How to: Ford Explorer Ranger Fuel pressure test procedure

[ranger7ltr]

When it doesn't start what is the fuel pressure?

The 99 and later models run a higher fuel pressure to avoid the issue you are seeing...If you are not getting 65-73 psi of fuel pressure, I would start by replacing the fuel filter and rechecking the fuel pressure...

If the fuel pressure is still low the fuel pump would be next...

 

[Afboy143]

A lady at work had that problem on her 93 buick regal. Sit for a while, fine, but going in the gas station and stuff she couldn’t turn the car off. I replaced her fuel filter and it helped, ess. when she held the throttle down, but she ended up trading it in. I bet since I changed that fuel filter, the line was clogged somewhere or the pump is just getting old and needs replacing

 

[airfabtech]

I have replaced the FF. The pressure is consistently 66 psi. It does not bleed down rapidly when you turn it off. Why the air or vapor in the line?

 

[ranger7ltr]

That is a surprise...

With the fuel pressure at 66 psi you should not have the opportunity for vapor to form or air to enter the fuel system...

Do you notice an odor of fuel around the truck anywhere? I can't think of many possibilities for fuel to vaporize under these conditions...

Could there be a fuel leak somewhere?

 

[airfabtech]

I' ve looked, can't find any leaks. Also if it were leaking I would think it would bleed off the pressure when not running, but it holds for a long time... I dont see the air /vapor when it is cold so thats why I think its vapor. I think I will insulate the fuel line through the engine compartment. Don't know for sure that the line is original or routed in it original location. Will fuel vaporize at 66 lbs if the line gets warm enough???

 

[ranger7ltr]

Hmmm...

I ran my truck today in 104 F heat for the better part of 8 hours...If the fuel was going to vaporize it would have today... Truck was rock solid; a/c cooling the cabin well and getting 37 f at the vent...

The only thing I am thinking of is an injector leaking down or the fuel pump bleeding down back into the tank...If the fuel is leaving the fuel rail then when the pump re-energizes there would be air, or vapor I guess, coming out of the rail...

But if the pressure is staying @ 66 psi then that can't be happening...And that is more than enough pressure to keep vaporization from happening...

 

[stocked]

I had a similar problem with a Tempo i had, It would start on the first revolution of the starter when it had sat for a couple hours or overnight (very nice in the mornings lol), but if i left it sit for just a few minutes the injectors would leak and bleed out pressure and flood the engine slightly. One thing that helped was to hold the throttle to the floor before turning the key on and while cranking, then quickly letting off after it started.

 

[airfabtech]

Joe Dirt, Just wondering if you've found the magic solution???

 

[lizzard1953]

pressure buildup after shutdown

If you're concerned about the pressure bleeding down to nearly zero psi after an hour I think that is normal. Your 97 has a return fuel system so the fuel pressure regulator could be allowing the fuel to return to the tank. Also, I believe there is a check valve at the fuel pump that prevents back flow but isn't perfect.



I don't know why the ignition Off fuel pressure increases with multiple cycles but since the fuel pressure is 40 psi at ignition On it should not be a factor in the engine starting.



I've read of something called injector heat soak susceptibility that occurs on short trip vehicles. The heat from the engine transfers to the injectors when the engine is off after a short trip. The hot injectors perform poorly upon engine start until the flowing fuel cools them. Some vehicles with electric cooling fans continue to run after engine shut off to prevent the problem. Do your injectors still have the stock insulators? If so, you might try adding fuel injector cleaner to your tank. I only use Techron because some of the cheap cleaners remove the deposits in the injectors but cause them to collect on the valves.

Another thing to try is disconnecting and reconnecting the crankshaft position sensor a few times to clean the contacts. A faulty connection can create all types of start and running problems and typically is not reported by the PCM.

Is the EGR system in good condition? EGR failures are often detected and reported by the PCM but not always.

Heat from the engine is what I would say is the cause of the pressure building up after shutting off the engine. And is probably the cause of the hard start ups at the 10 or 15 minutes after shut down due to gas turning to vapor in the injectors from the heat. As the engine cools the gas returns to liquid and again cools the injectors and things return to normal.
Does this sound like a possibility ?

 

[SoNic67]

As it was said, the high pressure would keep the fuel from turn into vapors at the temperatures of the block/heads/engine compartment - less than 190F.

 

[lizzard1953]

pressure buildup after shutdown

As it was said, the high pressure would keep the fuel from turn into vapors at the temperatures of the block/heads/engine compartment - less than 190F.

And I'm sure your rite. However when a engine shuts down and the water in the cooling system stops the water jacket temp will rise for a while as the high heat in the cylinders dissipates. Also the rise in the fuel pressure after shut down tells me that some of that heat is also moving into the fuel system that is connected to the heads. It is only a suggestion but it could be checked out by doing something to stop the rise in temperature in the injectors on shut down. Something that may work and could be tried is to before shut down take a fan open the hood and turn the fan on to the injectors then turn the engine off and test it again. I have witnessed this rise in pressure many times in pressurized systems and seen 200 psi raise to as much as 210 psi just from being in the sun. That is the reason I suspect heat from the head to be causing the expansion i.e. pressure rise in the system. One thing is for sure. It will cost nothing to try. If it works then you have some thing else to think about. Like how do you keep this from happening in the first place.

 

[Joe Dirt]

Joe Dirt, Just wondering if you've found the magic solution???

Mine ended up being a crank sensor, it was completely unrelated to the fuel system...

