crankshaft position sensor gap

[JohnnyLong]

Does anyone know the gap measument for the Crankshaft Position Sensor on a 93' D250 pickup 3/4ton 2wd?

 

[B.G. Smith]

I have a couple of manuals but can't find any reference to the gap. It does say to only use the original bolts(this is on gas engine) so I suspect it is self locating. The sensor is a hall effect device so if it is adjustable I would give it about . 010 clearance, about the thicknes of a file card. bg

 

[Paychk]

FSM page 14-109 states 0. 049 - 0. 051 inches using a brass feeler gauge.

 

[Bob Beauchaine]

When I fixed the 5 case bolts on my '93 I checked the gap before hand and found that the thickness of three sheets of ordinary copy paper worked just fine. When I put everything back together that is what I used - it has worked just fine since then and that was 12 years ago.



Bob

 

[SRay]

Paychk is correct, . 049-. 051 with a feeler gauge. If you don't have the size, just join a . 020 and . 030 together to make a . 050.

Shawn

 

[JLEONARD]

I checked the gap before hand and found that the thickness of three sheets of ordinary copy paper worked just fine

That would be about . 012". Not to spec but you cannot argue with success

 

[JohnnyLong]

Thanks for the info everyone...
I got a new crank/speed sensor yesterday but haven't put it on yet. Tested the old one that is still on my truck like it describes in the FSM. There are 3 pins... a,b,c ... on the sensor plug. The FSM says to test between b & c with an Ohm meter. The Ohm meter doesn't give a reading between these two pins... but is reading "no resistance" between a & c. When I test the new sensor off the vehicle I get no readings with the Ohm meter at all... nothing. This seems strange to me. Does it need to be on the vehicle? I still don't really know for sure if the old sensor is bad. It would be great to know this before I install the new $130 sensor... . which I could still return. I've already tested and ruled out the ASD relay, alternator, and PCM (just had the pcm just rebuilt). I know i'm close. Does anyone have any more enlightening info on this situation?
thanks
blue skies
johnny

 

[cerberusiam]

Depends on what problem you are trying to solve. Those sensors seldom go bad, why do you think you need a new one?





FYI, when trying to track down any problem associated with the CPS the harness the first place to look. At the bottom of the head below the thermostat housing is a connector that can be problematic. It can vibrate aprt and not make connection, or, the female portion of the plug will expand too much on 1 or more pins and not make contact. You will want to check that out first and verify you have continuity thru the plug.

 

[JohnnyLong]

I did look at the connections already a few times and they seem good ... but hey... i'll do an idiot check... . I could have missed something obvious.
thanks
johnny

 

[cerberusiam]

I did look at the connections already a few times and they seem good ... but hey... i'll do an idiot check... . I could have missed something obvious.

thanks

johnny

No idiot on this one. That connector can be seated properly and look great and still have no signal or not enough thru it. You have to check continuity on the pins because they can be bad. Good luck.

 

[JohnnyLong]

Sorry... didn't really say this before. I have been trying to run down a problem with charging in the truck. I've already tested and ruled out the ASD relay(new),ignition wiring, alternator(new), and PCM (just had the pcm rebuilt). I can bypass the pcm at the relay and the alternator will charge. Otherwise... the alternator isn't getting a signal from the pcm to charge. Then I was lead to the crank sensor by other dodge owners online. Maybe it's not giving the pcm any info. That's where I am now.
Thanks
johnny

 

[JohnnyLong]

So... took your advice and rechecked the sensor setup.
I checked the plug and the pins. I bent in the tabs of the female sides to make sure all 3 pins were making contact and plugged it back in... nothing. Couldn't see all the wire connections so I pulled the sensor off. Wires all seem perfect. I don't know how to check the continuity on the sensor. There are 3 pins on one end... and the wires are sealed to the magnet on the other. Do I pierce the wires with the meter ends to check this 10 inch length? Also... the Ohm readings I took before are still the same. There are 3 pins... a,b,c ... on the sensor plug. The FSM says to test between b & c with an Ohm meter. The Ohm meter doesn't give a reading between these two pins... but it does give a reading between a & c. I know the "b" pin is a hot wire on the female side. Maybe this isn't supposed to be a closed circuit and have a reading at all... and so the OLD sensor is bad. I'm not sure. When I test the NEW sensor off the vehicle I get no readings with the Ohm meter at all... between any pins... nothing.
I'm confused. Is there a way to test these sensors off the truck and be sure they are working? Think I might just put the new one on a give it a try.
thanks again
blue skies
johnny

 

[cerberusiam]

When I test the NEW sensor off the vehicle I get no readings with the Ohm meter at all... between any pins... nothing.

