Quit running not starting

taroo · **Joined:** Sun Apr 27, 2008 2:14 pm **Posts:** 276

LMWatBullRun wrote:

olypopper wrote:

Are you able to work on your CRD this weekend? Made any headway?

Yup.

Torque Pro tells me I have low rail pressure- 150 psi resting, 900 cranking max, (varies betw 600 and 900)

Pulled and checked #1 injector since I had a GP code for that cylinder. Nothing wrong. dry tip, too.

Now I am thinking that unless I have a bad pump, it may be either a bad injector or a bad rail regulator. Going to check the rail regulator first.

Will keep y'all posted.

Guess this is the obvious, but when mine just quit last year it was the original fuel head that blew out at the heating coil and was sucking air and therefore not reaching pressure.

I replaced the fuel head with second generation, primed and was back on the road.

LMWatBullRun · **Posted:** Sun Jan 01, 2017 10:04 pm

taroo wrote:

LMWatBullRun wrote:

olypopper wrote:

Are you able to work on your CRD this weekend? Made any headway?

Yup.

Torque Pro tells me I have low rail pressure- 150 psi resting, 900 cranking max, (varies betw 600 and 900)

Pulled and checked #1 injector since I had a GP code for that cylinder. Nothing wrong. dry tip, too.

Now I am thinking that unless I have a bad pump, it may be either a bad injector or a bad rail regulator. Going to check the rail regulator first.

Will keep y'all posted.

Guess this is the obvious, but when mine just quit last year it was the original fuel head that blew out at the heating coil and was sucking air and therefore not reaching pressure.

I replaced the fuel head with second generation, primed and was back on the road.

Have the new fuel head installed as well as a lift pump. Air is not a problem- the low pressure fuel supply was the first thing checked, but it DOES need to be checked.

LMWatBullRun · **Posted:** Mon Jan 02, 2017 1:57 pm

LMWatBullRun wrote:

olypopper wrote:

Are you able to work on your CRD this weekend? Made any headway?

<snip> Now I am thinking that unless I have a bad pump, it may be either a bad injector or a bad rail regulator. Going to check the rail regulator first.

Will keep y'all posted.

OK, pulled the hose out of the fuel rail regulator return. No fuel coming out of that after cranking.

Injector returns next.

Sir Sam · **Posted:** Mon Jan 02, 2017 3:31 pm

check the output line from the pump to the rail and see if it dumps fuel into a cup?

LMWatBullRun · **Posted:** Mon Jan 02, 2017 3:37 pm

LMWatBullRun wrote:

olypopper wrote:

Are you able to work on your CRD this weekend? Made any headway?

<snip> Now I am thinking that unless I have a bad pump, it may be either a bad injector or a bad rail regulator. Going to check the rail regulator first.

Will keep y'all posted.

OK, pulled the hose out of the fuel rail regulator return. No fuel coming out of that after cranking.

Injector returns next.

Virtually no fuel out of the injector return.
(Double checked low pressure fuel supply- still pumps when I turn the key, no air from bleed.
Also, am getting some fuel at the rail, it does move fuel when I crack the #1 rail nut)

Sam, will check the HP pump output next, GMTA.

LMWatBullRun · **Posted:** Mon Jan 02, 2017 3:48 pm

Sir Sam wrote:

check the output line from the pump to the rail and see if it dumps fuel into a cup?

Very little fuel. 15 seconds cranking just barely covered the bottom of a cottage cheese container.
I'd get a lot more from the in-tank pump.

So far, I have-
replaced the fuel filter;
checked for LP fuel line air;
Replaced the cam position sensor;
Replaced the crank position sensor;
unplugged the CP3 pump plug and cranked the engine with no results;
Checked injector #1 where I had a GP code, replaced with new copper washer and seal;
Disconnected the rail pressure regulator return line and checked for flow when cranking;
Disconnected the injector return and checked for excessive flow;
Disconnected the HP supply from CP3 and found low flow.

No fuel in oil, either, btw that my nose can detect.

It seems as though either I have bad sensor wiring to one of the two critical sensors, or I have a bad CP3 pump.
The fact that I am getting some flow inclines me to the thought I have a bad CP3 pump.

Thoughts?

GordnadoCRD · **Posted:** Mon Jan 02, 2017 3:51 pm

Disconnect Fuel Quantity servo and retry?

If no change it would seem to be the pump or pump drive as unlikely as it sounds.

LMWatBullRun · **Posted:** Mon Jan 02, 2017 3:58 pm

GordnadoCRD wrote:

Disconnect Fuel Quantity servo and retry?

