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Discussion Starter · #1 ·
Good afternoon im back with more 6.5 headaches. My 6.5 is throwing p0251 injection pump fuel metering control a (cam/rotor/injector) I just had the Injection pump replaced with one from Heath diesel, Had new injectors put in as well, Mechanic said while he was in there redoing the injection pump there was a line under the injection pump or near there that was cracked and jacked up so he replaced that as well. Truck ran fine for 100 miles then The darn mechanic left the battery terminals loose it wouldnt crank then while I was tightening the terminals the bolt was too long stripped out the connection bought 2 brand new batteries . Pmd is relocated under front bumper with the heath diesel plate, It also has a big fan now blowing on it. New liftpump as well from ss diesel supply. Truck runs and starts fine cold runs great for 30 mins then at a stop light or while slowing down to the stop light dies Try to restart it very long crank time surges and runs for maybe a couple seconds then dies again. It wont throw p0251 until the second before it dies then it quits all out gives up. After sitting on the side of the road trying to restart it after a few attempts and maybe 15-20 mins it will start idle fine then die again, another 15 mins goes by it will start and idle fine run fine but it feels like its in some kind of limp mode wont go over 30. Some things I have already tried, Replaced crank shaft postion sensor, The t valve in front of engine while running test, I can feel the lift pump pumping when its running. PMD gets SUPER hot when idle the aluminum plate is very hot to touch But it is not hot when driving it cools down cool enough to put your hand on it but its still hot so I dont think its pmd overheating issue. I may have cooked the pmd already, when I swap pmds on the side of t he road truck still does same issue starts cranks then dies cranks cranks then dies so It dosnt lead me to believe pmd issue. It seems like it is a heat issue after the engine gets so warm. where I live its average 105-115 for the next 3 months. the motor was never overheated at least coolant level never goes over 200-205, Any help is much appreciated next im going to pull off the Optical sensor filter harness. Any help is greatly appreciated you guys here are all great dudes who know what they are talking about thanks in advance. HAPPY 4Th of JULY
 

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Discussion Starter · #2 ·
It has a 3 month old ops switch as well new glow plug, fluidampr harmonic balancer, new cdr.
 

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Check your grounds. It might not be the problem but worth a check especially with the intake having been removed. I had a bad ground to the pcm on mine that didn't show itself till I removed my intake. Mine was almost broke inside the plastic loom and removing it showed me the weak spot in the wire. I don't know if that was my entire problem but after fixing it i haven't had a issue yet.
 

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When you replaced the CPS did you use an AC/Delco brand?
"Feeling the lift pump" is not a diagnostic test. You need to verify fuel flow from the lift pump.
Apply a jumper wire to the lift pump relay and then crack open the T Valve and allow fuel to flow into a container. The lift pump should produce 1/2 pint of fuel in 15 seconds.

Another way to check is to start and run the engine then open the T Valve for 30 seconds. If during that time the engine dies or you see no fuel low from the drain line then the lift pump is bad and too weak to support the engine.

Install a piece of clear fuel line on the return side of the Injection pump to help locate any air in fuel issues.
OPS also needs to be AC/Delco
 

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Discussion Starter · #5 ·
When you replaced the CPS did you use an AC/Delco brand?
"Feeling the lift pump" is not a diagnostic test. You need to verify fuel flow from the lift pump.
Apply a jumper wire to the lift pump relay and then crack open the T Valve and allow fuel to flow into a container. The lift pump should produce 1/2 pint of fuel in 15 seconds.

Another way to check is to start and run the engine then open the T Valve for 30 seconds. If during that time the engine dies or you see no fuel low from the drain line then the lift pump is bad and too weak to support the engine.

Install a piece of clear fuel line on the return side of the Injection pump to help locate any air in fuel issues.
OPS also needs to be AC/Delco
Well as I sit here on the side of the road typing this after another test drive, it passed the test didn’t die after 30 seconds of the t valve being open, cleaned all grounds checked resistance with a fluke meter got low resistance on all grounds to each other, it only seems to happen after about 5 miles and it’s at a stop or low speed, I’m going to have to get some clear tubing and check for air bubbles, the cps isn’t ac delco they didn’t have it in stock anywhere in town it’s standard idk if that was the issue truck is doing exact same thing pre changing out the cps, the ops I bought from Heath diesels website. It runs fine until I slow down after about 30 mins of driving and it surges and bucks and dies. Very long crank then starts runs for maybe a second or two and dies. It’s a heat issue I’m thinking just don’t know where. I will get another heat sink and try and use my other pmd for my 5 mile test drive, I’m already ordering a tuned pcm from quad star as a cel I had during one of my break downs was p0606 I haven’t gotten that code again only once along with my p0251. Any other ideas would be awesome guys thanks for everything always
 

