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Unread 06-25-2013, 04:38 PM   #1
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1998 XJ Cherokee 
Join Date: Oct 2009
Location: st.pete
Posts: 128
hard start fix, I think.

Lately, as in, for as long as i've owned the xj, its always had a rough time starting. I tracked it down to being the fuel rail losing pressure due to a bad check valve. I dont want to drop the tank and replace the pump for a $.25 part. I was thinking though....

What or where is the module that makes the fuel pump turn on for two seconds prior to starting? If i could make it so the pump primed for 5-10 seconds then i wouldn't have a hard time starting it. Right now i just turn the key on, then off, then on again to get the pump to prime twice. I just feel like thats putting unnessacary wear on the ecu and other things. I think if i could get the pump to prime longer then i wouldn't have to turn the key on and off multiple time just to get pressure in the fuel rail.

Let me know what you think. Thanks.

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Unread 06-25-2013, 06:32 PM   #2
It's the crank sensor!
tjwalker's Avatar
1999 XJ Cherokee 
Join Date: Nov 2007
Location: Central Minnesota, MN
Posts: 8,433
The way the fuel pump operates is a function of the computer. Trying to fix a factory designed function would not be wise to even think about undertaking.

You are definitely not putting any undue wear and tear by turning the key on and off a couple of times; no worries. Continue to do that or drop the tank and replace the fuel pump assembly with a Bosch or Carter replacement. There are 2 check valves; one on the regulator (primary) and another on the fuel pump itself. My advice is when you have the tank down and pump out, replace the entire assembly. The pump itself is usually getting close to tired and unless you like doing things twice, it is just good common sense.
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
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