Injection troubleshooting

cmpbiker · **Joined:** Mon Mar 29, 2010 1:26 pm **Posts:** 62

UPDATE READ BELOW

While waiting for time to continue troubleshooting my no-start I have been studying all of the info on the forum including the awesome troubleshooting flowchart. I do have a couple of questions about the electronic control side of the equipment, the flowchart seems to deal with more mechanical faults. I hope that someone can answer the following questions.

1. Regarding the fuel pressure solenoid. If I understand this correctly the solenoid will hold shut up to 5000psi on spring pressure only, higher pressure is regulated by electro-magnetic force. I assume that the pressure sensor feedback loop regulates this action? During startup It should be held tight by the magnet, is there enough mechanical force to force some fuel into the cylinders? I would assume that for the first seconds of cranking no fuel should flow out of the solenoid. What happens if the fuel pressure sensor is faulty, does it release the pressure solenoid or the quantity solenoid? is there an easy way to test voltage to the magnet coil to verify if the solenoid is bad or just not getting the electro-boost?

2. What is regulated if the camshaft sensor or crank sensor do not produce a proper signal? Is it the firing of the injectors, the pressure solenoid or is it the fuel quantity solenoid? I have replaced both sensors as a preemptive strike, is there a weak spot in the wiring I should be aware of?

3. My understanding is that in a normal start sequence for the first few seconds the quantity solenoid is full open (flow) and the pressure solenoid is shut (electrically) to build maximum pressure quickly, when and what starts regulating the pressure after that time?

I do not think I have a mechanical issue based on the intermittent nature (starts 1 time in 10) of my problem so I am focusing on an electronic issue.

I would like to see a step by step logic process on the electronic side to go along with the diagnostic flow chart.

cmpbiker · **Joined:** Mon Mar 29, 2010 1:26 pm **Posts:** 62

OK no bites, how about a simpler question. Besides the ECM and Cam Position Sensor what is responsible for creating an injection signal? Seems that after running the troubleshooting flowchart it looks like the injector is not getting a pulse? If you had to look for a bad wire where would be the most likely place?

papaindigo · **Posted:** Tue Aug 07, 2012 3:14 pm

On 06 I'd suggest looking at wire bundle behind fuel filter head for chaffed wires. Might be worth a look on your 05

Hoosier CRD · **Posted:** Tue Aug 07, 2012 3:34 pm

I have been told that the CRANK Position Sensor is what sends the signal for injector firing. I have been told that it can cause a myriad of problems as it ages.

As a precaution, I changed out the one on my CRD recently. I tackled it from the top. Accessed from the bottom, I've read that it is easier to replace. I suppose that it all depends on how much equipment you have, i.e. jack, jack stands, etc.

Hope this will help.

Hoosier CRD

cmpbiker · **Joined:** Mon Mar 29, 2010 1:26 pm **Posts:** 62

Yes I read the same regarding the Crank Sensor, already replaced it (and cam sensor) leaning towards the wiring between the sensors and ECM.

Is there a good source for a color wiring diagram?

cmpbiker · **Joined:** Mon Mar 29, 2010 1:26 pm **Posts:** 62

FYI validated that the cam sensor was working, nice square uniform wave on the scope measured at the ECM and sensor. Noid on the injector plug flashes once dimly then not when cranking.

Hoosier CRD · **Posted:** Wed Aug 08, 2012 6:41 am

How many miles are on you CRD? Did you buy it used? If yes, did the PO take good care of it with filter changes and use good fuel? Was there ever GASOLINE run through the system?

At some point, I think that you should also consider the mechanical side of things, i.e. the CP3. I'm uncertain at this time as to how to diagnose a failing or failed pump-but I can find out.

Prior to buying my CRD, I was told to RUN away from them. This came from a Service Manager at a Jeep dealer. At the time prior to my purchase, there were one or two CRDs, with lower miles than mine, that came through his shop regularly with a myriad of problems. To date, I have experienced few problems myself. I have 117k miles on mine currently, bought it with 85k on the clock. I keep up with the fluid and filters, buy diesel from high volume fuel facilities, i.e. truck stops, high volume gas stations and use fuel additive regularly. I have all of the original components, turbo, injectors and injection pump. (Knock on wood)

FWIW,

Hoosier CRD

cmpbiker · **Joined:** Mon Mar 29, 2010 1:26 pm **Posts:** 62

90k on the miles and I was not the first owner and I have limited knowledge of it's history. I bought it with 45k.

The CP3 was bench-tested and proclaimed "Cherry" including the fuel quantity solenoid.
Other items to check off the list are-

timing- belt replaced and double checked
Cam sensor
Crank Sensor
Fuel supply (bypassed filter to a stand alone tank)
ECM (I have an 05 for sale by the way)

It is interesting, I find vague references to the other subsystems involved in injection timing including the pressure sensor, temp sensor, MAP etc. I would love to have something that breaks down what can cause a no-squirt decision on the ECM.

