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Unread 08-11-2013, 11:08 AM   #1
Hilblee
Registered User
1989 YJ Wrangler 
 
Join Date: Apr 2013
Location: Layton, UT
Posts: 16
Fuel Pressure

First---89 YJ with 93 HO 4.0---Jeep runs great once started.

I've had this problem since I bought my jeep and thought it was time to fix. I have to prime the pump 2 cycles and then shortly turn the motor once and back off then it will start. The pump will only cycle approx .5 seconds before stopping. I checked the fuel pressure and all was good while running but as soon as the key goes to off, it drops immediately to zero. Changed the fuel press regulator but no fix. Thought the check valve in the fuel pump was probably bad. Dropped the tank and changed the pump. Still drops to zero immediately and the prime cycle is still about a half a second.
Ive read on hear that a pressure drain over a couple minutes is a leaking injector but mine is instant.

Why is the prime cycle so short and why does my fuel pressure drop so fast? There are no leaks between the pump and the fuel rail.

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Unread 08-12-2013, 02:02 PM   #2
Hilblee
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1989 YJ Wrangler 
 
Join Date: Apr 2013
Location: Layton, UT
Posts: 16
Nobody??
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Ive owned 74, 75, 76 and 79 CJ-5s. 76 J10 (prob the best jeep ever) 89 YJ (current) and a 98 TJ. I consider all of them "Money Pits" Always throwin money at em whether they need it or not!
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Unread 08-12-2013, 03:11 PM   #3
GrantYJ
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1992 YJ Wrangler 
 
Join Date: Mar 2009
Location: Neosho, Missouri
Posts: 857
We have very different equipment ('92 2.5L MPFI here), but mine also has a very short prime (like yours). As for the immediate pressure drop ...it sounds like you've already addressed any suggestions that I would've made.
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“The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed.” ― Robert M. Pirsig, Zen And The Art Of Motorcycle Maintenance: An Inquiry Into Values
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fuel pressure , fuel pump , pressure regulator

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