If no change it would seem to be the pump or pump drive as unlikely as it sounds.

I tried that already once, and it is a PITA to get at. Would I get any fuel at all if it were a wiring fault?

And if it were a wiring fault, how would I find it?

GordnadoCRD · **Posted:** Mon Jan 02, 2017 4:04 pm

Did you try it with the HP output disconnected? If so, sorry, I missed it.

From what I understand, if you crank it disconnected, you should get full unregulated volume from the HP pump.
If there is no change it would either indicate that the servo or wiring is at fault.
If there is a change, then downstream from there. (rail - injector - Pressure Control Valve - High Pressure Sensor.)

LMWatBullRun · **Posted:** Mon Jan 02, 2017 4:19 pm

GordnadoCRD wrote:

Did you try it with the HP output disconnected? If so, sorry, I missed it.

From what I understand, if you crank it disconnected, you should get full unregulated volume from the HP pump.
If there is no change it would either indicate that the servo or wiring is at fault.
If there is a change, then downstream from there. (rail - injector - Pressure Control Valve - High Pressure Sensor.)

Just to make sure we are talking about the same thing, I disconnected the plug on the CP3 (underneath the alternator)
To get at this nasty little fitting, I removed the alternator and the air hose to the intake elbow.
If there is an easier way to access this plug, I might consider redoing this test.

When I disconnect this plug, then the CP3 pump bypass is closed and it ought to provide full flow with unregulated pressure.
If it does NOT do that, and there are NO other leaks and I see low flow from the HP supply to the rail, then the CP3 assembly is bad, right?

LMW

GordnadoCRD · **Posted:** Mon Jan 02, 2017 4:40 pm

Nnnnnnnot quite.

I believe you have the correct electrical plug. I don't have to remove the Alternator on mine, but the CAC hose is a yes.

This servo controls volume out of the HP side of the CP3.
It works together with the Pressure Control Valve at the rear of the rail, to control rail pressure at the current specific requirements, as determined by ECM programming. (which controls both)
Fuel Quantity Valve (on CP3) controls (restricts) volume into the fuel rail.
Pressure Control Valve (at rear of fuel rail) controls (releases) excess volume (overpressure) out.
Fuel Pressure Solenoid (Middle of rail, kinda hanging over intake) Is the device the ECM uses to continuously monitor what is happening and make it's decisions.

At this point you're not looking specifically for pressure yet. You need to verify that disconnecting the servo will allow the CP3 to deliver max volume to the rail.

If not, you need to find out why.

If it does, THEN we find out why the volume isn't building pressure.

EDITED for clarity

LMWatBullRun · **Posted:** Mon Jan 02, 2017 5:02 pm

GordnadoCRD wrote:

Nnnnnnnot quite.

I believe you have the correct electrical plug. I don't have to remove the Alternator on mine, but the CAC hose is a yes.

This servo controls volume out of the HP side of the CP3.
It works together with the Pressure Control Valve at the rear of the rail, to control rail pressure at the current specific requirements, as determined by ECM programming. (which controls both)
Fuel Quantity Valve (on CP3) controls (restricts) volume into the fuel rail.
Pressure Control Valve (at rear of fuel rail) controls (releases) excess volume (overpressure) out.
Fuel Pressure Solenoid (Middle of rail, kinda hanging over intake) Is the device the ECM uses to continuously monitor what is happening and make it's decisions.

At this point you're not looking specifically for pressure yet. You need to verify that disconnecting the servo will allow the CP3 to deliver max volume to the rail.

If not, you need to find out why.

If it does, THEN we find out why the volume isn't building pressure.

EDITED for clarity

So, previously, I did disconnect the CP3 valve. In theory, as I understand it, that eliminates constraints on flow.
If flow constraint was an issue, then the CRD should have run. It did not.
Checking the output of the CP3 there is low flow. This indicates that either the high pressure pump is bad, or the flow control valve is bad.
My understanding is that the assembly comprises both the high pressure pump and the valve. Am I misinformed?
If I'm correct, then the next move is to replace the CP3 high pressure pump and flow control valve assembly, right?

The only other thing I can think of is that there may be a bad wire elsewhere, to the Cam Pos Sensor or the Crank pos sensor, but that should not affect the CP3 assembly.

Thoughts?

GordnadoCRD · **Posted:** Mon Jan 02, 2017 5:18 pm

Wwwwelll,

kindanotreally.

