Okie dokie. Turns out my oil pressure switch was dead, causing my lift pump not to work (could they have put the OPS in a easier place to access???). My LP always had voltage but would not run until the OPS was replaced. So now, my new OPS, new batteries, and new LP allow my 95 6.5TD to start and run... for a couple minutes. Then it dies. All this for only $300!!!:ro)

I now, for the first time, have fuel coming out of both my air bleeder valve AND water/fuel separator valve. That's at least some progress!

I guess my PMD might be trashed too. I have heard that if the LP and or OPS are bad, it can cause the PMD to fail prematurely. Is this true?

I have a new PMD on the way from eBay. Poor guy lives in Gulfport, MS. May be a while!

What's the condition of your fuel filter?

less than a 1000 miles since changed out. Gets fuel to injector, but after 2 minutes the engine dies. Is it heat buildup killing the PMD? Or, I have heard you have to cycle your engine 10 times before things get back to normal. True?

I guess my PMD might be trashed too. I have heard that if the LP and or OPS are bad, it can cause the PMD to fail prematurely. Is this true?

I don't think that's true. The LP and OPS shouldn't have any effect on the PMD, and vice-versa. The only thing the PMD is tied to is the IP and the computer. If the PMD is bad, its because it died on its own accord. But I'm still a newbie, so FWIW. :o:

I have one on order. Since the engine still dies and everything else is checked, I guess I'll go ahead and swap it out. I sure hope that PMD does the trick- I need my truck back!

The theory is...
PMD may die an early death if the OPS/LP aren't working because less fuel is traveling thru the injection pump, so less fuel is available to cool the pmd. So the pmd runs hotter and dies prematurely. This is assuming the pmd is mounted on the pump. If it's remote mounted, then I think Stingray is correct.

My PMD is still pump-mounted. My truck is BONE stock! I'm not so sure I believe the air-cooled PMDs are better than factory located models. Liquid cooling is much more efficient. Maybe a liquid cooled relocation kit is OK- but people price these things like they are made out of platinum!

I used to believe the same thing, steve, until someone posted the fuel temp. from a scanner. A lot warmer than I would have thought or liked.-:t

maybe I'll look into a fluid cooled relocation kit. I am just tired of dumping money right now! This is whining, but everything is SO expensive these days.

My PMD is still pump-mounted. My truck is BONE stock! I'm not so sure I believe the air-cooled PMDs are better than factory located models. Liquid cooling is much more efficient. Maybe a liquid cooled relocation kit is OK- but people price these things like they are made out of platinum!

Liquid cooling is more efficient. However, the flaw in the design of the liquid cooled PMD is when the engine is turned off, no more fuel flow, and no more cool fuel to cool the PMD, yet there is a ton of heat still in the engine and the PMD for quite a while after the engine is turned off, especially in warm weather.

That's a good point. Hadn't looked at it that way. I'll check eBay to see what I can find. I know that any relocation kit AT A MINIMUM would make it a heck of a lot easier to access!

Liquid cooling is more efficient. However, the flaw in the design of the liquid cooled PMD is when the engine is turned off, no more fuel flow, and no more cool fuel to cool the PMD, yet there is a ton of heat still in the engine and the PMD for quite a while after the engine is turned off, especially in warm weather.

Just cause i was curious i ran some tests after reading this post.
Idling @ 1000 rpm for 30 minutes

Engine temp @ 190F - Fuel Temp Stable @ 117F

Shut down engine and 30 minutes later

Engine temp @ 168F - Fuel Temp @ 142F

Ambient outside temps @ 60F - These are off my scanner. These fuel temps would probably be hotter on a warmer day.

CR's numbers are right inline with my observations too. The hottest fuel temp I've ever seen was after a long hard run on a hot day and heat soak where I watched the fuel temp rise to a maximimum 180F, Coolant was 220F.
I was checking to make sure that we had solved a hard start hot complaint, the truck started right up and as soon as it did, fuel temps started to drop and after a short drive returned to ~145F.

Just for a update on my above numbers, i went for a 200km drive, probably averaged 70 MPH ECT's were 190F and the highest fuel temps i got were 138F. Ambient at that time was about 70F.

I'm looking at FSD coolers online and I am AMAZED by how much some heat sink aluminum fins cost.

See what I mean? Look at the #s CR and TDG posted. You're going to cool the PMD with fuel that is almost as hot as boiling water?

I see what you mean, but I thought about something overnight. A heat sink is just that- something that attracts heat (supposedly away from hot objects that need to cool). Has anybody tested a heat sink's temp while driving and then again after the engine has been shut off for 30 minutes? My guess is it will be pretty hot still?

If so, it's then an issue of "lesser of 2 evils"...

I see what you mean, but I thought about something overnight. A heat sink is just that- something that attracts heat (supposedly away from hot objects that need to cool). Has anybody tested a heat sink's temp while driving and then again after the engine has been shut off for 30 minutes? My guess is it will be pretty hot still?
If so, it's then an issue of "lesser of 2 evils"...