I'm confused. Is there a way to test these sensors off the truck and be sure they are working?

That may be the best indication of a problem there is. The only way to test the sensor accurately is on the truck and with a scope to see if it actually outputting a sinal as the crank rotates. Since its an Hall Effect sensor the actual signal is rather hard to test without the correct equipment.

 

[B.G. Smith]

http://www.wellsve.com/sft503/Counterpoint3_1.pdf bg

 

[HHhuntitall]

Having had encountered a similar problem on a customer's ride, I'd also encourage you to check out the ignition switch to make sure it's connecting on all pins when engaged. I had one that wasn't getting fire back through to feed the PCM... . and another that made the Wait to Start light stay on in the dash, although the heaters weren't operating. Both I tracked back to the ingnition switch. Both trucks started and ran fine, but the first wouldn't actuate certain guages or tell the alternator to charge. I thought it was an easy fix with the crank sensor, and ended up having the truck 3 days..... not saying it is your problem, but checking it might find the problem.....

 

[JohnnyLong]

Thanks for all the input.
Still trying to rule out anything else, other than the sensor, that could be the cause of this.
I checked the ignition power to the pcm and it is ok. The pcm has power and is sending 8. 7 volts to the sensor when the key is on. I took the 8. 7 volt reading where the 3pin female plug connects to the sensor's 3pin male plug. With the key on: one pin has a reading of 8. 7volts... . this wire comes from the pcm, one has a reading of 5 volts... also to the pcm, and the last one has a reading of 0 volts. According to the wiring diagram in the FSM all three wires connect to the pcm.
I'm wondering about these readings and if they are ok. Especially the pin with the 5 volt reading... . is there supposed to be 5 volts on this wire?
blue skies
johnny

 

[Paychk]

Here are some jpg's, hope they help

no_crank_signal_1 - Photo Gallery

no_crank_signal_2 - Photo Gallery

no_crank_signal_3 - Photo Gallery

 

[Moe]

On my old 92 the crank sensor had moved enough that it was touching the balancer every time I would hit a bump. The result was a no charging condition. Replaced sensor and set gap with brass feeler gauge since it is a magnetic pickup. The motor will still run w/o the sensor but wont charge. Good luck, Moe

 

[JohnnyLong]

Hey all... .
I finally put on the new crank sensor. It didn't work. I got a friend who is a mechanic to help me and we finally got it working. Great to have a fresh set of eyes on it. The sensor wouldn't work until the gap was less than spec ... around . 047. It began working but the voltage was very erratic... jumping all over the place. We began tracing wires, checking continuity and resist, and looking for shorts again... . anything. Well after testing and testing wires etc... we came to the conclusion that my PCM was rebuilt incorrectly. Here's why. There are 3 wires leading to the Crank Sensor. One is power to the sensor from the PCM... 8. 7volts, one is ground... which is ground for other sensors as well, and one is a "sensor return" going back to the PCM. The PCM is feeding this ""sensor return" wire 5 volts of power. We initially though this was a short but traced it all the way back to the PCM. In the FSM wiring diagram this wire is the return and shouln'd have any power coming from the PCM... only 5volts or so coming from the sensor with a signal. This wasn't my inital trouble but seems to be causing the current problem. Just in case my mechanic friend and I are way off... does anyone know if this wire actually is supposed to have 5volts on it?Otherwise... I am sending back the PCM to the company who rebuilt it.
thanks so much.
johnny

 

[College Cummins]

personally, just if it were me... i'd bypass the PCM and use an external voltage regulator for the alt and then it really wouldn't matter.



here's a good read on it not charging as you decribe:

Dodge Diesel - Diesel Truck Resource Forums - View Single Post - wont charge



here's a good one on how to change to an internal regulator:

NipponDenso Alternator Regulator - Dodge Diesel - Diesel Truck Resource Forums



here's a good one on how to change to an external regulator:

FAQ



the last two will be much cheaper than the 130 you paid for the CPS



James