Good informative link. However, you should keep in mind that the article talks mostly about Electronic Returnless Fuel Systems, while the Ford Ranger employs a Mechanical Returnless Fuel System. The differences between the two are as follows:

The Ford Mechanical Returnless Fuel System still uses a spring-loaded fuel pressure regulator, only it's mounted in the tank along with the pump and not on the fuel rail (see pic below). Fuel pressure is kept constant at all times.



Ford Electronic Returnless Fuel Systems, on the other hand, do not use a fuel pressure regulator at all. Instead, these system employ a fuel pump driver module (FPDM) which modulates voltage to the fuel pump in order to achieve and maintain proper fuel pressure. (The FPDM receives a duty cycle signal from the PCM, resulting in variable speed fuel pump operation). A Fuel Rail Pressure Sensor and an Engine Fuel Temperature Sensor measure fuel pressure and temperature at the fuel rail. This information is used by the PCM to vary the fuel pressure and avoid fuel system vaporization.

 

Replacing the 02 sensors @ 100K isn't a bad idea. But I doubt the 02 sensors are responsible for the rich codes. Odds are against both sensors "suddenly" failing at the same time. And when 02 sensors do kick the bucket, 99.9% of the time they fail lean.

 

Did you remember to reset the computer after replacing the sensors????

 

Well back to the Ranger. I was able to use a OTC Genisys scanner.

Fuel pulse width 2.6 msec @ idle and 8+ when driving.

I did find a P1705 that I need to check out. (KOER)

 

Don't give up on me.

The O2 sensor switching speed is quick (hard to read) and the range is between .1 and .9 What should the (Fuel Pulse Width) be? Mine is between 2.6 and 2.6 msec at idle. the Short Term FT both banks is close to zero. Remember the Long Term is -25 . I feel this tells me the injectors are not leaking.

When I drive the the Short Term FT is -10 to -19 +/- The Fule Pulse width will increase to above 8 msec and even higher.

QUESTION - What should the MAF show at idle and a full throttle. Mine is about 1.xx at idle and about 30 at close to full throttle.

Thanks

 

Well I thought maybe one of the fuel injector gurus would wade in on your questions, so I'll try to get the ball rolling again.

Did you ever reset the computer????

Good check & feedback on the O2 sensors, sounds like their switching speed is good, so we can set them aside now.

On the MAF sensor, my manual says .2-1.5 volts at idle & that should increase to about 2.0 volts at a rpm that you would turn at 60 mph. I have no idea what it would likely be at WOT, obviously something greater than 2.0 volts!!!!

I'm not sure what the injector pulse width should be, but I'll bet we have a fuel injection system guru that does.

Or if you don't get any replies, maybe try a forum search, or post the question on one of the engine or fuel system forums, bet they would know.

Seems to me I remember someone posting fuel trim tables last year, but I'm not finding any links in my favorites.

 

I have reset the computer.

I do have a question - Does this truck have a MAP sensor? I feel the correct answer is NO

I have found one item I question. The engine calc load is too high at idle. The ironic circumstance is my 97 chrysler is now setting a lean code on the L & R bank. I discovered there is a big difference between the two vehicles engine load at idle. The chrysler is about 2% and the ranger is close to 20% I feel the 20% is too high. A new direction to work to.

Priority is now the chrysler, I had to drive it 90 miles (in the mountians) not knowing the fault. I think I hurt the engine. (running lean)

(Moral of the story - Always keep your scanner at hand)

Thanks

 

More Questions

What determines engine load? MAF and Throttle position and what else? I have 30% at idle and don't feel that's correct.

Replaced MAF after finding (AT TIMES) the output voltage would exceed 6 volts. I felt for sure this would fix the rich problem. It took longer to set rich codes, but it did.

Next step is to
1. Run it with the MAS unhooked and measure fuel pulse width.
2. Verify the correct ECU is installed. dynamite may be a option?

Thanks
Chuck-AZ

 

Yup this vehicle has a MAF sensor, not a MAP sensor.

Now seeing as how you've replaced the MAF sensor, did you remember to reset the computer again, so it can begin to relearn it's fuel trim with the new MAF sensor????

