Hi folks,
1993 4 cyl 5 speed 2wd.
been trying to clear up two problems that I thought were related, but now I think they never were.
I have a semi-regular CEL code 172 (Engine bank 1 running lean). I think the code usually doesn't show up until the engine is warm, but it doesn't always show up right when the engine warms up.
I also had a coolant leak and thought they might be related. I fixed the coolant leak (bent hose clamp) but I'm still getting the CEL.
Months ago, I had an issue where the idle would stick high. Someone recommended that the IAC was the problem. I took it off and cleaned it, and that fixed the idle problem, but not the CEL.
I had a bad coil pack that I replaced which seemed to improve a low power issue, but I still feel like I'm short on power, and I think the fuel mileage is lower than it used to be.
Sometimes when the engine is cold (it doesn't get very cold where I live) I have acceleration issues - bucking when taking off from stop. It clears up when the engine warms up.
I have cleaned the MAF and the throttle body, and I'm getting good fuel pressure.
Whats the next move to try and diagnose the CEL? My AC compressor failed last summer, and I'd really like to fix the AC before it gets any hotter, but I'd like to get the engine issue fixed before I do that.

Any help is much appreciated,
Duncan

 

I see you have 62 reads but no replies, so I'll see if I can get things started. Have a read here on the OBD-1 172 code. A Lean condition can be caused by a number of things from a vacuum leak to a fuel pressure, or delivery volume problem from a wimpy fuel pump, or clogged fuel filter, to an acting out fuel rail mounted pressure regulator, to dirty fuel injectors, to a old tuckered out & slow switching O2 sensor, to an exhaust leak ahead of the O2 sensor, to, well you get the idea, as you've cleaned the MAF sensor & throttle body, checked fuel pressure but not delivery rate over time???? Rate should be something like 1/2 pt. / 15 seconds pump run time. Also post up the fuel pressure Numbers you measured with the pressure regulator vacuum line dis-connected & connected.

Use, borrow, or come by a scan tool like the Actron CP9145 or other brand with the Ford OBD-1 DLC hook up that can scan a OBD-1 system & have it take a look at fuel trim & O2 sensor switching range & speed & post the findings.
If you can't come by a scan tool, then hook up your vacuum gauge & scroll down here EDIT, add link, http://www.secondchancegarage.com/public/186.cfm, to have a look at the various test scenarios to see if any of them can help give a clue. Be sure Adobe Flash Player is on, so the test scenarios show & activate
If a vacuum leak seems to be the cause, rig a smoke test using a Swishers Sweet cigar & blow its smoke into a vacuum line to look & sniff for a vacuum leak from a dry rotted vacuum line or dried out gasket or loose fastener, or a faulty vacuum operated component.
Some beginning thoughts for consideration, let us know what you find.

 

Thanks so much for the advice. I haven't been able to work on the truck for a while but today did some more testing.
I picked up a vacuum gauge, thinking that was the issue, but I got a steady 20 inches. It reacted as expected when bumping the throttle.
I got a fuel pressure gauge to re-test and it seems I'm getting low numbers now. I can't remember my numbers last I checked, but here's whats going on now:
First Test: 25 psi up to 30 if I on/off the key. 25 while running and no change when pulling vacuum line from regulator.
Here's where it get's weird: Now when I test again, I can barely get 10psi running or not. no change when pulling the vac line. (There is vac coming from regulator line I can hear it.) Strange that it seems to run still with such low numbers and I was suspecting my gauge was faulty, but I verified it with a bike pump.
The fuel filter is only 4 years old, but due to the pressure decreasing after the pump runs for a while, I'm thinking the pump is the culprit. Would you agree?
What is the best method to test delivery rate? Or should I go ahead and replace it?
Thanks for your help,
Duncan

 

Ok, good trouble shooting finds & feedback. So, lets think about this some more. 25psi fuel pressure is on the Low Limit side. !0 psi is Way low & out of spec. Question is, what's causing the variation???

