Fuel Crank/No-Start Issue

[dzolalaw]

Hello,

Trying to diagnose a crank/no-start issue. Starting with fuel. When I turn the key the fuel pump makes the prime noise and fuel pressure goes up to about 20 (just prime no crank) but then rapidly goes down to zero. I Pulled the fuel delivery line off after the fuel filter, getting fuel. Pulled the fuel delivery line (after where the autometer gauge mounts to the line), getting fuel. I’m trying to figure out if the drop in fuel pressure after prime is the reason for the no start. If so, what can the issue be? The inertia switch works, I popped it and got no fuel pressure whatsoever then reset and got the fuel pressure as described above.

I am going to try to attach the video of what it is doing.



Any help would be greatly appreciated.

Daniel

 

[89ripper]

Hi Daniel. What kind of fuel setup are you using? You can have fuel pressure loss and still be able to see fuel coming out, so that wont really tell you much.

 

[General karthief]

20 psi is not enough, install a new fuel pump.

 

[AeroCoupe]

I believe the fuel pump has an internal check valve. I know several cars that do no hold prime pressure and take just a bit longer to start due to this. Low fuel pressure can be a couple of things. Bad pump, clogged filter, pressure regulator failing, or kinked line. Filters are cheap so I would start there.

 

[dzolalaw]

Hi Daniel. What kind of fuel setup are you using? You can have fuel pressure loss and still be able to see fuel coming out, so that wont really tell you much.

Aeromotive 340 Stealth pump. Very few miles on it. Stock lines, fuel rail and aftermarket fuel pressure regulator. All installed at same time, low miles since install. Everything was running well last year and then I decided to swap the stock intake for a gt40 setup. Had to put the project on hold and when I got back to it this year this happened. Watching the gauge drop like this led me to believe I had a leak, but I didn’t. No leaks.

It could be something else (spark/timing) but before I move ahead I wanted to see if what I’m seeing with the gauge could be anything else but fuel. It always primed right up to 42 (if I recall correctly) and held without problem. I just don’t see how it can be anything else but fuel. If it can be then I will continue on.

Thank you

 

[General karthief]

I believe the fuel pump has an internal check valve. I know several cars that do no hold prime pressure and take just a bit longer to start due to this. Low fuel pressure can be a couple of things. Bad pump, clogged filter, pressure regulator failing, or kinked line. Filters are cheap so I would start there.

Yeah, I kinda did oversimplify but in my defense he did not give any other info, when I first got the 'Junk Pile' I replaced all pump, filter and regulator.

 

[General karthief]

Aeromotive 340 Stealth pump. Very few miles on it. Stock lines, fuel rail and aftermarket fuel pressure regulator. All installed at same time, low miles since install. Everything was running well last year and then I decided to swap the stock intake for a gt40 setup. Had to put the project on hold and when I got back to it this year this happened. Watching the gauge drop like this led me to believe I had a leak, but I didn’t. No leaks.

It could be something else (spark/timing) but before I move ahead I wanted to see if what I’m seeing with the gauge could be anything else but fuel. It always primed right up to 42 (if I recall correctly) and held without problem. I just don’t see how it can be anything else but fuel. If it can be then I will continue on.

Thank you

That's more like it, now we can get into the meat of it....I suspect the hose between the pump and line on the hanger is cracked or come loose.

 

[89ripper]

Aeromotive 340 Stealth pump. Very few miles on it. Stock lines, fuel rail and aftermarket fuel pressure regulator. All installed at same time, low miles since install. Everything was running well last year and then I decided to swap the stock intake for a gt40 setup. Had to put the project on hold and when I got back to it this year this happened. Watching the gauge drop like this led me to believe I had a leak, but I didn’t. No leaks.

It could be something else (spark/timing) but before I move ahead I wanted to see if what I’m seeing with the gauge could be anything else but fuel. It always primed right up to 42 (if I recall correctly) and held without problem. I just don’t see how it can be anything else but fuel. If it can be then I will continue on.

