1996 F250 7.3L vacuum issue - Diesel Forum - TheDieselStop.com
Power Strokes 1994-1997 General Technical discussion of topics related to vehicles powered by the Power Stroke engine in 1994 through 1997 models.

 
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post #1 of 9 (permalink) Old 02-12-2016, 06:51 PM Thread Starter
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1996 F250 7.3L vacuum issue

Hey guys I drive a 1996 f250 7.3 powerstroke, The truck sat for about a month in my garage and mice decided to make a home in my blower motor, so i pulled the blower motor out today and cleaned it all up and stuck it back in and I have air again. However, now when i drive the truck when i first get on the gas it acts as if something is blocking a vacuum and i lack power, and at a certain RPM the pressure is released and power comes back like normal. Any idea what It could be? the truck drove absolutely fine until i messed with the blower motor.

-StormTrooped 7.3
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post #2 of 9 (permalink) Old 02-12-2016, 07:42 PM
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Diesels do not make vacuum of any sort. You have a vacuum pump mounted to the front of the engine to provide vacuum for the HVAC controls and for the brake booster.

Time to go over the area you were working in to be sure that everything is connected properly. You may have disconnected/broken the MAP sensor hose, which is on the passenger upper/inner side of the head/valve cover.
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post #3 of 9 (permalink) Old 02-12-2016, 09:01 PM Thread Starter
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Will do, Could that cause a loss of power in the truck? its not significant loss and could honestly be my mind playing tricks on me. But there definitely is a suction noise up until about 2k RPM and then that "pressure" is released

-StormTrooped 7.3
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post #4 of 9 (permalink) Old 02-13-2016, 12:27 AM
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Get on the gas? Don't do that!

Is it a whhssssshhh sound? Goes away when you floor the go-pedal? Goes away completely when the engine is good and hot? That's your EBPV - exhaust back-pressure valve. Closes if the outside temperature is below 37F and the oil temp (EOT) is below 150F. Opens at 150F EOT, and opens temporarily when you floor it. It intentionally increases exhaust back pressure supposedly to speed up warm-up time. A lot of people don't like it, and disconnect the electrical connector to it and wire it open.
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post #5 of 9 (permalink) Old 02-13-2016, 06:29 AM
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Sounds exactly like the exhuast back pressure valve (EBPV) doing it's job. Butterfly valve in the outlet of the turbo. When it's cold, oil pressure closes it to help the engine warm up. If you really hammer on it going down the road, it'll open up. Normal, but a lot of guys here have unplugged it.
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My Truck:

97 F250 4 door shortbed, E4OD
DIY intake
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otherwise stock
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post #6 of 9 (permalink) Old 02-13-2016, 09:19 AM Thread Starter
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Thankyou so much guys that's exactly what i wanted to hear!

-StormTrooped 7.3
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post #7 of 9 (permalink) Old 02-13-2016, 10:57 AM
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If you think it might be coming from the blower motor, check the white vacuum line near the Right hood hinge, shown here:



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post #8 of 9 (permalink) Old 02-21-2016, 04:07 PM
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I replaced my white vacum line with the 3/32 vacum hose over the weekend , made a big difference in my AC
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post #9 of 9 (permalink) Old 02-22-2016, 09:00 AM
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Quote:
Originally Posted by madpogue View Post
Is it a whhssssshhh sound? Goes away when you floor the go-pedal? Goes away completely when the engine is good and hot? That's your EBPV - exhaust back-pressure valve. Closes if the outside temperature is below 37F and the oil temp (EOT) is below 150F. Opens at 150F EOT, and opens temporarily when you floor it. It intentionally increases exhaust back pressure supposedly to speed up warm-up time. A lot of people don't like it, and disconnect the electrical connector to it and wire it open.
Quote:
Originally Posted by AaronSEIA View Post
Sounds exactly like the exhuast back pressure valve (EBPV) doing it's job. Butterfly valve in the outlet of the turbo. When it's cold, oil pressure closes it to help the engine warm up. If you really hammer on it going down the road, it'll open up. Normal, but a lot of guys here have unplugged it.
AaronSEIA
Just learned something new today. Thanks.
I'd recently noticed that exact "problem"over the last month or so, just during the first few minutes of driving. I guess I'd never noticed it before since it rarely gets cold down in South Texas.
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