When the rear gas tank on my '94 F150 gets low and I switch it to the front tank, the front tank seems to be backfeeding the rear tank significantly while the truck's running. At the same time, the 302 started taking too much cranking to start up when it is hot. May not be related. Any ideas?

Thanks.
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Very common problem on this vintage truck. The Fuel Delivery Modules (FDM) contain backflow valves to control fuel flow. When the front tank is energized the pressure in the line is supposed to close the rear backflow valve. When that valve fails the front tank will pump fuel to the engine and the rear tank. Same thing can happen if the front tank backflow valve does not work properly, then the rear tank will try to fill the front.

 

i have this problem also, and have been wearing the search function out the last few days. From what i have taken in, it is recommended that you replace the fuel pressure regulator and Fuel pump assy that is giving you problems. It really seems like the simplest way to fix the problem. Especially for your 94 and my 92.

 

I did a lot of looking at web sites after I posted the messsage, and it is a recurring post. Apparently, the system changed in 1990 from dual, low pressure pumps in each tank with an external switching valve and high pressure pump, to dual high pressure pumps in each tank, switched electronically from the dashboard switch.

Each pump assembly has an internal check valve that prevents the other tank from backfilling it. The check valves can fail over time, sometimes due to a failing fuel pressure regulator that puts too much pressure on them.

Ford had a recall, 93S68 (Google it) years ago on failed check valves, that has expired. Ford's fix was to put an inline ball check valve in each fuel line from each tank as a redundant valve to the failed valve(s).

The Ford part number for the external check valve off of a web site(???) is 1L3Z-9J274. I checked with Advance, Car Quest and NAPA, and no luck. I ain't going to the Ford store, since I'm mad at them and read they are real proud of their valves if they will even own up to it (but I will get over it).

I will work off of my rear tank and eventually replace the rear pump assembly ($160). It looks easier to raise or remove the truck bed than to wrestle the tank down and up.

This is my understanding of the problem and parts of it may not be as right as they should be. Sure is nice to have this web site and support, though, cause you ain't going to get this kind of straight poop from your local, friendly Ford dealer. But, you wouldn't get it either from GM, and I don't acknowledge imports.

 

Good info Magnumea, But do tell where you found a full pump assy for 160 ? i keep finding them in the 180-190 range. Im looking to replace both my pumps in the near future and would love to have the best deal possible..

thanks
Mario

 

I had the fuel transfer from back to front tank on my truck. Installed a new aftermarket FDM (can't remember the brand) and I think it made the problem worse. Perhaps it didn't have the check valve installed??? Put a new fuel pressure regulator on just in case and that didn't help either.

Installed one of the Ford recall check valves (1L3Z-9J274-AA) a couple of weeks ago and all is good now. Local dealer had them in stock...geez...wonder why...and it's way cheaper than a new FDM. Plus you only have to disconnect the supply line to install it.

 

Try Parts Guy Ed, one of the vendors on this site. There is usually a link to his site on the left hand side of the screen. I put in part no. 1L3Z-9J274-AA on the website, it showed a price of ~$78.

 

Having same problem ,ft. tank sends gas to rear rapidly. installed new ft fuel pump and just gut done putting in new fuel press regulator,still does same thing . I,m sick of this. Will try new back pump.Truck runs much better on ft pump now,was weak before hard to start.U can see gas drop from ft and go to rear tank also put in a new tank switch.

 

Had same problem with dual tanks on E250. Had to put in new fuel pumps (no help) then fuel selector switch, then a check valve. This helped some.
Pretty much have to keep both tanks filled....
bsdetectr@aol.com

my apology here for someone who sent a reply to my question about breather hose on top of gas tank... I stupidly lost the email.....and your advice.

 

IF U FIND OUT HOW U FIXED YOUR TRUCK ,PLEASE Let me Know.Thanks KILOG69 Sent to u by mistake,sorry,unless u have the anser?

 

The answer is replacing the entire fuel delivery module or trying the Ford band-aid fix of installing the inline check valve mentioned earlier.

 

Thanks for your i,m, put i will replace rear pump instead of band aid ,thanks .

 

replacing rear pump (been there, done that) may not be enough. Had to replace main pump on frame, and also fuel selector switch. Then put in check valve. Good luck with it!

 

The OP has a '94 F150, there is no high pressure pump mounted on the frame. Both in tank pumps are high pressure.

 

Thanks to All on This site For Your help .My P.U is A 4x4 351W -92,Got A matching Brand air Tex ,I think Came from advance auto same co as the Ft pump i just put in. Got online from my Home town store ,Had a $30.00 off on online sales over $100.00. $123.99-$30.00 =$93.00+ Tax what a way to go no dealing with kids, i,m being polite . Plus Great savings call this am had it on shelf with a print sheet from online sale. Ft Pump was about $40.00 more.This should fix the transfer night mare Thanks to all I will update.if it,s a fix,s Nothing left to replace.