'97 K2500 Fishbite???

[KallyI]

My '97 just started doing the 'fishbite' thing this morning. I was driving home from work this morning, (about 35 miles), and I was sure I was going to be left sitting on the side of the road. I made it home, but from what I've been reading, the 97's don't do this, just the 94 and 95's. Some of the bites were extremely abrupt, and lasted about 1/4 sec. In total, I counted about 20 of these, but when I got into town, at lower speeds, it wouldn't do it. I shut down, lifted the hood, opened the water drain at the front of the engine, and turned the key to the start position. A good stream of fuel was present, and the lift pump was obviously running. Didn't have time to get a new fuel filter, yet, but thought that might be it. Any thoughts??:confused:

[JoeX87000031]

Forgive me for being ignorant, but I very new to GM diesel ownership and I was real curious by what you meant by the water drain in the front of the engine? I notices a couple of brass looking things near the front of my engine, one on the thermostat and another one near it. How does what you are talking about and what does it do. Is it even on 94's. I would greatly appreciate any info you have on this. I am new to this and I love my truck and the 6.5 TD and I am trying to learn all the tricks of the trade of ownership. Take care

[a5150nut]

Forgive me for being ignorant, but I very new to GM diesel ownership and I was real curious by what you meant by the water drain in the front of the engine? I notices a couple of brass looking things near the front of my engine, one on the thermostat and another one near it. How does what you are talking about and what does it do. Is it even on 94's. I would greatly appreciate any info you have on this. I am new to this and I love my truck and the 6.5 TD and I am trying to learn all the tricks of the trade of ownership. Take care

The Brass thing on the thermostat is an air bleed. It is to relieve trapped air in the cooling system.

The Tee handle Brass thing is the fuel water bleed. It lets you drain the water from the bottom of the fuel filter housing. Also lets you see if your lift pump is working. The drain hose just hangs down so if you use it it is best to pull it up and drain it into something so not to make a mess.

And welcome to TDP and the diesel world! :D

[Hubert]

I think to some degree fishbite can be a problem to all electronically controlled 6.5's not just the 94-95’s. But quantifying the event along with speed, load, and fuel coincidences seems to lead to differences as to the cause or diagnosis.

The difference in OBD-I and II and some hardware and/or programming differences of the PCM’s ..MAY?.. add to differences in severity comparing two different vehicles.

Could be voltage, electronic control, connectivity, or transmission related. Try and pinpoint the consistencies of the event severity compared to gear, speed, rpm, load, and fuel rate.

[KallyI]

Thanks for the reply. Another issue reared it's head after I changed the fuel filter. I took it for a 30 mile drive and it seemed to work great at speed. When I got back to town, the engine shut right off, started ok, but wasn't expecting that. Perhaps the PMD is acting up again, it has been 5 years now.
The other issue is my vacuum pump. I have noticed for a while that I was only getting a maximum of 6-7 lbs of boost, but I wasn't pulling anything, so I figured I'd look at it later. However after the engine just shut off, I noticed some extra noise, and no boost at all. It's the vacuum pump, so I have to sort that out before I do anything further.:(


I think to some degree fishbite can be a problem to all electronically controlled 6.5's not just the 94-95’s. But quantifying the event along with speed, load, and fuel coincidences seems to lead to differences as to the cause or diagnosis.

The difference in OBD-I and II and some hardware and/or programming differences of the PCM’s ..MAY?.. add to differences in severity comparing two different vehicles.

Could be voltage, electronic control, connectivity, or transmission related. Try and pinpoint the consistencies of the event severity compared to gear, speed, rpm, load, and fuel rate.

[Robyn]

How much fuel was in the tank??

If you get a partially plugged sock or a safety suction valve in the pickup tube that is going south the little beast can suck air at any tank level below about 1/3 of a tank.
It will usually run easy with light throttle and do ok but when you ask it to work it will stumble and run rough.

If your tank was down, fill it up and if the issue goes away you have your gremlin

Best

Robyn

[KallyI]

How much fuel was in the tank??

If you get a partially plugged sock or a safety suction valve in the pickup tube that is going south the little beast can suck air at any tank level below about 1/3 of a tank.
It will usually run easy with light throttle and do ok but when you ask it to work it will stumble and run rough.

If your tank was down, fill it up and if the issue goes away you have your gremlin

Best

Robyn


Tank was full, so don't think that was an issue, thanks for the input, though.

[Robyn]

A shut down for no aparent reason can very well be the infamous PMD

The vacuum pumps do go south (Been there done that)
Bearings can go away as well as the diaphram unit.

If your stalling is intermitent I would certainly look a the PMD
Even with a remote cooler they can and do fail.

Good luck

Robyn

[JohnC]

...I shut down, lifted the hood, opened the water drain at the front of the engine, and turned the key to the start position. A good stream of fuel was present...

Re-do the test while the engine is running. (Skip the starter...)

[KallyI]

Re-do the test while the engine is running. (Skip the starter...)


Funny thing, I had the lift pump fail back in 2000, and I was 800 miles from home. It started great and never missed a beat, just going up hills it made itself evident, by missing every so often. Different than what it's doing this time, but it has been 8 years, and 80,000 miles since then.
Well, I will check the lift pump while running, thanks.