Hoosier CRD · **Posted:** Thu Aug 09, 2012 9:26 am

Best thing that I can offer to you at this point is my "Rule #1"

Rule #1: Look for the obvious.

Fuel in tank Y/N

Fuel getting to and through filter head Y/N

Fuel at fuel rail Y/N (not sure how to SAFELY check this one-please be VERY careful)

Injectors being signaled Y/N

No double gasketing (inside or outside gasket) at the fuel head with the filter Y/N

If all of that checks out and you have also ruled out the Fuel Pressure Solenoid and Fuel Pressure Sensor, then, congratulations, you have the conundrum of the forum.

Hoosier CRD

cmpbiker · **Joined:** Mon Mar 29, 2010 1:26 pm **Posts:** 62

Hoosier CRD wrote:

Best thing that I can offer to you at this point is my "Rule #1"

Your rules are good advice, I have looked at so much and struggled I am getting confused.

Injectors being signaled Y/N -N
This is the trouble spot. I dont know where else to look for problems. The wiring has been checked so we can count out a short. I can see a one flash on a noid light then nothing. Its as if the start sequence begins but something comes up in the first couple of seconds. What would tell the computers to stop the injectors within 1-2 revolutions? Would the fuel pressure sensor kill the process if it had a weird signal?

If all of that checks out and you have also ruled out the Fuel Pressure Solenoid and Fuel Pressure Sensor, then, congratulations, you have the conundrum of the forum.

My fear is that I have the conundrum of the forum. Yeah for me.

Hoosier CRD

Hoosier CRD · **Posted:** Thu Aug 09, 2012 5:41 pm

My Rule #2 is: If it was built by men, then it can be fixed by men.

I just had a conversation with a professional technician about an Isuzu box truck that was frustrating him. He could not remember if it was the Fuel Pressure Sensor or the Fuel Pressure Solenoid that was the problem, BUT, he would get a 1-in-10 crank too out of this vehicle. Said that he cycled the key all the way off then on every time too. Replaced the solenoid / sensor with a new unit and it made the problem worse. Put the old one back for now until he can figure it out. Bottom line, you're not alone.

Another round of questions for ya:

Does your Check Engine Light function Y/N

Is the CEL on/do you have any codes Y/N

Have you REPLACED either the Fuel Pressure Sensor or the Fuel Pressure Solenoid Y/N

In my opinion, it would be quite rare, but not unheard of, if either of the sensors are in fact new, it is possible to have a bad one out of the box.

Deduction and analysis can only take you so far. That is why there are test tracks. I am assuming that you have had the ECM verified for function.

FWIW,

Hoosier CRD

cmpbiker · **Joined:** Mon Mar 29, 2010 1:26 pm **Posts:** 62

Hoosier CRD wrote:

My Rule #2 is: If it was built by men, then it can be fixed by men.

Does your Check Engine Light function Y/N

Y

Hoosier CRD wrote:

Is the CEL on/do you have any codes Y/N

N

Hoosier CRD wrote:

Have you REPLACED either the Fuel Pressure Sensor or the Fuel Pressure Solenoid Y/N

N- next round of testing is focused on these two items. Would be great if I knew what normal looked concerning the electrical signal. I figure the solenoid can be checked bu seeing if there is outflow during cranking then checking if there is votage to the magnet. That would isolate a mechanical problem versus a computer problem.

Hoosier CRD wrote:

In my opinion, it would be quite rare, but not unheard of, if either of the sensors are in fact new, it is possible to have a bad one out of the box.

Deduction and analysis can only take you so far. That is why there are test tracks. I am assuming that you have had the ECM verified for function.

Yes have a spare flashed by Keith at GDE.

FWIW,

Hoosier CRD

Thanks!
Clay

Hoosier CRD · **Posted:** Thu Aug 09, 2012 7:40 pm

Ohm readings should be something that can be gained on both Fuel Pressure units while they are at rest/on the bench, yes?

Could taking these readings and then comparing them to new-in-the-box units be of help?

My thought is that as long as the readings are gathered and administered in the same way, you should be able to deduce which sensor is errant, no?

FWIW,

Hoosier CRD

Hoosier CRD · **Posted:** Tue Aug 14, 2012 3:27 pm

Clay,

Did you by chance have the injector harness off of the top of the engine at some point? The #4 injector plug and the fuel sensor plug at the REAR of the fuel rail are identical. If they get crossed up, which can easily happen, then a no start will occur. The #4 plug is identified on my harness with a black wrap around tag; Yours may not be though. If all of this is possible, swap those two plugs and see what happens. Hope this helps.

FWIW,

Hoosier CRD

Injection troubleshooting

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