2.9 losing fuel pressure overnight

[Adobomb]

Hello, I have been trying to figure out why my 1986 ranger 2.9 is losing fuel pressure overnight. It goes from 30 to 0 overnight. Replaced FPR & rail HP fuel pump. Injectors dont seem to be leaking when I do engine flood test with gas petal to the floor motor doesnt start. From my understanding the check valve that is supposed to hold the pressure for months is in the rail mounted fuel reservoir. These are a discontinued item to buy. How do you fix the check valve in the reservoir so it will hold pressure for months?

 

[Angie]

hi, any chance the fuel pump is seeping? and the "gas pedal" on a fuel injected vehicle is actually an air valve. meaning, when you put the right foot down, you are opening up the air intake for the engine. the fuel is regulated from the pressure to the injectors. hope this helps


added... re-read and lost train of thought.... the check valve (can't get one from ford? if it is shot?

These are a discontinued item to buy. (we talking about this item)

fuel pressure check valve ford ranger 2.9 - Google Search

 

[RonD]

2.9l Ranger doesn't have an inline check valve, it should be in the high pressure pump in the frame rail

The pressure is held by the FPR at the engine end and the check valve inside the fuel pump, its part of the fuel pump

On the 1994 and earlier OBD1 Rangers you can turn in the fuel pump manually, jumper, and let it run for a bit, with engine off, to see if you can find any leak points

Find the OBD1 connector in engine bay, usually passenger side on the main wiring harness coming out of the firewall from computer
May still have a Cap on it, has EEC on it

Then look here: https://www.therangerstation.com/tech_library/OBD_I.shtml
2nd drawing shows the OBD1 connector
Fuel Pump Slot is labelled
If you GROUND that slot the fuel pump will come on with key on and stay on, until key is turned off

You are grounding the fuel pump relay, which is what the computer does but only for 2 seconds with key on, computer doesn't ground it again until it "sees" RPMs above 400
Or unless you cycle key off and on again to get another 2 seconds

With fuel pump on, engine off any leaks at engine end or fuel filter should show up pretty quick
Doesn't hurt anything at all

 

[Adobomb]

Thank you all for your replies. I am getting mixed information on the check valve that keeps fuel/pressure from going back into tank. Some are saying check valve is in the HP fuel pump mounted to the frame rail, others have said it is actually in the fuel reservoir (plastic canister) between the fuel tank and the HP pump. The fuel reservoir (black canister) is also mounted on the rail just aft of the HP pump and has two lines going in and two coming out. So does the reservoir canister have a check valve in it also or just the HP pump? Or is the check valve in the reservoir canister for later models that had the HP pump in the tank?

BTW... I blocked off the return line coming out of the FPR so to isolate only the injectors and the check valve in the pump or canister and same results press 30 to 0 overnight.

Thanks Ron for the tip on how to run the HP pump with KOEO. The Chilton manual I have tells you the same procedure and have been using it during my recent troubleshooting.

Thanks Angie! when you "floor the gas" push the gas petal to the floor, the computer senses the TPS voltage and shuts off the injectors. This is so you can "clear" the cylinders or test for an injector leak. Is my understanding correct?

 

[gaz]

Adobomb,

1st off RonD is correct; once the fuel rail is pressurized, the FPR, if working correctly can hold that pressure for YEARS.

You need to consider the components between and the FPR and an the intake manifold, including FPR any other new parts.

 

[RonD]

Both pumps have a check valve, pretty much all electric fuel pumps do, its nothing fancy just a hinged flap that is pushed open when pump is on and closes when pump is off, its held closed by pressure in the fuel line

For sure not in the reservoir/canister

The FPR uses a spring valve set for 43psi, +/- 2psi
Engine running vacuum lowers that to 35psi average, so the pressure doesn't fluctuate too much between low demand(idle, high vacuum) and high demand(WOT, low vacuum)

Drop to 0psi, key off, is an annoyance
But each key on adds 10psi to system, 2 second pump run time
So key on and off 2 times should get 20psi and plenty of pressure to start engine
One key on and 10psi, cold engine should start but stumble until pump starts again(400rpm), so cold engine may die
Warm restart shouldn't be an issue, just a bit of a stumble

Cold engine needs 2 or 3 times more fuel depending on outside temperature

 

[Adobomb]

Thanks RonD! I removed the black canister between the HP pump and tank and removed the cap to find a fuel filter full of gunk, sand and dirt. Also wanted to report on the inside of the canister two of the inlet ports into the fuel filter bowl was a little plastic valve that looks to be broken with a little light spring protruding beyond the valve. Is it ok to remove these little valves inside the fuel canister and run it that way? They are broke and stuck. Thanks

 

[franklin2]

I would not remove those valves, you might have to replace the reservoir if you can find one. Its my understanding that the return fuel from the FPR on the engine does not necessarily go back to the tank unless the reservoir is full. This gives the high pressure fuel pump a supply of fuel if the fuel pump in the tank is having a hard time pumping. This system with the dual pumps was their way to use a regular fuel tank without baffles, and keep the engine supplied with fuel when the fuel level gets low in the tank.

