5.0 Fuel pressure test gauge?

[leoJr]

Where do I find a pressure gauge that I can connect to test the fuel pressure while running the engine or, better yet, driving it?

This new to us '99 5.0 has a long crank to start that gets longer when it is warmed up. When warmed it slowly stumbles from crank speed to an idle speed.

I've cycled the key to prime the pressure up to 8 times with no improvement.

Fuel filter was opened and looked to be fresh and a new one installed.

Update: I do have a fuel pressure test gauge in transit.

 

[koda2000]

Where do I find a pressure gauge that I can connect to test the fuel pressure while running the engine or, better yet, driving it?

You could borrow one from most auto parts stores (with a deposit). Or you could buy one at an auto parts store, from Amazon, Harbor Freight or eBay. The only consideration as to whether you can drive with it connected would be, is the hose long enough so you can see it with the hood down, which it probably will not be.

 

[leoJr]

I have one on order...should be here next week sometime. Should be long enough to drive with it but not sure how I would route it out from under the hood. I am chasing a long crank issue so driving it will likely not be needed.

 

[ranger7ltr]

I ran my electric fuel pressure gauge to a gauge pod mounted on my A-pillar...I ran the wires from the sensor to the firewall and up to the gauge and the power leads to an ignition source and the light to a powered lead for the lights...

I will attach pics from my V8 Ranger but it is similar to an Explorer...First pic shows an older supply fuel rail with the sensor screwed into it...Second pic is how I mounted the gauges to the A-pillar in the truck...Makes it eay to keep track of the status of the engines conditions while driving...

But how new is your fuel filter???

 

[leoJr]

I ran my electric fuel pressure gauge to a gauge pod mounted on my A-pillar...

I hadn't thought about a gauge and sensor, even if the gauge is temporarily used, this is likely cheaper than some test gauges. Another plus to using a sensor is not having fuel plumbed into the passenger compartment. Double win!

But how new is your fuel filter???

I had really hoped it was nasty and all clogged up. But I opened it up and it was practically brand new. I suspect the previous owner changed it for the same reason I did.

The long crank gets longer when it is warmed up. Slowly stumbles from crank speed to an idle speed.

Thanks ranger7ltr!

 

[imp]

I hadn't thought about a gauge and sensor, even if the gauge is temporarily used, this is likely cheaper than some test gauges. Another plus to using a sensor is not having fuel plumbed into the passenger compartment. Double win!




I had really hoped it was nasty and all clogged up. But I opened it up and it was practically brand new. I suspect the previous owner changed it for the same reason I did.

The long crank gets longer when it is warmed up. Slowly stumbles from crank speed to an idle speed.

Thanks ranger7ltr!

Be careful with sensor-fed gauges. Their accuracy is often poor. When you walk through your Walmart store next time, look at the display of thermometers, usually in Lawn & Garden. Few dozen in a row, reading anywhere from, say, 70`F to 78`F., and they are simpler mechanisms than pressure gauge sensors. Ain't Chinese Industry something?

 

[410Fortune]

any check engine light?
I suggest simply hooking up the fuel pressure test gauge when the truck is hot and has the long crank issue, no need to try and drive around and watch the gauge. If fuel pressure is the cause of your long crank it will be obvious when the long crank is happening.
Your 99 should have 62-68 psi of fuel pressure at the rail

 

[leoJr]

any check engine light?

Yes but, like our others, it comes and goes. I will put a scanner on it to see if there are codes.

Your 99 should have 62-68 psi of fuel pressure at the rail

It took about 6 or so key cycles to get it up to 30 PSI and after it started it stabilized at 35 to 37 PSI. I let it run for a minute or two, then turned it off and it the pressure crept up to about 40 PSI where is stayed for 30 minutes before I disconnected the pressure gauge and came in to type this.

Edited to add: Chilton manual seems to read that 35 PSI is correct for all 4, 6 or 8 cylinder SFI engines. I have ready where there is a 35 PSI rating for '98s and occasionally read that the '99 models need a 65 PSI reading. I have not found conclusive sources for the 65 PSI requirement. I'll keep researching... Also, I guess I should ask for a fuel pump assembly for a 2000 model just to make sure?

 

[ranger7ltr]

Starting in 99MY Ford did not use the return fuel rail back to the tank..The operational fuel pressure for the return fuel rail systems pre-99 model year was 35-43 psi depending on vacuum at the fuel pressure regulator where the 99 through 01 possibly 02 in the Explorer Sport was 62-73 psi...and Ford has the fpr in the tank on the sending unit and no there is no vacuum on the in-tank fpr...

If your 99 shows low fuel pressure at the rail port I would start at the fuel filter and work back to the tank mounted pump and rubber lines there...They can split with age and leak under pressure and the engine runs poorly if at all...

Since you already replaced the fuel filter and it was not clogged up with dirt or rust I would verify that your Ex is a 99 with no return line to the tank...If it has no return line then you have ruled out the fuel filter as a restriction or leakage point and I would examine the lines from the fuel filter back to the tank for kinks or bends...If they are good drop the tank and check the line that connects the pump to the sending unit and finally the sock on the pump and the tank itself for rust...

If the vehicle has a return line your measured fuel pressure is within specification...

But you need to check the pressure with the engine under load...The pressure can show fine at idle but drop under load... That pressure under load will tell whether the pump is good or not or the pump inlet is clear or not...

I don't have a source for these specs anymore but I have used these as guidelines for my Ford vehicles and they have been spot on...

