down pipe in....car shuts off =(

[dsun87]

ok guys i know finally have my downpipe made and O2 sensor in


but now my car is shutting off!!!! i have a fmu 12:1 a 255 fuel pump and a missing link and intercooler with all piping, external waste gate and bov, colder spark plugs

when i start my car it takes a few times for the car to turn over and when it does turn over i give it some gas it just dies!!!
or when i leave it alone it reves a few rpm and it dies again!!!

help!!!!!!!!!!!!!!

 

[turbodsm18]

Boost leaks.....

 

[dsun87]

how do you know its a boost leak?

 

[turbodsm18]

I dont, but being that its a turbo car, you need to boost leak test it.

I worked on a 98 GST the other day and the guy could not get the car to boost under load. It would always die upon start up. Guess what, it had five moderately sized boost leaks that he had no clue of.

 

[bling5tatus]

it's probably 80% of the time a boost leak.

 

[Locke]

It is not a boost leak.

2gnt's use a speed density air metering system, who's MAP sensor is located in the IM. Boost leaks mean overworked turbo's, not fuel cut and improperly metered air, like on the 4g63.

Make sure the ML is very secure. How is your FMU plumbed in?

 

[dsun87]

my missing link is secured the lil filter thingy is a bit dirty though
but its secure

my fmu is plugs in like wut everyone says fuel line from pump to in and line out from fmu to fpr it worked b/c before i turboed my car i was running my fuel pump and fmu installed already and ran it for like a wk

what else could be the problem?

 

[Locke]

The FMU should be in the return line, between the FPR and fuel tank. From your description , it sounds like it is in the feed line. (Could just be a mis-communication) If it is, correct it before you start boosting.

How is your fuel pressure? It should build to ~47-50, and stay there, even after you shut the car off.

Make sure all of your sensors are plugged in, check any sensors near where you were working. If you removed the IM or injectors for any reason, check for gnarly vacuum leaks there.

Other that you unhooking some sensors and forgetting to plug them back in, or unknowingly knocking some connections loose, I cannot think of anything in particular related to a turbo install that would cause a no start.

 

[dsun87]

i dont have a fuel pressure gague so i dont know how much pressure i have =(

fmu is connected right i guessed i worded it wrong cause i installed it a wk b4 i turboed my car and it ran fine w/o a problem
i didnt take out any injectors or my intake manifold

what are symptoms of a boost leak? or vacum line leak?

 

[Locke]

The only negative side effect of a boost leak on your vehicle would be an over worked turbo. You may hear it hissing, whistling, or whooshing, if it is a substantial leak.

Vacuum leaks at or near the plenum, or a vacuum line, will cause extra air to enter the plenum. This air will then be metered, and the appropriate amounts of extra fuel will be added by the ECU. This will cause a high idle, which the ECU will attempt to negotiate by closing the IAC. If the leak is big enough that the IAC cannot negotiate a proper idle, you will be stuck with a high idle. Leaks in a vacuum line may cause the vacuum controlled/piloted component to not function properly.

If the leak is where the IM mates with the head, or at an injector, the ECU cannot meter it, and the cylinder(s) at the leak will become lean. Mis-fires and a choppy, sometimes low, idle will be symptoms of this. A severe leak here can lead to pre-ignition, as the piston becomes extremely hot.

Your engine needs fuel, air, compression, and spark, to run.

Test for fuel pressure by purchasing an inexpensive fuel pressure gauge. Required FP on our vehicle is completely static while out of boost, so it should be around 47-50psi at prime, start, idle, and WOT (again, sans boost.) If you have fuel pressure at the fuel rail, use a noid light to check for a signal at the injectors. If you cannot find a noid light, don't worry too much about this right now.

To check that it is getting air, see that the timing marks line up, and that you don't have a baseball or some such object stuck in your intake obstructing flow.

You don't need very much compression to start a motor. This isn't likely your issue, and you shouldn't be to concerned about it right now.

To check for spark, you can pull a plug, (or use an old one) connect the plug wire to it, and hold the threaded end firmly against a ground while somebody cranks the engine. Have the fuel pump disconnected while doing this. You can also shove a screw-driver in to the plug boot, and hold it very close to a ground. The spark should be blue, and spark at fairly even intervals.

First, double and triple check all your sensor connections. Most of the time if after a modification, the motor won't start, it is just an unplugged sensor connector. Then test for spark first, since it is free. Then purchase a FP gauge, and check that.

 

[dsun87]

how about the O2 sensor

could that do anything?

 

[Locke]

While you definitely need it to run properly, you don't need it to start your car. Many of the sensors on the vehicle are not actually required to start and drive. TPS, IAT, ECT, and O2 are examples of some sensors not required to actually drive your vehicle. Your car will run like crap without them, though.

I recommend you install the front O2 anyways.

 

[dsun87]

is it ok to route a vac line though the EGR line?