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Unread 12-16-2008, 09:17 PM   #1
ChiroSean
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1994 YJ Wrangler 
 
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High fuel pressure at the fuel rail

Just wondering what kind of problems running my jeep with high fuel pressure may cause? Back when I was having trouble getting the jeep to start I found that the fuel pressure was up around 80psi when the engine was running. I changed the fuel pressure regulator and it didn't make any difference. Still had very high fuel pressure. The only thing I have noticed is the gas mileage is terrible maybe 8-10 mpg. I thought it was from the larger 31" tires but some people I talked to said the bad gas mileage was from the high fuel pressure. Other bad gas mileage, can the high fuel pressure cause any other damage or problems???

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Unread 12-17-2008, 12:07 AM   #2
bigsquat
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high pressure is caused by a bad regulator or a kink or restriction in the fuel return line.

High fuel pressure will make it run rich like yours is.


To isolate the cause of high pressure, relieve system pressure and connect a tap hose to the fuel return line.
Direct the hose into a container and energize the fuel pump.
If fuel pressure is now within specifications, the fuel return line is blocked.
If pressure is still high, the new pressure regulator is faulty.


High pressure is usually caused by a bad pressure regulator or when a pressure return line to the fuel tank is kinked.
When there is a vacuum line to the pressure regulator, part of the procedure is to pull the vacuum hose off while the engine idles.
The pressure should rise about 8-10 psi in most systems when the hose is pulled.
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Last edited by bigsquat; 12-17-2008 at 09:36 AM..
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Unread 12-17-2008, 12:26 AM   #3
bigsquat
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one other thought is that your not getting vacum to the regulator. maybe a small crack or kink? put a vacum guage on it or take a hand vac pump and put it right to the regulator and see if the pressure drops
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Unread 12-17-2008, 05:16 AM   #4
drew2000
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High fuel pressure can also mess up your emissions if that applies to your locality.

Drew
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Unread 12-17-2008, 07:18 AM   #5
TSEJEEPERS
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If your return line is blocked or kinked it will make your new regulater go bad.
Most likely it is pinched in the rear where it goes through the cross member. Your supply, return, wires and the hoses for the vacume canister go through at the same place. Over time that cross member rusts and the hole gets smaller.
One way to make it bigger is with a 1" body lift. I ended up running hard lines through that area. They are smaller diam. than the rubber lines.
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Unread 12-17-2008, 01:02 PM   #6
ChiroSean
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Thanks for the reply's, I won't get a chance to check it out until this weekend, but I'll probably start by disconnecting the return line and routing it to a bucket. If it is blocked should I remove the old line and replace it or can I just run a new rubber fuel line back to the back? I think the vacuum to the regulator is good.
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