OK... another nudge from me trying to get some collective insight here.
Whenever my truck sits for a while, it doesn't want to start right up. Takes a couple seconds of cranking to get it to fire up. I've found that if I cycle the key twice and let the fuel pump run twice it will fire right up. Guess this means I'm losing fuel pressure somewhere? Could the fuel regulator be causing this?
Also, when I'm driving down the road and I give it alot of gas, it won't really respond like it should. Sometimes it even backfires like the mixture is too lean, and if I let off the throttle slightly, it actually develops MORE power. I thought this might be the TPS, but now I'm wondering, could these 2 symptoms be related?
Truck is a '93 Dakota 4x4 with the 318 Magnum.
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Your latter problem is exactly what I have been experiencing for the last few months, though actually much worse. My fuel pump has been slowly dying for the last few months and recently got too bad to drive even around town. If i were to take a guess i would say more than likely it is a fuel pressure issue, and quite possibly is the fuel pump. I'd suggest you get your hands on a fuel pressure gauge (if you don't already have one, I got mine at harbor freight for 12 bux) and first check the pressure after the pump, make sure that is sufficient. If that's ok, check it at the fuel rail, if its down there it could be the regulator, also check under load, mine didn't show much of a loss at either ends, but once it was driving, it dropped significantly above idle.
I have been told the fuel pump assembly has an check valve installed. If this check valve is leaking and not holding pressure while the engine is off then it will slip back into the tank and will have to depressurize the system before it has enough pressure to start the engine. Most hesitations can be the TPS or the MAP sensor. It may also be a vacuum leak too.
I already changed the fuel filter and pressure regulator. I guess the only thing left is to get a fuel pressure gauge and see if the fuel pump is getting weak. Does anyone know what the running pressure should be?
One thing that I've noticed is that when accelerating, once the engine gets up into the higher RPM's, the power will increase all of a sudden without me changing the position of the throttle at all. WTF could this be? It's driving me nuts!!! I hate this computerized crap!!
i would say tps sensor. hook a volt meter to it and get someone to press the gas and see if there are ant voltage spikes as they roll into the gas. this is with the engine off and key on by the way.
17" R/T wheels, v6 to v8 swap, 9 1/4 inch rear with trac lock, Mopar performance computer, built A500 tranny, Poly bushings, rear sway bar from an R/T, Mopar PPH headers with custom y pipe and 3" exhaust, and modified throttle body.