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Low fuel pressure?


fletcher969

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Hi folks,

I like to provide as much information as possible (too much for some people), but in all fairness, if you skip to the questions I have at the end of this post, you can probably answer them as-is without context. Either way, I've covered the bases.

Base info:
  • 1998 Ranger XL, 3.0L, regular cab, auto trans, approx 170K miles
  • Replaced fuel pump and fuel filter 2 years/10K miles ago
  • No CEL, No ODB codes, no line breaches, inertia switch isn't tripped, relays and fuses all checked good
  • Pump cycles on each time key is put in On position
  • Truck has always started immediately and with much confidence.

Description:
A few days ago I started my truck started as usual and ran perfectly about 5-10 seconds, but instantaneously it started to stumble very badly for another 10 seconds, then died. All subsequent restart attempts have failed. It still cranks with confidence so long as the battery has juice, and it wants to start after cycling the key several times, but doesn't.

Tried spraying starting fluid into throttle body in short bursts once per second while cranking, and while it did run, it ran roughly with detonation or possible valve clutter. Tried the same with a spray bottle throwing a somewhat fine mist of gasoline, and again, it ran roughly but without the clutter. It's possible in both situations that there wasn't enough fuel getting into the throttle body which would explain the roughness, but it does appear to have spark.

Eventually hooked up a gauge to the rail, and it read zero PSI before, during, and after key cycles to the On position. Being a rental gauge with what appeared to be a possibly-abused Schrader valve, I can't rule out the gauge isn't working properly. Subsequently I decided to cycle the ignition key several times, and simply push on the Schrader valve with a small screwdriver. Fuel only trickled out each time I tried that. Replaced the fuel filter, tried the same thing several times, and the result was a 1/2" high "fountain" of fuel gently coming out of the valve which would last about 1 second.

Questions:
  • When I push the Schrader valve in after cycling the key several times -- and assuming proper pressurization -- shouldn't I expect fuel to spray wildly with much vigor from the valve (i.e. requiring eye protection)? As is it, I could place my face a few inches directly above the rail's Schrader valve, and not worry one iota about getting fuel in my face.
  • Could a broken grounding strap cause a low fuel pressure situation? At one point I noticed a broken frame-to-?? grounding strap located near my fuel filter. I'll replace it regardless, but my truck is 20 miles from here, time is limited, and I'm curious if that should be a priority item as it relates to my fuel pressure, or remain an item to fix once I've got it running?

Thanks!
 


Denisefwd93

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You can't have too many grounds, on engine chassis, electrical system.

Get a proper fuel pressure gauge and check it, no way the know if the pressure is + - otherwise,

Replacement fuel pumps don't seem to last as long as the original I've experienced this in number of vehicles over my lifetime.
Good luck
 

alwaysFlOoReD

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I would suspect the pump is gone.
 

fletcher969

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You can't have too many grounds, on engine chassis, electrical system.

Get a proper fuel pressure gauge and check it, no way the know if the pressure is + - otherwise,

Replacement fuel pumps don't seem to last as long as the original I've experienced this in number of vehicles over my lifetime.
Good luck
The truck is 20 miles from home in a private lot, so getting to/from isn't a trivial task as I have to borrow a vehicle (and I don't want to be a demanding mooch). That said, having gathered as much information as I could at the time with the time and tools I had, I thought I'd see if anyone might confirm that at proper Key-On+Engine Off rail pressure (56-72 PSI?) that the fuel should "blast" out of the Schrader valve. I've checked the internet over and over, and I can't find a single reference (video or written) that indicates what happens when one pushes the rail's Schrader valve when it's under proper pressure. My gut tells me fuel should blast out of the rail's valve in much the same way air would from a tire inflated to 56+ PSI.
 

alwaysFlOoReD

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Yes, it should blast.
 

Denisefwd93

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AAA = still a great deal
 

fletcher969

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Yes, it should blast.
That's what I would expect. Thanks. I think I'll make a trip to my truck, pull the bed back a couple of feet, yank the pump assembly, inspect everything possible, replace that broken grounding strap, and see if by luck I find and/or solve a critical fault. The only decision I have now is whether or not to purchase only the pump and sock, or the whole assembly. I'd rather not have to do this again in another 2 years, or worse, discover this is related to the pressure regulator (which is part of the pump assembly). If there's any silver lining, it's that my truck quit in a private lot, and not on the road somewhere, especially since I'd traveled over 25+ miles of hilly, winding roads with little or no shoulders very shortly before it died.


AAA = still a great deal
I can't necessarily disagree with you. I had AAA when I lived in the Chicago area until a couple of years ago. Considered it a necessity, because getting stranded on the roads up there takes on some urgency given one's vehicle can get towed and impounded pretty quickly ($$$). In the rural world there's less urgency; however, because I currently don't travel much at all, and because there is typically at least one friend with resources who can get a stranded vehicle back home, AAA is arguably an unnecessary expense. As luck would have it, the one buddy who has a trailer with a big enough winch is on vacation until the end of next week, and the trailer is locked away. It's been that kind of year so far.
 

Rearanger

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My gut tells me fuel should blast out of the rail's valve in much the same way air would from a tire inflated to 56+ PSI.
No, compressed air has much more potential and sustained force when pressure is released. Gas (liquid) is non compressible so a little release of pressure will quickly dissipate the force.

Pressure testing of vessels is always done with water, using air could produce catastrophic explosion.

That said I can't say how high the fuel will squirt when the Schrader is pressed, but it should only be for an instant.
 

fletcher969

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No, compressed air has much more potential and sustained force when pressure is released. Gas (liquid) is non compressible so a little release of pressure will quickly dissipate the force.