 

[410Fortune]

98 was the first year of returnless fuel on our trucks by 99 they all had them. Only early 98 will still have two fuel lines (return fuel)
All 99-01 Explorers and mountaineers have one fuel line from the tank to the engine, this is returnless fuel


Your fuel rail pressure should be 65 psi

NOT 30 psi

 

[koda2000]

98 was the first year of returnless fuel on our trucks by 99 they all had them. Only early 98 will still have two fuel lines (return fuel)
All 99-01 Explorers and mountaineers have one fuel line from the tank to the engine, this is returnless fuel


Your fuel rail pressure should be 65 psi

NOT 30 psi

I could be mistaken, but I though we recently had this discussion, re when the return v return-less fuel system was first introduced, and someone here said 1999 was the year where early Explorers/Mountaineers may have still had the return-style and later Ford went to the return-less style. Whenever it was, it's easy enough to verify.

 

[410Fortune]

so we have an early 98 here with return style, I know some 98 still had two fuel lines.
98 Rangers were ALL returnless, by 99 so were all explorers

I have NEVER seen a 99 that still had two fuel lines, not OHV, not SOHC, not 5.0
seems by mid 98 they ALL were returnless?
I have only dismantled about 100 of these suckers.....unless something got passed me? (quite possible! Just because 100 explorers have gone through my shop does not mean my memory is perfect!)

 

[leoJr]

Whenever it was, it's easy enough to verify.

Where and I looking for presence or absence of a return line?

Also, I noted that even though I cycled the key until the pressure was about 30psi, while cranking it took a big, momentary dip which was when I presume a bank of injectors fired.

I will put the gauge back on, start it, let the pressure stabilize, turn the engine off and see how long it holds the pressure.

 

[koda2000]

Where and I looking for presence or absence of a return line?

Also, I noted that even though I cycled the key until the pressure was about 30psi, while cranking it took a big, momentary dip which was when I presume a bank of injectors fired.

I will put the gauge back on, start it, let the pressure stabilize, turn the engine off and see how long it holds the pressure.

Look at the top of the fuel tank. If there you see 2 metal lines going into the top of the fuel pump assembly then you have a return-style system. I would think you could also tell by examining your engine compartment. I'm pretty sure your '99 will have a return-less style fuel system. That being the case, you should be seeing around 65 PSI at the fuel rail and not 30 PSI.

 

[1998Exp]

...
I have NEVER seen a 99 that still had two fuel lines, not OHV, not SOHC, not 5.0
seems by mid 98 they ALL were returnless?
I have only dismantled about 100 of these suckers.....unless something got passed me? (quite possible! Just because 100 explorers have gone through my shop does not mean my memory is perfect!)

Mine has a manufacturing date of 8/98. Never had a reason to work on the fuel system so not 100% sure, but I clearly see two braided lines coming to the engine. Odd, because in several other respects, like the absence of an oil cooler, it's more like a 99.

 

[410Fortune]

Wild! Similar to the 98 we have here, two fuel lines, no oil cooler but it was still sold as a 98 model year

 

[imp]

98 was the first year of returnless fuel on our trucks by 99 they all had them. Only early 98 will still have two fuel lines (return fuel)
All 99-01 Explorers and mountaineers have one fuel line from the tank to the engine, this is returnless fuel


Your fuel rail pressure should be 65 psi

NOT 30 psi

A moot point, but might prove important to a "builder": the early returnless fuel system did not control fuel pressure by varying pump speed. Instead, it had a relief valve built into the pump in the tank which "dumped" the excess fuel back into the tank. Pressure was controlled by a vacuum-controlled valve mounted on the rail, which "saw" max pressure as determined by the in-tank relief at all times. This system proved troublesome in comparison to pump-control which Ford was developing in the meantime, and stressed the pump more.

Not sure of introduction year, may have been 2003; my '04 has returnless with pump speed (voltage fed) continuously varied depending on fuel demand. Earlier, a "Fuel Pump Control Module", remotely mounted, controlled pump speed based on inputs from sensors, primarily Fuel Temperature and Pressure Sensor, a new one, mounted on rail. It has both electrical and vacuum hook-ups. This scheme works amazingly well, providing pump longevity of incredible duration. My '04 has it's original pump with 171,000 miles on the vehicle. But, the FPCM went out twice........first replace was H.S. from the factory, lasted a month. Second one at 110,000, still working.

With FPCM not working, my concern was for being stranded: not to worry, PCM lacking it's inputs, simply runs pump at max speed, excess being dumped in tank, engine running very rich. Ford thinks of almost everything!

 

[leoJr]

..but I clearly see two braided lines coming to the engine.

A muddy driveway has kept me from getting under and exploring for one or two fuel lines, but should both visible here?

 

[leoJr]

...but should both visible here?

Nevermind. There are definitely two lines. Strange that the filter is on the smaller line though.

I know that a few years ago when I asked for a regulator for our other '99 I had to buy the whole in tank assembly. I'll look under it tomorrow.

 

[410Fortune]

You have ONE fuel line to the engine = returnless fuel

The other line is the EVAP system, vapor control
The fuel filter is ALWAYS mounted on the fuel feed line
In a return style system there would be three total lines, two fuel and one vapor.

96-98 return fuel, two fuel lines to the engine, 34 psi. the FPR (fuel press reg) is on the fuel rail
99-01 returnless. single line to the engine, 65 psi, FPR is in the tank

On both systems jut the pump and strainer can be replaced
FPR only need to be replaced when they quit regulating pressure properly
USE BOSCH blue or MOTORCRAFT pumps, watch out for fakes on Ebay or Amazon........