How to: Ford Explorer Ranger Fuel pressure test procedure

[2000StreetRod]

Background

When other forum members describe their performance issues I frequently suggest that they replace their fuel filter if due and check their fuel pressure. Yesterday Harbor Freight Tools offered their fuel pressure test kit for $10 so I bought one. The following procedure is the result of me trying out my new test kit.

In 1999 Ford switched from a return fuel system with a rail mounted fuel pressure regulator (FPR) to a returnless fuel system with a rail mounted fuel pressure damper and a tank installed FPR. My 2000 Explorer shop manual states that the fuel pressure for the returnless system should be 65 psi +/- 8 psi.

Test Procedure for pre 1999 return fuel system

1. Locate the fuel pressure test port on the engine as identified in the photo below.

2. With the engine ignition switch Off insert one end of the test kit fuel pressure hose into a container and connect the other end to the valve to relieve the existing pressure as shown below.

3. Remove the container and attach the gauge to the free end of the hose. Wrap the connection fittings with a rag to catch any leaks as shown below.

4. Turn the ignition switch to On and then off. The fuel pump will only run for a few seconds since the engine was not started.

5. Check for leaks at all of the fittings and tighten fittings as required. In my case it was necessary to use Teflon tape at the hose to gauge connection to prevent leakage. Leakage is indicated by a rapid reduction in the fuel pressure reading on the gauge.

6. Start the engine and record the pressure at idle. It should be 30 to 45 psi.

7. Slowly increase the engine speed to 3000 rpm while watching the pressure. The pressure should increase slightly as the engine speed increases because the vacuum decreases. Record the pressure and then let the engine idle.

8. Very rapidly increase the engine speed while watching the pressure gauge. The pressure should increase significantly while the engine speed is increasing since the vacuum drops significantly.

9. Turn off the engine and watch the pressure gauge. The pressure should not drop below 30 to 65 psi in 5 minutes.

10. Disconnect the vacuum line to the fuel pressure regulator and plug the line to prevent a leak. I plugged mine with a vacuum gauge as shown below.

11. Start the engine and record the fuel pressure at idle with no vacuum to the regulator. It should be 40 to 50 psi.

12. Compare the recorded pressure gauge readings. The pressure at idle with no vacuum should be the greatest. The pressure at idle with vacuum should be the least. The pressure at 3000 rpm should be between the idle readings.

 

[2000StreetRod]

Fuel pressure test kit

Below is a photo the the Harbor Freight fuel pressure test kit.

 

[ranger7ltr]

Your truck has the returnless fuel injection system...

Which has the fuel pressure regulator on the sending unit in the tank next to the fuel pump...It is the round black and silver unit pointing to the right in the picture below...There is no fuel return line back to the tank and no vacuum line to the regulator...That applies to the return line type of fuel system prior to 99MY..

I believe the device you removed the vacuum line from is the fuel pulse damper...What it does is to reduce fluctuation of the fuel pressure during injector operation.

And in my monitoring of the fuel pressure in my 99 with the same fuel system the fuel pressure doesn't vary at all... It starts off at 65-70 psi and stays there give or take 1 or 2 psi on my Autometer Electric Fuel Pressure Gauge...

 

[2000StreetRod]

Returnless fuel system

Thank you ranger7ltr for the information! After your comment I did more research and verified your comments. My fuel pressure fluctuated +/- 2 psi from 65 psi at idle but was steady at 65 psi at 3000 rpm. After shutting the engine Off the pressure dropped to 62 psi in the first minute and remained there for more than 10 minutes. I have modified the test procedure accordingly.

 

[Afboy143]

Hey guys,
I am about to try this procedure out tomorrow. I went to harbor freight and bought the kit. My question is what if my truck fails the test? What are the next steps to take in fixing the problem? I have a 99 Sport SOHC with the returnless system. Do I need to drop the tank and replace that thing? If so, where in the world do I buy it. No local parts shops carry it

 

[ranger7ltr]

What test are you concerned about failing?

Hey guys,
I am about to try this procedure out tomorrow. I went to harbor freight and bought the kit. My question is what if my truck fails the test? What are the next steps to take in fixing the problem? I have a 99 Sport SOHC with the returnless system. Do I need to drop the tank and replace that thing? If so, where in the world do I buy it. No local parts shops carry it

Whether the system fuel pressure gets up to 65-72 psi or that the pressure stays there when the key is off?

Are you having driveability/starting issues?

On the returnless fuel system, the fuel pump is the driving force behind system pressure...Remember, in this system design, there is no vacuum line to vary the fuel pressure based on engine load via vacuum...Since there is also no fuel return line, the injectors, fuel filter, and the fuel damper[which is used to smooth out fuel pulsations from the pump] will determine the delivery of fuel to the engine... The regulator is apparently in the system to "vent" excess pressure back to the tank while maintaining system pressure in case the system pressure goes higher than designed...

