code 543 in a '91 4.0 explorer
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Joined: Feb 2003
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code 543 in a '91 4.0 explorer
got the code from a 91 explorer (543) secondary fuel pump. what would cause this code? the truck runs terrible. it is running rich, it ran fine until it wouldn't start in cold weather. took it in and the told me it needed new fuel inj. (all of them) it runs better cold then when warm.
thanks
-Bigzero
thanks
-Bigzero
Post Fiend
Joined: Jun 2002
Posts: 13,873
Likes: 3
From: Atlanta GA
re:code 543
Not having a 91 4.0 Explorer in front of me and assuming it is like other 4.0/2.9 Ranger setups ... You have a low volume pump in your tank and a high pressure one inside your frame rail under the driver's side. It should be mounted inside a box/shield. If this pump fails, your truck will not run.
If the one in the tank fails, your truck might run, but, run roughly.
I would say the secondary (without a code book to look it up) is the low pressure one inside the tank.
Not having a 91 4.0 Explorer in front of me and assuming it is like other 4.0/2.9 Ranger setups ... You have a low volume pump in your tank and a high pressure one inside your frame rail under the driver's side. It should be mounted inside a box/shield. If this pump fails, your truck will not run.
If the one in the tank fails, your truck might run, but, run roughly.
I would say the secondary (without a code book to look it up) is the low pressure one inside the tank.
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
That code means that somewhere along the way, power was interrupted to the secondary side of the fuel pump relay. It could be due to a bad fuel pump, or a wiring problem, or a bad relay. If any of these problems were constant, the truck would not run at all. I'd check wiring first to be sure everything is ok.
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