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1998 2500HD 6.5 Detroit TD
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Discussion Starter · #1 ·
Hello everyone. Hope all of you are well during these times. I have a concern regarding my 1998 6.5 Detroit. Although very infrequent, the truck does a strange hiccup when idiling, almost as if I’m taping the peddle with my foot to imitate a lope. My thoughts are either injectors or a throttle issue. If anyone has any ideas or has experienced similar issues, I’d love to hear how you solved the issue as I am prepping the old girl for a 3200km round trip up north. Thank you in advance for any and all advice!
 

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Try another "Known Working "PMD w/ resistor installed and go through all grounds
 

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1998 2500HD 6.5 Detroit TD
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Discussion Starter · #3 ·
What is that? I’m newish to the truck game and haven’t learned all the toys.
 

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What is that? I’m newish to the truck game and haven’t learned all the toys.
PMD= Pump Mounted Driver.. This is a grey or black box attached to the drivers side of the Injection pump ( OEM stock location).
Here is a pic showing the PMD ( Labeled FSD in pic) mounted on the side of the IP
Automotive tire Motor vehicle Automotive lighting Font Automotive design


When you replace the PMD note the short electrical cable connected to it.
Use caution when replacing so you do not damage the connection ends.

Inside of the PMD where the connector attached is a resistor on the PINS.
Make sure your replacement PMD has a resistor installed onto the PINS before install. ( The resistor is important for proper PMD function)

Here is a picture for reference:
Product Circuit component Rectangle Font Automotive lighting
 

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1998 2500HD 6.5 Detroit TD
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Discussion Starter · #5 ·
Ohh right ok. I have relocated the PMD but you’d recommend swapping it?
 

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Ohh right ok. I have relocated the PMD but you’d recommend swapping it?
If you have the PMD relocated that is good. Just replace the PMD with a "Known Working" PMD w/ resistor installed to see if things improve and go through all of your ground wires.
 

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1998 2500HD 6.5 Detroit TD
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Discussion Starter · #7 ·
Ok will do! Is it worth checking my throttle body as well?
 

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There is no "Throttle Body" on a diesel engine.
 
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1998 2500HD 6.5 Detroit TD
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Discussion Starter · #9 ·
ThTs helpful haha thanks!
 

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Also verify your lift pump is working. You should hear it working when you turn the key to on. Make sure the fuel system is in good shape and no air is getting into the fuel lines. Lots of info on these in the 6.5 FAQ sticky.
 

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1998 2500HD 6.5 Detroit TD
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Discussion Starter · #11 ·
Ok thanks for the advice! I’ll update as soon as I have answers!
 

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1998 2500HD 6.5 Detroit TD
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Discussion Starter · #12 ·
Also verify your lift pump is working. You should hear it working when you turn the key to on. Make sure the fuel system is in good shape and no air is getting into the fuel lines. Lots of info on these in the 6.5 FAQ sticky.
Turns out it is the lift pump. I heard that changing out to a marine grade pump is something to consider. Would you happen to have a recommendation? I was considering just going with an ACdelco pump.
 

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AC Delco is a good replacement LP.
I like Carter #P74001. Because of higher pressure and flow rate. But I run a number of performance mods.
Upgrades like "marine" injectors, pump, ect are not needed or for a stock 6.5.
 

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Turns out it is the lift pump. I heard that changing out to a marine grade pump is something to consider. Would you happen to have a recommendation? I was considering just going with an ACdelco pump.
The preferred lift pump most choose is the AC/Delco EP158
 

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Whatever you buy, use the 1993 model year for the LP part no.
DO NOT USE 1998 MODEL YEAR.

The LP has the same shape, hook up, etc.
 

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1998 2500HD 6.5 Detroit TD
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Discussion Starter · #17 ·
Whatever you buy, use the 1993 model year for the LP part no.
DO NOT USE 1998 MODEL YEAR.

The LP has the same shape, hook up, etc.
I ended up getting the ACdelco EP158 for the pre 96 years
 

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95 K2500 Suburban, 6.5L
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Turns out it is the lift pump. I heard that changing out to a marine grade pump is something to consider. Would you happen to have a recommendation? I was considering just going with an ACdelco pump.
Get this bad boy and kiss all your lift pump issues goodbye for life... Probabably one of the best upgrades I did to my truck.

Raptor Lift Pump

Also make sure your lift pump is not drawing power through your oil pressure switch, which is the default way the factory wired most of the 6.5's. There are several wiring kits around to fix this. The one I got for mine also hooks to the glow plug controller so that it primes the fuel system while the glow plugs are on. Makes cold starts a lot easier.

I used this one

Upgraded Lift Pump Harness
 

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Also make sure your lift pump is not drawing power through your oil pressure switch, which is the default way the factory wired most of the 6.5's. There are several wiring kits around to fix this. The one I got for mine also hooks to the glow plug controller so that it primes the fuel system while the glow plugs are on. Makes cold starts a lot easier.
The OP has a 1998 OBD2 truck. The lift pump is powered thru a relay . Not the OPS. He does not need any kind of a kit. His truck was built with the upgrade installed.
OBD2 trucks (96 and up) also prime the fuel system when the key is turned to on.
 
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95 K2500 Suburban, 6.5L
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The OP has a 1998 OBD2 truck. The lift pump is powered thru a relay . Not the OPS. He does not need any kind of a kit. His truck was built with the upgrade installed.
OBD2 trucks (96 and up) also prime the fuel system when the key is turned to on.
Correct. That's why I told him to check.
 
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