Keith Browning Posted November 23, 2012 Share Posted November 23, 2012 The oil pressure switch in these trucks is wired to the PCM and then the info is multiplexed to the instrument cluster. I have come across a question as to whether or not the 6.7L would shut down if oil pressure is lost (other than blowing up) From looking at the PCED and the OBD book and the manual I cant find anything that would even suggest such a strategy exists. Anyone know any different? Quote Link to comment Share on other sites More sharing options...
GregH Posted November 23, 2012 Share Posted November 23, 2012 Back when I was still working on these things, I had one with an intermittent oil pressure warning on the dash. CND, so I replaced the switch and it never came back. Customer never complained about an engine shutdown, and when the warning indicator would illuminate, it would stay on for some time. Now, that was about 17 reflashes ago... Things may have changed since then. How about disconnecting the sensor (and shorting the pins if necessary) and see how one behaves? Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted November 23, 2012 Share Posted November 23, 2012 Ford ain't never been to keen on using the oil pressure switch for anything special. I doubt they have started now. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted November 23, 2012 Author Share Posted November 23, 2012 Not only that Brad but imagine cruising down the Interstate towing a trailer and the switch fails... and the engine shuts off. At least with a gauge and a warning you can pull the truck over safely and determine if the warning is is a really problem. I would imagine a loss of oil pressure would cause some noise from the engine. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted November 24, 2012 Share Posted November 24, 2012 Quote: some noise from the engine. Like a type writer noise? Quote Link to comment Share on other sites More sharing options...
Aaron Posted November 24, 2012 Share Posted November 24, 2012 I think NHTSA prohibits ANYTHING shutting the engine down aside from the key or an actual failure that prevents it from running. On the overtemp on the 6.4 it told you to stop safely, maybe it does the same thing on the 6.7? Pull the wire off teh sensor when the engine is running and see what happens? I like how the low oil pressure indicator was GREEN on the 6.4 Awesome LOL.. The oil light came on, but it was green so I thought it was OK! Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted November 24, 2012 Author Share Posted November 24, 2012 Pull the wire off teh sensor when the engine is running and see what happens? When I have the oportunity and remember to perform this little experiment I will. Of course, don't let me discourage anyone else from doing this and reporting back! Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted November 25, 2012 Share Posted November 25, 2012 Have we all forgotten the "Stop safely now" message? Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted November 26, 2012 Share Posted November 26, 2012 Pfft, I'll stop when I get to where I'm going! Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted November 26, 2012 Author Share Posted November 26, 2012 Quote Link to comment Share on other sites More sharing options...
DieselD Posted November 26, 2012 Share Posted November 26, 2012 I think NHTSA prohibits ANYTHING shutting the engine down aside from the key or an actual failure that prevents it from running. On the overtemp on the 6.4 it told you to stop safely, maybe it does the same thing on the 6.7? I think your spot on here. knowing how dumb some people are they wouldn't be able to figure out what to do if their engine shutdown on its own. I think at most you would get a warning and a stop engine message then prevent a restart but I do not know the answer on the 6.7 oil switch condition Quote Link to comment Share on other sites More sharing options...
Aaron Posted November 26, 2012 Share Posted November 26, 2012 I think NHTSA prohibits ANYTHING shutting the engine down aside from the key or an actual failure that prevents it from running. On the overtemp on the 6.4 it told you to stop safely, maybe it does the same thing on the 6.7? Pull the wire off teh sensor when the engine is running and see what happens? I like how the low oil pressure indicator was GREEN on the 6.4 Awesome LOL.. The oil light came on, but it was green so I thought it was OK! Originally Posted By: Jim Warman Have we all forgotten the "Stop safely now" message? Nosir Quote Link to comment Share on other sites More sharing options...
Fordracer Posted November 27, 2012 Share Posted November 27, 2012 Back in 1985 and 1986 the 460 had a carburetor and electric fuel pumps and the oil sendor had two wires on it and it would shut the pumps off if there was no oil pressure. Alot of good that would do when you still had fuel in the fuel bowls to run off of. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted November 27, 2012 Share Posted November 27, 2012 GM's were wired that way for years, also, I think it was the TBI years IIRC. Quote Link to comment Share on other sites More sharing options...
lmorris Posted November 28, 2012 Share Posted November 28, 2012 Back in 1985 and 1986 the 460 had a carburetor and electric fuel pumps and the oil sendor had two wires on it and it would shut the pumps off if there was no oil pressure. Alot of good that would do when you still had fuel in the fuel bowls to run off of. From my understanding, this was more to make sure it had oil pressure before supplying fuel, not to shut it down if it dropped off. Just like the 7.3L and 6L's were never designed to shut the injection system down when the oil pump gave out, it was more of an unintended perk. Quote Link to comment Share on other sites More sharing options...
