After some hassle getting a new fuel pump, I put it in this morning. I also blew through the lines when I had them disconnected so they're clear. I'm glad I pulled the bed back instead of dropping the tank because I had to do a lot of fiddling.
At first test I wasn't getting any pressure. Car wouldn't start. After some fiddling, I got it to start but I was still getting low numbers. 15 to 20psi. No change when pulling regulator vac line. Both pump and regulator are new!
I start tracing things and I notice that while I get 13.5 or so volts to the pump when idling, I get 6 volts while cranking. Is that normal? Either way I'm getting good voltage at idle and when I prime.
I put the old pump in and am getting the same numbers. Then I start getting no pressure at all.
I begin to suspect my gauge, so I borrow one from auto zone. 0 psi. When I push something into the shrader valve a good bit of fuel spews out. I think there is an issue with the gauge properly engaging the schrader valve. I suppose it's replaceable? Or at least I can pull the core? I'm beginning to think I solved my problem by tightening that screw a few days ago, but have been chasing non-existent problems due to the test being inaccurate.
I'm going to keep the new fuel pump in for a bit and see what fuel mileage looks like. I guess I can't really return it anyway unless I can verify it's not giving good pressure. Still no CEL, so I at least have solved that problem.
Thanks for the help! I'll update when I can figure out how to properly test pressure.

 

No 6 volts to the pump when cranking the engine isn't normal. It suggests the battery plates are sulfated & its capacity has dropped & or the B+ battery cable to the under hood power distribution box has a voltage drop problem, or the pump power relay contacts to its plug in are corroded, or loose fitting.

SO, check for battery voltage across the battery Posts when cranking the engine. If the battery plates are ok It shouldn't drop below 9 volts. If the battery is fresh, at full charge & the plates aren't sulfated, voltage across the battery posts probably wont drop below 12 volts when cranking.

If the under load battery voltage across the posts checks out ok, move to the battery Cable connections on both ends of their run, to look for under load voltage drop through them. If your not familiar with voltage drop testing, there is a easy to follow & read link to voltage drop testing in the battery tutorial sticky atop the forum index page here https://www.ford-trucks.com/forums/6...l#post13848327. Under load voltage drop tests can pinpoint hidden out of sight corroded, loose, broken wire strands in electrical cable or wire runs, or their end wire strand contacts. You could turn on the head lights, blower motor on High speed & maybe when ready to measure, push the cigar lighter in to add some more load when your ready to take a reading. Let us know what you find.

 

Ah! I missed your reply!
I was just returning to post that I'm still occasionally getting CEL 127 just less frequently. I'll do the battery tests you suggest and report back. I have in the past had connection issues with my positive terminal battery cable, so perhaps that's part of the issue.
Thanks for the help!

 

Alright, battery looks okay, I think. I'm getting 11.5 volts while cranking at the battery terminals. I'm getting about the same at the relay box when cranking. At the inertia switch, I'm getting 11.5 while cranking. I realized I was previously measuring both wires at the inertia switch connector and getting 6 volts after the pump primed and the relay clicked off. I was measuring incorrectly. I feel like I shouldn't see any voltage on either side of the switch, both leads connected to positive? Either way, when testing between both sides of the switch and the ground screw nearby, I'm getting 11.5 while cranking and about 14 when the engine starts.
I need to figure out how to get an accurate pressure reading. Should I try to replace the Schrader valve? I could pull one from a junkyard, I guess. Or should I get a 4 way tool and pull the core out? I don't think my gauges (I've tried 2) are properly depressing the pin inside the schrader valve on the fuel rail.
Thanks again for your help,
Duncan

 

I reread all the posts & realized I'd missed some important feedback in post #6 above https://www.ford-trucks.com/forums/1...l#post19321975, where you finally were able to measure a fuel pressure Incerase with the vacuum line Disconnected. So at that point the pressure regulator was acting normal & a lot like my 94 Taurus 3.8L pressure regulator behaves & about the same pressure readings too.

On the Schrader valve, fuel pressure gauge line connection / valve stem question, is the pressure gauge your using a Harbor Freight model??? If so, I had some what the same problems with my Harbor Freight fuel pressure gauge when measuring the 94 Taurus fuel pressure during a random stall trouble shoot. I too had to wrap the hose thread fittings with 3 turns of PTFE ribbon dope, to prevent them weeping fuel & on a couple of occasions had problems with the connection to & depression of the Schrader valve on the Taurus fuel rail connection. SO, look inside the pressure gauge hose line fitting & make sure the stem is firmly Centered in the fitting. Same for the vehicle fuel rail Schrader valve stem, make sure its centered & it & the hose mating stem aren't off center, loose or wobbly, so they properly align & Stay that way when the gauge pressure hose is threaded on the fuel rail.

