Testing a 1997 Ford Ranger 4.0 fuel pump

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  #1  
Old 07-29-15, 10:20 AM
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Testing a 1997 Ford Ranger 4.0 fuel pump

Hello to all and thanks for any help and advice you can provide.

Going nuts trying to clear some OBD codes on this old pickup truck I purchased, used with some 200k miles on it.

Getting three 02 codes for lean condition. P0136, P1131 & P1151.

Checked fuse #20 for 02 sensors and it's OK. Checked for voltage at heaters and their OK. Checked heater resistance and OK.

Changed the plugs last night. Tested the fuel pressure and got 28 - 30 PSI at idle and when giving it the gas. Specs say 35 to 45. Did the test with little gas in the truck. Filled up this morning and will test it again tonight.

Would 30 PSI be enough to give me lean codes?

Would 30 PSI mean I need to change the pump out?

The truck actually starts and runs fine. The only issues are these darn codes that are keeping me from getting the registration renewed. Have just nine days to find the cause : (
 
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  #2  
Old 07-29-15, 06:11 PM
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It may not be the in-tank electric fuel pump. Usually the pumps work or they don't.
It may be the fuel regulator that is attached to the fuel rail.
 
  #3  
Old 07-30-15, 04:59 AM
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Fuel filter been changed?
 
  #4  
Old 07-30-15, 05:37 AM
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Yes, the filter is new as of June this year.

Tested again last night with a full tank. Still steady at 30 PSI when running but got up to 36 PSI doing the three key turns (power on cycles) I was told to try.

Is there a way to check the regulator or just replace it?

Still, my question is not answered. Will running at 30 PSI give me lean codes on both banks?
 
  #5  
Old 07-30-15, 07:17 AM
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30psi sounds a tad low but on a '97 I would suspect a vacuum leak is causing your lean condition. Cracked hose, split in PCV elbow, intake gasket. If you clear the codes do they return immediately, or after driving a while?

I've had a run of bad luck with the last few used cars I've bought and all have had lean mixture & rough idle with OBD diagnostics showing extreme fuel trim values trying to compensate. On my 2003 car I had to replace 8 intake runner gaskets (individual on that motor), the rubber accordion boot between the intake and throttle body had a 2" rip hidden in the bottom, and a ripped rubber PCV elbow invisible behind brackets. Runs like new now.
 
  #6  
Old 07-30-15, 07:28 AM
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Hey thanks for the reply.

The codes come back in less than 10 miles if I stop the truck and restart. Seems that act of restarting is enough to trigger the codes again no matter the miles.

This vacuum thing is hard to trace. Do you think making up a DIY smoker is the way to go on this? Feed it in via the air intake after the filter?

I see no obvious cracks. The PVC was replaced due to it being a tad loose in the intake and that hose was checked, Even put a hose clamp on it.

Tried spraying card cleaner all around the intake last night and no changes in RPM's at all.

Here are two pics from my Actron code reader. Can you tell anything from this?

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  #7  
Old 07-30-15, 07:41 AM
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Have you disconnected the vacuum hose from the regulator while testing? (see link) What does the fuel pressure do after you shut the truck off and let it sit. From what I recall, it should maintain it's pressure for about 5 min and should not drop by more than a few pounds.

The pressure on my Ford F150 is around 30 lb at idle, so IMO thats normal.

I fought a vacuum leak on mine for a LOOOONG time. The thing for me that confirmed it was a vacuum leak was the O2 sensor readings on my OBDII scanner. Mine has the ability to show "live data" and I could see that my O2 sensors were flat line at idle, when they should be oscilating from high voltage to low voltage, and back again, like a sine wave. On the highway they acted more normal... but at idle they were flat. Additionally, my fuel trim was always showing a very high + %, which was the computer trying to feed the engine more fuel to compensate for the extra air coming from the vacuum leak.

On mine, I had to replace the isolator bolts on the intake plenum and also I replaced all the intake and carb gaskets while I was at it. When I started it up, all the vacuum leak problems were gone... O2 worked normally and fuel trim was closer to 0.

Also ignore data from your 2nd O2 sensor... it's beyond the CC, the one that matters is the data from the first one in line from the engine. Bank 1 sensor 1 and Bank 2 Sensor 1.
 
  #8  
Old 07-30-15, 07:51 AM
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With three key-on's the pressure gores up to 36 psi and stays there. With engine running at idle it drops to 30 psi.

As I recall, when I turn the truck off the pressure stays at 30 or maybe goes a tad higher. Did not time it for 5 minutes.

Did not pull the vacuum hose. I can try that tonight. I assume it should to up if I do, correct?

If yours stays at 30 and you have an F150... kind of close to my Ranger... and you have no O2 codes I do not think this is a fuel pressure thing.

My scanner is the Actron CP9575 with live data but, frankly, I do not know what I'm looking at. See the pics I posted. These was taken at idle.

How did you find the leak? Smoke test??
 