The pump and the injectors will also act to maintain fuel system pressure when the engine is off...My understanding is that Ford went to the returnless system and subsequent higher fuel pressure to fight iisues with heat soak causing vaporizing in the lower pressured fuel lines and difficult hot starting...

The pump has a typical check valve in the output port to stop backflow of fuel back into the tank and the injectors obviously have solenoids to turn on and turn off the fuel flow and keep the fuel supply at the ready on demand from the PCM...

Typical leakdown issues would be either a defective injector bleeding through the solenoid and/or a defective pump check valve in the pump itself...In the years that I have worked with the Ford returnless systems in converted Rangers and other vehicles using the Ford system I have only had to replace a fuel pressure regulator and that was when rust from the fuel tank caused the bladder to stick open and bypass the majority of the fuel volume back to the tank instead of supplying the fuel rail...

 

[Afboy143]

Good stuff Ranger7ltr! I hate to bring you to another thread but I have started a problem thread here

http://www.explorerforum.com/forums/showthread.php?p=2475100#post2475100

It seems to get a lot of views and I am wondering if a lot of people are having this problem. Basically the truck feels like it lacks power, MPG went wayy down, the truck can sputter or feel week while cruising, get up and go power way down, and the biggest thing I notice is while i am reversing, I put the truck in drive and the truck wants to stall out. it has a few times but now I apply a bit of gas and all is good.

I've replaced my plugs and o2 sensor on the driver side that said failed (per DTC).

 

[ranger7ltr]

This is from my POV...

Since our vehicles have metal fuel tanks and a lot of these vehicles have sat for extended periods with fuel in them rust is one of the many problems that comes to mind...

My truck sat for 2.5 years with a half tank of something you could call fuel in it but it would start to restrict the fuel filter within days of changing it...

If the fuel filter has rusty/dirty looking fuel in the inlet side when you change it, the tank is the problem here... When I started driving my Explorer, I thought the truck had gotten a watered load of fuel... The engine would not accelerate briskly, if I feathered the throttle I could get to 60- 70 mph but I couldn't speed up quickly; even the cruise control would put too much demand on the engine to keep up with a set speed...If I tried to spped up moderately quickly and didn't back off the throttle, the engine would sputter and eventually die if I held the throttle...I installed my fuel pressure gauge to monitor the fuel pressure and, to my amazement, watched as the pressure would decrease and then increase if I backed off the throttle...Oh and I would get the P30xx codes intermittently, letting me know that I was dropping fuel volume to the engine...

Of course I changed fuel filters; hell, I should have bought stock in the company...I couldn't go more than 2-3 months without changing a filter if I wanted to drive the truck at all and keep up with traffic...

This is what my filter would drain out the inlet side...And this is right before my 2nd fuel pump died...The "filter" on the pump is not there to actually filter small particulate but to keep out the big chunks...All of the rusty crap came through the fuel pump strainer, the fuel pump, and the fuel line supplying the inlet side of the filter... Fortunately the filter kept the lions' share of this mess inside the filter but it did cause a restriction that led to lousy driveability...And changing plugs and stuff helped to improve the performance some but it would drop off quickly...

My final solution was to buy a new tank and replace the pump since the new tanks arrival just happened when the pump decided to not run anymore; And this pump was 4 months old and brand new...BTW I am still using the same fuel pressure regulator I replaced from another sending unit last year... The original one would eventually leak fuel back into the tank at any pressure above 20 psi...

 

[Afboy143]

hmm I never thought of that! I will tell you that my truck has been my DD for the last 5 years so it hasnt sat longer than 3 days. I plan on changing the fuel filter and performing various tests in 2000hotrod's signature. Any thing else you can think of changing? Im trying to document and keep a log in my thread I posted earlier to hopefully help people in the future

 

[Joe Dirt]

Ok guys, I'm trying to diagnose this issue. Cold in the morning- starts fine. Drive, shut off truck, start up within 5 minutes- fires right up. Wait 1/2 hour+ and you have to crank 5-10 seconds to eventually start. Cycling the key 5-10 times does nothing to remedy. Fuel filter is new, no change in symptom.

I wrestled with starting a new thread, but figured I'd make a video of the test procedure as outlined above so eloquently, and post it here...

Thoughts? If you think it should be it's own thread, let me know and I'll edit this one to just be the video and link to it...

[Youtube]http://www.youtube.com/watch?v=s3U3SPGi6yM[/media]

I'm thinking weak fuel pump, but if it's a regulator I don't want to just do the pump as they're not cheap...

 

[2000StreetRod]

Increasing pressure with ignition off

The only thing abnormal thing I noticed is the fuel pressure gradually increases after the ignition is switched to off. I guess that could be attributed to the gradual decrease in vacuum causing the FPR to increase the fuel pressure.

If you had a weak fuel pump I would think the fuel pressure would drop when you "goosed" the engine. Instead, the fuel pressure increased as it should since the vacuum momentarily decreased. If your pump was weak I would think you would have low fuel pressure when cold starting. I don't know the typical fuel pressure numbers for your year and engine but to me I don't think you have a fuel pressure problem.

