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1990 Ford Ranger Pick-up Won't Start - Ignition System
Question: Hello again. ? Claudia here...You were helping me with my '90Ranger. I did some of the pinpoint tests...those I could do alone. One test seems to indicate a short in the harness of the crank shaft position sensor. I also replaced the ECU which seemed to be toast, and the Right side coil pack and spark plug wires. Alas, the symptoms prevail. The strange thing is, if the harness is shorted, why does the truck start and run beautifully for 30 or so seconds, then quit, and not start again for 48 hours, then after a long rest, it usually will start again, once...the pattern is start after sitting a long time. Then not start again. It seems to die for lack of fuel, rather than loss of spark. The fuel filter was replaced during this broken down spell, and the fuel pump was relatively new, replaced in 2001. The inertial switch tests okay. As does the DIS. Would the crank sensor harness short act like this? Oh and there are NO CODES! She just doesn't run! Any ideas? I dread the dismantling of the front of the engine to get to that harness, but I fear that is next.
Many thanks!
Claudia
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Technican: Hello Claudia, I'm sorry this problem continues for you.
When the engine will not start have you checked for fuel pressure? Spark? What was the resistance reading when the crankshaft position sensor was tested?
If you have an ac milivolt meter you can even test the output voltage of the crankshaft position sensor while the engine is cranking (even though the engine won't start). If there is ac voltage output indicated it may just be still working okay.
What is the indication that the crank sensor wiring is shorted? To ground? To voltage? Several sensors will share the same ground so it may be "fooling" you if you suspect a short to ground.
Owner: Hi,
How would I go about doing that test of the crank sensor? Would my mulitmeter have a millivolt scale? I am new to this...I have an AC circuit light, and a self powered circuit/continuity tester, a multimeter, and my home-made "brain prober" ... would any of these work? The brain probe is a circuit tester with the alligator clip on to the inside of another point from another circuit tester. It seems to work fine. The diagnosis I got from the pinpoints you sent proved true for the Rt.coil, secondary towers were bad. The test for the crank sensor was in the PinPt.Test B sequence, #24 "Check PIP circuit for short to VBAT. test light + lead to PIP S (J33) and -lead to BAT (J60). The light was ON, "...locate and repair short to VBAT in sensor harness." What is a VBAT?
I would not be at all surprized if sensors were in cahoots to fool me... ;-)
Thanks so much for your help. It is an education!
Claudia
Technican: A multimeter must have a milivolt scale. Does yours indicate mV~ or have auto-ranging?
To test the resistance of the crank sensor it must be disconnected from the wiring but does not have to be removed. Jumper wires connected to only the sensor terminals work best so you can test without so much atheletics involved. Once you've got jumpers connected, what is the resistance reading in ohms? With the same jumpers connected the same way switch your meter to ac milivolts. While someone else cranks the engine look at your meter and see if the sensor is generating ac milivolts. This number is not too critical unless it is zero.
If you can get your hands on a scanner it will test the sensor feedback readings for you, but not their resistance values.
VBAT = voltage; battery.
I'm studying...
Owner: Hi again, . I hope I did it right...I took a jumper wire with an alligator on one end and clipped that to the inside of the (male) connector, and then joined the jumper [wire end] into the matching female connector on the crank sensor, and took readings on each of the 4 wires, one at a time. Ohms were as follows: red:00.10; blue:121.3 (!); black:0.10; gray: 101.7... I was using the 200k scale. Is this what you meant for me to do? Does it reveal anything? I tried to repeat these hookups using the ACV scale, [200], and I got a no charge at all in the cranking phase. Even I could see it was a dud, zero...nada. Not even a spike. Is the sensor dead? The pattern of starting and failing continues. I tried to start her up and she sounded great for about 30 seconds, then begins to run rough and dies. I was able to start her once more, but she shut down immediately. The third attempt seems like she just jumps time, [sounds like the battery died--a hard crank--only the battery is fine, brand new in fact].
Pretty soon I'm going to have to cry UNCLE and have a mobile service guy come. Mucho $... No fun. Can I replace just the sensor? Or do you think the harness is the problem...that PIPEEC [#24]test has me worried, but so does the rest of it. I just don't get how the thing can run so strong and then crap out so fast! Arg. Thanks for your help!
Claudia
Technican: When you test resistance of the crank sensor it needs to be disconnected and you'll not test anything on the wiring harness itself. Test the resistance across the two terminals whose wires when connected go to the DIS.
