I had a PO089 code back in the summertime which was the last time I drove it and after erasing, it did not come back. That code is for higher than desired rail pressure by 20 Mpa or more. Now, I have the opposite problem. The desired is 44 but when it's cranking the highest it got yesterday was like 27 or something. This is really weird because after first noticing this difference, I replaced the FPRV and then the actual was exceeding desired by a few numbers but it still didn't start. Now however, the actual is far below desired again. This makes no sense at all. I'm stumped,
02 LB7 Crank no start
- Thread starter Fryerdiesel
- Start date
Does this look right?
What is the actual current reported by the ECM?
How many miles are on the fuel system?
How many miles are on the fuel system?
Right. Desired is 44 actual is roughly half of that. What I'm asking is should the control unit be commanding 38% if the actual is the far below desired? Maybe that's why the pressure is not building.
0% is max fuel volume, 100% is minimum fuel volume. There are limits within the factory tune, unfortunately I do not know what those are in the cranking area.
It's possible that's part of your problem. It's possible your regulator is dead. It's possible your pump is dead. It's possible that you've got very high return rates causing the pump to not keep up.
Not to sound like a dick/jerk but you're the one with the truck seeking help. The clearer answers you can provide the page the better.
Did you change anything on the truck or is this now how the truck is acting?
It's possible that's part of your problem. It's possible your regulator is dead. It's possible your pump is dead. It's possible that you've got very high return rates causing the pump to not keep up.
Not to sound like a dick/jerk but you're the one with the truck seeking help. The clearer answers you can provide the page the better.
Did you change anything on the truck or is this now how the truck is acting?
I need to go get another recording of the actual pressure while it's cranking but I'm at work right now and the truck is at home. It hovers in the teens and 20s sometimes getting up as high as the low 30s but never enough to run. Only immediately after changing the relief valve did it get higher than 44, both times I cranked it but it still didn't start. Now, for some reason it won't reach the desired pressure again even though nothing else has been changed.
So, the truck ran fine before sitting for a while maybe a month or two because it wasn't tagged and needed some odds and ends with minor bodywork to be done so when we had a chance to start working on it again, went to start it up and move it but nothing. Well, it did make some white "smoke" that smelled like unburned fuel and it acted like it wanted to start because at certain points in the rotation, it kinda seemed like a cylinder or 2 was firing because the cranking would speed up like it's about to start. So before I had the scan tool, because it showed the PO089 code before when it was still running and because I had nothing else to go on, I changed the regulator and repaired the damaged wire I found an inch behind the connector where the insulation was gone. Put it all back together and still no start. Went and bought a fuel pressure gauge for the manifold test port even though it does have a FASS pump, and I have 12 psi with the key on so no problem there. Read somewhere a guy shorted the battery positive to ground removing or installing the intercooler tube on the passenger side and fried his FICM. Asked my son if it's possible he and his buddy did something similar when they were putting the hood on, he said yeah it's possible because they were kinda struggling to hold the hood and get the threads started at the same time. So, I changed the FICM. Still no start. Then I finally got the scan tool and could see that my actual was not meeting desired rail pressure. I changed the relief valve threaded next to the pressure sensor and now my actual was exceeding desired by a couple numbers but it still didn't start! I was shocked, stumped and so let down at the same time. The next day, I went out there to look for injector signals on the screen and noticed that my actual wasn't meeting desired again. That's where we are now.
Previous owner replaced them less than 40k miles ago. Truck has 177k on it now.
So if I unplug the regulator, it should have maximum fuel? I might try that and see what happens
If the regulator is working correctly it would force the pump to full output.
Will it start on a sniff of starting fluid?
20 mpa is enough to start. That's 2900 psi. Only takes about 1500 or so to operate the injectors. Most will idle around 30 mpa +- 5. If I remember correctly 44 mpa is stock command during cranking. The demand and actual matching during cranking is not important. What is important is making enough pressure to open the injectors, and it looks like yours is. Cranking is a slow engine RPM speed and the pumps don't always make the commanded pressure. If cranking is slow due to weak batteries it will lower the pressure the pump can make.
To me it sounds like you have a different issue keeping the engine from starting. Maybe a cam or crank sensor, Sheared crank pin (which might explain the random white smoke that smelled like fuel), or the ECM is not commanding the injectors because a security issue. Possibly something else if I forget anything
To me it sounds like you have a different issue keeping the engine from starting. Maybe a cam or crank sensor, Sheared crank pin (which might explain the random white smoke that smelled like fuel), or the ECM is not commanding the injectors because a security issue. Possibly something else if I forget anything
Okay, tomorrow is supposed to be a rainout here and I have to work so when I get back on it Sunday I'll check every ground connection, wires and where they plug in because I have a feeling the problem is electrical. The thing was running when it was parked. It just wasn't all together yet so my son put the rest of the front body on and then it wouldn't start but I already checked every single fuse in the box under the hood and the one to the left of the dash.
Now for some reason, I lost the crank sensor signal. So, I doubt it will start on starting fluid. I traded sensors with a known good one from a parts truck, ohmed out the wires from the connector to the big harness connector on top of the engine and they all tested good but then when I tried to check them from the other side of the connector to the ECM, I found that my factory manual has no pinout diagram for the ECM connectors!
Attachments
I must've gotten some bad data though as far as the crank sensor. First I blamed this cheap Bluetooth scanner on my phone but then I noticed that even though the bolt was tight, I was able to wiggle one of the positive battery cables. I HATE these stupid GM side terminal batteries!!! Worst idea they ever had! Well, maybe making a diesel engine from a gasoline one was the absolute worst one but the side terminal battery is right after it in my book...
Actual
Actual current to the regulator was 829 mA and desired was 793
The information is in that schematic you posted. C1 - 2,12,21