Last week I ran out of fuel in my rear tank, guage was at empty, engine stopped and ran badly when restarted ... I thought that when needle shows 3/8ths and it fills with right under 8 gallons meant I may have alot more fuel left ... even at empty. I switched to the front tank, which thanks to Ford's ingenious fail safe plan cross flow fuel system, now had almost 1/2 tank. I filled the rear tank and the pump stopped after pumping 12.89 gallons ... it wouldn't take more. I have gotten under the truck, I know I have the steel rear tank, as well as the steel front one. In all my parts searches I can not find mention of a 13 gallon rear tank for a 90 F150 Standard Cab SB 4.9L, or any model/engine for that year. They only list an 18 gallon steel or a 19 gallon plastic. I believe the front might be 13 gallons on SB and 17 on the LB's. I am wondering if someone may have installed the wrong fuel delivery assy in the rear steel tank. Anyone who has removed the fuel pump units from both the front and rear steel tanks (different part #'s), can you tell me if the delivery assy is shorter for the front steel/rear plastic tanks than for the rear steel, seems like I will never get that bottom 5 gallons out of the rear tank.

 

The fuel pump is never going to pick up the last couple gallons. I have the same issue. I run the rear tank dry, and it only holds about 14 gallons. The last four must be still sloshing around in there. I know it's an 18 gallon tank.

 

When my rear tank ran out of fuel I needed 5 gallons minnimum just to get it started. So, you are right in saying that you need 4-5 gallons sloshing around and unussed.

 

Well ... That is just some of the shabbiest engineering I have ever seen, an 18 gallon tank runs "empty" after 180 miles but the vehicle gets 15MPG, that must be that new math I didn't take in private school. I think I just purchased my last Ford, I guess staying away from them for 20 years was not enough, excluding the pre emission versions. I overfilled my front tank ... well the rear tank crossflow did the overfilling, and it would not work till I removed 4 gallons of gas.

 

Both Ford trucks I have had were equipped with the 19.0 gallon front and the 18.2 gallon rear tank. I always run one of the tanks dry, switch, then get close on the other. When I fill up, I can always put MORE than the rated capacity in the empty one (i.e., 19.5 gallons in the front if it was dry, and 18.5 or so in the rear if it was dry).

The '90 shortbed std cab had a 16.0 gallon tank (I don't recall if it was front or back, but I think it was in the front, 18.2 in the rear). That was from the manual for my '90.

Jason

 

My tanks will both hold over 20 Gals if I run them DRY. DRY means the truck stops running from lack of fuel, not that the guage says empty. Every Ford I have ever had is set so you have a few gals. left when the guage reads empty so people won't complain when they run out of gas.

 

My 91 F150 4x4 has the 18ish gal ones. I can put 20 gallons in each one when they are empty. I have replaced both as one had a hole and I went ahead and did both because the second wasn't looking so good. I still get about 200 highway miles out of a tank.

 

Thanks for that info then .... mine did run near dry ... engine stopped and when restarted ran pretty badly till I switched to the front tank. So back to the original question. Anyone out there compare the fuel pump assemblies from the front steel and the rear steel and can post here what the difference is? Please see original post.

At this point I can believe this truck may have had the wrong parts replace the broken ones .... heck before I changed the water pump and radiator it had a Cheby radiator in it.