a miss nobody can figureout can you?

[jb carver]

I had cracked heads replaced after i was losing coolant and had air bubbles in the coolent tank,new heads installed put together and cranked it up and runs fine but has a miss at full throttle when the transmission shifts down and has black smoke but also has a puff of white smoke when it makes a very diesely knock, so I took it to the chevy dealer and they looked at it and said it needed a new injection pump, but it ran great before i changed the heads, so i took it to a diesel pump repair place got on the standine website and they did a compression check which was good, checked the injectors and replaced five (5). 3 were good, they said.and checked the pump and said it was just fine.but it still misses just like it did before and they say they dont know what to do to fix it. so if anyone has run into this problem or has any idea, please post it..
thanks
jb carver

[ucdavis]

What year rig, how many miles on rig & IP & FSD, what mods are you running?
Sounds like IP or FSD. Better info on rig would produce better advice.

[jb carver]

it is a 1995 k2500 sub 6.5 t stock

[jb carver]

also at has 135000 miles and it runs great till you floor it and it down shift's

[charliepeterson]

It sounds like it's starving for fuel when you hit warp speed. Try opening the water bleed valve when idleing. Watch the fuel coming out. You should see almost a pencil tip flow coming out. Let it flow for a minute or so. The truck should not even miss this fuel coming out.

[jb carver]

bleed didn't change it still missing

[damork]

You might look at the fuel pump (lift pump) supply circuit. It could be possible while doing the engine work, you could have disturbed wiring from the Oil Pressure Switch to the lift pump.

Maybe look at voltage to the lift pump and if possible, connect a gauge to the water drain line so you can read the pressure - best if you can read the pressure while it is acting up on you.
You should have full battery voltage to the lift pump when running, and min pressure while you are pushing it should maintain at least 3-4 psi.

A relay to the lift pump is a very wise investment while you are in there.

[jb carver]

codes have shown up, codes are tdc 97 and 98
these codes came up as i drove it back from the standine shop do these codes mean that the pump is bad? as I just spent money to be told that the pump was just fine..

[whatnot]

I had a code 94 a while ago. It turned out to be some loose injector lines that were leaking.

[rustypig]

Did anyone check pump timing with all the stuff you've had done so far?

Does kind of sound like it could be fuel starvation. I assume the fuel/air filters have been changed etc.

Definitely check for voltage at your lift pump if you can't hear/feel it running. Our 94/95's historically have issues with burnt oil pressure switch contacts that allow the voltage to pass to the fuel lift pump.

[ucdavis]

DTC 91-98 are "cylinder balance fault" and indicate "possible mechanical or fuel delivery problem with" cylinders 7, 2, 6, 5, 4, 3, 1 & 8 respectively. You've got #1 & #8 indicating "issues."
Clear codes & recheck after next miss occurences, clearing each time.
Pull the upper intake cover & check for egr snot build-up (air restriction).
Check fuel delivery to each cyl. by cracking the fuel line @ the indicated injector. You should get fuel at each. Compare to non-indicated cylinders w/same proceedure. Obviously you can't do this at full speed, only idle, but if there's a problem @ idle, it'll be magnified @ speed.
If you don't find anything, pull some involved & non-involved injectors & have a shop pop-test them.
Could be the IP, but you've got time (if you can live with the miss) till you start getting code 35, 36 and maybe 17, 18 (latter two w/your 97, 98 would indicate fouling of the pump either w/fuel contamination or IP intenals descintegrating & pump needs to be disassembled to clean it out; former (35/6) is fuel solenoid failing & also requires rebuild).
Good luck & thanks for reporting further findings. Interesting problem.

[triggerman]

If the mechanic that did the heads did not put in a new oil pressure switch, looks like you will have to do it now. there was a artcle here on dp on how a bad switch can create a number of differant symtoms. On the rear of the heads there are a couple of harness ground wires to the manifold bolts, check them to be sure. If your lift pump has not been changed, consider it.The lift pump is capable of your problems. Also loosen your fuel cap, and run it. A bad fuel cap that doesn't vent has been known to collapes tanks and do what you have. get a cap for a gas job, they vent both pressure and vacuume. Finaly if you have a original FSD, its probably time to remotely mount a new one. If none of this fixes your problem, and your SURE the IP is good, it may be back to the heads.Best of Luck to ya.

[jb carver]

is the oil press sender a kill switch or what ,it has the ability to do what,

[triggerman]

the oil pressure switch tells the computer (PCM) that there is adaquite pressure in the block so the PCM can fuel the injectors. If the switch contacts become burned, the PCM may get a no oil pressure signal at which point the PCM shuts the IP down. The vibration you get at hi RPM could be sending a intermittent no pressure signal to the PCM. Hents, the miss. The switch screws into the block near the right side of your fuel filter.

[Kennedy]

How's the turbo/wastegate system?

[catmandoo]

as ucdavis points out by your codes you have problems with 1&8 i personally don't own a newer truck like that but i think maybe swithing 1&8 with 2 other injectors and see if codes set again and if they are the same it's gotta be either the pump or head related as thats the only thing different from before.if different i'd think injectors.just my 2 cents worth

[Inspector]

This might be a silly question but which injectors didn't they change. I'll bet it was the hard ones. Which would be under the turbo. You said they changed five out of eight. Just a thought. :rolleyes:
Denny

[jb carver]

it is still doing it!
with a load when it gets to 3000 it miss's and sounds like a very loud diesel ping,very loud!!!
the injecters that thay changed were under the turbo! but when thay said thay didn't know what is wrong with it and to come and get it they left the vac line to the turbo off and i drove it home with no power and smokeing like crazy under load?? I am going to put a press switch on tomorow.and to mr kennedy dont know about turbo seams to be ok and cant move wastegate rod when running.

[jb carver]

also have not got bad codes after clearing them and hooking up the wastegate vac line after they left it off