Hi Everyone,

I've been lurking on here for a while and I finally ran into an issue that I haven't been able to solve using previous forums.

I put a new crank position sensor in a few months ago after I had the truck not start on me at the dump. I got it going with some spray I know it's not good to do, but I disconnected the power to the grid heater had my wife crank while I squirted into the turbo. The truck ran great for three months or so when it developed a random hiccup.

This brief hesitation is totally random. Last summer I put on a Fass fuel system with a homebrew drawstraw and a Special X VP44 from Blue Chip.

I don't think that this is a fueling issue. I've made sure that all the fittings are tight and there are no holes in the 1/2 line.

last week I was driving home from work when the truck started acting like the crank position sensor was going again: super rough at times and the tach would drop, then right back to normal.

I put in another new crank position sensor two nights ago. ran fine for a day, now runs on spray.

I've checked the voltage from the ecm to the sensor and it's 4.95v.

once the truck is running it runs fine, not like it's running on the cam position sensor. Now there's no check engine light, the truck just needs to get started on the can.

I've been going through the truck and cleaning grounds. my plan for tonight is to do the alternator ground mod from W-T.

 

Let me know what you guys think

thanks

Any codes?

I don't yet have a scanner, but ill pick one up tomorrow to check if a code gets thrown.

there's no check engine light currently.

Can have codes without light

 A little info on the truck would help also. Exactly what year, trans, milage? Maybe put it in the signature line. 

 You will have to check for codes and once it is running look at the live data as well. That can tell you alot of the running condition. Get back to us, we will help as much as we can.

 Also, Happy New Year!

Happy New Year!

the truck is a 99 with an NV4500. It has 372xxx on it.

 You've done some work on the fuel system, double check everything to make sure it isn't drawing in air. Sounds like it may be loosing prime when it's shut off.  Rather than spraying with ether try cycling the key to start the lift pump, make sure you hear the LP running, then just bump the starter so the lift pump kicks on for 20 seconds. Then attempt to start. If it does start then your loosing prime when it sits. If you have a fuel pressure gauge I would also test that. Be sure the LP builds pressure before starting and maintains it after it's running.

Blue Chips special X is too advanced. That's your hard start or possibly the key is crushed and timing is advanced. I've seen both cases causing hard start.

 

Fuel pressure to high could cause hard starting. Fuel pressure should be 7 to 12 PSI. Should not be any higher during cranking. Try unplugging the FASS and see if it starts easy.

 

Excessive pop pressure on injectors greater than 330 bar. Make it tough to start cold.

 

For easy starts low fuel pressure and retarded timing is way easier to start.

Edited January 1, 20223 yr by Mopar1973Man

I've spent some time on the truck over the past few days. Still no Start.

I went over the fuel system looking for leaks and didn't find any. I went over every connection again and Didn't find any loose fittings. I tried letting the pump run for a while before starting and I tried disconnecting it to start, neither worked.

I did the ground modification and cleaned the ground connection from the PCM. I took off the harness to the ECM and cleaned/ dielectric greased everything. I have two Crank Position sensors. Both read ~1000 Ohms across the poles and when plugged into the harness they get 4.9v and I can see that they are toggling as I move them toward and away from the block. I can't tell if they're both good or they're both bad. The ground on the Crank position sensor plug is good.

I took off the gear case breather to check the VP44 timing. The gear is still aligned with the shaft and the woodruff key is intact.

I torqued to 125ft-lbs when I installed it.

when cranking there is no tach movement. usually I see 200rpm or so.

I picked up a code reader and there's a P0122 code. Accelerator position sensor. I recently re-calibrated the sensor and it was reading the same 5.8v that it has stamped on the side.

Short of buying another $75 crank position sensor, does anyone know how to test the ones I have to confirm that they're working?

2 hours ago, sawdust said:

Short of buying another $75 crank position sensor, does anyone know how to test the ones I have to confirm that they're working?

Even though they didn't code these links may help in the diagnostics.  You can find more by searching the OBDII codes in the 24 valve 2ed gen engine article section that pertain to your problem.

 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/obdii-error-codes_94/p0320-no-crank-reference-signal-at-pcm-r71/

 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/obdii-error-codes_94/p0336-crankshaft-position-sensor-signal-r72/

 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/obdii-error-codes_94/p0387-crankshaft-position-sensor-voltage-too-low-r80/

 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/obdii-error-codes_94/p0388-crankshaft-position-sensor-voltage-too-high-r81/

 

 

 

 

 

 

3 hours ago, sawdust said:

Short of buying another $75 crank position sensor, does anyone know how to test the ones I have to confirm that they're working?

Even though they didn't code these links may help in the diagnostics.  You can find more by searching the OBDII codes in the 24 valve 2ed gen engine article section that pertain to your problem.

 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/obdii-error-codes_94/p0320-no-crank-reference-signal-at-pcm-r71/

 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/obdii-error-codes_94/p0336-crankshaft-position-sensor-signal-r72/

 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/obdii-error-codes_94/p0387-crankshaft-position-sensor-voltage-too-low-r80/

 

https://mopar1973man.com/cummins/articles.html/24-valve-2nd-generation_50/51_engine/obdii-error-codes_94/p0388-crankshaft-position-sensor-voltage-too-high-r81/

 

Have you tried hot wire to the vp44 running test?

 

https://www.bluechipdiesel.com/runningtests

 

 

 

 

Thank you!

I took a ride in the company truck this afternoon to go find another crank position sensor. I've cleaned out the nearby parts stores, so a couple hours later I was back under the truck in the garage. After putting the sensor in I thought to test it against the others, out it came. 1000 ohms, the same as the other two.

I know there's more to the sensor than the impedance across the pins, but this still doesn't really pass the sniff test for me.

new sensor in and the truck fired right up. took her for a spin and shut down, then fired up again.

I got some more codes out of it after I figured out how to use my new scanner. 336- Crank Position Sensor Performance. 118-Engine Coolant Sensor (I had it unplugged when I took that loom apart to do the ground mod). 234- Boost Limit Exceeded.

IBMobile I'll have to do the test procedure for the P0336 code. I saw that there was voltage there and assumed that it wasn't a physical problem, but I'll have to check the resistance of that wire.

I am really hoping that the issue is fixed and this isn't just an intermittent period of functionality. I will buy a genuine Cummins sensor when I find one. It doesn't seem like the one from Genos is OEM.

 

that should cover the p0336 code.