I was about 5 miles down the road pulling my horse trailer on cruise control when the engine hiccuped (could have been the cruise reacting to the tach problem?), followed by about 15-30 seconds of the tach rising and falling out of sync with engine speed then the tach failed completely and the check engine light was on. The truck was still pulling ok so I continued the 30 minute drive to the fair grounds.

The truck idled roughly as I parked and wouldn't start after I shut it off. It appears that we aren't getting fuel to the injectors. There is fuel going into the injector pump.

Seems like an electrical problem caused the tach to fail and is somehow telling the injection system not to pump fuel. Any ideas what the failed tach has to do with injection system failure? Disconnecting the battery didn't reset anything.

It is a 98(and a half) 24 valve CTD.

 

Sounds like your crankshaft position sensor - mine had the EXACT symptoms last hunting season, MILES from anywhere - the tach began working again, the CEL went out, and the truck seemed to run fine; When I eventually got back into town, the CEL light was back on, but the tach was working - I got to Autozone the CKP code showed up. On the drive back from purchasing said item, the CEL went out again- so I have it under the rear seat for the NEXT time it happens.

I think the 'puter goes into a semi-limp mode? Mine ran crappy until the tach came back. My alternator showed no charge at the same time the tach was going crazy.....

 

Ditto, on the 01's and later (I believe) it would be the CAMshaft position sensor, but like Rauschbo said, yours is the crankshaft position sensor.

 

My sensor is bad also! How difficult is it to change?

 

On my truck it is a five minute job to change the CPS, also known as a ENGINE SPEED SENSOR. All that is needed is a 10mm socket. On my truck the starter is on the passenger side, on your truck the starter might get in the way of working on the sensor.

 

Thanks - the CPS is on order. Should be back on the road soon.

 

See THIS article on how to replace the crankshaft position sensor.

Taken from the tech facts section on this site, BTW.