Just how are you measuring/calculating engine load on the Ranger????

 

I did reset the KAM. -- It took 9 miles of driving to set rich codes again.
The scan tool (OTC genisys) is telling me the engine load at idle is 30%

I did post on the V6 forum about the fuel pulse width. No reply.

Thanks for your response!!!!

 

Ok, so the computer has been reset & your getting rich codes after 9 miles of driving, which should have warmed the engine up fully, so that it should be in closed loop operation.

SO, what does the scantool say that the computers engine coolant temperature sensor is telling the computer when the engine should be fully warmed up????

How do the MAF & O2 sensor readings look now????

How about the IAT sensor, whats it telling the compuer about inlet air temp????

How does the speed sensors output to the computer look????

Trying to get a feel for whats going on now, with some of the sensors that the computer uses, to decide what to do about controlling the fuel injectors on duty cycle.

 

I'm beginning to wonder if maybe the previous owner tinkered with the truck somehow.

Just to make sure, your Ranger has the stock air intake system, right?

Or, maybe the previous owner did something stupid like installing one of those garbage IAT resistor "chips" that are nothing but a scam. See:

http://cgi.ebay.com/ebaymotors/POWER...spagenameZWDVW

 

Exactly Joe & I'd add to that, maybe someone has had a tuner hooked up to the computer & messed with it that way too, or maybe installed a chip????

Anyway once he's sure all the computers sensors, that help it decide what to do about fuel trim are ok & within tolerance, then begin to look at the computer itself!!!!

 

OK - I had and opportunity to do some testing today.

Ambient Temp 65 deg RH 28% -- Freeze frame data from scan tool

Veh speed 0 After a warm start
STFT bank 2 -4.7
STFT bank 1 -.20
RPM 709
MAF volts .82
MAF G/S 4.48
LTFT bank 2 -25
LTFT bank 1 -25
Calc eng load 16%
IAT volts 2.8
IAT deg 95 deg
H02S B2 S1 .23
H02S B1 S2 .00
H02S B1 S1 .83
Fuel pulse w B2 3.0
Fuel pulse w B1 3.0
ECT volts .57
ECT deg 198 deg
Throttle pos CT
Throttle pos volts .9

Veh speed 30 Slight up hill
STFT bank 2 -5.2
STFT bank 1 -4.9
RPM 1700
MAF volts 1.82
MAF G/S 19.31
LTFT bank 2 -25
LTFT bank 1 -25
Calc eng load 28%
IAT volts 2.28
IAT deg 79 deg
H02S B2 S1 .41
H02S B1 S2 .07
H02S B1 S1 .16
Fuel pulse w B2 5.3
Fuel pulse w B1 5.5
ECT volts .57
ECT deg 198 deg
Throttle pos PT
Throttle pos volts 1.32

Veh speed 66 Highway with a very slight up hill.
STFT bank 2 -23.1
STFT bank 1 -23.1
RPM 2239
MAF volts 2.41
MAF G/S 36.87
LTFT bank 2 -3.0
LTFT bank 1 -4.0
Calc eng load 41%
IAT volts 2.98
IAT deg 72 deg
H02S B2 S1 .77
H02S B1 S2 .78
H02S B1 S1 .83
Fuel pulse w B2 8.5
Fuel pulse w B1 8.3
ECT volts .59
ECT deg 196 deg
Throttle pos PT
Throttle pos volts 1.66

Note the check engine lamp did not come on during these test recordings. The more I do the longer it takes for it to come on.

I found today the throttle position sensor is sensitive to tapping.

Thanks

 

Just wanted to throw this out to you. I have a 99 4.0L auto 4X4 and recently had a fuel issue my self. We tested the regulator and put a guage on it. When we disconnected the regulator, your fuel pump should increase the fuel pressure to compinsate. When we disconnected the regulator, the pressure dropped, telling us it was a fuel pump problem. I replaced the pump and when we did, the screen on the pump was jam packed clogged. Since then, no problems, except now need to replace O2 sensors since starving the engine of fuel because of the clog burned out the sensors. Just a thought.