PO251 and PO370 hard starting

[5delta1]

Cold start past 2 days ( 40 degrees) hard start and ran like crap. warm up seems fairly ok. yesterday replaced all glow plugs to see if that helped. this morning per child same thing. i have fuel smell and wetness on oil pan and bell housing but not in valley. can the leak and air in line cause this. also what size fuel line to replace all lines from steel line to filter can and wif drain and pump supply.? thanks in advance......................... also threw those codes yesterday. ? son checking later today to see what codes today came up.

[Big Bertha]

Those codes are otic sensor codes I would check optic filter and all connectors around the IP not sure what year truck is if it is after a 96 you can remove the optic filter,I would get some electric contact cleaner and pull the connectors around the Ip and spray cleaner in them and run some 2 stroke oil in your fuel.

[5delta1]

ok where is it . 98 (F) K2500 6.5. leaning toward fuel leak ?

[dondandd]

Your 98 should not have an optic sensor... pretty sure those went away with the 97+ trucks. Fuel leak can definitely cause your issues. Air in the fuel system can cause hard starting, or a start then stall followed by lots of cranking to restart it. When you get air into the ip, it can get caught up in the slots on the optic sensor wheel. This can affect the way the optic sensor reads, causing running issues, and codes.

So in short, if you can see a fuel leak, you should definitely start with that and make sure the system is leak free. Unfortunately I don't know the fuel line sizes off hand.

Once you fix the fuel leak, clear the codes and see how everything runs. We can trouble shoot any remaining problems from there.

Don.

[5delta1]

thanks will start with fuel filter housing maybe it .

[matuva]

Originally Posted by dondandd

Your 98 should not have an optic sensor... pretty sure those went away with the 97+ trucks...

[JMJNet]

The one that should not be there is Optic Sensor Filter Harness??? If it is there then you may want to remove it.

The Optic Sensor should still be there.

[IamDave0887]

Originally Posted by dondandd

Your 98 should not have an optic sensor... pretty sure those went away with the 97+ trucks. Fuel leak can definitely cause your issues. Air in the fuel system can cause hard starting, or a start then stall followed by lots of cranking to restart it. When you get air into the ip, it can get caught up in the slots on the optic sensor wheel. This can affect the way the optic sensor reads, causing running issues, and codes.

So in short, if you can see a fuel leak, you should definitely start with that and make sure the system is leak free. Unfortunately I don't know the fuel line sizes off hand.

Once you fix the fuel leak, clear the codes and see how everything runs. We can trouble shoot any remaining problems from there.

Don.

Don all DS4s have the sensor. It's the filter harness that you used to build the test rig for my truck that stopped in ~96. Some 96s had them(like mine) some didn't. By 97 none had the harness, supposedly.

It sounds like he's got the same issue my 96 had. Dead optic sensor.

Follow the codes. In this case they lead your right to the problem.

[HeavyChevy95]

IMO, most likely theres nothing wrong with your optic sensor. A fuel leak is your first clue.
If you have a fuel leak, and it sounds as if you do, as the fuel leaks out (and/or drains back to the fuel tank) while PARKED for extended periods, the fuel is being displaced with air READ AIR LEAK and the air likely accumulating in the fuel manager.
AIR in the fuel system can disrupt the numerous OS pulses, significant amounts will surely trigger DTC(s) and/or cause the PCM to default to backup fuel read hard starts and runs like crap for several minutes is par for the course, until the air is purged and the fuel system is reprimed.

IMO, you most likely you have a fuel/air leak in or under the fuel manager, thats draining off the back of the engine, down onto the bellhousing and oil pan.
Find and fix the source of the fuel/air leak, if the fuel hoses are old, dryrotted, cracked, split, and/or deteriorated, I suggest you replace them all, and dont forget the 2 on top of the fuel tank.
IIRC, you'll need aprox 3' of 1/4" (ID) fuel hose, and 2' of 5/16" (ID) fuel hose and it would probably be a good investment to upgrade to screw/band clamps if you still have the factory style spring clamps.
Once the fuel (leak) system is repaired, purged and primed, start the engine and check for fuel leaks. Allow the engine to idle for about 5 minutes to ensure all the air has been purged. Once the fuel system has been fully restored, shut it off, check for, make note of, and clear DTC(s). Then try starting the engine again, I suspect it will fire up right away, like normal.


See post #29


good luck

[matuva]

There's one truck with this exact same codes.

She came in a perfect working order, except the fact that at idle, she just fishbites a bit the moment you shut off. Other than that sha was OK.

We disconnected both batteries for an hour, time to install HID kits.

When we reconnect all things, we had the bad surprise of experiencing very hard start.
She idles fine once started, but as soon as you select a gear (R, D, 2-3-1...) she idles up and down (650 to 900 rpms up and down).

found codes PO251 and PO370.

We have checked for any possible fuel/air leak : none