You won't read ac milivolts on a 200 scale unless the scale shows 'mV' on it.
Yes, you can replace only the crank sensor. You may have to get the crank pully off for access. Thay are not an expensive part.
I'm out of town until Monday.
Owner: Hello again, I got a .5 reading between 2 leads clipped on to the 2 prongs aligned with the red/green, and gray/orange wires, which match 2 of the 6 wires on the top of the DIS unit.
I got a .8, and a .7 tryig to crank the engine on the AC VOLTAGE scale on my mulitmeter. But now I'm looking and it probably was the wrong scale. mV is on a DC scale. I tried that one too. But I didn't get any jump on the digial read out. It said .7 or .8 and that was it. No difference when I cranked.
The weird thing is though, after I hooked up everything again, I tried to start the truck. She started and ran until I shut her off. I did try driving her, and she pinged and nearly died, but when I gunned the engine, instead of dying like she has done for the last month, she responded! I put her in reverse and headed back up my driveway. It sounded to me like something was loose in the engine, maybe a wire or something...
Things I did that could have a bearing on this?
1)Three or four days ago I poured 16 oz of Chemtool in the gas tank. And started her up to run as much of it as I could through the fuel lines before she'd stall.
2)I cleaned a ground contact near the starter relay, two wires which screw into the passenger side above the wheel well in the engine compartment, near the battery.
3) I cleaned with alcohol in the top of the DIS [1--6].
4)I poked 2 copper wires down the harness side of the crank sensor harness connector. Just for fun...?
5)And I alligator clipped the leads as reported earlier, to do the ohms test. Go figure!
Just thought you might be amused. I sure was! She is still sick, but its like she's out of the coma! Any thoughts, Doc?
Thanks again,
Claudia
Technican: Yikes! My copies of all I sent you have been trashed. What scale were you using on the ohm meter for your .5 reading? What was the crank sensor ohm value specification in the data I sent you?
My multimeter has both ac and dc mV capability. I still believe we want to measure ac mV while the engine cranks. The improvement you've achieved is interesting and I cannot explain it...
Have you checked your engine for codes? History codes?
Owner: Hi,
The info you sent did have some of the ohm values. The .5 reading today was on a 200 ohm scale. Well under the 5 ohms or less specified...If I'm reading it correctly! I did try the cranking test with it set on ACV 200 V scale [200V to 100mV] I'm wondering if my meter is not good enough. It was a cheap one. Maybe the range of resolution is not refined enough. Mike has a better one, but he has not been around lately. [Busy and discouraged I think].
I don't know what to make of todays developments, but I know I'm not very clever with the multimeter. I can't seem to get any clear reading that will stay put to be trustworthy, and repeatable. When I tried the ACV scale, it would read .8 or .7 and not change when I cranked. The pinpoint tests I've done all point to a short in the connector or harness. That is why I stuck the two wires into the harness side of the connector today, also one of the prongs in the other side of the crank sens. connector was very slightly bent to one side. I straightened it. Maybe the contact was not good prior to that. Electrical stuff is so ephemeral. When I read codes, I got no codes, she passed with 11s on both 'O'/KOEO and Continuous Memory. Obviously KOER is a good place to go next. I'd just given up until today when she ran...now I'm encouraged to try again. I'll check in with a repeat of ohm and ACV tests and KOER Codes if any. By the way, my Multimeter shows a DC scale of 200mV-100uV +/- 0.5% of rdg +/- 2D. The next scale is: 2000mV to 1mV [same =?- as above.] Is this the mV scale I should be using?
Work for me tomorrow after I do my day job! I'm sorry our history is lost. Bummer.
Many thanks,
Claudia
Technican: On a 200 ohm scale, a reading of .5 would equal 1/2 of 1 ohm. Not good! You would not multiply .5X200=100 ohms because if the reading were 100 ohms it would fall in the 200 ohm scale range on the meter and simply display as 100.0 ohms. So .5 is below any spec I remember. I can go back to the library and recreate the data I sent if need be.
The range on your meter of 1mV-2000mV is the correct range to measure what we are looking for but needs to be ac mV. When ac volts are generated they must be rectified to become dc volts. The raw signal coming from a disconnected crank sensor being monitored by a meter is not a rectified value. It is created by magnetic pulse induction using a reluctor ring that is notched to break the magnetic field as the ring is rotated past the sensor. That results in an ac mV generated value relative to the speed of the spinning reluctor's breaking of the sensors magnetic field. Aka the "Hall Effect".
