I am a newbie as far as fuel injection. The original issue the truck had was no fuel. I tracked down the issues to a blown fuel pump relay and a melted inertia switch. I jumped the inertia wires with a new fuel pump relay installed and the truck ran at an idle and up to 3500 RPM when stationary. If the truck is going up a grade or needs more throttle it will start to lose fuel pressure and end up stalling. I had the fuel pressure gauge connected to the schrader valve on the fuel rail and had 30-35 PSI when idling. It runs good under light load on the throttle. Under heavy load it starts to drop quickly and if you back off the throttle it will stay running some times. I changed the fuel filter and also replaced the high pressure pump on the main frame and it still has the same problems.The original pump was pumping about 13 ounces of fuel in the 20 second test that the repair manual suggested. I have even placed a jumper wire direct to the new fuel pump to bypass original wiring and possible problems. When it stalls under load (No Fuel pressure) at the schrader valve you can hear the fuel pump running but there is no fuel pressure. If I turn off the ignition for a few minutes and then turn the key back to the on position it will start to pressurize and then start and run at an idle. I even replace the ignition switch as it was a little temperamental. I have not changed or checked the fuel pressure regulator as it is a pain to get to at the back of the engine. I would appreciate any and all suggestions. I do not want to spend a fortune tracking down this problem since the truck may not even pass its smog inspection and may be a parts truck only.Thanks

Matt
67 F-250 4x4
73 Crew 4x2 (4x4 Soon)
89 F-250 Super Cab 4x4 ( Needs Help)

 

You have a bad fuel pump inside the fuel tank.
It is what took out the relay and switch when it shorted. Hopefully it now has an open in it.
Sorry you spent money on the frame pump that you did not need. Always come here first and post your problem.

 

Why would this issue still happen on either tank? I thought the seconday fuel pumps are just to keep the primary fuel pump quiet not to supple main fuel pressure. If it's an in tank pump that is a problem why does it loose main fuel pressure at fuel rail on main or auxillary tank? Is there any way it could be a fuel pressure regulator letting all the pressure go back to the tank? Thanks for any advice.

 

You did not say you had two tanks.
Anyway my guess is that neither in tank pump is running and the high pressure is so I would look first at the fuel tank selector switch on the dash. It may have bad contacts inside it now. You would still might have a bad in tank pump with an electrical problem that may take out the electrical devices again once power is restored to its circuit.

The in tank pumps are still used when you have low fuel level in the tank or going up a hill.

My guess is that you are only getting fuel out of one tank now even if you select the other tank. The in tank pumps must run to switch tanks and lock the fuel selector valve to the selected tank. Very seldom are they needed to prime the system unless you run one of the tanks dry.

I would not think the fuel pressure regulator would be the problem. You can check it by removing the vacuum hose from the nipple on top and turning on the key a few times and see if any fuel comes out of the nipple. If fuel does come out of the nipple then it is bad and need to be replaced. But I do not think even if it is bad would cause you problems.

 

Bill,
Thanks for the additional information i regards to issues that may be related to the switch for the main and auxiliary fuel tank. I did notice last time when i drove the truck and tried switching the tanks. it appeared to switch as it stayed running but the fuel gauge went to full and I new there was less than 1/2 a tank of fuel. I priced the in tank pumps and the are in excess of $ 100.00 to $200.00 at the parts stores ( Not going to happen). I was wondering what your thoughts are on how to check the tank pumps. I also was thinking is it possible to bypass all the tank fuel line connections and route direct to a 5 gallon fuel can in the bed of the truck directly to the high pressure pump on the frame using 3/8 fuel line.then see how it runs with the pressure gauge at the fuel rail schrader valve. I can also hear the frame mounted pump kick on for a few second when the key is turned on. I appreciate your taking the time to answer my questions. Thanks.

