Engine wont start - no fuel pressure

[Turbo Buick 6]

Why are people still talking about if the rail pressure sensor is giving the ECM a funky reading etc...

THAT AND EVERY OTHER ELECTRONIC CIRCUIT on the engine is IRRELEVANT in this problem!!!!!!!!!!

IF you unplug the FCA and crank it, YOU WILL BUILD RAIL PRESSURE if there are no mechanical/fuel system problems. You dont even need the FICM, ECM, or anything else hooked up to test this. You could have every single wire crossed and shorted out, not gonna make any difference, it will still make rail pressure.

Really, there are not many things that could possibly go wrong here.

1. CP3...good?
2. FCA...good/not full open? (leave it unplugged for now until the engine gets running to make it default to max rail pressure to take the electronics out of the picture)
3. injector lines...tight?
4. rail pressure releif valve....tight and not leaking? Maybe replace with a race valve?
5. injectors...not hung open?
6. CP3 has positive fuel feed pressure to it...good?
7. rail pressure sensor...good? (disconnect and verify with a DMM)

THATS IT. There is nothing else that can cause a no-rail pressure situation, ECM, electronics, wiring, FICM, or otherwise...... I still think people are way overthinking/complicating this. My own guess is you have a small high pressure fuel leak somewhere. Just because its under such high pressure doesnt mean that you are going to see some geyser that shoots to the moon when there is a slight leak (I think people assume this because the system runs under such high pressure). Yes, the CP3 makes insane pressure, but at a very surprisingly small volume. If you have one tiny dribble and go to crank it, that tiny dribble that you might not even see can very easily bleed off enough pressure that the CP3 wont be able to overcome it. Ive had that happen before. Put a motor in, cranked and cranked and cranked. Wouldnt build rail pressure. ZERO visible fuel leaks. I rechecked all the injector lines, one was slightly loose, put another 1/8 turn on it, cranked again while watching the tech 2....sure enough after about 7 seconds, 200psi-350psi-500psi-800psi-1500psi-vroom.

Just my own stupid opinion.

ben

X2

 

[sweetdiesel]

We are still working on a manual gauge to confirm rail pressure.

Like you said mike it is only a gauge if it does blow that is a good thing

Man I feel bad for you Mick.....I must cranked mine over 100 times before it fired.

Tried swearing at it:angel: I have a feeling you will get it tonight.

 

[Turbo Buick 6]

Like you said mike it is only a gauge if it does blow that is a good thing

Man I feel bad for you Mick.....I must cranked mine over 100 times before it fired.

Tried swearing at it:angel: I have a feeling you will get it tonight.

Call it dirty names, they like it when you do that......if all else fails when no one is looking wisper to the truck that you are going to light it on fire......usually works for me

 

[Fingers]

I know this engine has dual fuelers. Have you totally removed the second CP3, the lines, and then capped/plugged all the holes? Testing one CP3 at a time will do no good if the other one is still hooked into the system in any way.

From your earlier description, you are getting some fuel out of the return line. Correct? As Ben said, these pumps don't spit out gushers so a little is an indication of at least some pumping.

Time to start isolating where the return fuel is coming from. Pop the return line off the pump(s) and run it to a bottle. Plug the line the pump return ran into. Unhook the FPRV line and put it into a another bottle, plugging where it hook in. Lastly, run the main return into a bottle.

Unhook the FPRs on the CP3(s) and crank the bad boy for 30 second. Now tell us which bottles have fuel and how much compared to each other.

The CP3 bypasses a fair bit of fuel all the time. It is how it cools and lubricates the pump.

The FPRV line should be dry.

The only thing left on the main return line now is the fuel injectors. These leak off constantly, but at low pressures it is almost nothing. I know there is a reference in the SI manual about how much fuel injector return to expect, but I can't find it right now.

 

[Fingers]

Found the leak off spec for the injectors. Each injector should leak off between 3cc and 5cc after a 15 second crank. So for all eight, that is 24cc to 40cc but tending towards the higher number.

 

[mick]

Why are people still talking about if the rail pressure sensor is giving the ECM a funky reading etc...

THAT AND EVERY OTHER ELECTRONIC CIRCUIT on the engine is IRRELEVANT in this problem!!!!!!!!!!

IF you unplug the FCA and crank it, YOU WILL BUILD RAIL PRESSURE if there are no mechanical/fuel system problems. You dont even need the FICM, ECM, or anything else hooked up to test this. You could have every single wire crossed and shorted out, not gonna make any difference, it will still make rail pressure.
Really, there are not many things that could possibly go wrong here.

