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Discussion Starter #1 (Edited)
I often wonder if my old injector pump in my 97 was good, but had bad optic sensor maybe?

Truck ran perfect, then one day it quit. It would start and run for about five seconds, perfectly run, sounded great then shut off. Wouldn't restart for hours. Switched pmd, same result.

Replaced ip, fixed.

I wonder....when the engine starts, does the pcm operate on last running data for first few seconds, then take new information from optic sensor into its calculations? Thusly, If optic sensor was failing it would tell pcm whacky things and just kaploot, shut down?

Next time, it seems like it could be ten min job compared to entire ip replacement. I exhausted all the possibilities like I should have, then after I prevailed I thought.....why didn't I try that sensor first?

Thoughts anyone?
 

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Discussion Starter #2
I still feel like the both IP's I replaced could have been avoided if I just replaced the Optical sensor in the IP itself.

The 97would start, run perfect for a few seconds and die. If it ran perfect, the injectors were working. I think the OS couldn't see anything, and the PCM "runs the show" when the engine starts for a few seconds then seeks info from the OS, which was unavailable because it was dirty or failed. I bet these rebuilt IP's are usually just OS replaced and checked out. It's half the cost of an IP to gamble on that idea though. If anyone concurs or disagrees please tell me so I'll be ready for next time.
 

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I still feel like the both IP's I replaced could have been avoided if I just replaced the Optical sensor in the IP itself.

The 97would start, run perfect for a few seconds and die. If it ran perfect, the injectors were working. I think the OS couldn't see anything, and the PCM "runs the show" when the engine starts for a few seconds then seeks info from the OS, which was unavailable because it was dirty or failed. I bet these rebuilt IP's are usually just OS replaced and checked out. It's half the cost of an IP to gamble on that idea though. If anyone concurs or disagrees please tell me so I'll be ready for next time.
The Optical Sensor is just about as expensive as a replacement IP..
If the OS filter is in place it can cause performance issues. It is recommended to remove the OS filter from the harness and throw it away.
DieselPro's IP gremlin eliminator post can help narrow issues down. Search his threads for the post
 

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I had a failing injection pump and started throwing parts at it. Gutting the shutoff valve, swapped PMDs (~$200), then tried the Optical sensor (another $250). Different problem than you, truck couldn't hold RPMs in park. One guy on here told me it was the fuel solenoid plunger, which it was. I drove it for a couple years like that. Until one day I was driving home and it started accelerating down the highway on it's own after I let off the pedal. I decided I better just bite the bullet an swap the pump. If i'd known I could replace that part I would of tried. It was over $1500 I think for a reman inj pump from stanadyne dealer.
 
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