Dies after a minute or so, rough idle, but starts right back up

Makobra

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UPDATE:

there is no rough idle. if i jump the fuel pump relay the car will keep running.

CCRM is telling fuel pump to shut off after a minute or so for some reason. I can use a scan tool to run the CCRM beyond this time so it seems like something is telling the CCRM to shut off the pump.

any ideas or thoughts?
 
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DSG2003Mach1

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Are you running the same tune from the previous motor? If so did you change compression, cams or cam timing?
 

Makobra

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As with most things on this car... not sure. the cams needed to be replaced so I replaced them with 99 cobra cams, which is what I thought the car had, but I later found out it has a 03+ aviator longblock so it probably had 03+ cams which means they would be slightly different.

all the guts are the same otherwise.

but even if that is the case shouldn't it be able to idle? it idles and revs up hella good while it does it.
 

01yellercobra

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It shouldn't die when you unplug the IAC. At least that's not how mine is set.

If it worked before and there's no major changes then something isn't hooked up or isn't hooked up correctly.
 

Makobra

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It shouldn't die when you unplug the IAC. At least that's not how mine is set.

If it worked before and there's no major changes then something isn't hooked up or isn't hooked up correctly.

I assembled the car from a pile of parts so unfortunately there are a lot of unknowns.

used parts are:

1. MAF
2. PCM
3. CAM/crank/O2 sensors
4. coil packs
5. TPS

everything else is new.
 

Makobra

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the fuel pump was cutting off after about a minute. bypassed the CCRM Relay PCM/Fuel Pump/Fan (passenger fender) and the fuel pump stays on. neighbor who is a Godsend is looking into that sucker. either something is telling the box to shut off or the box is shutting off on its own.

she ran for a few minutes tonight! man i LOVE the way this monster sounds.
 

railroad

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Tone ring or sensor that tells the computer, engine is turning or running might be out of alignment or bad.
Mine is behind the flywheel, ugh.
 

ashleyroachclip

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The CCRM has relays inside it . It is possible to repair / reace an individual relay. Memory is a little cloudy, but i think they are soldered in , and can just unsolder and replace .
 

Makobra

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okay party people here is the fix for my fuel pump shutting off after only a minute or so.

backstory: the previous owner killed the previous build by running a returnless fuel rail (mach 1) on this return style system.
I knew this when buying the car, got proper fuel rails, made a proper system, and even replaced all of the fuel pump, injectors, sender, the whole nine.

but apparently if you deadhead a fuel pump long enough on these cars it can take out this circuit which is in charge of monitoring voltage from the pump. so, not only did the cylinders get washed out causing piston slap but that particular circuit in the pcm was fragged.

last night we finally figured out exactly what the problem was; that circuit. so the fix? the relay just needed a ground so when we grounded out this one terminal for this one relay she ran exactly as she ought.

the fix was one wire. I didn't cut the old one, its taped up really well to the relay harness in case I ever actually replaced the PCM. if I do that all i'd need to do is revert back to stock and we're good to go.

UPDATE EDIT! Turns out I was wrong, dead wrong, I went to button things up and ground this green wire really well... car wouldn't start. why? because I was doing what the ECU was doing after a minute... this fuel pump relay is wried so that its always engaged and it exists only for the PCM to be able to turn the fuel pump off.

apparently this controls the secondary full power mode for the pump but the pump is getting full battery voltage at idle so i suspect the PCM has been programmed to shut off the two stage fuel pump setup.

TLDR: if your fuel pump shuts off after only a minute just jump this relay and you can bypass the PCM cutting off the pump.

DO NOT DO THIS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
fuel pump fix.jpg
 
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