On your original problem, you have already pinched the line shut from the FPR and it did not fix the problem. So now what you need to do is pump the system up and then pinch the line shut coming from the high pressure fuel pump. If it still leaks down, you know it's the injectors. Not sure about your "turning off the injectors" test. Never tried that, but it would need to be a pretty big leak for the engine to start.

 

[RonD]

That valve is a "back flow" preventer, a hold over from the mechanical fuel pump days

Kind of like a check valve, but was for something else
The gas tank fuel level will always be lower than the fuel line at the carburetor
If the mechanical pump stops at a certain position then it would be possible for a reverse siphon to start, and it would suck the fuel from the engine end back to the tank, some gas would stay in float bowl
So anti-siphon valves were used, back flow preventer

I personally don't think you need it(the valve) with EFI since its between tank and high pressure pump
But never working on a Ranger with that canister setup myself

 

[Adobomb]

Thanks guys for the quick responses. Im going try it with valves out and see. Looks like the return fuel from FPR without these valves will always end up in this fuel canister filter bowl. And would pressure of in tank pump overcome the fuel pressure coming from FPR return line not allowing FPR to work properly or backup. Do you think if i got rid of the fuel canister and connect return lines to go straight back to tanks and pressure lines straight to Hp pump, would that work as a option. I cannot find a good fuel canister to replace this one with bad valves. Thanks

 

[RonD]

Return line should never have pressure just flow, it's end is open in the gas tank

Yes, if Return line is blocked fuel pressure would go up to 80+ psi

 

[franklin2]

Thanks guys for the quick responses. Im going try it with valves out and see. Looks like the return fuel from FPR without these valves will always end up in this fuel canister filter bowl. And would pressure of in tank pump overcome the fuel pressure coming from FPR return line not allowing FPR to work properly or backup. Do you think if i got rid of the fuel canister and connect return lines to go straight back to tanks and pressure lines straight to Hp pump, would that work as a option. I cannot find a good fuel canister to replace this one with bad valves. Thanks

You could try it. I am up to try anything to see if it works. But if you have stalling issues when the fuel level gets low in the tank, you are going to have to go to plan B.

 

[Adobomb]

Hello, thank you for the replies. I have decided to block off the return port with JB waterweld that pours return line fuel back into the fuel filter bowl of canister. This will eliminate the return line fuel from the FPR from entering pressure side and therefore only allowing it to return directly to tank. With those valves broke in the fuel canister, i think this will prevent problems. Will install new fuel filter and o ring in canister. Also pulling tank, inspecting pump and cleaning tank since i found alot of sludge in canister fuel filter. Will report back when i get it all back together on results.

 

[svtcards]

Hello, I have been trying to figure out why my 1986 ranger 2.9 is losing fuel pressure overnight. It goes from 30 to 0 overnight. Replaced FPR & rail HP fuel pump. Injectors dont seem to be leaking when I do engine flood test with gas petal to the floor motor doesnt start. From my understanding the check valve that is supposed to hold the pressure for months is in the rail mounted fuel reservoir. These are a discontinued item to buy. How do you fix the check valve in the reservoir so it will hold pressure for months?

I feel your pain.kinda still dealing with same issue now

 

[RonD]

The Return line can't bleed off pressure unless the FPR is bad

So you are assuming the valves in the canister sends the 7PSI(in tank pump) back to the return in tank if Valves are bad, which is possible but shouldn't matter

The high pressure pump should have an internal check valve that holds the higher pressure on the engine fuel rail
The canister is there because high pressure pumps can not generate any suction like low pressure pumps can
The old mechanical pumps could suck fuel out, up and over the top, of a gas tank with no issues

When fuel injection was added and systems need at least 20psi, external high pressure pumps were added, but.........
The problem was that the external high pressure pumps could not SUCK fuel out of the tank, like the old mechanical pumps could
So an in tank pump was also required to feed the external pump(and canister) until a new design in tank high pressure pump assembly was made, I think 1989 is when that was first used in Rangers, fuel gauges also changed that year
The canister keeps the high pressure pump primed, it was dropped in 1989 as well, on most Rangers