Previously you disconnected the FQS valve when the pump output to the fuel rail was still connected. You're making the assumption that everything up there is functioning correct, but that may or may not be. We haven't got there yet.

Quote:

Checking the output of the CP3 there is low flow. Unless you've pulled it again, and checked with it disconnected, we don't actually know this yet. This indicates that either the high pressure pump is bad, or the flow control valve is bad.

OR the wiring could be bad.

Quote:

My understanding is that the assembly comprises both the high pressure pump and the valve.

The assembly, yes, but the valve is an externally removable component. The pump almost never fails. The valve has been known to fail, AND is much cheaper than the pump.

Quote:

the next move is to replace the CP3 high pressure pump and flow control valve assembly, right?

Honestly, I'd step back to the wiring connector again, until we know - for sure - what we're dealing with.

flash7210 · **Posted:** Mon Jan 02, 2017 6:44 pm

If there not much fuel going up to the rail, then there should be A LOT of fuel going throught the return line.
You already pulled the return hose off the rail and saw there wasnt any coming from the rail.
But...
Was there fuel coming out of that return hose? Or did you have it plugged?
Its the same return line as the cp3.

If little fuel up to the rail and little fuel out the return, then cp3 is bad.
If little fuel up to the rail and a lot out the return, then fuel quantity solenoid is bad.

GordnadoCRD · **Posted:** Mon Jan 02, 2017 7:09 pm

That's what we're trying to find out :wink:

Sir Sam · **Posted:** Mon Jan 02, 2017 7:24 pm

I'm on board with checking the FQS (Fuel Quantity Solenoid aka mprop aka metering valve).

Disconnect it. Now the CP3 should have full flow out when cranking. Now put your cup under the output line from the CP3 and check flow. Lets see what that does.

http://www.idparts.com/high-pressure-fu ... -4591.html

Sir Sam · **Posted:** Mon Jan 02, 2017 7:26 pm

LMWatBullRun wrote:

So far, I have-
replaced the fuel filter;
checked for LP fuel line air;
Replaced the cam position sensor;
Replaced the crank position sensor;
unplugged the CP3 pump plug and cranked the engine with no results;
Checked injector #1 where I had a GP code, replaced with new copper washer and seal;
Disconnected the rail pressure regulator return line and checked for flow when cranking;
Disconnected the injector return and checked for excessive flow;
Disconnected the HP supply from CP3 and found low flow.

Have you disconnected the output line from the filter head and verified that the lift pump is pushing plenty of fuel out of the head(and to the CP3)?

GordnadoCRD · **Posted:** Mon Jan 02, 2017 7:42 pm

He did say that the lift pump filled the new filter and was able to get a trickle coming up to the rail. Don't know if he checked it independently though.

Regarding the fuel quantity servo, what seems to happen a lot is the proportioning hydraulic valve sticks. sometimes with moisture sometimes with grit sometimes with hard freezing. I just went through a box of 6 "bad" ones that were replaced and there was only one bad one. (unresponsive to electrical) The rest were just dirty. I pointed that out to the shop owner who was working on a Duramax at the time. He backed the screws out one turn each (maybe a bit more) and lightly whacked the valve a few times, tightened it back up, and it started working. He replaced it anyway afterwards, but that's a shop owner's liability vs someone like us.

LMWatBullRun · **Posted:** Mon Jan 02, 2017 8:11 pm

Sir Sam wrote:

LMWatBullRun wrote:

So far, I have-
replaced the fuel filter;
checked for LP fuel line air;
Replaced the cam position sensor;
Replaced the crank position sensor;
unplugged the CP3 pump plug and cranked the engine with no results;
Checked injector #1 where I had a GP code, replaced with new copper washer and seal;
Disconnected the rail pressure regulator return line and checked for flow when cranking;
Disconnected the injector return and checked for excessive flow;
Disconnected the HP supply from CP3 and found low flow.

Have you disconnected the output line from the filter head and verified that the lift pump is pushing plenty of fuel out of the head(and to the CP3)?

Yes. Lift pump is moving a LOT of fuel.

LMWatBullRun · **Posted:** Mon Jan 02, 2017 8:13 pm

Sir Sam wrote:

I'm on board with checking the FQS (Fuel Quantity Solenoid aka mprop aka metering valve).

Disconnect it. Now the CP3 should have full flow out when cranking. Now put your cup under the output line from the CP3 and check flow. Lets see what that does.

http://www.idparts.com/high-pressure-fu ... -4591.html

OK, but that will have to wait until tomorrow or maybe Wednesday when I can work on it.

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