No start, electrical issues, need help. Please review

BigBad151

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Hello fellow members,
This is my first post here, however I'm no stranger to forums and their etiquette. I've been searching for weeks so please dont refer me to that. So with that out of the way, allow me to acquaint you with the situation. The truck is a 99.5 f350 xl. Has an intake, exhaust, new factory turbo, bullydog gt (that is currently uninstalled). The issue: while driving the vehicle cut out. No stumble, just shut off like you turned the key off. Then no start. This was a month ago. Since then I have replaced the IPR, fuel filter, CPS, IDM and batteries. Monitoring with forscan, I have been able to verify proper oil pressure (2800 psi) @ 45% duty cycle. Proper VREF voltage of 5v. As well as an rpm signal. I can see a demanded pulse width of 3.5ms, but they do not seem to be firing. As there is no smoke or smell out of the exhaust. A buzz test has been performed 5 times and tested great each time with no codes. Fuel pressure has also been verified as well as the pump operating as well. The inertia kill switch has also been tested. So seemingly at an end I whipped out the volt meter and started getting some interesting readings. While ohming out the harness and injectors starting at the idm plug I found high resistance on injectors 2 &7. So I disconnected the UVCH plugs and retested to confirm the issue is in the valve cover, which it did. However while testing the left bank injector power supply,pin #23, I found resistance between the IDM power supply, pin26, and the injector ground shield,pin 18. So i removed the 42 pin connection and retested between there and the idm plug with the same issue. I have searched high and low through that harness and all the plug connections for shorts or chaffing to no avail. Am I missing something? Is there another direction to take? Any explanation to the resistance between pins that should be infinitely open? At no point through all of this did the truck make the slightest inclination of starting. Please help me revive this old beast.

Btw, the only recurring dtc I have is the P1670

Thank you in advance
 

DieselDC

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Throw on a spare idm.


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BigBad151

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I have replaced the idm already, with no luck or inclination of starting.

Iam currently searching for a new harness, I have just acquired new to me uvch's that iam going to test with the meter tonight before install. In the mean time iam planning on removing the entire harness, and removing wire loom in search of a short to the injector shield ground.
 

DieselDC

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I must have missed the IDM you mentioned above then. The harness would be my last resort. Check the injectors for torn or aging o-rings.


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BigBad151

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I must have missed the IDM you mentioned above then. The harness would be my last resort. Check the injectors for torn or aging o-rings.


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I will be sure to check those when I replace the valve cover harnesses. But it is my understanding, that the resistance present between the left bank feed and the idm ground, will fry the idm. Which is an issue I have. I think that the harness is up there in priority. Not trying to knock your suggestion as I will certainly investigate it. But given the circumstance of how the truck died to begin with, and the P1670 code. The harness seems most likely given what I have found this far. Unless, there is some link between the orings and the electrical that I'm not aware of.
 

13fist

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It certainly sounds like you located a possible cause, shorting to ground, in the harness.
It is odd that it would buzz test with this kind of short. This is the very thing that should show up during the test.
Check everything in the fuse box under the hood, if you haven't already. I don't have diagrams handy at with me at work, but I'm thinking there is a diode or the like between the IDM & PCM.
The reason to check the orings is for oil pressure. I think it's 500 psi it needs to see or the truck wont start. Which could also be ICP. Not sure how your seeing 2800psi with no start, I believe that's the default the PCM throws out with the ICP failed or disconnected so I'd be looking at that too.
 

BigBad151

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Very true about the buzz test, which was the reason I waited so long to investigate the idm and wiring. I believe the ICP to be good, because when I originally replaced the IPR with a cheapo, it would not build oil pressure. No with factory motorcraft IPR it responds accordingly. As for the fuses, I have gone through every fuse, and also removed the under hood box to inspect all the wires and connections on the underside. I found one jumper wire exposed, on an unrelated circuit that I rectified.

But according to my tests, I have oil psi, battery voltage, vref, rpms above 100, proper oil level in hpop reservoir, fuel pressure,
And pulse width demand. But no fire.

With having an injector each bank with above normal resistance, would the idm shutdown both banks, or just those cylinders?

I'm hoping the rain holds off so I can get in there and do some more tinkering today. And report back.

Thank you all for responses. I have this posted on another site,and no one has said a word, I truly appreciate it. Nice to know the forums aren't dead.
 

BigBad151

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So I traced the left bank injector feed wire to the 42 pin plug, and then cut it about 4 inches from the 42 pin plug. Retested the 23,26,18 pin resistance and it came back as open.
So,my next step is to pull apart the 42 pin plug and inspect for a short.
 

BigBad151

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The resistance iam getting is between .0045 ohms and .0055 ohms. Am I chasing a ghost here or is the concern valid.

Btw the resistance from idm to cylinder 2 is 12ohms, and cylinder 7 is 4.4 ohms. If detected by the idm, would these prevent their respective banks from firing all injectors?

Thank you
 

13fist

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2.8-3.6 is the range for injector resistance. 12 ohms is out of range, but technically so is 4.4. Whats the history on your injectors? may just need fresh solenoids. Could try moving the connection on the high ohm injectors to see if it moves. Sounds like you've been through every inch of wire, but knowing if the resistance follows the solenoid, or the harness, would give you a direction to go.
I wouldn't worry about those sub ohm readings. I get that noise when i use cheap leads on my fluke.
 

DieselDC

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Solenoids should ohm out to 3.2-4.4. IH specs. 10 is bad


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BigBad151

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Roger that on the ohms, thanks for input.
I'm in the process of opening the valve covers up to inspect everything and determine whether solenoids or harness is in need of replacing.

My concern presently, is would the injectors explain the no start. Given there is a "bad one" on each bank, given whatever the reason. Would that be enough to prevent everyone for not firing?
 

13fist

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Here's the thing with these types of gremlins. Finding one problem leads to finding another, in a string of old nickle and dime issues that have likely been there for years without causing any issues individually. It may be that these little things added up to what you are facing with no single one being the cause.

Or, taking you in a direction of away from the real issue like bad fuel pump, relay, or neutral safety switch, etc.

If it were me. At this point I'd take a step back and reconnect everything. Leave the valve covers off, but hook it all up, make sure the batteries have a fresh charge, clear all old codes, and try to start it up while observing and logging whats going on.
 

BigBad151

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All sounds probable, I'm going to be getting to the valve covers in the next couple of days, after I test and check everything I will try again. I log everytime I turn it over, so we will see what happens. I will keep everyone up to date. Thanks for the help.
 

BigBad151

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Evening everyone.
Sorry I havent responded sooner. Life always has a way of getting in the way. I still have not removed the valve covers yet. Going to start after this message. I am unaware as to whether or not the uvch is factory or not. Truck has 190k on it, and I have just recently acquired the truck. So the history is a mystery ri me.

I was hoping someone can shed some light on this though. Can a fault in the wiring/ injector kill each of there banks and cause a no start? Or does history show that it would only cause it to run roughly, but in fact run? Just trying to grasp the process of why here.
 

DieselDC

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Yes...


As I said in the get go, remove your injectors. Check them. I’m still waiting to see what your results are...

Also check those ohms # too.
 

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