Engine fires for a few seconds and then shuts off. Lose all fuel pressure. Wtf???

[MarkIII4Me]

Ok, so I finally got around to getting my project running. At first I wasn't able to engage the starter, so I ran a relay from the battery and that fixed the problem. Now it won't stay running. This engine has never ran before in my vehicle. I have a SAFC2 and VPC wired into a factory JDM ECU through the VPC pnp harness. The VPC's pressure sensor is wired thorugh the SAFC to the ECU to clean up the signal. I have denso 550cc injectors and the MKIV bosch fuel pump installed and an Aeromotive AFPR.

So I turn the key to the ON position and after a couple of minutes my Aeromotive AFPR builds to around 12psi. But that's it. When I crank the engine, it fires-up and idles at around 1100rpm, sounds great, and then my fuel pressure drops to zero and the engine dies. No matter how much I crank-up the fuel pressure, it never builds more than 12psi in the ON position and drops right off when the engine is running. I only put around 3 gallons into the tank and it was bone dry before that. I found a small fuel leak, but there should still be enough gasoline. If there wasn't, how would I be building pressure at all?

When I did the SAFC2 intial setup, the pressure sensor was only reading .015v and does not change when the sensor is unplugged. Perhaps the sensor is bad or a splice became undone when cramming everything back in. However, even if the AFM is unplugged (ie. no Karman signal being sent from the VPC), shouldn't the engine stay running? I mean, could the problem just have to do with the VPC's pressure sensor or should I look elsewhere? Could the fuel pump relay be the problem? The AFPR?

Someone shoot me some ideas so I can get this baby running!

Here's what I'm dealing with. The engine idles at around 1100rpm, I give it gas a few times and then it dies:

 

[hvyman]

The Afm is what tells the pump to start. With the key in the on position you should not be building pressure.

Have you checked to make sure you have power and ground to the pump.

 

[D.J.T.]

well of course it just died. Your out of gas.

Better fill the tank & try again, if it persists then its a true problem.

 

[MarkIII4Me]

The Afm is what tells the pump to start. With the key in the on position you should not be building pressure.

Have you checked to make sure you have power and ground to the pump.

That's what I've heard, so I don't understand how I'm building fuel pressure without cranking the engine. I haven't had time to start trouble shoot the pump. But will start next week.

well of course it just died. Your out of gas.

Better fill the tank & try again, if it persists then its a true problem.

I don't have any free time until next Tuesday. The first thing I was going to do was add more gas. However, I don't really think that's the problem if I'm building pressure. Can't hurt though.

 

[hvyman]

Also the afm is what gives the signal for the pump to start pumping.

Try turning off or since you have the patch harness remove it and try starting the car with a afm. If it starts with a afm then the problem is either with the wiring or electronics,.

 

[jetjock]

His profile says GTE. That would mean the AFM has nada to do with the fuel pump...

 

[MarkIII4Me]

So jet, what would you recommend?

 

[Nick M]

So jet, what would you recommend?

Besides putting gas in the tank? I am quite sure the first thing in the owners manual says check gas. I don't have mine handy so I can't look.

If the car is off, the fuel pump is shut down. You have to mete certain conditions for the ECU to activate the fuel pump relay. With aftermarket control, I don't have any idea what you did. Based soley on your described symptom, you should jump the fuel pump circuit in the diagnostic box and see if stays running. I think it will. If it does, you can look at the two speed relay. After the engine starts, the low speed resistor is incorporated into the strategy. Maybe you are having a problem. And maybe not.

 

[MarkIII4Me]

Quick update. It appears it was several things. First off, my battery was a little low. Upon giving it a full charge my check engine light went out and the VPC's pressure sensor started producing a signal to through SAFC. So that's good. Car fires up fine initially, but then dies after about 30 seconds. After which it pretty much dies each time it fires up.

The problem seems rather simple now that I've been able to look in the engine bay while it ran briefly. I should note that I do not have my intercooler pipes ran yet. I plan on doing them this weekend. I didn't foresee this as being an issue since the VPC converts from AFM to Pressure signal from the intake manifold. I now realize that I made the mistake of attaching the BOV vacuum line. The Tial BOV only has a 9psi spring. My engine at idle produces well over 20psi of back pressure. Since that throttle body is just pulling from atmosphere this causes a massive vacuum leak. I saw with my own eyes the BOV slowly open until it was fully relieving pressure, causing the engine to stall. Pretty sure this is my problem. I knew it'd be something simple. lol.

Now if I could just get my AN fittings from my oil cooler setup to stop leaking. Should have known better than to incorporate used fittings purchased from a SM member