96 6.5td stalling with code P0251

[swg]

1996 chevy tahoe 6.5td (110K)the truck is int. stalling along with int.long crank. however alway will start up again, may need to give it gas. Snap-0n scanner shows p0251 inj. cam pump "a" rotor fault. scanner trouble shooters say air in system will also set fault. I have performed clear fuel line test and have found no air. fuel samples clear and filters new.keeping a 1/2 tank in truck at all times. lift pump also replaced but no change.

Also looking for good Chevy dealer in Boston, Mass. area. I saw Keigen Chevy(Franklin MA.) listed on diesel page, anybody have any recent experiances with them.

[bigmikestud]

My '96 K3500 4x4 is doing the exact same thing. Additional codes include: P0237 and P0216. Someone help us!

One thing that startled me, when I filled up the other day, it overfilled with very foamy fuel. I had added an anti-gel product beforehand. On the highway it started this bucking/cutting out deal. Later in the day, it would die at stoplights then restart okay. I had previously run out of fuel three days before(1/4 tank means 3-4 gallons)so I know about air in lines. I cleared my codes so don't feel I should still have these coming up. Also, I haven't heard my turbo whistling for a while and power sucks lately.

I made a call to the Conoco inquiring about any bad diesel complaints and they had none. I have 154,000 miles. Ideas?

[ucdavis]

0251 is Injection Pump Cam System circuit. That is black gizmo ("Optical Sensor") @ top of IP. Same as code 18 on 94/95 rigs.
The gizmo reads rotating disc inside IP to tell PCM where in cam rotation pump is. PCM matches readings against crankshaft position sensor readings to assure appropriate timing of engine controls.
You can get this code if you run out of fuel (get air in IP), or run low & are "performing hard acceleration or turining maneuvers," have poor connections on IP or PCM or wires between the two have rubbed to where you get leakage of signal, or have broken wire inside insulation. PCM will have stored Freeze Frame and Failure records for tech to read w/Tech2 or equal scanner.
If intermittent, it will clear MIL light after 3 consecutive trips w/out fault.
First check all connections & wiring for shorts or non-contacting condition. If everything in engine bay looks OK:
Sensor has 2 wires IIRC; you should have 5 volts +/- 0.2, and 50mA @ the hot wire w/key on-engine off, and good ground to the other. If you have a 10 meg-ohm multimeter (don't do these checks if you don't) w/Hz scale, look for 57-63 Hz on brown-wire-w/white-stripe @ terminal A4 @ PCM w/engine running @ 900 rpm (or factor the Hz down proportianately to your idle rpm (idle of 450 = 1/2 the Hz, etc.). If voltage is high it will probably be 12.6V and you have short to battery voltage; find it; if low, you have short to ground or open/partially open circuit & need to find interruption.
If gizmo is bad, you can replace it yourself if you pay mucho attention to cleanliness. Commencing removal, you will be opening IP & will contaminate it if dirt or ?? falls in. Clean off top of pump & all around 'operating area' first (actually first find Stanadyne dealer in yellow pages under "diesel injection" & get a new sensor & O-ring) then remove torx screws on lid of IP, lid, circlip, slip sensor upper piece out of lid, remove big torx screw on lower sensor piece and carefully remove lower sensor from thin metal ring that rides in sensor-slot. Install new sensor in reverse order. Activate lift pump to purge air from IP (w/engine off) & let run for 30 minutes or so. Key off & let rest for a while, then start up.
If you do this, post findings & success. And I almost forgot, if you have less than 120K miles, forget whole thing & let GM dealer handle it under IP extended warranty (way better than this messing around). Also, dealer has a scanner that will do additional tests B4 replacing anything.
And double check fuel filter; I have theory this code can come from contaminated fuel in IP; holes the sensor reads are real tiny and any blockage could cause a misread hole.

[swg]

Great info on the optical sensor. thanks
I have an appt. on monday with a large dealer in the area which has 2 desiel tech. will let you know

[seanmk2]

hey swg nice to see another m******* on the page if looking for a chevy dealer go to mirak chevy in arlington ma they do alot of diesel work covering special policy 64 if you have a gmc go to martys gmc in kingston good luck also stay away from vendetti motors in franklin

[jjbouwens]

If you want to have a look at this optical sensor you should vist the homepage of my Viking friend in Norway at www.turbodiesel.no He shows how to take out the old one and how to put the new one in


....................
96 Brave P32 with F engine

[5.7L oldsdiesel]

Thanks very much for allowing us to view the removal of the optical sensor.I found it very interesting.Thanks once again......

[swg]

Brought the truck into the dealership over new year's. They looked at it the fisrt day and call me and said it need's an injector pump and will be cover under warrenty.
My hats off to Randy at Tom Chevrolet, Norwood MA. they tell me thay have 2 deisel techs. the whole trip was three day turn around. I have been driving for a week and it been perfect. thanks all

[ANXIOUS-SUBMAN]

When I was leaving the soccer fields this afternoon I slipped the trans into drive and started to pull out of my parking space when the engine surged three or four times and then stalled. It started right back up but now I had the SES light on. I stopped at AutoZone on the way home and they pulled the P0251 code. The funny thing was the scanner indicated that it pulled two codes but both were the same. Is this possible? In any case it looks like I'm off to the dealer and likely a new IP (85K miles)

[ 03-28-2004, 03:40 AM: Message edited by: ANXIOUS SUBMAN ]