1. CP3...good?
2. FCA...good/not full open? (leave it unplugged for now until the engine gets running to make it default to max rail pressure to take the electronics out of the picture)
3. injector lines...tight?
4. rail pressure releif valve....tight and not leaking? Maybe replace with a race valve?
5. injectors...not hung open?
6. CP3 has positive fuel feed pressure to it...good?
7. rail pressure sensor...good? (disconnect and verify with a DMM)

THATS IT. There is nothing else that can cause a no-rail pressure situation, ECM, electronics, wiring, FICM, or otherwise...... I still think people are way overthinking/complicating this. My own guess is you have a small high pressure fuel leak somewhere. Just because its under such high pressure doesnt mean that you are going to see some geyser that shoots to the moon when there is a slight leak (I think people assume this because the system runs under such high pressure). Yes, the CP3 makes insane pressure, but at a very surprisingly small volume. If you have one tiny dribble and go to crank it, that tiny dribble that you might not even see can very easily bleed off enough pressure that the CP3 wont be able to overcome it. Ive had that happen before. Put a motor in, cranked and cranked and cranked. Wouldnt build rail pressure. ZERO visible fuel leaks. I rechecked all the injector lines, one was slightly loose, put another 1/8 turn on it, cranked again while watching the tech 2....sure enough after about 7 seconds, 200psi-350psi-500psi-800psi-1500psi-vroom.

Just my own stupid opinion.

ben

Thanks Ben - I tend to agree from what I have found out so far

 

[mick]

Like you said mike it is only a gauge if it does blow that is a good thing

Man I feel bad for you Mick.....I must cranked mine over 100 times before it fired.

Tried swearing at it:angel: I have a feeling you will get it tonight.

All the times I have had these trucks apart and back together I have never had to crank 100 times to get them going Simon. But Guy says hes done the same thing. Sounding more like a gasser each day

 

[mick]

Call it dirty names, they like it when you do that......if all else fails when no one is looking wisper to the truck that you are going to light it on fire......usually works for me

Done that Paul - Didnt work for this one

 

[mick]

I know this engine has dual fuelers. Have you totally removed the second CP3, the lines, and then capped/plugged all the holes? Testing one CP3 at a time will do no good if the other one is still hooked into the system in any way.

From your earlier description, you are getting some fuel out of the return line. Correct? As Ben said, these pumps don't spit out gushers so a little is an indication of at least some pumping.

Time to start isolating where the return fuel is coming from. Pop the return line off the pump(s) and run it to a bottle. Plug the line the pump return ran into. Unhook the FPRV line and put it into a another bottle, plugging where it hook in. Lastly, run the main return into a bottle.

Unhook the FPRs on the CP3(s) and crank the bad boy for 30 second. Now tell us which bottles have fuel and how much compared to each other.

The CP3 bypasses a fair bit of fuel all the time. It is how it cools and lubricates the pump.

The FPRV line should be dry.

The only thing left on the main return line now is the fuel injectors. These leak off constantly, but at low pressures it is almost nothing. I know there is a reference in the SI manual about how much fuel injector return to expect, but I can't find it right now.

Thanks John going to give that a try this morning

 

[mytmousemalibu]

Maybe one of the CP3's has a stuck open check valve and its all back bleeding/recirculating internally? One stuck one in one likly will bring both down? Just another idea

And, dunno why but when somthins not going my way, usually figure it out/find it, right as im giving up If ya real wanna tear at the trucks heartstrings, tell it your trading it in for a ford or dodge, should behave then:angel:

 

[05lly2500hd]

Why are people still talking about if the rail pressure sensor is giving the ECM a funky reading etc...

THAT AND EVERY OTHER ELECTRONIC CIRCUIT on the engine is IRRELEVANT in this problem!!!!!!!!!!

IF you unplug the FCA and crank it, YOU WILL BUILD RAIL PRESSURE if there are no mechanical/fuel system problems. You dont even need the FICM, ECM, or anything else hooked up to test this. You could have every single wire crossed and shorted out, not gonna make any difference, it will still make rail pressure.

Really, there are not many things that could possibly go wrong here.

