| Author |
Message |
    
Murray (Cdnrvr)
| | Posted on Tuesday, April 02, 2002 - 10:11 pm: | 
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I was in the process of replacing my O2 sensors on my 95 DI (3.9) and noticed a vaccuum line that was not plugged in at the back of the engine on the driver side. When the engine is running there is vaccuum from the hose. Two questions - is the fuel pressure regulator located on the back of the engine on the driver side and two, should a vaccuum line plug in to it. I suspect that it came off of there.
Thanks,
Murray |
jp
| | Posted on Wednesday, April 03, 2002 - 04:12 am: |
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YES, this is the pressure regulator line! Plug it back into whichever it is disconnected from asap - it should improve your response and economy. If you test pressure at the rail, idling, should be 30psi; pull the vac line - 37psi on mine. Somehow the richness caused when no vacuum is there to reduce pressure chokes them down, and is a bad thing.
I was warned about a practice at the dealer here of pulling this line on services. I check mine before a service, and after, and sure enough they had pulled it off. I went back and gave them heaps, but it was water off a duck's back. worst part is they are the only dealer in town, so we're stuffed for options. |
Murray (Cdnrvr)
| | Posted on Wednesday, April 03, 2002 - 08:30 am: |
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Thanks JP, plugged in.
Murray |
Randall Smith
| | Posted on Wednesday, April 03, 2002 - 09:55 am: |
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The fuel injectors are located in the ports of the intake manifold. There is always a vacuum inside the manifold, and the vacuum helps pull the fuel thru the injectors. So the total fuel pressure is what is is the fuel rail + vacuum in the intake equals total fuel pressure.
The vacuum hose between the intake and the fuel pressure regulator adjusts the regulator so that the total fuel pressure is the same most of the time.
Randall |
p m
| | Posted on Wednesday, April 03, 2002 - 02:38 pm: |
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Randall,
i think this is a simple patch for altitude compensation (without having to change the ECU program much). Less intake vacuum (at the same throttle position and rpm) means less air, so less fuel needs to be sent it. without it, if you live at higher elevations, ECU may be close to the limit of its operating range of injector pulse width.
It will work the same way for high-load conditions - increase fuel rail pressure when intake vacuum is low (WOT). Again, ECU can and will increase fuel delivery, too, but this simple patch will keep it within its operating range.
I haven't really noticed much difference before and after I replaced the rotten vac. hose to the regulator on my rangie, but I could have if I drove it to the mountains.
peter |
jp
| | Posted on Thursday, April 04, 2002 - 02:52 am: |
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Dont think it works quite that way. The air flow meter measures mass of air, and lower pressure caused by altitude causes lower mass to flow, so ecu gives correct fuel delivery. Low vacuum (WOT) allows full pressure to rail (+20%, 30->36psi), providing a little more fuel for accelerating before engine has started to suck more mass of air (like an accelerator pump on a carb). On overrun, or idle much less fuel is needed, so vacuum reduces pressure, in systems that dont have cut off on overrun capability. Less vacuum doesnt mean less air, it means more of the demand is being met. IMHO anyway.
jp |
Kingfish (Kingfish)
| | Posted on Friday, April 05, 2002 - 07:53 am: |
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Hey thanks guys for the info. I checked out my Disco last night and saw the hose connected to the fuel P. R. The hose looked kinda rotten so when I squeezed it, I saw that the OTHER end was not connected. I bought some new hose and put it in there. I hope I found the right thing to plug the other end to (a small pipe on back of intake, about 90 degrees to air intake, pointing straight to the windshield?). I noticed the car starts faster and has more response on the throttle (or maybe I'm just imagining?). Thanks again. |
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