sexyman23

Ok. After I post here, I'll go out and grab engine codes. But here's what I have so far. I have a 98.5 24v with some weird electrical issues. There are times when the truck runs fine, then times when idle will be rough, even at speed. Once truck is hot, if I'm just idling at a light, she'll get ornery and idle will become crap. Occasionally the rpm gage will say zero, then work under throttle. Then stop working then work again. I thought the issue was from fuse 9 "engine" on the inside fuse panel which had voltage increase. But that's a heiring as I have 2 fass lift pumps related to the ip pump. They'll eventually turn on with the ignition off and randomly when fuse 9 is pulled. But if I pull fuse 11. I get all my voltage back. I currently have the entire air intake heater relay system out, which is what fuse 9 operates mostly. A few other systems run off it too.

So there might be something off fuse 9 affecting stuff, but I'm unsure. Anyways plugged both fuses back in, inside the truck and decided to see what happens when I mess with engine bay fuse panel.

When I was just touching the fuel heater diesel relay, the Fass system would flick on and off. Instant replacement of relay. Now this is where the weird stuff happens. Disconnected all the wires to fuel filter and fuel heater. Zero change in fass system on. Checked with volt meter 2.9 to 3.1v. Weird.

Pulled fuel system relay. And another relay so I could hear what's clicking when I would connect and disconnect the fuel heater relay. There's a relay under the battery on passenger side, seems to be sticking on and off. I'm wondering why the steering relay is even hooked into the diesel heater circuit.

Also another odd thing whenever this ghost starts messing with stuff, brakes feel weird. Like really late before they come on. Have been searching for pinouts. Just finding the correct ones is being a pita.

I could be wrong, but I'm thinking it's the ecm or some odd thing with a relay not quite closing or not quite opening.

Anyone know of any other relays? My understanding is the vp44 runs direct off the ecm and has no relay. If it is the ecm and I relay the vp44 to the battery, would that at least temporarily fix things? I'm currently looking at ecm pinouts and want to pull the power steering solinoid just to see if fuel system shuts off. Tis a bizzare problem.

I've replaced all sensors as they had come up, high,low voltage etc. New injectors. No leaks. I know its electrical.

Any help. Appreciated.

sexyman23

Ah a few other things.

What the hell is this sensor under the battery?

So pulled wires to steering control box, and still the fuel system arms. So there is something bleeding voltage to trip on steering and fuel system. Or fuse 11.

Going to grind all the grounds I can.

The two things I forgot to mention. The alternator cable grounded out against the mount. Fixed this.

Also the heater grid, the one side that puts the heavy duty power to the intake heater. One side way was awesomely grounding out against the fuel rail. That's good right?

Now I'm wondering with these two major draws, whether one if these caused one of the computers to become toast.

Still thinking there's a wire hitting something somewhere.

How does the ecm turn on?

KATOOM

First off I'm curious about the 2 FASS pumps. Why two? And how are they wired? If there's no relay then they're pulling way too much amperage on the system.

As for potential reasons for the electrical issues..... I cant stress enough how sensitive these trucks are to electrical anomalies. If something is wrong then it can cause phantom issues having you run around looking for something which possibly isnt there.

This all means that the batteries MUST be in perfect condition. Which means load testing them for bad cells and proper charge fully disconnected and off the truck.

The alternator must be working correctly and not producing excessive AC voltage sin waves. Check that ASAP as AC noise can be damaging to electronics.

If there's ANY corrosion where you live from road salts then check battery cables for corrosion, check connections for proper tightness and continuity, check all major grounds for tightness and continuity, and make sure all the relays and fuses are in working order.

The sensor under the drivers battery monitors battery temperature. Its very important and is part of the charging system.

mopar24v

Also curious about the 2 fass pumps..

The RPMS readin zero is 100% the sensor behind the starter. I also have 98.5 and i had the same issue until i replaced it. I believe it was called a crankshaft sensor.

When mine went bad, i had very rough idle and several other issues. Its only about $30 and a fairly easy install with the truck off the ground. Its right behind the starter.

sexyman23

When I bought the first fass. Turned out it wasn't a direct replacement and my main fuel pump was dying. The first pump was designed to be secondary pump. So because my main pump was dying I threw it on as it was designed. Worked. But then the primary totally started dying and slowing down the dad's. So I made sure I got the correct direct replacement. So hence two fass.

I've already replaced the sensor behind the starter. ;-)

sexyman23

The fass pumps are relayed to the ip.

sexyman23

Batteries are brand new. I'll pick up and swap alternator today. But that still doesn't explain why the fuel system is turning on when truck is off.

Essentially the truck is turning on the ip when truck is off draining the system. I pull the battery every time I turn it off. And the original owner knew this as he had added battery shut offs.