1. CP3...good?
2. FCA...good/not full open? (leave it unplugged for now until the engine gets running to make it default to max rail pressure to take the electronics out of the picture)
3. injector lines...tight?
4. rail pressure releif valve....tight and not leaking? Maybe replace with a race valve?
5. injectors...not hung open?
6. CP3 has positive fuel feed pressure to it...good?
7. rail pressure sensor...good? (disconnect and verify with a DMM)

THATS IT. There is nothing else that can cause a no-rail pressure situation, ECM, electronics, wiring, FICM, or otherwise...... I still think people are way overthinking/complicating this. My own guess is you have a small high pressure fuel leak somewhere. Just because its under such high pressure doesnt mean that you are going to see some geyser that shoots to the moon when there is a slight leak (I think people assume this because the system runs under such high pressure). Yes, the CP3 makes insane pressure, but at a very surprisingly small volume. If you have one tiny dribble and go to crank it, that tiny dribble that you might not even see can very easily bleed off enough pressure that the CP3 wont be able to overcome it. Ive had that happen before. Put a motor in, cranked and cranked and cranked. Wouldnt build rail pressure. ZERO visible fuel leaks. I rechecked all the injector lines, one was slightly loose, put another 1/8 turn on it, cranked again while watching the tech 2....sure enough after about 7 seconds, 200psi-350psi-500psi-800psi-1500psi-vroom.

Just my own stupid opinion.

ben

I'm not an expert by any means and haven't read the entire thread. But I have to agree with Ben here, I had the same situation when I installed my new engine, luckily Ben and some others helped me through it. Exactly what I did was overcomplicate it, turned out the FPRV was loose and not allowing it to build pressure and he also walked me through unplugging the FICM? or somthing and defaulting to max psi.

I only had 200-500 psi while cranking, tightened the FPRV and wanted to shout in joy, she cranked right up and I slapped myself for overlooking something so small.

 

[Fingers]

With the connector in place: Orange - brown 5.0
brown - yellow 4.5
orange - yellow 0.5


With connector off pressure sensor: orange - brown 5.01
brown - yellow 0.0
orange - yellow 5.01 Seems strange as if the signal is shorted to 5v source?

This is a case of a floating sense wire. Not unusual to see in a three wire setup when the sensor is not connected. If you would short orange to yellow momentarily and watch the voltage it would go to zero then gradually ramp back up to 5 volts. The SI manual even says it should be 5 volts. The important one is the Orange to Yellow when the sensor is connected.

The question is what the voltage, Orange to Yellow, is while cranking?

 

[Mike]

This is a case of a floating sense wire. Not unusual to see in a three wire setup when the sensor is not connected. If you would short orange to yellow momentarily and watch the voltage it would go to zero then gradually ramp back up to 5 volts. The SI manual even says it should be 5 volts. The important one is the Orange to Yellow when the sensor is connected.

The question is what the voltage, Orange to Yellow, is while cranking?[/QUOTE]

.5 while cranking and plugged in.


Thanks Jon

 

[mick]

It LIVES!!!!

and is running well. Thanks to all for all the help and ideas. Seems like quite a few were on the right path. Simply put it just takes a LOONNGG time to fill those Fuel Rails up by turning those cp3s by just cranking the engine. With the EFI hooked up andwatching the screen, Mike gave me the idea to spin the 2nd cp3 over by hand (you can turn it by hand faster than by cranking with the engine.) When I saw the fuel pressure coming up to 2000 by hand I think I have a redneck idea and put a belt on it and wrap the other end around the chuck on a battery drill. That spun it up to 6000 psi. I guess after that the fuel rails were full, so I took the belt off and 1st kick it fired up. Engine sounds good. I have to hook the sc and tc pipes up tomorrow and on the road again. Thanks again all and look forward to posting some good numbers soon. Not a bad place here by the way......:rofl:

 

[Kat]

:happy2::happy2::happy2::happy2:

 

[Trippin]

:yup:

What she said!

 

[mick]

:happy2::happy2::happy2::happy2:

You know that feeling Kat

 

[mick]

:yup:

What she said!

You were on the money too Guy. Easier to believe how long it can take to fill those Rails up when you see the size hole the fuel needs to go through. Good lesson though. We will be trying those injectors out on the dyno soon Guy. Sound alright so far. Thanks for the good service there and the flow/balance sheets too.

 

[Mike]

You were on the money too Guy. Easier to believe how long it can take to fill those Rails up when you see the size hole the fuel needs to go through. Good lesson though. We will be trying those injectors out on the dyno soon Guy. Sound alright so far. Thanks for the good service there and the flow/balance sheets too.

I second that. Well the rest of it too. Oh, no phone calls at midnight I promise. :angel:


:joker:

 

[JoshH]

That's good to hear, fellas. Congrats on getting it figured out. Good luck on getting it to the dyno and hopefully the track later. I'm looking forward to hearing your results. :beer