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Old 07-30-15, 08:04 AM
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If you have the ability to put the thing on live data and take it for a test drive, do that. Watch your front O2 sensors (O2S11 and O2S21). Ignore the rear data (O2s12 and O2s22) As you drive, the voltage should be going from low (around .1 or .2 to high around .6 or .7) and they should average around .4. The 02 is a good indicator of how much oxygen is in your exhaust. Lean means there is too much oxygen (most often from a vacuum leak that is letting air into the engine) in the cylinders and exhaust.

If it acts normally while going down the road... going from low to high, low to high... but when you pull up to a stop sign... the voltage says low... and quits oscillating... well, that's just what mine did. My Fuel trim % would also be low at highway speeds but if I came to a stop sign, it would rocket up to like +33%. Both these things together indicated a vacuum leak.

So I don't know if that helps you but I would watch your live data and your fuel trim (FTRM). I don't know why it would be -100. Fuel trim is also Bank 1 and Bank 2, to represent the 2 sides of your V6 engine.

Just because you get an 02 code it doesn't mean the o2 sensor itself is bad or needs to be replaced. It is just telling you something about the engine, which is what it's supposed to do. If it seems unresponsive- low voltage for example, that also doesn't mean it is bad. It could be telling you exactly what it is sensing.
 
  #10  
Old 07-30-15, 08:14 AM
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OK. Will try driving with the scanner connected and report back tomorrow.

Took a look at the gasket kit. Looks like there are around a dozen of various sizes and shapes. Would I need to replace all of those? Not a small task it would appear.
 
  #11  
Old 07-30-15, 08:21 AM
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Well don't go buying any parts yet. *If* its a vacuum leak it could be coming from any number of sources, most of them hard to find. Take it one step at a time and resist the urge to just blindly buy/replace parts.

It could even be an exhaust leak... at/after the exhaust manifold but before the O2 sensor. The P0136 looks to be a code having to do with the 2nd O2 sensor so I would ignore it. It doesn't affect the engine performance at all.
 
  #12  
Old 07-30-15, 08:39 AM
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Has to be a better way to trace a vacuum leak.

Lots of videos on Youtube of guys using the smoker technique. Probably worth a try... after I get those readings.

As to P0136. My only concern is they say you start with the lowest # code and work your way up. Sometimes clearing the first code takes care of (some of) the others.

I had that happen with some other codes I had on this lemon. Cleared one and the other went away with it.

I'm not concerned as much about performance as much as getting passed emissions and that means zero codes. I have until next Friday to pass on this temp plate.

BTW:

Here is a way to find the vacuum leak. The easiest one I've seen.

https://www.youtube.com/watch?v=zMok2y05jNE

Another video has a guy using propane and a hose. Says it's actually safer than using carb spray but do either when the vehicle is cold.

Found this reply to a question about "fixing" a hole in an intake gasket. Worth a try if I find a hole.

http://www.saturnfans.com/forums/sho...71&postcount=6
 

Last edited by outdoormike; 07-30-15 at 09:20 AM.
  #13  
Old 07-30-15, 09:14 AM
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Like I said, the 2nd O2 sensor has nothing to do with the other codes and is not likely an issue. It's past the catalytic converter. Its the ones before the CC that affect the rest of the engine adjustments. But if you have to pass an inspection, that's different.

Number one... check your exhaust system for leaks, it's probably the most likely reason your O2's would throw a code. This may not be engine related at all. Could be a rusty exhaust pipe.
 
  #14  
Old 07-30-15, 09:32 AM
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I have no muffler on this truck. There was none when I got it. It was hacked off after the cat. I had a 4' tail pipe installed down and out the side just before the rear wheel thinking I needed that for emissions. Come to find out they do not sniff the pipe when you have OBD2.

The muffler place assured me I did not need a muffler for emissions reasons and now I wonder if this has anything to do with these codes?
 
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Old 07-30-15, 10:23 AM
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The part of the exhaust pipe that would cause an issue is anything in FRONT of the o2 sensors. So inspect the exhaust all the way from the exhaust manifold to the last O2 sensor. Keep in mind that any leak at the exhaust manifold gasket or any joint could allow fresh air into the system, which would make the O2 send the lean code.

All this talk is pointless until you actually do the test drive with the live data and give us more to go on.
 
  #16  
Old 07-31-15, 07:38 AM
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Took the truck for a ride last night and the wild values I posted in the pictures did not change at all. Today I tried the reader on my 1996 Toyota and the values did update in real time as they should so the reader (Actron CP9575) is working correctly.

I have long suspected this was electrical. Earlier in the week I tested the connector for the O2 sensor after the cat. The voltage and ground was correct as was the heater resistance.

This morning I did the same tests for the passenger side O2 sensor before the cat and got 12 volts (to battery -) on both top pins. This is not correct. The pin at 10:00 on the female side is the ground through the computer. Monitoring the voltage between there and the positive at the 2:00 position should be 12 vdc and it is not. Measuring to chassis/battery ground from there should be close to 0 ohms with the key on and it is not. Therefore, the O2 sensor's heater is not getting a ground and cannot be working correctly.