KATOOM

OK now I'm even more confused.....

So let me just explain how everything "should" be.
If you have two pumps on there then thats no good. There is no "secondary" pump made by FASS. All their pumps are to be run by themselves. Its never a good idea to run two pumps in line because one will always be working harder by either pushing through or sucking through the other. Hard to isolate a problem too.

Fuel pumps cant relay to the VP either. Not sure what you mean by that. The OEM lift pump has a connector which comes from the ECM whereby the ECM is what delivers power to the lift pump. That means that any aftermarket fuel pump which pulls more amperage than stock must NOT be connected directly to the ECM otherwise you'll burn up the circuitry. The correct process of adding an aftermarket fuel pump is to plug the OEM lift pump connector into a relay which is connected to a hot lead, and the relay delivers the new fuel pump 12 volts. This way the relay takes the amperage load and you still retain all the normal fuel pump functions and prime cycles.

This is how the fuel pump is supposed to function:
When you turn the key to the ON position the fuel pump will cycle for 2 seconds and shut off.
When you bump the key over to the START position, only allowing the starter to momentarily engage, then back to the ON position, the fuel pump will run consistently for 25 seconds. Even if the key is OFF.
When the engine is cranking over to start the ECM pulses the 12 volt signal to slow the fuel pump by half speed in order to lower the cranking pressure by half.
When the engine starts the fuel pump runs 100% of the time.

You can still wire a fuel pump up to a regular keyed source if the ECM circuit is no longer functioning but you'll loose the prime cycles and the safety features of the fuel pump.

Batteries being brand new doesn't always mean much today. Getting a bad one off the shelf is all too common. Thats not to say one of both are bad either but just pointing that out. And they cant be checked if they're connected to each other or the truck.

Dont run down and get an alternator either as yours may be fine. Just check its AC voltage output. VERY easy to do with any voltage tool.

The CPS is definitely the problem for the intermittent tachometer. And the CPS can affect starting too. Your truck came with a crank position sensor and not a cam position sensor. Whether or not the CPS is faulty or there's electrical problems affecting the CPS, I cant say.

sexyman23

I can change the relay back to original pump wiring. I wish I had a pic of the box and book for ya. Fass does have a inline secondary pump to help with primary. I'll recheck the cps. Perhaps its grounding out as it has on other trucks.

I had pulled the relay for the fuel pumps. And still the truck is turning on the fuel heater relay while the truck is off. Not sure where the 3v is coming from. Ecm?

Found ecm pinout and the other bug I noticed is the tach signal comes from the ecm. Which explains the rpm dropping to zero while driving.

Ill try tracing the wire....

Couldn't be the ignition by chance could it?

sexyman23

I'm just pulsing the fuel heater relay... Am I mistaken or is there actually a solenoid for the ip, in the ip? I can hear clicking in the general area.

KATOOM

No solenoid but a relay in the power distribution center under the hood.

VADSLRAM

Phantoms when the key is off..
Have you thought that maybe your key switch is bad and even when it is "off" you still might be making some of the connections sometimes?
Just a thought that could fit your symptoms.

sexyman23

Ya. I'm thinking there is a possibility it is key.

Power distribution.... Is that relay replaceable or is it one whole unit that's super expensive and is rarely replaced when the vp44 is rebuilt?

It's a bizzare problem. Quite literally a ghost. See the reason I can also think its the ecm and whatever tiny switches on the board are crapping out is due to the rpm gage just hitting zero when it starts stuttering randomly while driving. And sometimes it'll stutter without affecting the rpm gage. Like the gage is affected 40%.

Also the transmission can be affected by the stutter, and I can even swear the brakes seem weird when it's happening.

Been cleaning and working on all connections and grounds. Have to swap out steering shaft that's done then continue on wiring.

Will pull ecm off motor, look inside and redo ground today. Not looking forward. I hate removing the starter on this thing.

Ivan

KATOOM

The power distribution center is merely the fuse/relay box under the hood on the drivers side fender. Pull the cover off and you'll see all the relays and fuses. There's also a small fuse box on the left side of the dash accessible when the drivers door is open.

The VP has a relay in the PDC.

But I cant stress enough that you need to test the alternator for AC voltage. Excessive AC noise will affect things.....especially the transmission torque converter by making it lock and unlock rapidly.

sexyman23

I didn't know the acronym of the fuse panel under hood.

Trucks not on at all and heater relay system is activating. I asked about the clicking in the ip unit itself because I pulled all the other relays that turn on so I could hear what was activating when I pop the heater diesel relay in to try and single out area. Just can swear there's a clicking noise coming from underneath the throttle section where the ip is.