Engine/Transmission (1998.5 - 2002) help!!

[dd76522]

ok i'm a 12v dude and i'm workin on a buds 99 24v while he's in iraq the truck died i've chaned the lift pump and fuel filter and the truck will start and idle but it starts missing and breaking up around 1500rpm but not always the cel isn't on though it did come on once the code was 1689 but it hasn't come back yet it seems like theres an electrical problem like a short somewhere or something and if the engine dies the lift pump doesn't normally come on when it finally does is when the engine will restart also the fuel gauge is swinging around some i pulled the sending unit and the sending unit seemed to be good but does any one know how many ohms it should read full and empty i wanna say it was . 021 full and . 216 empty could these problems be tied together? i gotta say i'd rather be workin on my p7100!

 

[rkressg]

The 1689 is related to an electrical failure on the circuit board internal to the VP44. It is typically only resolvable via replacement of the VP44 with a rebuild unit (as getting the electronic parts can cost more than a rebuilt unit).

I had the identical failure on my truck many years ago.

The Lift Pump will only run when the engine is running. If you bump the starter, it should run for 20 seconds, but if you try to start, it drops to 20% duty cycle. The VP44 will not start well if it has more than about 3psi of fuel pressure behind it.

The Lift Pumps on these models are a POS and the VP44 is not much better.

As for the fuel sending unit, if you check around in this forum, it is also a common failure unit. I have replaced mine about 5 times now.

You are probably dealing with a failing VP44, a failing Fuel Level Sending Unit, and a failed Lift Pump. If you are going to repair his truck, put in something like a FASS (get the one with 2 filters). While you have everything apart, change the Fuel Sending Unit.

If you drop the tank (and get a FASS 150), run the fuel return into a new and seperate return (so you can pump fuel with the engine running), and clean the screen on the bottom of the fuel pickup (you will know when you remove the fuel sending assembly from the tank).

As for the VP44, just run it until it dies. If you give the VP44 a good supply of fuel, it might just run for a little longer, but it might also be shot.

Just my $0. 02
-Rich

 

[dd76522]

i appreciate the response i've read some really interesting posts about this codes here and on some other forums it seems to me like a wiring issue possibly so electronics is gonna be the way to go i think but before i tear anything apart a bud of mine that works with industral vp44's has some extra harness plugs i just have to wait till monday to get one then i'll do what i can to test it but i've got a happy feeling about doing the pump