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Old 08-01-2005, 11:31 AM   #5 (permalink)
Texas Diesel Guy
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[SIZE="2"]Once again, great write up, just let me add a couple things
Quote:
Originally Posted by knkreb
What does the PMD do? The PMD is the boss telling the IP what to do. Open the fuel solenoid, close the solenoid.
The PMD has 2 roles. The main role is to amplify the signal from the PCM (boss) to energize and close the fuel solenoid.
The second, is to monitor Fuel Solenoid performance, and reporting a Closure Time back to the PCM.
The most common failure is when the amplifier portion of the driver fails and you get stall and no start problems.
The way to detect this is to watch a scanner when you are in a no-start condition. If your CTIME = 0.00, then your Fuel solenoid is not closing because of the PMD, blown fuse or wiring problem.
Quote:
Originally Posted by knkreb
Doesn’t this design keep them cool enough? For the most part, yes it does. Especially while running, fuel is constantly being circulated through the pump, removing heat constantly. Problem arises, as the theory goes, that during the off-cycle, the heat build up from the engine damages the PMD. There is an amazing amount of heat held under the hood during off cycle. Just imaging snuggling up to that engine after being on the open road for a while.
During normal operation, driving, idling, towing even on a hot day, usually fuel temps inside the pump will peak around 140-150F.
During a heat soak, the highest temps I've ever observed, after getting the engine as hot as possible, Coolant temp 220F+, shut the truck down and watched the scanner for over half an hour, I never saw it quite reach 180F.
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Last edited by Texas Diesel Guy; 08-01-2005 at 11:46 AM.
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