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Discussion Starter · #6 ·
Well as I sit here on the side of the road typing this after another test drive, it passed the test didn’t die after 30 seconds of the t valve being open, cleaned all grounds checked resistance with a fluke meter got low resistance on all grounds to each other, it only seems to happen after about 5 miles and it’s at a stop or low speed, I’m going to have to get some clear tubing and check for air bubbles, the cps isn’t ac delco they didn’t have it in stock anywhere in town it’s standard idk if that was the issue truck is doing exact same thing pre changing out the cps, the ops I bought from Heath diesels website. It runs fine until I slow down after about 30 mins of driving and it surges and bucks and dies. Very long crank then starts runs for maybe a second or two and dies. It’s a heat issue I’m thinking just don’t know where. I will get another heat sink and try and use my other pmd for my 5 mile test drive, I’m already ordering a tuned pcm from quad star as a cel I had during one of my break downs was p0606 I haven’t gotten that code again only once along with my p0251. Any other ideas would be awesome guys thanks for everything always
after sitting in the car I decided to start recording, It is a heat issue just dont know with what, im going to get heatpaste and try out the other pmd fully on my 5 mile test. It seems after about 5 miles and 30-40 mins is when it happens. Takes 40 mins to drive 5 miles because I dont want to leave my neighborhood I already blocked up a busy intersection once haha.The heat issue dosnt make sense though because the pmd isnt Excessivly hot when the truck shuts off I put a 10 in 80 watt fan bolted to the heat sink to blow air over it and dissipate heat. and when the truck does die i jump out and feel the pmd its hot but not unbearable hot. The thing does produce heat i have seen people say it gets hot thats just how it is. It isnt untouchable hot but its pretty warm. Its bolted under the front bumper. thanks guys
 

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Discussion Starter · #7 ·
after sitting in the car I decided to start recording, It is a heat issue just dont know with what, im going to get heatpaste and try out the other pmd fully on my 5 mile test. It seems after about 5 miles and 30-40 mins is when it happens. Takes 40 mins to drive 5 miles because I dont want to leave my neighborhood I already blocked up a busy intersection once haha.The heat issue dosnt make sense though because the pmd isnt Excessivly hot when the truck shuts off I put a 10 in 80 watt fan bolted to the heat sink to blow air over it and dissipate heat. and when the truck does die i jump out and feel the pmd its hot but not unbearable hot. The thing does produce heat i have seen people say it gets hot thats just how it is. It isnt untouchable hot but its pretty warm. Its bolted under the front bumper. thanks guys
Further more, After I leave the truck off and it cools down stone cold I fire it up let it warm up and drive around its back as if nothing happend. The SES is still on for p0251 but it will drive around for another 5 miles till it warms up and shut off and do the same **** its been doing. long crank hard start, may start run for a few seconds die, start again run for a few seconds, Give it about 15 mins it might start might not, Itll run for a few mins then die again, after about a half hour of messing with it and trying to get it firing again it will run and idle fine but its in some kind of limp mode like in the video i sat there cranking triyng to get it to start for about a half hour. It goes in a limp mode and will then drive but not a very fast. That grggling reving up and down through the intersection its never done that to me before. any help appreciated thanks guys
 

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after sitting in the car I decided to start recording, It is a heat issue just dont know with what, im going to get heatpaste and try out the other pmd fully on my 5 mile test. It seems after about 5 miles and 30-40 mins is when it happens. Takes 40 mins to drive 5 miles because I dont want to leave my neighborhood I already blocked up a busy intersection once haha.The heat issue dosnt make sense though because the pmd isnt Excessivly hot when the truck shuts off I put a 10 in 80 watt fan bolted to the heat sink to blow air over it and dissipate heat. and when the truck does die i jump out and feel the pmd its hot but not unbearable hot. The thing does produce heat i have seen people say it gets hot thats just how it is. It isnt untouchable hot but its pretty warm. Its bolted under the front bumper. thanks guys
That's exactly how a non AC Delco CPS sensor would react at startup. long cranks before starting. Check Rock Auto.
 