lmorris Posted November 28, 2012 Share Posted November 28, 2012 GM's were wired that way for years, also, I think it was the TBI years IIRC. You are correct, and it made them easy to deplete the system of pressure before changing fuel filters. Quote Link to comment Share on other sites More sharing options...
amailloux Posted November 28, 2012 Share Posted November 28, 2012 All of the GM's I remember were wired in parallel, not series, so as long as the relay, or oil pressure switch was closed the fuel pump would run. It does not shut the pump off with just low or no oil pressure. Quote Link to comment Share on other sites More sharing options...
Aaron Posted November 28, 2012 Share Posted November 28, 2012 GM's were wired that way for years, also, I think it was the TBI years IIRC. My LT1 in my Impala SS had the oil pressure switch tied into the fuel pump relay, I remember the diagram but I can't specifically remember if it was in parallel or series like someone else mentioned. Quote Link to comment Share on other sites More sharing options...
cbriggs Posted November 29, 2012 Share Posted November 29, 2012 I believe they bypassed the oil press switch in start, but once in run it required oil pressure to keep the fuel pump running. GM's version of our inertia switch. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted November 29, 2012 Author Share Posted November 29, 2012 I believe they bypassed the oil press switch in start, but once in run it required oil pressure to keep the fuel pump running. GM's version of our inertia switch. That is pretty stupid if it's accurate. You could still have a collision that does not shut the engine off and have a fuel leak somewhere. The purpose of a fuel pump shut off switch is to disable the pump after a collision that could cause a leak and result in a fire... not necessarily shut the engine down though I think that is desirable as well. Quote Link to comment Share on other sites More sharing options...
lmorris Posted November 29, 2012 Share Posted November 29, 2012 Originally Posted By: cbriggs I believe they bypassed the oil press switch in start, but once in run it required oil pressure to keep the fuel pump running. GM's version of our inertia switch. That is pretty stupid if it's accurate. You could still have a collision that does not shut the engine off and have a fuel leak somewhere. The purpose of a fuel pump shut off switch is to disable the pump after a collision that could cause a leak and result in a fire... not necessarily shut the engine down though I think that is desirable as well. I did a bit of digging and oddly enough it is correct. The only thing I can't find is what actually shuts off the engine. My theory is that if a fuel line ruptures the engine loses fuel pressure and shuts off, oil pressure drops as a result and shuts down the fuel pump. Quote Link to comment Share on other sites More sharing options...
cbriggs Posted November 30, 2012 Share Posted November 30, 2012 The theory I was told in trade school (trying to remember back 13 or more years) is that if the accident was bad enough to kill the engine they wanted the fuel pump shut off, but if the engine stayed running they assumed the fuel system was intact. Kindof goofy logic, but seems to be less problematic than out inertia switches. Also works as an accidental failsafe, if you run the engine out of oil. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted December 1, 2012 Share Posted December 1, 2012 Leon, where did you find the reference to the oil pressure? FWIW, the 6.7 still has an inertia switch but most (if not all) gas engines now depend on a signal from the restraints control module to the fuel pump driver module as an "electronic" inertia switch. This electronic switch action can be reset by turning the key off and then on again. IIRC, GM using oil pressure as a control for the electric fuel pump was a Chevy Vega/Pontiac Astre feature - unsure about what other models use this strategy. Others would shut down the fuel pump if RPM signal was lost. Quote Link to comment Share on other sites More sharing options...
cbriggs Posted December 2, 2012 Share Posted December 2, 2012 Throttle body injected small blocks used it for sure,(87 thru 95) and I think the early vortec small blocks ,also I seem to remember some late 90's car v-6s that had it. Quote Link to comment Share on other sites More sharing options...
lmorris Posted December 5, 2012 Share Posted December 5, 2012 Leon, where did you find the reference to the oil pressure? FWIW, the 6.7 still has an inertia switch but most (if not all) gas engines now depend on a signal from the restraints control module to the fuel pump driver module as an "electronic" inertia switch. This electronic switch action can be reset by turning the key off and then on again. IIRC, GM using oil pressure as a control for the electric fuel pump was a Chevy Vega/Pontiac Astre feature - unsure about what other models use this strategy. Others would shut down the fuel pump if RPM signal was lost. Look at page 21 of this: http://www.gmceast.com/technical/Swartzendruber_Generic_TBI_SlidesNotes.pdf Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.