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I did not check the driver side O2 sensor as I'd need to get under the truck and I had my office duds on but I suspect it will best the same.

When I took the truck out last night I got the P1131 and P1151 codes to show up in less than 2 miles. They may have been there before but I did not look at the screen until then. No way the system had time to compute any kind of emissions data. Has to be the fact that the O2 sensors are not getting to the computer.

I need to locate a good wiring diagram for this truck, on line if I can, and trace back from the 4-pin female connectors of the two O2 and find out where the break is.

If anyone has had to do this or knows if the computer can go out but only partially, which I would kind of doubt, let me know.
 

Last edited by outdoormike; 07-31-15 at 08:15 AM.
  #17  
Old 07-31-15, 08:26 AM
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Yeah. Well, that would explain the wild numbers. I am no mechanic, but I went through this myself. One of the problems with your wild readings is the fuel system status. It is listed on your scanner as "open 2". Generally speaking, CL (closed loop) is what you want to see. When the PCM is operating on CL, it is using the data from the O2 sensors to help it control the amount of fuel being delivered. So the fact that its on OL (open loop) seems to say there is a problem with the 02 sensors turning on.

So that is something else to watch on live data. My truck will start out OL (open loop) for maybe 15 seconds after I start it. Once the O2 sensors heat up, they should send the signal to change to CL. Under heavy acceleration, it might change to OL-Drive

So it's "possible" that all you need to do is change the O2 sensors. On the other hand, if it is an electrical problem TO the sensors, then you would need to track down the reason for that (bad PCM?)

Here is a link to some informative material on open/closed loop and the O2 sensors.

And a link to understanding scan data.

And a link to troubleshooting your O2 sensors electrically. (I know the model and code isn't exactly the same but the info is good)
 
  #18  
Old 07-31-15, 08:39 AM
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The sensors are probably not bad. The connection TO THEM is the issue. I have located a good diagram off the web and will use this to track down those connections tonight. Hoping it is not the PCM but they do not seem to be that expensive to buy. Around $150 for a new one.

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Once I get this sorted out I think all will be well with the scanner data. Until those sensors are working again nothing else I do will get me passed emissions and that's all I care about right now.

Question: Looking on the Autozone site there are tons of these listed for my 1997 Ranger 4.0 all with the same brand. What's the deal? How hard are these to install, calibrate and set up?

http://www.autozone.com/engine-manag...mString=search
 
  #19  
Old 07-31-15, 08:42 AM
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I think you need to double check your multimeter results. Look over that last link I provided, follow it step by step and see where it gets you. Maybe you already did this if you have identified the ground problem.

The test should show (with KOEO key on, engine off) your 10 o clock pin to positive as 12V and should show your 2 o clock pin as 12V to ground. Unless I misunderstood, it seems like you said you got 12V at each, which would be expected.

Did you test the resistance of the sensor itself? (test when cold, not hot)
 
  #20  
Old 07-31-15, 09:00 AM
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Tested between 10:00 and 2:00 with the female (power side) connector and got nothing. If that ground was there at 10:00 (like it was on the sensor after the cat) it should read 12 volts.

The ground is not there.

The heater tested good at 3 ohms.

I have that article you posted. Located it several days ago and that's what I used.

Le's wait for me to check the wiring further now that I have something to work with.
 
  #21  
Old 07-31-15, 09:09 AM
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Yeah if there is no ground at 10:00 there must be an open along that ground line. Did you try the jumper wire?
 
  #22  
Old 07-31-15, 01:09 PM
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When you check for 12v to the sensors..... use a test light from 12v+ line to the switched ground line. I'm pretty certain that the PCM doesn't use relays on those outputs and without a load on them the electronics won't supply the ground. The load of the test light should be enough to trip the circuit.

I think normally an inline breakout box, in the sensor line, is used to check for voltages.
 
  #23  
Old 08-02-15, 02:51 PM
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figure anything out yet, outdoormike?
 
  #24  
Old 08-03-15, 06:18 AM
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Found three other corroded/rusty grounds to the chassis in the engine compartment. Cleaned/burnished them all.

Did a resistance trace, lead-by-lead, of the three O2 sensors back to the connector to the PCM. Found no issues.

Bought the three O2 sensors and replace them all. First thing I noticed was on the scanner that notation for fuel system "open" was now reading as "closed". Good sign I hoped.

All the other O2 indicators still reading as -100 or 0.00 (perhaps the scanner does not like Fords)

Anyway, went for a ride about 30 miles yesterday afternoon. All the I/M tests got an "OK"... even the one for the catalyst which never read as OK. The Actron scanner has a function for state OBD test and it says I'm good to go.

No codes showing up. Plan to take it to emissions station this morning and see what happens.

Wish me luck.
 
  #25  
Old 08-03-15, 07:46 AM
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Passed

On with my life!
 
  #26  
Old 08-03-15, 10:22 AM
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thats great, nice job!
 
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