Make sure the pump B+ voltage feed, all the way from the under hood fuel pump power relay, through the in cabin inertia switch, to the fuel pump electrical connector atop the tank, is ok,
No under load voltage drop when the pump is running & the fuel pressure measures low. Easiest place to get at the pump wiring for a under load voltage drop test that'll test most of the wiring run the fuel pump power relay electrical contacts & the inertia switch wiring, electrical connector contacts & the inertia switch Internal contacts, is at the in cabin fuel pump inertia cut off switch electrical connector. Check on Both sides of the inertia switch for under load voltage drop when the pump is running & fuel pressure is reading low. If the inertia switch voltage drop test looks ok, so your fairly certain the pump isn't seeing a voltage drop when its running & fuel pressure is low, use you multimeter to perform a inline current draw test, to see if the fuel pump is intermittently acting out & drawing too much current, so look to a large fuel pump current draw change, when fuel pressure is low.

If all that checks out ok, then put the fuel rail mounted fuel pressure regulator on the suspect list. It too is easy to get at for replacement & testing.
When fuel pressure is low & you have the pressure regulator vacuum line Off, do you see, or smell raw fuel at the vacuum line port, or in the vacuum line, as it would suggest the pressure regulator diaphragm has a vacuum leak problem, so replace the fuel pressure regulator.

If your tests can't confirm the regulator is a problem but you still suspect it, Murphy's Law may be messing with you & maybe you have more than one problem, so go ahead & replace the fuel pressure regulator first, as its way less expensive than first tossing a replacement fuel pump at the problem.

More thoughts for consideration, let us know how the trouble shoot goes.

 

Woops, I forgot to answer your question about fuel pump Volume testing. On your OBD-1 system, the under hood DLC, also has a separate wire that when grounded will cause the fuel pump to run, so you could use that to check for delivery rate over time after you satisfy yourself the pressure regulator is ok & the voltage drop to the pump checks out ok.

 

Thanks for the info - that's super helpful. I ran the fuel pressure test again after it sat for a while and here's how it went:
first prime: less than 10 psi.
second prime: ~20 psi
3rd prime: 30 psi
4th prime: just over 30 and it topped out.
Started it - dropped to 25.
Pulled vac line from regulator and pressure went up to just over 30.
Slowly dropped but I kept getting a 5 or so psi spike when pulling the vac line.
I realized I had a leak in my gauge connector so I fixed that. After reconnecting - I could only prime up to 10psi. I could hear the pump kick on every time I primed but it wouldn't pass 10. It would hold 10 steady. After starting - it stayed at 10. No change with or without vac line. After turning off it stayed at ten. Hard to sniff test the regulator because everything smells like gas.

Unfortunately, I'm not at home so I don't have a multimeter available. I could buy a cheap one, but I'm thinking it might be the better bet to swap the regulator. Or maybe I could get a loan a tool from auto zone. It's probably worth it to just get the regulator if I'm going to the parts store anyway.
How do I reach these dang screws, though? The heads are on the under side of the flange that the regulator attaches to - unlike the pic in my Haynes manual. Here's a pic of mine:

3 Allen head screws - hard to reach.
Do I need to pull the upper intake and the fuel rail?
Thanks again for the advice,
Duncan

 

I see what looks like damage to the vacuum line in the upper right of your photo????

 

Ah yeah, it does look like that in the photo but I think it's just gunk:


End of the line sticks to my finger pretty well when engine is running.

 

Your picture doesn't look like my 94 Taurus fuel pressure regulator, which was up top on the fuel rail.