Thank you

Hmmm....so when you replaced the intake, you disconnected the fuel rails, correct? Did you relieve fuel pressure in any way?

 

[89ripper]

I made this mistake before. What you see is some debris i found in the regulator and a fitting that I used on it. It was enough to cause my fuel pressure issues. Wouldnt hurt to double check your work. Apologies for the random stuff on my work bench, Im not very organized....

 

[General karthief]

Apologies for the random stuff on my work bench, Im not very organized....

What's that?
You wanna talk about unorganized? I gots a whole garage full of unorganized!!
Need something? It's in there (as I point a long wrinkled finger at the old garage) good luck.

 

[dzolalaw]

Hmmm....so when you replaced the intake, you disconnected the fuel rails, correct? Did you relieve fuel pressure in any way?

Yes, I disconnected the fuel rails and removed them altogether in order to get the lower intake on. I did not relieve the fuel pressure before disconnect. My line doesn’t have the Schrader valve because the auto meter gauge is mounted there. I could have simply removed that carefully but now that you say this, I did not. I just disconnected the lines at the lower disconnect points and let everything drain into a spare can. Could that have created an issue?

Thank you for your help

 

[89ripper]

Yes, I disconnected the fuel rails and removed them altogether in order to get the lower intake on. I did not relieve the fuel pressure before disconnect. My line doesn’t have the Schrader valve because the auto meter gauge is mounted there. I could have simply removed that carefully but now that you say this, I did not. I just disconnected the lines at the lower disconnect points and let everything drain into a spare can. Could that have created an issue?

Thank you for your help

No...just a point of where to start looking I suppose. If it ran fine before intake swap, made me think of the fuel rails. What happens if you turn key on and off a few times...will it build up fuel pressure?

 

[dzolalaw]

No...just a point of where to start looking I suppose. If it ran fine before intake swap, made me think of the fuel rails. What happens if you turn key on and off a few times...will it build up fuel pressure?

No...just a point of where to start looking I suppose. If it ran fine before intake swap, made me think of the fuel rails. What happens if you turn key on and off a few times...will it build up fuel pressure?

Tried that and unfortunately it still won’t build pressure. Continuously jumps up to below 20 then rapidly falls back down so fast that no pressure builds. It’s so fast that one would suspect a major leak somewhere in the line but there are no leaks.

 

[General karthief]

See post #7

 

[dzolalaw]

Yep. Gonna drop the tank and pull it to see if there is something going on there. Thank you!

 

[Noobz347]

Check the regulator.

Pinch off the return line after the regulator and see what you get when you prime the pump.

Also, check the vacuum line for the smell of fuel.

 

[dzolalaw]

That's more like it, now we can get into the meat of it....I suspect the hose between the pump and line on the hanger is cracked or come loose.

Ok, so I dropped the tank checked the hoses and everything is still solidly connected and no cracks damage. Is there a way I can test the pump while I have it out? I want to be 100% certain the fuel pump is working properly before I reinstall it. I would also like to make sure it is getting enough power to rule out a wiring, fuse or relay issue.

 

[dzolalaw]

Check the regulator.

Pinch off the return line after the regulator and see what you get when you prime the pump.

Also, check the vacuum line for the smell of fuel.

Pinched off the line as suggested and unfortunately still won’t hold pressure. It’s actually only going up just above 10psi now as opposed to 20 psi before. Can this be a sign of a pump slowly going bad or do they normally just stop working altogether?

 

[Mcmahst]

just to clarify, you checked the hoses inside the fuel tank, right?

 

[Noobz347]

Pinched off the line as suggested and unfortunately still won’t hold pressure. It’s actually only going up just above 10psi now as opposed to 20 psi before. Can this be a sign of a pump slowly going bad or do they normally just stop working altogether?

At this point, yeah... I would start suspecting the pump if you have no fuel leaking anywhere (including into the intake).

I think somebody already mentioned the internal pop-off in this thread.