Would help to know the model year of your van.

 

2000 gmc savana. It it throttle related. At light throttle, its ok. If you roll on it give it heaavy throttle, it pops the fuse. It does not seem to be related to bumps in tne road or a traditional short. As long you baby it around, its fine. ....even on rough roads and bumps. Work it hard, and she pops pretty easily. All i can think of is ip and computer.

 

On the C/K trucks, one of the things that causes the ECM-B fuse to blow is a short in the fuel heater wiring.

I have no experience with the Savanna........

Suggest sending Glagulator a PM. He is a whiz on the electrical systems for these vehicles. If anyone can point you in the right direction it is Glagulator.

 

The ECM-B fuse on your 2000 van only feeds the PCM and powers the lift pump thru the lift pump relay. You do not have an Oil Pressure Switch to control the lift pump like earlier models. Could be a short, a bad lift pump, a bad LP relay, a PCM problem or something else.

 

A malfunctioning fuel heater in its final death throes can blow the ECMB fuse.
By chance have you noted what the ambient temperature was when these malfunctions occur? Anywhere near 45° and note that at night the fuel can cool down and remain several degrees cooler that outside air temps for several hours.. So although it may be 65°F when you leave for work, the fuel may be still thawing from the chilly night before

Speculating.. Heavy foot increases fuel flow, light foot decreases fuel flow allowing the fuel to soak up more engine heat before encountering the fuel heater at the base of the FFM.

If weather permits, I would unplug the fuel heater and see if the problem goes away...

 

Unplugging the heater and water in fuel sensor makes no difference. Glag, you are right the op switch problem does not apply to me. , a quick application of throttle pops it almost every time. If you roll on it slowly, its way better. Ive looked and looked for bad wiring, push , pull, shake....the whole deal. I have now replaced the pmd and the pmd extension cord. No effect. Its looking like computer or ip. I use this truck daily and dying while in traffic is getting really old.

 

Oh, and its summer here in texas. Its hot as hell here. No worries about cold temps now.

 

I guess i could try a new lift pump. Mine seems fine. It "motorboats" along just like always. Do these have any history of working fine yet pull too much current?

 

On your 2000 van the fuel heater and WIF sensor are on the ENG-I fuse.
What happens if you put it in gear, hold the brakes and apply as much throttle as you can, like power braking?

 

On your 2000 van the fuel heater and WIF sensor are on the ENG-I fuse.

Same as it is for most all EFI 6.5TDs.

How a malfunctioning fuel heater affects the ECMB circuit directly is complicated but in a nut shell. A faulty fuel heater can backfeed 12vts to other circuits that share common grounds.
The same concept applies to other operating systems that share common grounds with a malfunctioning device.

Remember "The PCM is designed to process the various input information and then sends the necessary electrical response to control fuel delivery, timing, and other emission control systems. The input information has an interrelation to more than one output, therefore, if one input failed it could effect more than one systems operation."


ECMB circuit provides provides for the PCM (B+ memory) and Lift Pump Relay circuits. The ECMB (hot at all times) circuit ground is shared by ECM1 (Hot in Start or Run) circuit that powers the PCMs solid state voltage regulator that generate the 5vt reference signals used by numerous sensors and solid state switch that provides the APP with reference voltages.




Shot in the dark... Check to see if the coolant level is full, not low and uncovering the sensor during hard acceleration. :confuzeld

 

If you power brake and apply throttle quickly, it pops the fuse. If you apply throttle slowly, its ok. Its the same when driving. Apply throttle quickly, and you are dead. If you take 2 or 3 minutes to get to 60mph, then its ok.

 

Success!!!! Thanks glagulator. You suggested the "power brake" idea. That got me thinking about how the engine torques in the mounts. I looked right where the main wiring harness meets the engine wiring harness. At that big plug, under the plastic loom, there were 3 rubbed wires. It is the big connector on top of the drivers valve cover. I got those wires fixed and all is well with my truck. Hey, even my oil pressure gauge doesnt flicker anymore!!! I guess one of those was my oil pressure wire. Anyway. Thanks to all.

 

That's what I figured. Glad you got it solved.
How are your motor mounts?

 

I call grounds. Why? Because that same fuse kept on blowing and it was my frame to body ground strap. With all electrical gremlins on our motors, vans and trucks I always start with grounds first.