I picked up a 2000 Ram 2500 with the Cummins a few months ago. The PO said that he'd replaced the fuel pump a couple of times, which I should have paid more attention to. Ran fine though for a few months. Recently I had a big miss, or shudder under heavy acceleration onto a highway but ran fine for the rest of the trip. It happened several more times on later trips, usually at gradual acceleration. No CEL at that time. I did get the 0237 code, so got a new MAP sensor hoping that would fix it, but it didn't. I cleaned all grounds and harness connectors. Since then, a few test drives have been OK, with no missing, but even though I cleared the codes, they come back.

I have AutoEnginuity, so got the Chrysler enhancement package and found a few things. The MAP sensor checks out with 5.2V key on engine off. Test run yesterday, backing out of the driveway the voltage dropped to 4.93 briefly. Once going down the road, it stayed above 5V and responded seemingly correctly to acceleration. I suppose that the brief drop below 5V would be enough to throw a code. Let me know if otherwise. I haven't tried bending the diaphragm yet as described in a HOW TO DIAGNOSE VP44 FUEL SYSTEM ISSUES document.

Another thing I noticed was that the VP44 input voltage was dropping from 12.18V down to ~9V. Occasionally it would jump up to 13.5V, which is what I was measuring at the battery when it was running and the alternator was charging. 12.18V was what the battery read before starting. They were brief excursions either way, but it got progressively more frequent going down to 9V as my test drive went on. I can log and provide these charts.

The Banks tuner was unplugged during my testing, but was plugged in when I first started having the miss/shudder issue.

I thought I might be in limp mode, but I was getting boost pressures of 5-8 psi with just moderate acceleration on a test drive yesterday. Didn't feel too bad.

34 minutes ago, timsch said:

Another thing I noticed was that the VP44 input voltage was dropping from 12.18V down to ~9V. Occasionally it would jump up to 13.5V, which is what I was measuring at the battery when it was running and the alternator was charging. 12.18V was what the battery read before starting. They were brief excursions either way, but it got progressively more frequent going down to 9V as my test drive went on.

I would be looking into this before doing any parts replacing. Was the intake manifold heater post-cycling when you were seeing the voltage drop on your test drive. If you are not certain, then I recommend to disconnect the intake manifold heater to simply troubleshooting the voltage drop.

In normal operation, when the manifold heaters have finished their post-cycling, the voltage powering the VP44 should be steady around the 13.5 - 14.2 volt range. Steady is the key word.

If the voltage continues to fluctuate wildly at the VP44, then you should check the power supply to the VP44, ECM and the PCM; but more importantly you should check that you have good operating ground circuits.

• John

Agreed. I cleaned all grounds I could find, using several references on where those grounds would be. There was a ground on the firewall near the ECM & PCM, as well as near that fender. I also disconnected those three connectors and sprayed them with Deoxit 5

I didn't check the manifold heaters, not knowing anything about them. I'll do the checks you recommend and post back, hopefully today. Thanks.

Sounds like you are on the right track.

The intake manifold heaters draw about 100 amps each - there are two of them. They are automatically in operation below 60°F ambient temperature. With the key on, engine off, the heaters are on while the "Wait to Start" lamp is lit. After the engine is started, the heaters post-cycle until a specific engine operating temperature is reached, or the vehicle speed reaches approximately 25 mph. The post-cycling current is higher than the alternator output, so it is normal to see the dash voltmeter drop significantly.

This is why I recommend disconnecting the intake manifold heaters while diagnosing a low voltage electrical problem.

• John

Edited 13 hours ago13 hr by Tractorman

I've tried to find the best way to disconnect the heaters, but am coming up short. I'm not sure I've identified the connections at the intake manifold, but am fairly certain they are the two large cable connections at the base of the air intake housing. I didn't think disconnecting those there would be the best idea. I traced them down to the solenoids, which I thought may be a decent option, but then figured that there was probably a fuse or relay in the fuse box that I'd be better off pulling. That send me looking for a fuse location diagram, but haven't found one yet. Searching this site and the Cummins forum had no luck either. Any recommendations on where to find this fuse layout? I do have the 2001 FSM, but fuse box wasn't in the index that I saw, and didn't dig deeper.

What's the best way to disconnect the heaters if none of these options are best?

When looking at the heater solenoids, I found that one of the four 90deg boot connectors on top of the solenoids was disconnected. I did miss the ground cable from the air intake housing to the manifold, so just cleaned those connections up.

2 hours ago, timsch said:

What's the best way to disconnect the heaters if none of these options are best?

There is a single connector with two black wires that are connected to the positive post of the driver side battery. These wires supply power to the intake manifold heaters (grid heaters). Within a few inches of the battery connection, you will see two fusible links - no fuses. Disconnect the the single wire connection.

2 hours ago, timsch said:

That send me looking for a fuse location diagram, but haven't found one yet. Searching this site and the Cummins forum had no luck either. Any recommendations on where to find this fuse layout? I do have the 2001 FSM, but fuse box wasn't in the index that I saw, and didn't dig deeper.

There are two fuse group locations. One is called the Power Distribution Panel (PDC), and the other is called the Junction Block. The PDC is located right beside the driver side battery. Th Junction Block is located on the left end of the dash. The driver's door must remain open for access.

Hope this helps.

• John

Edited 7 hours ago7 hr by Tractorman
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