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fish biting?

indybeck

indybeck

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Messages
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Location
SE South Dakota
after reading forums, and old threads, and FAQ i've got an idea of the ins and out of my 6.5. but now i am at a standstill. i have a 1996 GMC 6.5 turbo k2500, and i love my truck. I am having same issues, surge/hesitation. I have replaced OPS, LP, PMD, put new 3" exhaust from turbo to tip, relocated PMD with 6' extension, removed fuel tank cleaned, removed sock, put inline fuel filter on between tank and LP, and cleaned out intake of oil. yet i still have this issue. 85% of the time pickup runs GREAT! rest of the time surges and misses like a gasser with fuel troubles. I have guage on t-valve cruising, 3 psi, idle 5-6 psi. no accompanying smoke. any suggestions? I would appreciate any and all ideas. hope someone has a suggestions! I have been dealing with this for some time, about 2 months. :mad2:
 
Old PMD or NEW?
If old, you might wanna try a new one.
If new, you may have air entering upstream of the LP.A pinhole in the supply line or the hose at the tank or a bad O ring at the LP or tank connection could be the culprit.Vacuum in the tank might make it worse.
At what tank fuel level do you experience the most hickups?
 
new PMD, and have also put new fuel cap on. had tank down, checked lines, and all looked good. does the harness on the IP go bad?
 
new harness came with PMD, but, i did not put it on. what are the symptoms of failed harness? i will also check for leaks in fuel system tomorrow.
 
indybeck said:
new PMD, and have also put new fuel cap on. had tank down, checked lines, and all looked good. does the harness on the IP go bad?
Click to expand...

Check to see if your IP has a filter harness on the optic sensor... this is NOT the same one as runs to the PMD.

It looks like this:
106394_3.jpg


If it does, take the filter harness out and re-connect the wires - they just plug right inline.

If that solves your problem, then you probably don;t need to buy a new one - the OBD-II systems were supposed to have that filter built into the PCM - and can just run without one.
 
Last edited:
Thank you dan, I enjoy working on it, and i have fun doing it. as far as the harness, i built that myself. it took time, and patience, but it turned out very nice. the PMD is located behind the front bumper. J, the optical filter is already gone. was gone as soon as i read it was built into the ECM. Thank you guys!
 
indybeck said:
new harness came with PMD, but, i did not put it on. what are the symptoms of failed harness? i will also check for leaks in fuel system tomorrow.
Click to expand...
Your self build harnass could be suspect though.fishbyte, stall ,no start,same as bad PMD.
On the fuel lines, Looking good dont mean IS good.

put a clear hose on the IP return and check for air bubbles coming trough.
 
Good idea B, thank you, but as far as PMD harness, truck was doing that before i relocated. i will try some clear line! thank you! oh, and i will check the supply lines again.
 
not always, but every now and then it dies throw some codes. here are the ones currently...

P0251 - control a malfunction cam/rotor/injector

P0370 - high resolution signal a

Pending

P0711 - trans fluid temp sensor circuit range/performance

P0070 - ambient air temp sensor circiut

the 251, and 370 went away for some time after i started using stanadye additive, truck would still surge/hesitate, but would not throw code. after about a 250 mile trip, it began to do the same, and now threw code again. thanks again guys!
 
Crisk1500 ment fuel rate per inj,should be around 7mm.you need a by directional scanner to see the fuel rate .Not fuel press,altough 5+ psi is good. No air bubbles,OK

The codes may suggest a wiring issue.Intermitted probs are the hardest to find.
IMO,you need to check the entire engine harnass from the CPS all the way to the firewal harnass,and pay special attention to connectors(corrosion), wire chafing,and broken wire cores in side the insulation(soft spots) at the flexpoints + the engine grounds at the IP and pass side back of head
 
Thank you, B, i do not know rate/injector, and i don't believe i will buy a scanner. Family likes to eat, and i am on a budget. I will check wiring, long procedure, but i can get it done. while i am doing that, i will replace the IP harness with the new one. I did check the large 15 pin harness for corrosion, and it was spic and span, is that the one you are talking about by firewall, or are you referring to the bulkhead fitting. thank you, and keep me in mind if you have any other ideas!
 
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