You have several possibilities here.
First is that you picked up a batch of bad fuel, possibly contaminated with
water or algea. I would suggest draining the fuel/water seperator and then
replacing the filter again. If it helps for a little while then starts
again with the same problems, do it again but add a batch of diesel fuel
treatment as well.
The second is that your new lift pump may be on the fritz. Possibly a bad
connection or ground and it is only intermittently working.
The third concerns the PMD and fuel injection pump. When you replaced the
PMD (aka - FSD or Fuel Solenoid Driver), did you also have the FI pump
replaced or rebuilt? If not, then you may need one. One problem is that
excess heat from the FSD can also bake the optical sensor inside the pump
which will fry the pump and require a replacement. In addition, the heat
from the FSD also thins out the fuel which reduces its lubricity and
accelerates wear on the FI pump and will also lead to a replacement.
I always recommend that whenever anyone installs either a new FSD or full FI
pump that they remotely mount the FSD off of the pump body onto a device
known as an "FSD Cooler". This is nothing more than a finned heat sink that
the FSD bolts onto and is mounted somewhere away from the FI pump. With
this, the heat from the FSD is bled off into the atmosphere and not absorbed
into the body of the FI pump causing all of the problems I just mentioned.
The DS4 electronic fuel injection pump is actually a pretty good unit and
worked very well on the test bench. But drop it into the V of a diesel
motor, keep the FSD bolted to the front and then cover the whole thing with
a plastic "Turbo Diesel" cover and you have a formula for heat-related
problems. If you end up replacing the FI pump, throw away the plastic cover
and remote-mount the FSD.
Cheers - Jonathan
I had the same problem a year or two ago. I replaced the PMD (and remote
mounted it with a heat sink that I purchased from ebay) and it worked just
fine. Just yesterday, the engine stalled again. I was driving 50 mph and
it just stopped. I cursed a little and restarted it. On the way home from
work, later the same day, it stalled two or three more times. Today, it did
not stall at all. I'm hoping that it's not the PMD again. My truck is a
1995 and it has 245,000 miles in it. With the price of diesel fuel (over $3
per gallon) and the fuel milage that I get (not good), I'm not too convinced
that I want to put a whole lot more $$ into it. If I remember correctly,
the lift pump is quite expensive and so is the injection pump.
You may want to check/replace the PMD wiring harness
(connects to the PMD/FSD when mounted on the fuel injection
pump, about $20) -- the wiring or connector may have gone
bad. Mount the FSD remotely (from the FI pump, that is) to
protect both the pump and FSD.
Dirty fuel will give problems to the fuel lift pump, diesel
injection pump ($$$$) and the diesel injectors ($$).
Install a Racor 645 fuel filter/water separator with a 10 or
2 micron element (around $90) for ease of maintenance and to
protect your fuel injection system.
Try slowly removing the fuel filler cap after shutting off
the warm/hot engine -- does air get sucked into the filler?
If so, your diesel injectors (one or more) may be leaking
air BACK into the fuel system causing the hard-start
condition, in which case just release the partial vacuum in
the fuel tank after every warm/hot engine shutoff.
Do the diesel fuel treatment as Jonathan stated -- high
concentrations, several/continuous treatment may be
Reinstall the fuel lift pump you removed earlier to see if
the new one you installed may be the culprit -- check the
grounds, or better yet, drill/tap new ones.
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