 

Also make sure the return line from the FPR to the tank is clear, not kinked, or being pinched closed,

 

Seeing as how you like to turn your own wrenches, you might find this site's index of trouble shooting your OBD-1 Ranger 4banger helpful. https://troubleshootmyvehicle.com/fo...-of-articles-1

 

Thanks for the info. I've used that site before to troubleshoot an F250 I had a few years ago. Very helpful - thanks for reminding me!
Interesting update:
I placed an order for a regulator online for in store pickup, and went to see if I could access the screws with the tools I have in case I needed to buy something while I was there. I noticed one of the three screws was loose so I tightened it up and went to the store about 20 miles away. No CEL!
I re-did the pressure test and got:
~10psi on first prime
~20 psi on second prime
~30 psi on third and it held there
Started and it dropped slightly, but held steady at 30.
No change when I pull the vac hose from the regulator. Does this mean it's not working as it should? Should I go ahead and install the one I just bought?
No CEL is great, but I'm thinking I should have higher pressure when priming? Perhaps this could improve power/fuel mileage?
I guess ultimately my pressure while idling, 30psi, is in spec so perhaps it's fine.
Thanks again for the advice! Glad to be making progress!
Duncan

 

If the battery under load B+ voltage is ok & the wiring & connections To the fuel pump check out for under load voltage drop as outlined in earlier posts, then A sign that the fuel pump is getting tired is having to cycle the ignition switch several times to have the fuel pump turn on-off a few times to build fuel pressure. SO, yes, right now the pump also belongs on the suspect list, as does it's under hood fuel rail fuel pressure regulator.

If you haven't checked it yet, also put the fuel return line from the pressure regulator back to the fuel tank on the suspect list too, as noted in my last post..
Try blowing through the return line with the gas cap removed. If its fairly easy to do, then the return line isn't likely seriously clogged, kinked, or pinched along its path. Be sure to replace the fuel cap after the blow down test.

My 94 Taurus fuel pressure typically runs between 29-31 psi at idle. My manual has the fuel pressure range with the vacuum line Disconnected, as 35-45 psi. So, since yours doesn't change with the vacuum line disconnected, both the regulator & pump are on the suspect list.

 

Okay, voltage looked good at the relay box and both sides of the inertia switch. My new (very cheap) multimeter is only rated for 5 amps and the fuse isn't replaceable so I'm nervous to test current.
I put the new regulator on since I already had it and I don't see any changes. Sometimes I get 25psi, sometimes 20, never any change when the vac line is removed.
I can't get to connectors to blow through the fuel lines. They connect to the fuel rail at the back and between 2 lower intake ports. Now I'm realizing I should've done it when the regulator was off.
I can pull it again to check them. It's not the easiest but I cleaned the screws up so it's not too bad. I unbolted the AC compressor and tied it forward and that gave me enough room. I'm thinking it's the fuel pump due to the need to cycle multiple times.
It seems to be running a bit better, and no CEL, but I imagine mileage is suffering a bit and who knows when the pump will decide to give up the ghost. It's not exactly the easiest part to replace and I'd hate to attempt it roadside somewhere.
I'll check the lines in the morning and if they look good I'll pickup a pump. Should I be able to blow through both, or only the return? Upon visual inspection, there aren't any obvious kinks.
I'll have to decide whether to drop the tank or pull the bed off to replace the pump. I guess dropping the tank means I can clean it out?
Thanks so much for your help,
Duncan

 

OK, more good trouble shooting feedback. Seeing as how the voltage drop tests looked ok, I don't think a excessive current draw is the problem of the wimpy fuel pressure readings, sounds like the fuel pump is just plain tired....no Tard, you know, plum wore out, sorta like I felt yesterday after mowing & trimming in 89 deg heat!!!! lol

Do the blow down test on the Return line only.

On the fuel pump replacement, those that have done it say its easier to disconnect the fuel filler hose & rear tail light connector & remove the tailgate to make the bed a little lighter. Then remove the bed bolts & set the bed back on the rear tires & some saw horses & the fuel pump & wiring are right there & easy to get at.

While your there, you might check the fuel pump electrical connector & pump contacts for corrosion & snugness of fit, as a last electrical check, before installing the new pump. Sounds like your drill down trouble shoot is about to come to an end. OH, be sure to check fuel pressure on the New pump Before putting the bed back on, so Murphy's Law doesn't get a chance to mess with you. Just because the pump is new, doesn't automatically mean its good, make it prove itself before reinstalling the bed, so if its bad, its easy to get at for replacement.

More thoughts for consideration, let us know what you find & how it goes.