 

Alright, long overdue update:
I removed the core of the schrader valve and put the gauge back on without it to eliminate that variable. Of course I dropped it, so now I have to hunt that part down....
I was using a HF gauge when I was getting 0psi but I got the same results with a AZ rental gauge.
I'm getting 35psi when I prime, and about 20 at idle. At first it looked like I was getting closer to 25 at idle, but testing again gave 20psi. Removing the vac line on the regulator makes little to no increase in pressure.
So still not getting an ideal pressure reading even though the pump and regulator are new and the pump seems to be priming correctly.

I started getting an intermittent no voltage issue - battery voltage is good, and accessories come on and then when I go to start it - click and then no accessories. I traced this to the positive battery terminal connection. While I was testing, the car died at idle once.
When idling, the terminal connectors are reading about 14.6 volts. I finally managed to get the positive terminal clean enough and situated so that it makes a good connection. Perhaps this connection is causing an intermittent voltage drop to the pump?
Occasionally, the idle will drop for a couple of seconds and then recover.

Could all of this be caused by the intermittent positive terminal connection? Should I replace my battery cables? Would this explain the regulator creating no pressure change whether or not it's hooked to vacuum? Possibly because the pressure is too low to start (should be 25-35psi at idle).

Thanks for your help,
Duncan

 

Good trouble shooting feed back & find on the B+ cable anomaly. Which end of the B+ cable has the problem??? Difficult to determine at this point what grief, intermittent or otherwise it's causing, just get it put right, so you don't have it mucking up your trouble shoot results.

Still not clear to me why the fuel pressure is low at idle, but ok before starting the engine, with a new pump & pressure regulator. SO, lets think about it some more, taking into consideration the test results so far. Seeing as how you can measure 35 psi at KOEO, we know the fuel pump can make enough pressure, question is why isn't it able to maintain at least the minimum 25psi at KOER? Seeing as how the fuel pressure regulator is vacuum operated & doesn't seem to react much with the vacuum line Disconnected, hook up your vacuum gauge to the regulator line & see how much vacuum the regulator has to work with. If you have a vacuum line T fitting, add it to the FPR vacuum line connection, so you can leave the vacuum gauge in line to see whats happening with the vacuum line connected to the FPR. Just because the FPR & pump are new, doesn't automatically make them good. I've seen bad new parts right out of the box, so make these new parts prove themselves.

You have a "return" type fuel system, so there is a fuel line that returns unused fuel from the pressure regulator back to the fuel tank & that line needs to be open & unrestricted, just like the fuel line from the tank fuel pump, through the fuel filter & up to the FPR. Any flow restrictions in these lines can muck up fuel delivery Rate over time, so perform & post the numbers of the delivery rate over time from the fuel rail test port with the test gauge pressure bleed off valve & a measured container. The pump should be able to deliver about 1/2pt-per 15 seconds pump run time. With the fuel cap loose, or removed, you should be able to blow air through the fuel return line from the FPR end.
More thoughts for consideration, I think your about to come to a trouble shoot conclusion.

 

Great, thanks for the quick reply.
The connector on top of the battery is sometimes not making a reliable connection. What is the best way to replace it? should I cut the wires and add a generic terminal like this: https://www.autozone.com/batteries-s...E&gclsrc=aw.ds
I'm having trouble finding a cable with connector that looks right. The ones on Rock Auto and AZ don't look like the cable that goes to the starter solenoid is long enough. Perhaps it's just a generic picture.
I'll go test vac at regulator hose and flow rate and report back. What pin in the test connector runs the fuel pump? And do I connect it to the single gray connector like I was checking codes?
I have blown through the fuel lines when I replaced the pump and regulator and both are clear.

 

Okay, I just used a jumper wire under the fuel pump relay for the flow test - I got half a pint in about 5 seconds. I'm getting a steady 20 inches of vac on the regulator, too. Could it be that the new regulator is faulty? Perhaps I should try and return it for replacement even if it is only to rule it out?
Still looking for a B+ cable that looks good.
Thanks again for your help.

