More fuel pump issues ,,,low idle ??

[Erik727]

just bought a 1999 Explorer EB, 4.0 SOHC, 161K a couple weeks ago,,been reading this sight since ,,fixing all the little issues..Truck is mint inside and out ,,paid $2700..decent deal.

Low idle issue,,,, No matter what i've done,,the truck idles in gear at 500 RPM.
I've changed the plugs,wires,fuel filter,cleaned throttle body and MAF sensor..Tried a new IAC valve,,all no help..With instructions found on this site,,i ck'd the TPS,,all volts good at all times,,did the idle adjust procedure..Have it idling nicely at 750 in park ,,but when in Drive ,it still drops to 450- 500. Turning the a/c on or off,the iac adjusts accordingly ,but then it searches a little up and down and then settles at 500..What else can i do to isolate and fix this issue ? If it had a vac leak of some kind,which i cant find ,,wouldn't it idle high ? I know i have to be missing something oblivious...It's done this since the day i bought it.

Fuel pump,,,This started about 8 days after buying...Longer crank times,but always starts..Already had put a new filter on.
Yesterday,ck'd the fuel press at the rail..Only about 10 psi..Cycle key a few times and gets to about 30,,crank over and it builds to 35 and starts..As soon as started ,it goes to 65,,and will stay 65psi as long as it's running..As soon as you shut down,pressure bleeds off immediately,,drops like a brick..Is the only remedy for this a new pump/sender assy ? It I've read a million fuel pump/regulator posts via the search,,but culdn't find the answer..Is there a fix for this short of buying and replacing the whole assy ? Would like to aquire all parts needed before dropping the tank..

Thanks,
Erik

 

[Lube]

No need for the new sender, but a new pump is definitely in your future.

 

[RomeovilleIL]

750 idle & 500 in gear isn't abnormal. 99 should be a returnless system, meaning there is no separate fuel regulator to replace. The pressure when running at 65 is normal, but the quick drop after turning off and hard start/rpm searching indicates you likely need a new pump. Pump only, it is mounted on the sender and can be purchased as a unit but certainly doesnt need to be.

I've always dropped tanks to replace fuel pumps and it isnt too bad using 2 floor jacks with 1 foot long 2x4 pieces wired to the jack plate to keep it steady and spread out the contact points. There is a sticky on cutting an access panel under the rear seat which many people on the forum say works well. Biggest pain is usually getting the quick disconnect fuel lines to actually disconnect, followed by getting the tank retaining strap back into place and starting the bolt as it invariably gets bent around.

Since you have time, shop around. The pump is substantially cheaper by mail order than picking up in the local parts store. Check Rock Auto.