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Any part you replace that is electrical in nature must be AC/Delco brand or you'll introduce electrical gremlins into the issue
When you switch out the PMD also try removing the PMD from the extension cable and plug it into the OEM cable on the IP.
This will eliminate a bad extension cable issue.
 

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I would be hooking up a fuel pressure gauge to make sure you always have positive fuel pressure before the IP especially when its being angry.
 

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Fix P0251 change IP , Fix long spin cycle to start engine replace CPS with genuine AC Delco. Problem solved.

Long standing problem with non genuine CPS..... Signal is not compatible with ECM... Wish someone would determine why but no one yet has scoped it out. Could be as simple as air gap. Several people on this site have struggled with the non oem sensor only to find out the extremely hard way that was the cause.

NoN related.> I worked on a Toyota one time that needed a CPS. Aftermarket Bosch was $75 ,a genuine OEM was $175. We figured the Bosch would work just as well and quoted the customer. It worked, but not as well on the scope. We had to replace it with the OEM and the customer refused the higher price and we had to eat it, Moral to the story: You seldom regret buying the right stuff the first time, cus cheap stuff will bite you in deass.
 

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Discussion Starter · #12 ·
Fix P0251 change IP , Fix long spin cycle to start engine replace CPS with genuine AC Delco. Problem solved.

Long standing problem with non genuine CPS..... Signal is not compatible with ECM... Wish someone would determine why but no one yet has scoped it out. Could be as simple as air gap. Several people on this site have struggled with the non oem sensor only to find out the extremely hard way that was the cause.

NoN related.> I worked on a Toyota one time that needed a CPS. Aftermarket Bosch was $75 ,a genuine OEM was $175. We figured the Bosch would work just as well and quoted the customer. It worked, but not as well on the scope. We had to replace it with the OEM and the customer refused the higher price and we had to eat it, Moral to the story: You seldom regret buying the right stuff the first time, cus cheap stuff will bite you in deass.
Injection pump is brand new from Heath diesel not even 70 miles on it
 

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Discussion Starter · #13 ·
That's exactly how a non AC Delco CPS sensor would react at startup. long cranks before starting. Check Rock Auto.
It only has long cranks after it starts to act up from running for 30-45 mins. Cold start it cranks fine runs fine for 30-45 mins I’ll still get a ac delco.
 

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P0251 is a fuel injection problem. Replace IP The CPS borrows 5 volt reference voltage and those sources can also cause problems.
 

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P0251 Indicates IP, Problems that will throw the code is air in the system or very dark fuel. Typically it's the optic sensor is going bad or the encoder ring has a defect. One other thing that needs to be disposed of is the optic sensor filter harness that plugs into the outside of the pump.
 

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Discussion Starter · #18 ·
P0251 Indicates IP, Problems that will throw the code is air in the system or very dark fuel. Typically it's the optic sensor is going bad or the encoder ring has a defect. One other thing that needs to be disposed of is the optic sensor filter harness that plugs into the outside of the pump.
Optic sensor filter isn’t there I pulled the intake off and didn’t find it in there hooked up in line with the optical sensor, I will change crank shaft position sensor but how can I be positive of bad injection pump, like I said I just bought it from Heath diesel less then 100 miles on it dark fuel or air I will check that when u get clear tubing from auto parts store
 

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Optic sensor "Encoder" is expensive and most fuel shops only replace when they absolutely need to. The data track disc that it reads can easily be damaged as well. Only thing you need to know is the death code P0251..
 

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Discussion Starter · #20 ·
Optic sensor "Encoder" is expensive and most fuel shops only replace when they absolutely need to. The data track disc that it reads can easily be damaged as well. Only thing you need to know is the death code P0251..
So can I ask what do you think my next course of action should be?, I get my new pmd soon and my new cps ac delco but what your saying is p0251 is the death code for optical sensor, Everytime I call heath diesel I never get ahold of anyone they dont return my emails. Is the injection pump a dud or the Optical sensor ontop a dud, That's something I can do myself right? I have seen videos on it they all just say be very very very gentle. Thank you for all your help also. Im going to try and give heath diesel another call tomorrow but every time I do I get nowhere.
 
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