 

Ok good feedback. Sounds like the fuel pump is doing its thing, the fuel lines & filter aren't clogged, crimped, or otherwise restricting flow. SO get the B+ battery cable problem put right first, so you know all the vehicle systems are getting reliable under load battery power. Wimpy, or intermittent B+ to the fuel pump, fuel injectors & coil pack sure won't help a fuel pressure, or engine run problem. If the fuel pressure problem doesn't improve with the B+ cable fixed, then suspect a problem with the FPR. After engine shut down, does the fuel pressure hold after you get the KOEO pressure reading? Will the FPR hold 20" of Test vacuum???.

EDIT; Opt for a Real battery cable, with plated copper end connections for the battery distribution box end & Real copper wire strands, not copper coated aluminum, or aluminum strands & make sure the wire Gauge is at least as large as OEM, or just pony up for a OEM cable. If you want to try & fix the old cable, take it to a electric welding shop that makes their own cables & have them make one that'll be as good as, or better than OEM. Don't opt for one of those wire clamp connectors, they don't make a good lasting connection & leave the wire strands exposed to oxidize, corrode & cause more mischief later.

 

Alright after a long search to get a B+ cable setup that I was reasonably satisfied with, I've got it installed and noticed an improvement. I also realized that the valve core in my pressure tester setup had broken down due to fuel contact, so that was giving me faulty FP readings. You'd think they'd use fuel rated components for a fuel pressure tester, but it is Harbor Freight so no big surprise.
When I test, everything looks good - solid 30psi jumps to 40 when vac line on FPR disconnected.
I HAVE had the CEL come on twice since changing the battery cable with the same code, but on my last few trips to work - no light. It came on only after I had been going at highway speeds for a few minutes. I haven't had a chance for a long interstate drive to stress test again.
I don't have a way to monitor fuel pressure while driving unless I remove the hood. I guess I could setup a multimeter at the inertia switch to monitor pump voltage.
I confess: I only replaced the cable terminations with crimped ring terminations and a new marine style battery connector. I did the crimps with the proper tool and used heat shrink, but I guess If I'm still getting problems I'll fully replace. I had trouble finding an already made cable that matched what I have. Everything I've seen listed as a replacement looks different from my setup.
Thanks for all of your advice. I'll update again after further testing.

 

Ok interesting feedback, but I'm not clear on a couple of things that might be worth thinking about some more. Not sure where you've used "heat sink compound", a crimped on battery cable lug connection isn't a place you'd want to use heat sink compound, if that's where it was used???? So don't take the battery cables off the suspect list. Now if you were brushing some silver loaded "Cool Amp" on the battery cable Cleaned & bright battery cable wire strands & brightly cleaned lug, before crimping the lug well where the wire strands go before crimping the lug, I'd be comfortable with doing that, but I'm not comfortable with using heat sink compound on that Electrical connection. We only have 12 volts to work with, so any electrical connection, especially a low voltage, heavy current carrying connection like a vehicle battery B+, or B- cable, needs a good Low resistance connection to do its thing & heat sink compound isn't likely the answer.

What were the trouble code Numbers that came up a couple of times???

Sounds like the fuel pump & pressure regulator are doing their thing.

Keep us posted on how it goes.

 

Just to clarify, I used heat shrink tubing to protect the terminations. I got code 172 again.

 

WOOOPS, old eyes & I looked at that 3 times & read it wrong All three times. A 4th reading I Finally see it says heat "Shrink!!! lol

Anyway back to the cables, make sure the B- cable & its connection to the engine is in good condition too. Both battery cable connections need to be clean, bright & tight. Same for the body to engine connection. The ECM likes to have a good electrical connection to the engine & battery.

Roger on the 172 code. Says the O2 sensor isn't switching, so are these the original O2 sensors???

 

I've had the CEL come on only a couple of times since replacing the battery cable, so there's been an improvement. The negative terminal looks okay, but I might as well replace it too since I have the connector already. I'll check and clean up grounds, as well. If that doesn't do it - are the O2 sensors next? They are likely original - 1993. I'm hoping since symptoms have improved that the issue is still electrical. Hopefully cleaning up the grounds and replacing B- will be the fix.
I suppose the other option is clogged injectors? Is one issue more likely than the other?
I think I've noticed a power increase so that's nice. Not bogging down as much.
Thanks for the advice,
Duncan