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Solved Fuel pressure problem.

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Might this be a vapor lock problem?
Vapor lock is virtually nonexistent with efi because the boiling point of gasoline held at 35 psi is quite high. At typical temperatures encountered underhood, bp can range from about 95 degrees f and up, depending on many factors, including blending of the fuel. Actual boiling rarely occurs, but rather begins as small bubble formation which allows compression to occur within the liquid, thereby reducing it's volume. Certain design factors are important. The old Chevy 230 cu. in. six was notorious for vapor locking, for example.
 






^ Same question, what tool is needed to disconnect the PR hose connector from its male mating connector.

I have this picture, it's supposedly the male end that the female end on the PR hose plugs into. Looks like a couple o-rings on it, which was giving me thoughts like if you want to see if fuel pump still runs after initial 2 seconds, you could just disconnect the hose to it, and stick it in a gas can to see if fuel is still flowing while cranking to start the engine. I mean the thought was, if you disconnect this 25 year old connector, it may need a couple new o-rings to seal again.

I got the pic from the following topic on JustAnswer where someone came up with a few coupler adapters to make regular fuel line work with the other pressure regulators.

For some reason I couldn't get that Justanswer page link above to load on latest version of chrome, stopped 10% of the way but an old version of Firefox worked.

View attachment 432925

On a side note, my mother may have COVID, have to care for her, so if I disappear for a long time, I'm probably dead. My immune system has been poor for a while now so who knows....
You take care of yourself, sorry about your mother. Hopefully her symptoms will lessen.

I think the standard quick release fitting tools will disconnect the fittings. Once you get just the right one that is. I have a metal scissor type set, the white set and the multi color plastic set with finger handles. Seems you need all of em at one time or 'nother.
 






@J_C All of your Ford family on this Forum are praying for you and your family.

Hang tough, and glad you are so supportive of your Momma.
 






The Connection removal….

There is a “Quick connect” on the steel braided line, about three feet from the fuel pressure regulator. It looks like an air conditioner connector. There is a steel clip over the top, similar to the fuel tank line and filter retainers. This can be released easily.

I thought the connection was similar to the fuel tank and filter connectors, only larger. I had planned on buying a larger fuel line release tool, but when I sprayed the connection with carb cleaner, then penetrant, cleaned it with a towel and a Q-tip, and started wiggling it around to free it up, it just came apart. I don’t see anything holding it together, except for the steel retainer clip on the outside of the connection.

@ J_C posted a picture of the female end… this is the male end.

2F4A07F1-B9B2-449F-BA6C-CC767FE055C5.jpeg
 






^ Same question, what tool is needed to disconnect the PR hose connector from its male mating connector.

I have this picture, it's supposedly the male end that the female end on the PR hose plugs into. Looks like a couple o-rings on it, which was giving me thoughts like if you want to see if fuel pump still runs after initial 2 seconds, you could just disconnect the hose to it, and stick it in a gas can to see if fuel is still flowing while cranking to start the engine. I mean the thought was, if you disconnect this 25 year old connector, it may need a couple new o-rings to seal again.

I got the pic from the following topic on JustAnswer where someone came up with a few coupler adapters to make regular fuel line work with the other pressure regulators.

For some reason I couldn't get that Justanswer page link above to load on latest version of chrome, stopped 10% of the way but an old version of Firefox worked.

View attachment 432925

On a side note, my mother may have COVID, have to care for her, so if I disappear for a long time, I'm probably dead. My immune system has been poor for a while now so who knows....
Yikes! JC you and your mom are in my prayers now.
 






Ok, the battle continues.

I got my new fuel pressure regulator, and had a hydraulic line company fabricate a steel braided for the unit and the quick disconnect part. Yay. But when I got it all back together, it did not resolve the no-start issue. Rats.

The fuel pump could still be heard, and fuel still gushed out of the fuel return line. And the fuel pressure still dropped to zero within one second of the fuel pump prime.

This got my nerve up to “cork” off the system, deadheading the fuel pump by crimping the return line above the fuel tank. I did this with a pair of paint can opener devices and a pair of vice grips. The deadhead attempt worked, and fuel no longer gushed from the return line after the pump primed.

But the fuel pressure still bled off instantly and immediately after the fuel pump primed!

At this point, I believe it can almost only be fuel injector(s) stuck open. This seems to be the case, even though it is not hydro locked, never belched black smoke, and ran well except for when it didn‘t. (Huh?).

What wisdom does the geniuses of this Forum have?
 






Ok, the battle continues.

I got my new fuel pressure regulator, and had a hydraulic line company fabricate a steel braided for the unit and the quick disconnect part. Yay. But when I got it all back together, it did not resolve the no-start issue. Rats.

The fuel pump could still be heard, and fuel still gushed out of the fuel return line. And the fuel pressure still dropped to zero within one second of the fuel pump prime.

This got my nerve up to “cork” off the system, deadheading the fuel pump by crimping the return line above the fuel tank. I did this with a pair of paint can opener devices and a pair of vice grips. The deadhead attempt worked, and fuel no longer gushed from the return line after the pump primed.

But the fuel pressure still bled off instantly and immediately after the fuel pump primed!

At this point, I believe it can almost only be fuel injector(s) stuck open. This seems to be the case, even though it is not hydro locked, never belched black smoke, and ran well except for when it didn‘t. (Huh?).

What wisdom does the geniuses of this Forum have?
It could be the fuel hose(in the tank) between the fuel pump and the sending unit assembly. If you pinch off the fuel supply line right after the fuel pump shuts off and it holds pressure you will have your answer = hose between fuel pump and sending unit. If it doesnt hold it is the injectors.
 






