LP and OPS question

[vault]

I think I have an OPS problem. I'm going to check it out tommorow. befor I dig in I have a question. the problem I'm having is erratic. it doesn't happen under hard exceleration. If anything it is after altough very infrequently. tonight I nearly floored it accelerating up to highway speed (unloaded) and no problem. everyonce and a while it will seem to "miss" like a gasser. It is not very frequent. maybe once every 15-20min of driving. it will happen while cruising, may be more freq after acceleration but not during. From reading about ops and lp failures it seems that I should be getting a miss during hard acceleration and it would be fairly repeatable. I've only put 400mi on since I bought the truck and I'm new to the diesel world so I'm not sure how the past maintaince was on this truck.

[vault]

I replaced the fuel filter, to prime it I jumped the relay bottom left top right contact as you face the fuse box standing on the drivers side front quarter pannel. I got a weak stream of fuel comming out of the vacum line I attached to top of fuel filter. does this sound more like a weak LP?

[gmctd]

At 115kmi, it's probably about due, so why not replace both while it's on your mind?

Check with Heath Diesel or Kennedy Diesel for a higher output version

[vault]

I replaced the fuel filter, ops. and lp, bled the fuel system for air bubbles. The "miss" is still present it's a split second loss of power. It occurs erratically maybe one in 45min of driving. any ideas?

[gmctd]

Good job - your fuel system should be no problem, now.

You should probably start by cleaning the battery cables at the battery end and where they attach to the block, then do the grounds on the passenger-side rear intake manifold - pull them and clean everything up so the PCM will have good power and ground.

Check the underhood fuse center for loose fuses, relays, connections and such.

Disconnect and reconnect all the harness connectors, checking each for oxidation\corrosion, clean if necessary.

Make sure there are no broken\frayed wires, and check the main harness at the lower passenger-side firewall, near the ac pipe, for fraying where it crosses the pipe.

If no SES indicator and no stored DTC's, the FSD\PMD may be at fault - you can check for DTC's by shorting a paperclip between pins A & B of the ALDL connector -

F - E - D - C - B - A
G - H - J - K - L - M

Turn on the Ign, but don't start the engine, and the SES indicator will flash the 2-digit code(s) -

blink - pause - blink - blink - pause is DTC12, meaning good communications, which will repeat three times, pause, then flash the next code three times, pause, the next, etc, then start over after the last code

[Robyn]

Good advice so far.
Do you have any idea as to what has been done to the truck before you got it. IP replaced ect???

There are several things that can cause this issue.
Another area other than the PMD is the filter harness on the IP
This plugs into the rear of the IP with a rectangular plug and the harness has a small black box looking thing in it.
The harness is fairly short, Maybe 8 inches long.

If the IP is a high miler it could be suffering internal issues with the optical sensor but that will usually trip a code.

PMD's can cause intermitent issues but its been my experience that when they start to go the engine will just quit and refuse to start untill the box cools off.

Good plan to replace the PMD and remount a new one with a remote heat sink . There are several extension cables and heat sinks available commercially in the aftermarket.

Good luck

Robyn

[vault]

robyn- I don't know what has been done to the truck. I suspect not a whole lot. I'm going to try gmtd's advice here in a few days. Arrgh I hate electrical issues.

[gmctd]

The Optic Sensor Filter, as Robyn pointed out, is a known problem due to poor oem crimp procedures - remove it temporarily for testing.

If the problem goes away, you can get a new one from Bill Heath, or possibly Kennedy Diesel - Bill serves the 6.5 community more than the DMax and others.

If the problem increases, same deal - you will need to replace it.

The filter was designed to cure the hard-start\fishbiting symptoms in the OBD1 EFI systems.

[vault]

On a somewhat similar note. when I change the fuel filter the new filter did not have the workd front on it. (I should have check the site better before changing the filter) I could not see anything that would indicate a specific orientaion so I just put it in. Would an incorrectly installed filter cause any problems also

[gmctd]

It can cause air leaks with resultant bubbles and skipping, misfiring, and usually a DTC35, but not always.

It is keyed, so fits in only one position, but sometimes the original gasket sticks in-place, so you wind up with both gaskets, and the leak(s).

Pull the top and check the rubber seal ring, to be sure.

[DickWells]

Vault: You've gotten some great data from some really experienced 6.5 people. Just a couple of things that nipped me while I was using the old Burb.
The first ground that bugged me was the one that goes to ground under the tab at the trans dip stick tube. Passenger side rear of engine. Intermitent. The one that escaped me for months, was on top of the frame, below the starter. Corroded self-tapping screw. I shot a 5/16 hole through the frame from behind the tire, and put in a SS 5/16 X 3 inch bolt with two nuts around the ground tab. Never corroded again! The last bug wasn't a ground. One of about 16 or so wires near the front of the IP. Purple with white tracer I think. Goes through a rubber block there. A filter of some kind I think. GMCTD? Anyway, I cut it off both sides of the block and jumpered around it. Never had another problem with it. But, before I wiggled that bundle of wires with the engine running to get the skip/stall to show, I had bought a new FSD! Another $180 down the tube! Could have been any of those wires. It was open inside that rubber block, by the way.
Like the others have said, check all the simple stuff first. Saves dollars.
FWIW, the only time the Burb ever left us stalled on the road, I could have been mobile in five minutes if I had just given the ECU that I had in my hands a shake! The Banks chip that I had put in there had fallen out! Two -hundred something bucks that time.
Good luck.
Dick Wells:)