Fsd?

[hayhauler69]

Hi,
OK all you experts I need help.
My 1995 K2500 4x4 6.5 TD is raising a little heck.
It dies intermittently at will. I can drive it for 30 miles fine, then go around the block and it dies constantly.
Had it diagnosed and the shop thought maybe a crank sensor, they saw some sort of spike on the tester I guess. So it was replaced.
It'll 'miss' then run fine. Doesn't matter what rpm it's running at or on throttle or off, it'll die.
Any help would be appreciated.
Thanks, Buzz

[Robyn]

Sounds like the infamous PMD/FSD issue

This is the little black box on the drivers side of the IP.

If its still bolted there get a new one and an extension cord and heat sink and mount the sucker down on the inside of the front skid pan under the radiator.

Easy to do the pan hinges down by removing two bolts from the front of the lower frame and the aluminum pan will drop right down.
Use tie wraps to secure the longer cable and be sure and use heat sink compound on the back side of the new PMD when you mount it to the heat sink

The issue you describe has been a very common issue.

let us know

Robyn

[hayhauler69]

Thanks Robyn for the reply.
I have a new unit comming Tuesday. Already to go installed on a heatsink.
I'm changing the fuel and air filter too.
Told the shop the truck was at I thought it was the FSD. But just being a 737 jet aircraft mechanic I guess I was ignored:)
I keep telling myself, yes the truck is worth it. It's in really good condition with only a 100000 miles on it.
I'll keep you posted, Buzz

[Robyn]

Its amazing that once you take your rig to a shop they think you dont know anything :eek:

Had a bad fuel pump (tank type) on a 95 gas burb and it was failing.
Took it to the Chevy dealer and told them to replace it.
The mechanic argued that the pump was fine and that the truck run fine.

I laughed at him and told him to take it out for a 20 minute hard run, he did so grudgingly and then did not return.


Haaaaaaaaaaaaaaa :D funny thing the fuel pump quit and he had to wait for the shop tow truck to go out and fetch him up.

But what did I know, Im just the customer :rolleyes:

I do hope the PMD fixes the sucker for you.

Generally if the issue is inside the IP the computer will set a code.

Seldom does the PMD set a code.

I have had several 6.5's with the DS4 and had all of them suffer PMD failure without setting a code.


Later and good luck

Robyn

[hayhauler69]

I changed the fuel filter and air filter.
Drove it for about 20 miles and it started acting up again.
I'm almost positive it's the FSD/PMD.
Drove around my country block at least three times gave the Wife a thumbs up each time, then took it out on the road for a spin. Climbed a steep hill and it hiccuped went on for a few more miles with no glitches. Stopped at a stop sign and it died soon after. Wouldn't start for a few tries in fact it wouldn't even turn over once, sounded like the battery was dead, you know just the solenoid was clicking, but it started and I went straight to home.
Truck ran beautifully with new filters. Straight pipe sounds good, a little loud though. But, that's OK:)
So Tuesday I get new unit, hope it works.
Buzz

[Robyn]

Now this little tid bit of info changes the mix here.

You may well have battery cable issues.

Check all the cables. Better yet if they have a lot of time on them change all the cables out.
The GM cables have a nasty habit of coroding in the core and under the boots where you can't see it.

If you are getting goofy voltage the sucker can do all sorts of wierd stuff.

The ground cables where they bolt to the engine are notorious for going south in the crimp.

The power from the alternator comes from the alternator to the left battery and then across the header in the cross cable to the main battery.

These cables are soldered at the cripm (factory cables) but the core is not bonded and will corode leaving very little actual cable to do the work.

Both of the 94's we have had did this trick.

Check this out. :D

let us know

Robyn

[hayhauler69]

Hi Robyn,
Yep, doing new cables tomorrow. My one day off from work.
I read on another forum the same thing. The positive cable running from right to left is not in very good shape, hard in places. All the connectors are the type with two quarter inch bolts squeezing the cable ends. So I bought factory cables, 250.00+ bucks, sounds like maybe that was a bad idea?
I'm doing that in the morning so I'll post my results after a test run. Wish me luck:) Gawd, I hope that's it.
Thanks for all your help. I've learned a lot.
Buzz

[Robyn]

The litle aftermarket cable ends that bolt on are a very poor choice for a replacement in my opinion except in a pich to get going temporarily.

You will find that things will be a lot better after you get the cables replaced.

I wont tell you thats all your troubles but it is a good place to begin.

Battery voltage and grounds are a real biggy on these computer rigs.

The older trucks with the DB2 fuel system and no computer were pretty forgiving.
As long as the suckers would get enough power to run the glow plugs and turn the thing fast enough to fire you could get off down the road.

Always in any rig its a good idea to keep tha cables and such up to snuff.

Everything works so much better and you dont get wierd stuff happening.

Good luck and let us know how it all comes out.

OH BTW

If your truck has the PMD mounted on the IP and it has any real time on it, I would sure consider a new PMD and a remote mount on a heat sink just to eliminate any greif later.

Robyn

[hayhauler69]

I have one more cable to go, just came up for coffee refill:)
Yeah, I'm getting a new PMD tomorrow with a heat sink. Ordered from SSD.
Seem like good people, but there's a lot of competition out there for after market diesel stuff.
Had a little trouble with positive cable going to relay box. Everything wanted to turn, but I got it.
Going to drop starter now.
Buzz

Well my little red wagon runs like a champ! Battery cables did the trick!
I must admit though that one nut kicked my behind. Nuts and bolts usually don't get the better of me but this one did.
It's forward of the starter on top, think it's attached to the heat shield, so that cable is still old:( I'll let some poor smuck at the shop do it.
Thanks again Robyn for all your help. I'll be around to talk about my upgrades.

[Robyn]

Sweeeeeeeeeeeeeet :D

I love it when a plan comes together :)

Best to ya

Robyn