Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

[MadPSI]

This is just a video of the issue we're having with trying to get Nick's truck up and running. The truck will barely start and won't idle. I've tried fuel pressures from 50 to 20 PSI and everywhere in between, nothing. We also connected the fuel pump to a separate power source to take it out of the equation from an electrical standpoint, nothing...

However...

Disconnect the fuel pump and the truck will start and idle unassisted. Turn on the pump and it kills the motor. Because we separated the pump electrically, we at least know that it has to do with the actual fuel pressure in the rail. What the hell could be causing this. It's completely backwards, logically...

It's an Aeromotive A1000 pump, 85# injectors, F.A.S.T. B2B.

Anyways, see for yourself. Right-Click Save-As (9.3 Meg Quiktime Movie)

http://www.lkcollectibles.com/madpsi/fuelproblem.m4v

Any ideas would be great, we're running out.

 

[Daron]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

Stuck open injector?

 

[MadPSI]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

I'd assume that all the injectors would have to be stuck open for that to happen, not just one. The injectors were all cleaned, tested, and flow matched literally a week or two back, so they're functioning properly AFAIK.

 

[WyoSyclone]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

Is the fuel return line kinked or clogged??

 

[denny]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

Double check your settings on the FAST.

 

[turbodig]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

This is just a video of the issue we're having with trying to get Nick's truck up and running. The truck will barely start and won't idle. I've tried fuel pressures from 50 to 20 PSI and everywhere in between, nothing. We also connected the fuel pump to a separate power source to take it out of the equation from an electrical standpoint, nothing...

However...

Disconnect the fuel pump and the truck will start and idle unassisted.

Like, forever? Or just until it runs out of pressure in the rail.

If it runs without the pump, *something* is pumping fuel up there. What does FP do when you turn the pump on/off?

 

[nick041881]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

it will run without the pump on for several minutes. We have not tried to let it run until it runs out of gas or to see how long it will go, but it will go for a minute or two. It will die as soon as you push on the throttle and take the motor past an idle. The fuel pressure goes immediately to wherever you have it set at when you turn the pump on, and it drops to zero as soon as you turn the pump off.

Like in the video, if the truck is running with the pump off, it will die as soon as you turn the pump on. We have hooked the pump to an external 12v source and it makes no difference, so I do not think that it is an electrical problem. Just an FYI, the injectors were just profesionally cleaned and flow tested. The only thing that we have not tried that we can think of is checking the current settings on FAST. The laptop is broken and we need to get another one, but I do not see how FAST peramiters could be wrong if it runs perfectly with no fuel pressure. Any help is greatly appreciated.

 

[midnightbluS10]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

Have you tried another fuel pump?

 

[mattw]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

Those injectors have to be stuck open.. Here is my theory and I don't know if its even possible.. I bet the engine vacuum is pulling enough fuel to make it idle. As soon as you create fuel pressure it floods and stalls. Since the injectors were just cleaned and tested I'm gonna bet its either a wiring or F.A.S.T. issue.


-Matt

 

[leroy]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

What does your oil smell like? You can get enough gas in the crankcase to support combustion. Fuel is delivered through the pcv valve.

Maybe the FAST is set too rich, causing it to die, and pump extra gas into the crankcase?

The carbon canister can also be a fuel source, if your tank is pressurized somehow.

If you fpr diaphragm is broken, I don't think it would hold pressure long.

Just some wild ass guesses.

Jim

 

[nick041881]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

truck has no pcv valves, no carbon canister......the fpr is doing it job as it will hold a steadt fp

 

[mattw]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

Will it run with the injector harness unplugged?

-Matt

 

[TYHOGG]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

Have you checked the fittings on the pressure regulator? If your using an aeromotive first instinct would be to plumb the feed into the bottom port on the regulator, its actually the return port that will control the pressure. The feed should be one of the 4 around sides.

Have you checked to make sure the feed and return aren't reversed?

 

[WyoSyclone]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

What on the motor was changed from when it was running with the tune that is now present in the FAST system.... different size injectors maybe??

Why is your fuel pressure dropping to zero when the pump is off? Does the Aeromotive not have a check valve in it??

Injectors couldn't be stuck open unless they were being fed a constant 12v source, correct? I would think they'd be getting really hot if that were the case.

I'm with MattW...has to be an issue with FAST... :dunno:

 

[nick041881]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

GreenTyGuy- The feed and the return are definately not reversed. They are set up like they were before the rebuild (running perfectly) with -8 AN line with completely different fittings on the ends. No way these are reversed. The fuel lines were not removed for the rebuild. They stayed in the engine bay and were simply re-connected when I put the new motor in.

The FAST is running the exact same program that was running when the motor was pulled. It ran perfect. The reason that I do not think that it is FAST is because it idles nicely with no FP. That would mean to me that the FAST has the injector size/duration correctly. Wouldnt it?? I could be wrong.

I have tried to start the truck with the injector harness unplugged when we were checking the timing. Perfect timing. Did not even think about starting.

The fuel pressure climbs immediately to the preset psi when the pump is turned on and drops to zero immediately when shut off. This makes me believe that the pump/lines/fpr is opperating as it should.

As seen in the video, the truck will idle perfect with no FP. As soon as you put fuel pressure to the rail, the motor dies. The pump has been hooked up to an external source. Same thing. This has to be an easy fix, but I have no ideas as to what to do.

 

[JSM]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

I would unplug inj. harness, give it fuel pressure and no fuel pressure and see if it will run.

Or while it is running unplug harness.

 

[nick041881]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

I will try these three scenarios as soon as I can and post the results. Thanks for the ideas...wish me luck!

 

[kentuc]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

I think the fuel pressure should hold when shut off. Fuel pump diaphram might be gone.

 

[BoostedSUV]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

it looked to me as if the truck shut off as soon as the fuel pump was plugged in, even before it built any fuel pressure. Almost as if the fuel pump robbed voltage needed to keep the motor running?? It also doesn't make sense how the truck can run with out any fuel pressure. I thought a certain amount of pressure was required to even fire an injector. Unless like others have stated the injector(s) are stuck open and engine vacuum is pulling fuel right out of the rail. When the diaphram went bad in my AFPR I couldn't even get the truck to start beacuse it wouldn't build any more than 20psi. The injectors wouldn't fire any fuel.

 

[nick041881]

Re: Built Sy runs w/o fuel pressure, dies with f/p - VIDEO INSIDE

In the video, the pump was wired to an external 12v source, so it was not robbing any voltage from the truck. I fuel pressure will adjust with the afpr and it stays steady with the pump on so I am assuming that the afpr is good. It will not run with any fuel pressure at all. It will idle until I shut it off with no fp. With no fp I can actually put it in reverse and idle out of my garage and then back in!!