Heat sinks only work well if there's cool air surrounding them. Depending on where you mount the FSD cooler, you could run into the same heat soak issue after the truck is shut down if the heat sink is exposed to hot air and no air flow for a period of time.

I'm surprised no one has tried mounting a fan to the heat sink, in a similar fashion as a computer processor heat sink fan setup (maybe someone has, but I haven't seen it). A good CPU fan is cheap, already setup for 12v DC current, and will make the heat sink much more effective. A good fan system would be hooked up to some sort of timer to run for say 10-15 minutes after engine shutdown to avoid heatsoak issues, then shut off automatically to save the batteries. Or, you could have the fan hooked up to a small thermostat mounted to the FSD's heat sink, so it only comes on when the heat sink gets hot. Just a thought.

I thought of that but a big ass hunk of extruded finned aluminum heat sink should do it ok without me worrying about the pita fan failing

Question: how are you guys measuring fuel temperatures? temp. gun, gauge in the fuel line? I'm very curious.

Incidentally, I have Heath's remote PMD cooler and have put my hand on it after a long trip with 60-70 degree ambient temps. and have not felt it to be more than warm to the touch. It just seems that the heat up off the blacktop is making it about as warm as when it's in operation.

SnowDrift

I moved my heat sink (remote cooler) out of engine bay and mounted it behind front bumper in a fashion that wind directly hits the cooling fins, I will do some studying over the next few days to see how hot PMD gets while driving and how hot PMD gets heat sink after shut down. There is obivioulsy no air flow after shut down, it got me curious not too.

Question: how are you guys measuring fuel temperatures? temp. gun, gauge in the fuel line? I'm very curious.

Incidentally, I have Heath's remote PMD cooler and have put my hand on it after a long trip with 60-70 degree ambient temps. and have not felt it to be more than warm to the touch. It just seems that the heat up off the blacktop is making it about as warm as when it's in operation.

SnowDrift

Mine are measured with the scanner and i can only assume it takes it from the ECM probably via the IP, so i'm only guessing its the temperature of the fuel in the IP, Tex should be able to clarrify that though.

fan on PMD- now THAT is a good idea. I haven't seen anything like that on the web. I will try the PC fan and maybe wire it in with some sort of thermostatic control.

Excellent idea!

First post for me...

I have a 4x8" finned heat sink bolted to the plenum. After driving hard in good ole Texas Summer weather, the handy dandy temp probe (usually stuck in the vents to check ac efficiency) measures 140 to 170F when I stop and cools to about 130 after about 15 minutes.

My MacGuyver-ish solution works against me though: true I am sinking heat AWAY from the driver, but I am also sinking heat from the intake as well. I need to isolate one from the other but NASA is not interested in selling the foam tiles from the shuttle right now... (to shield the heatsink from the engine). Any ideas (cheap ones)?

My two cents: I would rather go with higher CONSTANT temperatures under way with the ABILITY to replace the remote FSD in 3 minutes rather than bolt it to the PUMP and have it cook every time the engine is shut down and eventually spend hours getting to it for replacement.

God bless the shade-tree wrench-turners and vendor folks who preceed me in this endeavor to make the 6.5's run more reliably. She is a good engine but a tempermental pig when the electronics start to fail. We deserve Stanadyne's best efforts in their $300 FSD's and I for one would like to see an improved version. A 300,000 mile engine should not need a $300 stepper driver board every 40k miles.

I thought of that but a big ass hunk of extruded finned aluminum heat sink should do it ok without me worrying about the pita fan failing

Computer fans are very reliable - they typically run 24 hours a day, everyday, for years without failure in servers and computers. The only thing that would knock the fan out would be corrosion, moisture and weather from the road, so if you went the fan route, the FSD would need to be mounted in a clean, dry area, away from any weather the truck will encounter on the road (i.e. not the front bumper).

From just doing the hand temp test, it doesn't seem to heat up anywhere near what it used to. I had a concearn about corrision, being mounted on front bumper, I am assuming the PMD can handle the weather since it could handle the extememe conditions of where it is mounted from factory, but I agree the front bumper is surely not a place for a fan. Althought I contimplated mounting it under the dash or driver's seat on heat sink, and I'm sure a fan would work for ever there.

Keep it simple, yes? I calibrate and repair big buck test equipment for a living and the fans do fail even in a lab environment. The bearings do not last forever. A chunk of aluminum, passively cooling the PMD will.

Well, I can see both points of view. PC fans do fail but are, overall, highly reliable today. Of course, a heat sink has no moving parts, so it will last indefinitely.

The point I find interesting at this point in the discussion is that no vendors offer a fan cooled PMD! If it were mounted to the PMD on a heat sink, seems the best of both worlds!