Matt
67 F-250 4x4
73 Crew 4x2 ( 4x4 Soon)
89 Super Cab 4x4 (Problem Child)

 

I would run a hot wire from the POS (+) post of the battery through a 30 amp inline fuse to each of the wires one at a time going to each in tank pump.
Unplug the plug on the back of the selector switch so you can get to each wire.
The front tank pump is the RED wire and the back tank pump is the Brown wire with a white stripe.

Here is a diagram:


/

 

Bill,
I will try this when I get a chance. I appreciate the wiring diagram. The manuals from Haynes and Chilton do not compare. Thanks again for the information.

Matt
89 Super Cab 4x4 ( Problem Child)

 

I've had that same problem over the years with my dual tank setup. There were 3 problems at 3 different times but the symptoms were nearly the same.
1st time it was the fuel filter, apparently the filters tend to trap water easily and won't pass enough fuel to keep the pressure up at speed under load. It would stutter and stammer if I tried to accelerate away from a stop or if I tried to pass someone on the freeway. I started changing mine every other oil change and had no more problems.
2nd time I had a bad low pressure pump (in tank). My symptoms were the same as yours and similar to what I had before. Apparently the high pressure pump will create enough vacuum in the fuel lines to just run the vehicle but under load it falls on it's face. It bucks and feels like it's running out of gas (which it is).
3rd. My distributor was failing. Not the module but the TFT goodie inside the dist. It would get hot and act just like it was running out of gas. If I let it sit for a while it would restart and run just fine for a bit. I live in Phoenix and it was during the summer so it wouldn't take long for it to overheat again and stall out. This is the 2nd dist I've had to replace in my truck since '86.

JohnF

 

Help, i have a 1989 F250 with a 460 EFI. It is 2wd, heavy duty, duel tanks. I am having a fuel pressure problem. At idle i have almost 90 psi. the return lines are working and so are the supply. the engine is all over the place,running real rough. i can mix a can of paint on it. anyway, it is running very rich, the tailpipes are black. oh also all ne plugs,wires,cap,rotor. and they are wired correctly. this problem was doing this before the tune up. any suggestions? thank you Daniel

 

Fuel pressure regulator. I don't know where it is on a 460 but they're easy to change.
I had that problem once on my '86 F150. Change oil after you replace the regulator too. It will be full of fuel.

 

thanks, i will let you know tomorrow when I install a new one. Daniel

 

Ok, I looked at the fuel lines again before i did any other work. Turns out that I some how traced back the wrong line, they do cross over a few times.the plastic return line was kinked in several places, including on top of the rear tank, so I will have to drop the rear tank and replace the return fuel line. i believe I can use rubber fuel line instead of plastic. If I can that is what i will do. I'm so glad you guys were there for the advice and guidance, thank you very much, I hope to someday return the favor. if not, i love talking about ford trucks. Thanks again guys. Daniel

 

89 f250 fuel pressure problem. So I have a silly question and im embarrassed of having to ask but what the heck... so I just bought an 89 ford f250 lariat 4x4 with a 460 and dual tanks that has been sitting in a warehouse for about ten years . It ran ten years ago when the guy parked it. I cannot get it to start unless I spray carb cleaner into the intake. I have replaced the front low pressure in tank fuel pump and the high pressure fuel pump, fuEl filter, fuel pressure regulator and I still can't get it to start or get any fuel to start her up. Now I didn't replace the rear tank low pressure pump as my funds are limited. Do I need to in order to get it to run even if u don't plan on using the rear tank? And when I tried to use switch on dash board for selecting which tank I noticed that it's saying I have both tanks full but I know better and there is not that much in it. So I'd this due to a bad selector switch or so I need to replace both low pressure in tank fuel pumps to get it to work? And is there a way to bypass the rear tank and just put a hose from fuel going in and return. Sounds stupid but I guess how ypu would bypass a heater core in a sense lol. OK silly yes I know forgive me and help me please!!!

 

First you need to check the fuel pressure with a gauge before replacing parts. You should be able to rent a gauge at most auto part stores.