 

[pcsullivan91]

so my issue i've been having is that when starting my truck cold if i throw the key in and turn it immediately it will turn over for 5 or so secconds before starting. If i turn the key in and let the fuel pump run for a couple seconds the truck starts fine. I dont have the pressure tester but plan on getting one tommmorow.
Is this a prett good indication that my fuel pump is dying?
Also, could be unrelated wanted to ask anyways when i start cold i have the infamous low idle(almost stall out) followed by high idle for a few seconds. Thought it was the IAC like it was on my previous explorer but replacing didnt help. Could this be related to fuel pressure?

 

[SoNic67]

I keep the key at ON for 3 seconds on all my cars to build up the fuel pressure, before switching on START. I never have been worried if a car doesn't start right away "on dry".

 

[pcsullivan91]

I keep the key at ON for 3 seconds on all my cars to build up the fuel pressure, before switching on START. I never have been worried if a car doesn't start right away "on dry".

o ok i mean ya it doesnt seem to be an issue at all as long as i leave it on for 3 seconds so i guess no big deal. never had a vehicle i needed to do this on before though. not even my old explorer sport.

 

[clamb]

1999 explorer 4.0 L fuel pump leaking

I just removed my pump from the tank after a mechanic tested it and said it wasn't building up pressure. I then hooked up a presure guage & ran the pump in a gallon of fuel to check the pressure again, & found that it was leaking fuel from the connections between the pump & the resonator or fuel pressure regulator, (not sure what they call the round silver & black piece above the pump) on the fuel pump assembly. I was able to build up to about 42 lbs. I replaced the hoses & new clamps & I can now get it to about 55 lbs, with no leaks. Is this still too weak? Can poor fuel pressure hurt fuel economy? I just calculated that I was only getting 11.8 MPG (imperial), which is about 9.8 Mpg (US) pulling a small snowmobile trailer with a quad on it. All highway driveing.
I just used a spare 12 V battery sitting in the garage, Will the pressure improve with a running vehicle when alternator is putting out a charge?

UPDATE: I just reinstalled my old pump after tightening the in tank connections. I started it up & could tell there was an improvement already. After taking it out for a drive & topping it off with fuel, I tested the fuel pressure at the rail @ 64 lbs. But it doesn't seem to hold the pressure for more than a few seconds after shutting the vehicle off. Before doing this work I had it in at the shop for a checkup they said it was only building up about 40 lbs of pressure, & wouldn't hold after shutting off. I will run a tank of fuel through it and see how it runs.

 

[Afboy143]

Hola Canadian neighbor! How’s it goin’ over there, aye?

65-73 PSI is what’s needed to achieve optimal performance from what I’ve read back when I was doing a ton of research on things. I haven’t been back out to test my pressure recently, but what led me to suspect I had a problem was lack of power.

I can personally say I get 15 MPG city and 18 highway.

Sorry I couldn’t be of more help. Good luck!

BTW- I did replace my fuel pump and gas tank possibly thinking I had rust in my tank or the pump was weak. The change didn’t really do anything, but atleast I know those parts are new now Next thing I want to do is reflow and clean my injectors

 

[clamb]

It would be going a lot better if my Explorer would run better. I have owned it since 2001, & I used to be able to get 20-24 Imperial MPG hiway, & now I am down to 14 at best. I am also on my third engine & rebuilt the automatic tranny on the last engine install. I only have 223000 km or about 140000 miles on it, with about 25,000 km on the last engine. We are getting snow here this morning -9 deg Celcius or 15.8 F. I guess winter is coming.

 

[Afboy143]

Wow- sounds like the weather up there does a toll on your truck! That’s crazy ! I am on 132,000 miles and, knock on wood, the only big replacements I’ve had to do is battery, water pump, and radiator. I live in Florida so it’s either warm or hot here. No snow, no salt, no hills, and I never tow with her. Stock motor, stock transmission but I took a lot of steps to prevent premature failure.

It was 68 degrees this morning before the sun came up and I was a bit chilly. I had to throw my hoodie on to walk the dog

Take this with a grain of salt from a Floridian, but could moisture be in your line somehow and the freezing weather froze it causing the drop the pressure you’re experiencing? I once thought I had moisture in my line and someone told me to run a bottle of … now I cannot think of it. It’s a red bottle and only about $2 at the store. Or Valvoline makes something similar

http://www.valvoline.com/products/brands/valvoline/water-remover/27

I didn’t see this in your post- but did you replace your fuel pump with new? I know you must drop your tank to do this.

 

[clamb]

No I haven't replaced the fuel pump, just contemplating whether it is necessary now. I had it tested & wasn't building up the pressure that it should. When I removed the pump from the tank I tested the pump, where I could see it & noticed that it was leaking past the connections between the intank pump & a fuel presure regulator, Resonator/ fuel damper, not sure what it is called and have seen different people call it different things. It will build up to 55 lbs pressure with the old 12 volt battery, & was thinking that it might put out the required 65 lbs with the vehicle charging system working.
I can't blame the weather for my truck problems, I think I might just have a lemon. Know others with the same vehicle & engine with no problems. I have had 2 engines fail because of blown head gaskets & hydrolocking the engine (filling cylinder with coolant so they will not turn over).
By the way temperatures are still seasonal, by January or Feb we should see some -40 degree temps. I try to run a synthetic 0-30 oil in winter, or park it in garage or plug in the block heater.
Calvin

UPDATE: I just reinstalled my old pump after tightening the in tank connections. I started it up & could tell there was an improvement already. After taking it out for a drive & topping it off with fuel, I tested the fuel pressure at the rail @ 64 lbs. But it doesn't seem to hold the pressure for more than a few seconds after shutting the vehicle off. Before I done this work I had it in at the shop for a checkup they said it was only building up about 40 lbs of pressure, & wouldn't hold after shutting off. I will run a tank of fuel through it and see how it runs.