some I've seen are gooey and some are fine.

OUCH!
As long as the front bumper is left in place it acts as a cross member you can run with out the one you bent up.

Now if you have access to a press or maybe the weight of the truck? you can bend it back into shape.
If using the truck with the member off place wood blocks on the ends on the bottom and use a bottle jack placed where you bent it up and start jacking and see what happens.

In a press you would do the same thing just that you would be standing when jacking and I would think if the truck is not heavy enough it will start to lift before the bend is out, not so with a press.

On the fuel system:
As for tank size that looks to be a side tank or mid ship tank and a easy way to know the size it how long the bed is.
Short bed trucks / flare side have a 16 gallon tank.
Long bed trucks have a 19 gallon tank.
And yes the sending units are different for the 2 different tank sizes so check before odering sender you have the right one. I think some places list the same part number for the senders and this is wrong.

I am with Gary on get a new tank & sender as you will never get any rust that may be in it out.
Besides that filter you see between the pump & carb you may also have a filter that screws into the carb.

I had to open my carb up and found rust in the bowl. This was a little over a year after getting the truck on the road.
Tanks looked good before I installed them back in the truck with new senders as part of the 4 year rebuild so was a little shocked on the rust.

Anyway my truck had 2 filters, one like you pictured and a screw in one. When the carb was apart I backed flushed both and the first (like yours) was pretty bad with crud.
I had to take the carb apart a 2nd time and the rust was not too bad but I replaced the first metal filter (like yours) with a plastic see through  and ran 2 rear tanks through it and I dont see any rust.
I just started to run on the front tank and will run 2 tanks to see what one if either gives me rust and go from there on a fix.

If you want to run the motor and move the truck under its own power while you get the fuel system fixed get some 5/ 16 hose, you need some to replace it on the system anyway, to go from the pump inlet to a small gas can you can place on the inner fender and run the motor from it.
I did this for years as I did not know how long it would be before my truck was on the road and did not want gas in the tank(s) going bad from sitting.
You can see the gas can on the inner fender.

 Dave ----

Gary Lewis wrote

I think all of the fuel line is the same size.  I bought several feet of new hose that's rated for ethanol and used it everywhere.

The fuel filler hose is probably fine, but the vent valve's hose should be inspected.  Some I've seen are gooey and some are fine.

Do you know what size the vent valve hose is?