Hi I have a 98 Chevy 3500 with the 6.5 diesel in it. I have a problem with it running erratically. Just brush the pedal with your foot and it’s in burn your tires off speed. Idles rough when cold smooths out when warm. I have a pdm relocate on. I’m thinking of replacing the throttle pedal. But not sure if it’s a pcm. Any help greatly appreciated
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98 6.5 trouble
- Thread starter Jeffy
- Start date
jrsavoie
Recruit
Could be the Injection Pump.
Do more diagnostics before firing the parts canon.
Do more diagnostics before firing the parts canon.
Will L.
Well-Known Member
Jeffy, welcome.
PMD is suspect. But read & learn first:
A low dollar code reader at a minimum should be owned. Dont buy one yet- lets learn more before spending money….
Never just start replacing parts aka firing the parts cannon.
There is no faster way to go broke and create more issues as you do it.
There is one thing that seems to fly in the face of that rule= PMD. The pmd is not a diagnose-able component, so GM said the way to diagnose it is “Replace with Known Good”
So unfortunately for this engine’s ds4 injection pump, you need to own a spare good one just like you would a spare tire.
Best solution for this is on your front bumper where it should be relocated to, you have 2 PMDs on two heat sinks (or one huge heat sink). Get an extra connector and fill the backside either silicone & let cure. Then install it in the spare PMD you have always in place next to the one in use.
Always when you have anything wonky happen with the fueling system- you swap to the known good spare PMD. On occasion the harness extension can fail- especially if it’s a cheap one.
Leroydiesel.com sells lifetime warranty PMD. I suggest start there, getting an extra heat sink if needed, and if you don’t know the quality of the extension harness - his are good.
When you have an old but good pmd, keep it as the backup, drive on lifetime warranty unit until failure then switch to the known good while you ship out the warranty one for its replacement.
In fuel diagnostics there are 2 other items to do.
Clear line on 1/4” return line off the ip (injection pump) and getting a fuel pressure gauge permanently mounted in dash, tapped in metal fitting at the ip inlet after the rubber hose.
99.9% of time I tell people start with those two, but you are most likely a bad pmd.
Do those two after pmd, but before replacing ip.
PMD is suspect. But read & learn first:
A low dollar code reader at a minimum should be owned. Dont buy one yet- lets learn more before spending money….
Never just start replacing parts aka firing the parts cannon.
There is no faster way to go broke and create more issues as you do it.
There is one thing that seems to fly in the face of that rule= PMD. The pmd is not a diagnose-able component, so GM said the way to diagnose it is “Replace with Known Good”
So unfortunately for this engine’s ds4 injection pump, you need to own a spare good one just like you would a spare tire.
Best solution for this is on your front bumper where it should be relocated to, you have 2 PMDs on two heat sinks (or one huge heat sink). Get an extra connector and fill the backside either silicone & let cure. Then install it in the spare PMD you have always in place next to the one in use.
Always when you have anything wonky happen with the fueling system- you swap to the known good spare PMD. On occasion the harness extension can fail- especially if it’s a cheap one.
Leroydiesel.com sells lifetime warranty PMD. I suggest start there, getting an extra heat sink if needed, and if you don’t know the quality of the extension harness - his are good.
When you have an old but good pmd, keep it as the backup, drive on lifetime warranty unit until failure then switch to the known good while you ship out the warranty one for its replacement.
In fuel diagnostics there are 2 other items to do.
Clear line on 1/4” return line off the ip (injection pump) and getting a fuel pressure gauge permanently mounted in dash, tapped in metal fitting at the ip inlet after the rubber hose.
99.9% of time I tell people start with those two, but you are most likely a bad pmd.
Do those two after pmd, but before replacing ip.
jrsavoie
Recruit
I like to have 2 extension harnesses plugged into the 2 PMDs
That way they can be swapped without getting down on the ground in inclement weather.
It does throw an extra variable in the system - the extra harness.
Make sure you have a resistor in each PMD or I think the resistor might be able to be placed in the extension harness.
I've heard of those but never tried it.
That way they can be swapped without getting down on the ground in inclement weather.
It does throw an extra variable in the system - the extra harness.
Make sure you have a resistor in each PMD or I think the resistor might be able to be placed in the extension harness.
I've heard of those but never tried it.
MrMarty51
Well-Known Member
When You order your spare, test, PMD from Leroy Diesel, also just buy his kit. It comes with the extension harness and heat sink and specify the No.5 resistor.
Then you will have the components hanging right next to the IP to switch out if a failed PMD test ever needs to be tried out.
I have three PMDs on harnesses behind the front bumper on My 2000 K3500.
I also ordered some spare harness ends to plug into the spare harness ends, as suggested by @Will L. I slightly filled the spare wire ends with silicone sealer so dirt can not enter there in
I also scribed numbers into those spare wire ends so I can keep track of which PMD went bad to make it easier to replace that one bad PMD.
Then you will have the components hanging right next to the IP to switch out if a failed PMD test ever needs to be tried out.
I have three PMDs on harnesses behind the front bumper on My 2000 K3500.
I also ordered some spare harness ends to plug into the spare harness ends, as suggested by @Will L. I slightly filled the spare wire ends with silicone sealer so dirt can not enter there in
I also scribed numbers into those spare wire ends so I can keep track of which PMD went bad to make it easier to replace that one bad PMD.