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P0370 P0251 codes again...

HighSierra86

HighSierra86

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Ok guys. I think my luck has finnaly run out on this one. Our 2000 chevy express van with the 6.5 has developed quite the problem. Ive had a common problem with these codes (p0251,p0370) but once cleared they wont return for months. This is the link to my last bout of issues with the truck http://www.thetruckstop.us/forum/showthread.php?30665-Need-some-input....&highlight=optic+sensor Long story short, I found a bad lift pump which i thought was the culprit.

Now the codes are back and here to stay. Truck started acting up, very low rpms, stalling, would rev up in rpms after you let off the pedal. Found the above codes. They do not clear. As soon as you clear them they come right back, both with truck running or immediatly after a resart. I drove the truck back to the yard and the entire way the rpms would surge up and down, not allowing for more than 25mph speed. It does idle perfectly fine however.

Van has the original injection pump, remote mounted heath PMD. Im leaning towards a fried pmd or maybe optic sensor? Any tips or hints would be greatly appreciated. Thanks

Nick
 
Ok, just dismissed the pmd theory. Took the heath unit from my 96 and plugged it into the van. Exactly the same problems.

If you let it sit for a few hours it starts fine and runs good for about 2-3 min. Then it stalls and runs like crap. Throttle control becomes erratic and engine sounds different.

Im thinking the pump is toast, but just want to hear someone else say it :rolleyes:

-Nick
 
ak diesel driver said:
have you verified fuel pressure at the IP? I'm thinking plugged last ditch screen
Click to expand...

I just put a new LP in about a month or so ago. So it should have feed pressure unless blocked like you said. Testing the fuel pressure on this thing is a bastard because instead of a t-valve like the older trucks, it has a quick disconnect fitting for a specialty pressure tester (which i dont have of course).

Well ill stop bitching about how long it takes and just go do it

-Nick
 
Fuel pressure burried the 8psi guage I have. So thats fine

2000rpm test is kinda a crap shoot IMO. I was playing around with that a long time ago, and according to that test the pump in my 95 failed. Well it lasted another 20K miles until the engine let go. But Ill grab my scan tool and give it a try as there is no tach on the dash.

-Nick
 
So according to the test, the IP passes. However, if i hold it at 2000rpms and then quickly let off the pedal it jumps right up to 2800rpms and comes slowly down. Quick jabs at the pedal have similar results, along with stalling.

Im afraid to try any more of theses "tests" as I fear a runaway of the motor. At that point an injection pump would be cheap compared to other repairs.

I was wondering what the symptoms of a bad ACC pedal would be, but judging by how crappy this thing runs, im not sure that is the problem

Thanks for all the help so far guys

-Nick
 
Before I replaced my pump, I had the same codes, cruising town, CEL would come on, and I would immediately feel the the truck go into limp mode. My vote is IP. I also had a run on at the grocery store! I'll never forget how big that old ladies eyes got! HAHA
 
Looking like an IP is in your future, to test APP or not drive in cruise control mode if it is crappy still then it isn't APP because in cruise APP isn't in the speed control loop. Try adding some 2 cycle or SAE 30 non detergent to your fuel mix, see if that helps any. The 2000 rpm test is a valid one, Bill Heath is the one who shared it with me years ago 95% or better success with that test to ident a bad IP according to Bill. I've found a couple bad ones myself that way but he's tested many more than I have.
 
Turbine Doc said:
Looking like an IP is in your future, to test APP or not drive in cruise control mode if it is crappy still then it isn't APP because in cruise APP isn't in the speed control loop. Try adding some 2 cycle or SAE 30 non detergent to your fuel mix, see if that helps any. The 2000 rpm test is a valid one, Bill Heath is the one who shared it with me years ago 95% or better success with that test to ident a bad IP according to Bill. I've found a couple bad ones myself that way but he's tested many more than I have.
Click to expand...

Its to the point now that I cant even drive it long enough to use cruise control. Im gonna try replacing the pump and see what happens.

Thanks for all the help guys. Ill keep you posted on the results

-Nick
 
Try one more thing before you replace the pump. iirc (and my memory sucks) I had fuel supply issues when I had those codes. Make sure you get 1 liter/minute from the water drain on the FM, with the lift pump on, with the engine shut off. I DO remember I didn't have to replace the pump to make them go away. Still have the OEM tank sock? Worth trying first!
 
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