Engine/Transmission (1998.5 - 2002) long crank or rev up at start

[BDahm]

Here is the problem im having. It either takes 5 sec of cranking to fire or starts right up and revs out completly the dies and no restart until i remove the engine fuse and put it back in. I replaced the vp, lp, crank sensor. Im thinking its an ecm issue. You guys heard of this???

 

[JLandry]

Are you saying that once the engine does start (either immediately or after extended cranking), it'll rev up out-of-control until it shuts off dead?



Did this problem begin all of a sudden with no warning, or did it happen gradually?



Have you done any other maintenance or repairs on the truck just prior to when it began?



After one of these episodes, have you checked for any stored trouble codes BEFORE disconnecting the engine fuse?



Regards,



John L.

 

[BDahm]

Yes the truck will either fire right away, rev up out of control then die or long crank them stumble and start normally. This problem started to happen after i installed the new vp and lp. I reomved the vp again sent it to industrial inj to have it checked, found no problems but was storing a crank sensor code. Got it back and installed new crank sensor and the pump. same problems. Havent checked codes while its doing it though. Need to do that. It seemed as if it was losing its prime so i checked the fass for leakage, replaced the overflow valve and checked for leaks, all ok. the fass does have the check ball inside. Thats why im thinking both of these problems are connected. any help is appreciated! thanks

 

[JLandry]

Havent checked codes while its doing it though.

That might be very helpful to narrowing down the problem... check for stored trouble codes immediately after one of these events before you shut the ignition key off. It seems if there was something way out of whack enough to cause a no start or a runaway engine, you'd get a trouble code of some kind.



As to the crank angle sensor, I believe I've read of others getting bad ones right out of the box... rare but possible. It could also be a wiring harness or connector problem. Interestingly, the engine will still start and run without a crank angle sensor because the VP44 also calculates the crank angle internally as a backup to the ECM.



I suppose you could have a problem with the ECM or wiring harness all of a sudden. One way to eliminate that would be to connect a Cummins fuel injection pump "hot box" to the VP44 and try starting the truck with that. This device bypasses the ECM altogether and relies solely on the VP44 to operate the engine at a low or high idle. You can often find them used on eBay, buy them new from Cummins or Miller SPX, or any Cummins repair shop should have one.



John L.

 

[CumminsAholic]

Could also be a bad apps. I don't think so, but a possibility.

It could be the ecm is on it's way out. My truck's ecm went out, when it did it had erratic throttle resopnse, but it was usually a intermittent dead petal, not a high rev situation. Also I had a ton of codes when it happened.

Corey

 

[BDahm]

How do you check/reset the apps?? thanks

 

[JLandry]

How do you check/reset the apps?? thanks

The simple and quick way to test the basic functioning of the APPS is as follows:



1. Completely remove the APPS assembly from the engine. You'll be able to disconnect the TPS (Throttle Position Sensor) wiring harness hidden behind the APPS when you unbolt it from the engine.



2. Using an inexpensive ANALOG multimeter (one with a needle... not a digital model), measure the resistance (Ohms) between pins 3 and 5 of on the TPS connector as you SLOWLY open and close the accelerator linkage on the APPS assembly. If the TPS is working properly, you should see a smooth sweep of the needle on the multimeter from about 2300 Ohms when closed, dropping down to about 850 Ohms when open. The exact starting and ending resistance doesn't matter. The important thing is that you observe smooth movement of the needle on the multimeter. If the needle jumps around or hesitates as you move the APPS linkage, then the TPS needs to be replaced.



3. Measure the resistance between pins 4 and 5 on the TPS connector. You should see about 2200 Ohms and this reading should not change when you open or close the APPS linkage. The exact reading isn't critical so long as the needle on the multimeter doesn't move.



4. Measure the resistance between pins 1 and 6 on the TPS connector. With the APPS linkage CLOSED, you should have a closed (completed) circuit showing no resistance. With the APPS linkage OPEN, you should have an open (incomplete) circuit showing infinite resistance.



5. Measure the resistance between pins 1 and 2 on the TPS connector. With the APPS linkage OPEN, you should have a closed (completed) circuit showing no resistance. With the APPS linkage CLOSED, you should have an open (incomplete) circuit showing infinite resistance. Note how this is exactly the opposite of step 4 above.



If the TPS passes the above tests, it's probably fine and can be reinstalled. There are more accurate tests and adjustments that can be done with the APPS installed on and connected to the engine, but the above simple tests will reveal any major problem that could cause a runaway throttle condition.



To "reset" the APPS (which is actually reteaching the TPS voltage range to the ECM):



1. Disconnect both of the trucks batteries and turn the headlight switch on. Leave it this way for 10 minutes or so. This helps drain the memory from the ECM and PCM.



2. Turn the headlight switch off and reconnect the batteries.



3. WITHOUT STARTING THE ENGINE, turn the ignition key to the run position.



4. SLOWLY depress the accelerator pedal to the full down position and then slowly release it back to the full up position.



5. Turn the ignition key off.



You're done!