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Discussion Starter · #1 ·
Hi Diesel people,I have a '94 HD with 6.5, the pump was changed out about 3 years ago. Not sure of the pump number but I could get it. Truck quit suddenly so diagnosed it to the optical sensor, put in a good used one,(I had access to about 6 old pumps) away we went ... for about a day and a half. Then same issue.

I get about 2 days of trouble free use, then usually its when you shut it off and go to restart that it gives trouble, but the last time the truck was running and its like someone shut the key off.
I can pull it apart clean the sensor by running a tissue through the slot. Reinstall and starts up and away I go for 1 or 2 more days.
The one time it quit at an intersection, I simply unplugged the sensor, started it up and drove home. 70 miles! Truck ran great no smoke or other issues besides check engine light came on and next to no power! Made it up to 60 mph but took awhile.
I've tried resistor, no resistor and a variety of different years of sensors. Anyone have any suggestions?
 

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1995 GMC Suburban
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Welcome!!!

x2, Air leak???

Have you checked all the electrical cable leading to the IP?
Have you checked the LP and OPS that runs the LP when engine is running?
 

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Discussion Starter · #4 ·
Thanks for the quick replies, lift pump has been wired direct for about 12 years now, turn the key on and lift pump starts.
As far as air leaks are you talking in the injection pump itself ? Or sucking air between fuel filter and tank? I guess maybe anywhere in the system along the way. I will look into that, but you would think there would be some hard starting or hesitation etc.
 

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1995 GMC Suburban
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Check the Fuel Filter bowl and the hoses that goes in and out of it.

There are 2 o-rings at the filter bowl.

1 input hose and 2 output hose (one of them to the IP).
The output hoses go under the intake so you never know if if it is leaking.
Unless you change it when you change the OS.

As for LP, you need to measure the pressure. LP does go weak as years go.
Hotwiring does not mean that the LP is still the same condition 12 yrs ago.

Have you check electricals?
 

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Mine did this. . . until i discovered the encoder wheel was broken. Might check that
 

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Mine did this. . . until i discovered the encoder wheel was broken. Might check that
Where would I locate the encoder wheel and the optical sensor. Mine has been having these same symtoms, I thought it was a bad transmission solenoid. Are these easily accessible?
 

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Where would I locate the encoder wheel and the optical sensor. Mine has been having these same symtoms, I thought it was a bad transmission solenoid. Are these easily accessible?
The encoder wheel is inside of the injection pump.
The optical sensor is located on the top of the Injection pump
 

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1995 Chevrolet Silverado Z71 6.5 TD
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460 Posts
With the engine stalling suddenly as it did what about the PMD.
 
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