Pressure testing of vessels is always done with water, using air could produce catastrophic explosion.

That said I can't say how high the fuel will squirt when the Schrader is pressed, but it should only be for an instant.
I didn't mention it, but do know the difference in general regarding the compressibility between fluids and gasses, and I do observe an almost instantaneous dissipation of pressure from the valve as you noted would happen. That said, I would think the initial burst of pressure from my Schrader valve would be more representative of the starting pressure. What I'm observing seems consistent with low pressure, and why I'm looking for some confirmation, particularly from somebody who may have tried it or is willing to do so. :)

Perhaps what I'm currently seeing can best be described using an analogy. Imagine a garden hose without a nozzle on it, pointing up, and filled with water with the water turned off. Now, very quickly turn the water on, then immediately off. One would observe the water billow out versus blasting or shooting out before it immediately dissipates. The effect is similar to water billowing from a spring in the ground if it were to do so for only a moment. In contrast, imagine that hose with a nozzle attached, through which water is allowed to flow full stream, after which the nozzle is closed so everything is pressurized before the water is turned off (the condition would be much like the Schrader valve when the rail is pressurized during Key-On/Engine-Off). Quickly open the nozzle, and one would see an initial "jet" of water before it immediately dissipated. That's what I would expect if my rail was pressurized to 56+ PSI. As it is, I could put my face 1-2" over the rail's Schrader valve, and not worry one bit about getting fuel in my face.

Blab over. :)
 
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Denisefwd93

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Game of chance

"because I currently don't travel much at all, and because there is typically at least one friend with resources who can get a stranded vehicle back home, AAA is arguably an unnecessary expense"

The logic Escapes Me

30+ years driving old cars and now rangers.
AAA is a mandatory expense. imo

I had 4, AAA Flatbed trips for my old car back to my house in one year.

I just find it staggeringly unbelievable
So many people run around vehicles that will break down, and really "think" they can go without some kind of plan or other road service.

And it's not because I'm old I was young once and I had road service then too lol.

But hey, the entertainment value of these kinds of threads; "I need help , i'm stranded/ broke down" ? "priceless".

Certainly, not funny for the person broke down, but it makes for some interesting reading!
 

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That said, I would think the initial burst of pressure from my Schrader valve would be more representative of the starting pressure. What I'm observing seems consistent with low pressure,
Pressure tester that works.
 

fletcher969

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Pressure tester that works.
For all I know the fuel pressure gauge I had did work; however, its built-in Schrader adapter looked worse for wear, and it was reading zero, so it was difficult to tell. That coupled with the notion I have that the fuel exiting the rail seems to have at least 1-2 PSI (purely a guess), and the gauge registered nothing.

I'll rent another gauge from a different place, and see what it reads. If it also reads zero, I'll go with my gut and replace the pump assembly unless I find a different fault that rectifies the problem.

Question:
If I remove the core from my rail's valve, will the pressure gauge (with its built-in Schrader adapter) register pressure, or does it require a Schrader-to-Schrader connection? I only ask, because I'm not sure if the screw-on Schraders are pass-thru or opened mechanically with the other Schrader, and I didn't see any adapter in the kit that would allow for a hose/fuel line style connection.
 

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I believe the gauge needs the center pin of the rail to be there to work. So don't remove the valve expecting the gauge to work.
 

fletcher969

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Game of chance

"because I currently don't travel much at all, and because there is typically at least one friend with resources who can get a stranded vehicle back home, AAA is arguably an unnecessary expense"

The logic Escapes Me

30+ years driving old cars and now rangers.
AAA is a mandatory expense. imo

I had 4, AAA Flatbed trips for my old car back to my house in one year.

I just find it staggeringly unbelievable
So many people run around vehicles that will break down, and really "think" they can go without some kind of plan or other road service.

And it's not because I'm old I was young once and I had road service then too lol.

But hey, the entertainment value of these kinds of threads; "I need help , i'm stranded/ broke down" ? "priceless".

Certainly, not funny for the person broke down, but it makes for some interesting reading!

I wrote that "AAA is arguably an unnecessary expense." In other words, it's debatable, and you debated it. You didn't have to condescend and pass judgment in the process.

I have my reasons why AAA makes less sense for me in my current situation (along with 3/4 of American drivers who don't have AAA), and you have your reasons why it makes perfect sense for you in your situation. Beyond that, if the logic escapes you regarding a community of acquaintances, colleagues, friends, and family, wherein everyone willingly helps others, and some ask for help on rare occasions; and you're entertained by an idea as "dated" as community, then good for you if it benefits you.

As I stated previously, AAA made more sense to me when I lived in the Chicago area where time was much more constrained, consequences of a slower response could be very costly, and logistics were more difficult. In my current environment, it makes far less sense when those considerations are almost non-existent, and whatever other considerations I might have to ponder are trivial in the big scheme of things. While you seem to think there's a correct opinion regarding purchasing AAA services, there's no right or wrong about it, and whatever logic and/or reasons one applies to arrive at either decision regarding one's need for AAA is a personal one.

That said, AAA makes a LOT of sense for anyone willing to continue driving a vehicle that's prone to breaking down 4 times in a single year. I haven't been stranded that many times since I got my license 41 years ago, and I typically drive older vehicles also, and more recently, Rangers. Having an old vehicle that "will break down" in my case is once every 20.5 years. My "community" plan and foregoing AAA seems more than viable to me.
 
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fletcher969

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I believe the gauge needs the center pin of the rail to be there to work. So don't remove the valve expecting the gauge to work.
Thanks. I kind of expected that answer. :)
 

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