Will you be able to change the crank sensor? If you decide to..take your meter to the parts store and perform the same resistance test on the new one before you buy it. If you do this in the presence of the counter clerk they can see you are not abusing the part and confirm the difference in readings compared to your "old" part. Most will allow this test before you buy and before you leave. If you buy the part and leave their sight you will not be permitted to return the part for a refund.
Are you still getting the pinging but no real power?
Owner: Hi,
Thanks for explaning that Hall Effect. THe AC voltage testing available on my meter, listed as "range resolution(s)" are: 200V to 100mV and 750V to 1 V. They show this in the instructions. So it looks bad for my using this little meter.
I'm thinking that to remove the front of the engine fan, serpentine belt, timing cover and crank pully etc, etc is a big job. To get to the harness and remove the cranksensor is more than I'll be able to do by myself. My friend Mike might be able to, but with him it is a matter of when. I may have to sell my dear ol' pal, "Gracie" as is, to a mechanically oriented buyer. I hurts my heart and wallet too. I had planned to keep her "forever". So I'd put a 94 engine in her [currently with 70k miles on it], and new brakes and new clutch, new battery, 2 new tires and a new EGR sensor, a new[used] brain!, new spark plug wires and the new [used] coilpack. She's been my pal for 10 years. I just don't know what else to do. THe cost of replacing the sensor and harness in the labor alone will erase any benefit to fix her before selling her. It is a sorry tale.
As for the pinging, well, she acted like she'd run happily then a quick burst of pinging began and she felt like she was not getting gas. I reved the engine and she responded. She has power. There seems to be not a thing wrong when she's running. No missing, no loss of power. I wondered to myself if the "no spark" problem was solved when I replaced the right coil. If she might have had a fuel problem at the same time. She is good at having 2 things go on the fritz at once. I had poured in some Chemtool just in case there was a gasoline problem. Maybe that helped. But she did ping and try to stall for a moment. Then she recovered. Running for a nice long time...until I shut her off, is something she's not done for a month now.
Go figure.
On the ohms, I'm going to try again just to make sure I didn't read it incorrectly.
Thanks for sticking with me on this. It is really a mystery to me. And to Mike. If I ever find out what it is, I'll let you know. I'm not done yet, but if someone makes me an offer on the truck, I'll probably take it!
Claudia
Technican: Claudia,
Consider contacting any auto vo-tech school in your area, especially at the college level. They sometimes take on a diagnosis and minor repair and do not charge labor. I did lots of repairs in high school auto vo-tech. The owner provided the vehicle, and the parts my instructor verified to be needed, and I learned with "hands-on" opportunities that do not begin to compare in a text book scenerio. It's not always a time friendly path because you'll need to fall in when the class is at the skill level that would apply to your need.
If the crank sensor really turns out to be faulty through diagnosis it's going to be hard to believe the engine started and ran. My experience has been that the sensor heats up from the radiant heat of the engine block and fails electronically. But, when it cools down it just might work again and the cycle repeats. The second coil you replaced must have awakened the no spark condition you had. But there is only one crank sensor signal and you did have spark on the "other" coil even through all of this, correct?
Owner: That is a great idea about contacting a school. I live outside of Eugene, there is a community college in our area. I'll look into that option. Thanks for that idea!
The 'other' coil did have spark. And tested okay in the pinpoint test. Who knows by now? I have not ever tested for spark, Mike did that when he took this on in the beginning of our trial by fire. Things seem to change from moment to moment with this problem.
So I re-ran the ohms, first I got the same reading .5. Then I resituated my clips trying to keep them from touching each other in the connector, and I got a 6.5 ohms reading on the 200 ohm scale. I didn't try the ACmV because my meter doesn't have that refined a scale as far as I can tell. As for the phenomena yesterday, [running at length], it did not repeat today. She cranked but would not start. I reread codes, today she said 'pass' on the first set, and #66 "MAF voltage lower than expected" in Continuous mem. I had forgotten I'd moved the large hose off the manifold so I replaced it, but that didn't change the code. I have not messed with the Mass Air Flow sensor, though Gracie has shown me that code when I forgot to replace the hose one time. I even repeated some of the things I did yesterday to see if poking a wire into the harness did anything...Alas, she just didn't want to start today. Thanks again for your help and patience.
Claudia
Technican: You might take a look at the screen on the MAF Sensor for debris. And a look at the wire filement the air flows past. It must not have broken or have dirt or debris caught on it. Here's How To Get Guaranteed Solutions In Minutes
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