I doubt your ECT sensor is bad since you don't have an immediate restart problem.

I assume that you have no DTCs. I can't think of something that would take 10 or more minutes to affect engine start.

 

[Joe Dirt]

Correct- I have no DTC codes at all. It's a frustrating problem, as my starter is now making noises on the last few turns, and I don't want to kill that too...

When I went back out to the truck after an hour or so, I saw this on the gauge...

Now I didn't see any fuel leaking when I checked at the start, and didn't see any there, but I know it wouldn't take much of a gap over an hour to drop the pressure.

Also- that was the second time I hooked up the gauge. (when I ran the video) I tested it about an hour earlier, and when I cycled the key (and the relay) a few times, the pressure gauge followed this path:

1st cycle: 40psi drop to 24psi
2nd cycle: 40psi drop to 32psi
3rd cycle: 40psi drop to 36psi

Start truck (took 7-8 seconds of turning over to start)

I'm at a loss on this one. The truck runs "rough" just a touch for about 1 to 1-1/2 seconds after it starts when I crank the long times, and once running, runs awesome.

Could the regulator have anything to do with it? Could it be flooding the engine somehow when it's warm?

 

[2000StreetRod]

Pressure bleeding down

. . .
When I went back out to the truck after an hour or so, I saw this on the gauge . . . (almost 0 psi) . . .
Now I didn't see any fuel leaking when I checked at the start, and didn't see any there, but I know it wouldn't take much of a gap over an hour to drop the pressure.

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.

Also- that was the second time I hooked up the gauge. (when I ran the video) I tested it about an hour earlier, and when I cycled the key (and the relay) a few times, the pressure gauge followed this path:

1st cycle: 40psi drop to 24psi
2nd cycle: 40psi drop to 32psi
3rd cycle: 40psi drop to 36psi

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.

Start truck (took 7-8 seconds of turning over to start)

I'm at a loss on this one. The truck runs "rough" just a touch for about 1 to 1-1/2 seconds after it starts when I crank the long times, and once running, runs awesome.

Could the regulator have anything to do with it? Could it be flooding the engine somehow when it's warm?

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.

 

[Joe Dirt]

Thanks Dale,

I'll have to try the crankshaft position sensor tip. The injectors are stock, don't think anything has ever been changed/removed. I have run a few bottles of Chevron Techron (my favorite also) since I bought the truck a few months back with no change in performance.

I assume the EGR is working ok with no DTC's, but I'll have to check that out too...

Back to work...

 

[Afboy143]

Hey Joe- im curious- did you solve the problem? If so, what did you do to resolve it?

 

[Afboy143]

So either I feel like an idiot, or my pressure is just that bad

I got some time today to hook up the testing kit. I plugged it up to the test port and got rid of the pressure and as you can see in the last pic, that's how much fuel was dumped. I then put the guage on the end and turned the key to the ON position. The gauge didn't move.... I then started the truck....gauge didn't move. I then revved the truck....still didnt move.

I checked for leaks at the guage... none. Took the gauge off and reset it...nothing. Is my pressure just that bad or is my gauge defective? my truck starts right up and revs as necessary... I just have horrible power and gas mileage. Oh yeah- I pressed the test port in with a screw driver and it shot fuel all over so I know there's pressure there

 

[2000StreetRod]

Schrader valve

Some members have had problems with their fuel gauge connection not depressing the Schrader valve stem enough to open. You might try unscrewing the stem some or entirely just for the test.

 

[gear_grinder]

joedirt, i would almost guess leaky fuel injectors or regulator. A poor pump usualy wont reach operating presure (or very slowly). does it take 7-8sec of cranking to get it started after it sits overnight?

 

[Joe Dirt]

No- after sitting overnight it starts right up. If I run it and get it warm, then start it up after a few minutes it's great. If I let it warm up, stop at the store for 45+ minutes and come out, that's when it takes 5-8 seconds to start. It only does it after warming up then being off anywhere from 45 minutes to 3 hours. Other than that it's stellar.

I'm going to put in a crank sensor and see what it does, becasue there is a lot of gas smell right after startup, I think it's dumping fuel even when warm, and effectively flooding it out with the readings coming from the CKP to the PCM.

 

[airfabtech]

I have the exact problem you've described. 2000 XLT 4.0 OHV. Starts great cold. Starts great hot if started within a few minutes of turning it off. Let it sit 30 min. - 1 hr and 30 min when hot and it cranks over and over and over. Even to the point of running the battery too low to start on three occasions. It also seems worse on really hot days. When it does finally start in this condition it runs rough at first then smooths out in 3-5 seconds. I have noticed that with a fuel guage attached there seems to be a lot of air coming from the shrader valve when it is hot. Is there a poss. of a vapor lock condition here? Problem is my system is returnless...??? Hayes manual says to check the fuel return line for blockage but I believe that is only for pre-99 models?