The fuel has four ways out in a return style system, and five in the returnless type. The FPR can allow too much to pass(low or no pressure at the injectors), the rubber lines at the pump can be split(one on the pre 99's, two in the 99 and newer(the FPR is there with an extra rubber hose)), the pump's check valve, plus the injectors can leak into the engine. That's in a sealed system with no leaking to the outside.

Given the now new pump and what should be a new rubber hose there, it should leave the injectors or FPR. The injectors are very old and high mileage, and the FPR apparently is all new now, it shouldn't be the issue. I'd say it's time to pull the injector rails and see how those six test.
 






I hope it is not my fuel injectors, although they are original. This is my basis for addressing the fuel pressure regulator.

Would you agree with the diagnosis and logic?
Yikes !! No. Not at all. I would check the injectors first.

I did this FPR replacement on my 98 SOHC several years ago when parts were available. But original fuel injectors at this age. Yikes !!
 






I think you can still buy injectors for under $15 apiece on eBay, refurbished and flow matched. I put a set of them(for 302 Explorer) in my 91 302 Lincoln ages ago, the set was about $85 then.
 






THE FIRST PHOTO below shows location of fuel pressure regulator on the return style fuel systems for the 1997/1998 Explorer 4.0 SOHC engine.

THE SECOND PHOTO below shows the OEM fuel pressure regulator removed from the fuel rail. The steel braided line is permanently attached to the OEM fuel pressure regulator. There were no DIY fasteners that could attach the OEM steel braided line to the new fuel pump regulator.

There were some comments on other forums about snipping back the steel braided line, then slipping the flexible inner rubber line over the new regulator hose barb. This connection does seem to be on the low pressure side. But you can see how flimsy and thin the remaining rubber fuel hose loois without the steel braid. I would not use the exposed rubber hose for a connection, even on a lawn mower.

THE THIRD PHOTO below shows the OEM fuel pressure regulator, and the custom braided hose that the hydraulic shop formulated. Looks fantastic, and they tested it up to 100 pounds of pressure. No problems. I did switch the OEM o-ring from the fuel rail port onto the new fuel pressure regulator. The OEM o-ring looked a little tougher, and others reported leakage without this switch.

This work-around allows us to to replace our twenty five year old OEM fuel pressure regulators as needed.

C877ED4F-BC28-488E-B7D2-0FB4D6C321E7.jpeg 175E0135-A5A8-4C8C-A8EE-A3F312D7BEA3.jpeg E3A30D88-6EAB-45C3-ACEF-D1F29C872225.jpeg
 












This was another tough project for me. I have been fighting fuel pump issues for a several years, and have probably changed six fuel pumps on my truck in the past five or six years. At least one fuel pump was defective out of the box… the internal fuel pump check valve was not functioning. Do not buy cheap fuel pumps. The access panel that has saved me from delays, tow bills, and mechanic bills caused by failed fuel pumps, and is shown in the photo below.

Initially on this repair, the truck had little or fuel pressure at the rail. The substitution of the Walbro fuel pump did not resolve this issue, but the Walbro fuel pump was clearly “priming” with the ignition. I was measuring fuel pressure, without a fuel pressure gauge, by checking the shraeder valve at the rail with a small screw driver. There was sometimes pressure, and sometimes no pressure- “on” or “off”. This primitive method was adequate for all of my previous fuel pump replacements. But the lack of a fuel pressure gauge and primitive reading almost surely led to confusion later in this troubleshooting effort.

When I was finished with the fuel pressure regulator project, the system still did not seem to be building fuel pressure consistently. But it was discharging fuel through the fuel return line. Per the suggestions in this thread, I crimped/corked off the soft return fuel line above the tank. I did this with vice grips and a pair of paint can screw drivers, making every effort to protect the fuel line. This did “deadhead” the fuel pump, but did NOT cause any other problems.

But when I was done, I still had no-start. I communicated with @donalds, who gave me several insightful suggestions (1j. next time, get a fuel pressure gauge. The existing fuel pressure is quickly discharged from the fuel rail at the shraeder valve, does not have compression characteristics like tire pressure, and is tough to monitor. (2). The fuel pressure that was currently squirting rapidly from the shraeder valve was probably an indication of adequate pressure at the rail. (3). Re-check fuel pump hose connections and the assembly in the tank. (4). Check crank shaft position sensor, as this would shut down fuel pressure and spark during engine cranking and would contribute to my confusion.

I did all of these things that Donald suggested, and the truck fired to life! The truck seemed alive. Yay.

I followed this wisdom, and many of the suggestions and thoughts in this thread and from this Forum. I am sure that most of the ideas that did not help me here were based on inaccurate information I provided. I was humbled, and grateful for everyone’s help. Part of this final comment is an apology for my lack of mechanical expertise. But I did want to complete this thread with a conclusion, as the threads that vanish into nothing do not seem very helpful.

As always, I want to thank everyone for the help and ideas on this Forum. Without this support, it is almost certain that my truck would have been mashed into a beer can at a salvage yard years ago. Thanks again.

Drive safe and have fun.

62506A53-D294-4537-B667-AD38A2365C88.jpeg
 






Congrats on the final result, and thanks for the full update. I like that storage location for your fuel line disconnect tool, on the tire hoist tool.
 






Glad to hear that Explorer is up and running again! Great job on persisting with it until you got it figured all out.
Some problems we have with our vehicles can really be a pain in the but to figure out.
 






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