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Can anyone clear this up for me? If I have a good buzz test but I have a CCT that identifies cylinders not contributing, do I absolutely need to replace those injectors? I've already replaced the IDM, the CPS, the ICP, and the IPR.
The cylinder contribution test IS NOT an injector test.
It's a piston crack, broken ring, burned valve, broken rocker arm, bent push rod, or any other mechanical problem test as well as injector test. It's also a way to see lots of false #3 and #8 readings and lots of money spent due to chasing white rabbits.
There have been lots of new injectors put in broken/worn out engines because of failed CCTs because fuel is only 1/3 of the equation.
Hi Cletus and thanks for clarifying. OK maybe I need to give a bit more information. My truck is an early 99 and has 127K miles on it. I recently upgraded my injectors to 238/100 injectors. I also upgraded the turbo, put in Bee Hive valve springs, added an Air Dog II fuel system and a CNC Fab 4 line fuel feed with fuel bowl delete and CNC Fab stainless HPOP lines with a cross over, and a new transmission to handle the new power. I already had a 4" turbo back exhaust, an intake, gauges, and a PHP Hydra. I had about 500 to 1000 miles on the new injectors when the truck broke down and the CCT is giving me a cylinder 1, 2, & 4 not contributing test result.
The break down was very sudden. I pulled into the left turn lane with the intention of making a u-turn and it suddenly started running like crap. I ended up having it towed home. Twice since I had it towed home it has run great when I started it, but only for a few seconds. Then it was right back to running on only about half of the cylinders. I suspect it has to be something electrical but I haven't found anything yet. The one change in symptoms that I noticed was when I changed the IPR I saw an ICP of over 3000 PSI at idle, but it still was only running on about half of the cylinders. Any other suggestions or experience that may be related will be greatly appreciated. I'm at a loss.
Last edited by deanramey; Aug 7, 2021 at 08:44 PM.
Reason: Corrected the ICP reading I saw
What are you using to read codes and watch ICP/IPR? Want to make sure you are getting all the info the truck will provide.
Might be good to start checking the the injector wires from UVC to 42 pin connector, and if good, to IDM.
I'm using FORSCAN and my laptop. I used a multimeter and checked the wiring from the IDM through the injector solenoids and back to the IDM. I checked the resistance for the left bank between pins 22, 7, 19, & 9, to pin 23 and got 3.2 ohms for each of those paths. Then I checked the resistance for the right bank between pins 6, 21, 8, & 20 to 24 and got 3.2 ohms for each of those paths. then I checked for a short between pins 23 & 26 and then pins 24 & 26 and both of those paths were open. then I checked for a short between pins 23 & 18 and 24 & 18 and both of those paths were also open. please correct if I'm wrong but I believe the resistance tests I conducted checks all of the wiring for the injector circuits from the IDM through the 42 pin connector through the UVCHs and back to the IDM.
Doesn't a good buzz test also confirm all of those paths are good too. Thanks for the suggestion. Please keep them coming until we figure this out.
Did you perform the buzz test with the engine cold?
I was thinking if the problem was somewhat intermittent, it might buzz test good sometimes, but wiggling the wires, especially when reading #1, 2 and 4, might reveal an open/short.
No, no P1316 code so I shouldn't have replaced the IDM, but my problem hasn't been intermittent since it started, except for the 2 times it ran great for just a few seconds. it was also suggested the I remove the DR side valve cover and check to see if the # 2 & 4 injectors are discharging oil from the spouts. I'm going to do that but I don't know what that will tell me other than if I do see oil coming from the spouts it means I'm getting oil from the high pressure side that should be activating the plunger.
I did perform the buzz test on a cold engine. It was the first thing I did yesterday. Today I did run it with the DR side valve cover off and verified there is oil coming out of the #2 & 4 injectors. Also I hadn't paid any attention to a P0476 code I was getting because I assumed it was due to the EBPV delete I did when I replaced the turbo pedestal and turbo. Turns out I had a hole in the EBP sensor tube so I replaced it. When I ran it after replacing the EBP sensor tube, it got significantly better but now has a P0475 code and still has an ICP issue so I put my old IPR valve back in and it got significantly worse. Next I'll put the new IPR valve back in and change out the ICP sensor. While it was doing better before I put the old IPR valve back in I did see that the #1 injector contribution fault was no longer there. Still had the #2 & 4 contribution faults. Batteries are low now so I'm charging and done for the day. I assume the P0475 code is definitely due to the EBPV delete I did. I'll install a 10 ohm resistor in the plug I disconnected from the old pedestal to correct that. Does anyone think it's possible that I had a bad EBP sensor tube, a bad IPR valve, and a bad ICP sensor, all at the same time? And if so why did my breakdown happen so suddenly
Dean,
You may have already wrote about tjis so i apologize if you have. Is there a chance there is a open wire on your icp or ipr pigtail? This seems entirely possible and could trick or confuse the pcm. Could also intermittently work and not. You can pinpoint test these pins from the 42 pin connector to the correct pin at ea pigtail.
I would also suggest reading perdels with your scanner. When i was sure i had a bad injector (freshly rebuilt) perdels made me sure i knew which one. The cct gave me the reason to dig further.
I suppose it is possible I could have a wiring issue to the IPR or IPC. I haven't verified those electrical paths yet and it would make sense as to why changing those items did not really change anything. I will have to look those wires up so I know exactly what I need to check. As for checking perdels is that a PID I can load and check with a live scan?
Yes you can monitor perdels on forscan. You load a pid for ea cylinder. You run this test on a running motor with temps above 150. Im sorry If you are a nostart this one wont help.
Whats your icp while cranking with the icp plugged in?
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