im waiting on the edge of my seat!!!

 

The focus should be on the AFM or a vacuum leak. The FSM illustrates the way to check the AFM to see if it is within spec. You could also rely on the FSM section 4B for a list of the ECU pinouts voltage values and compare the factory readings to yours to possibly narrow down your problem.

Don't know if you checked the fuel pressure either as this would give you more insight to what's going on.

 

ok... guess its time to dig deeper.

fuel pressure is good. aem fuel pressure reg. says 40psi

 

Pin 3B at the ECU should read about 10 volts, if that when cranking the engine. If the ECU doesn't get this signal then the AFM will control how much fuel is used at start and this amount is a fraction to what it would be if the ECU did have this signal so this would be an important ECU pin to check.

Pin 2I is the Water Thermosensor and it should read from 2 to 3 volts w/key to on. When it reads this value more fuel is used upon startup. If the reading is too low then less fuel is used. With a fully warmed engine it would read slightly below .5 volts.

A clogged exhaust could also kill the engine. Perhaps if all else fails you could disconnect the exhaust connection after the exhaust manifold to see if it changes anything.

And the fuel pressure reading taken at the return hose via a T mount would be the best place to measure the pressure I would think.

The voltage on pins 3C and 3E should read about 8 volts w/key to start as the engine is turned over and 12 volts w/key to on. If it indicates 8 volts w/key to start/cranking then that indicates the ECU is attempting to fire the primary injectors and a 12 volt reading w/key to start indicates the ECU is not firing the injector(s).

In addition, low voltage can also prevent the electrical circuits from operating properly so make sure the battery is strong but you really can't measure the voltage output of the alternator since you can't get the car running though.

Perhaps you could disconnect the electrical plugs, two of them) from the trailing coil and rely just on the leading coil to start and run the engine to help reduce the variables involved but this again is likely not your problem.


You could also disconnect the four wire plug from the Main relay and jumper the B/G wire to the B/Y wire and the W/L to the B/W which will bypass the relay which helps to provide voltage to the engine circuits (leave plug unplugged when jumpered). Make sure the B/G and W/L wires have constant voltage on them as an intermittent voltage would kill the engine. This is not likely to be your problem but it is something else to check. Also, don't leave jumpers in place as this will eventually drain the battery

 

alright thanks. time to dig.
the exhaust is def not clogged. 3 in dp and racing beat exhaust with 700ish miles on both.

 

pin 3b does not read 10 volts when cranking. closer to 3 volts

 

I've heard of a reading lower than the 10 volts specified in the FSM but "3 volts" seems really low as most posters when measuring this signal will generally get closer to 8 volts or so. This indicates the ECU is receiving the "start signal," but the extremely low voltage could perhaps be creating other issues.

If you test for spark the bluer the spark the stronger it is while the more orange it is the weaker the spark tends to be.

EDIT: you also might want to dial down the fuel pressure closer to 30 to 35 or so as you might be flooding the engine w/too much fuel.

 

if im doing it right... 3c and 3e have very low readings not even the 8 volts

ok maybe my battery needs a good charge up.

sorry for the noob question. im kinda new to tracing electrical problems. what setting should my multimeter be on when testing?

 

DCV as it appears that is what you have it set to. Placing the red meter lead to the positive battery terminal and the black lead to the negative battery terminal should read about 12 to 12.5 volts.

 

Red meter lead to the ECU pin (stuck into the back of the plug as it is plugged into the ECU) and the black meter lead to a suitable ground like the ECU mounting bolts towards the front of the unit.

 

well this thing is all f-ed up it seems. im getting like 12 volts at the thermosensor pin 2i? and 3c and 3e im getting much lower voltage than that. what is going on here?

 

Pin 2I should have a Green/White wire running to it. Does yours or did you mistakenly identify which wire position is 2I?

Pin 3C and 3E would have 12 volts w/key to on and a fair amount less w/key to start.

 

your right. lol my mistake. 2I is a lil over 2 volts and 3c and 3e are 12 when key is on and around 8 when in start position

 

Those numbers are correct then. Did you try to tone down the fuel pressure a bit? Did you test the AFM according to the FSM. Does the AFM flapper door open fairl easily?

Also, when you tested pin 3B (Black/Blue wire) did you test the correct pin w/key to start?

 

turned fuel pressure down. no difference
afm checks out to specs. and flapper opens easily
i have nothing at 3b in either position

 

Pin 3B would be in the smallest ECU plug, bottom row, far right position and the wire is Black/Blue. As stated before this wire should have 8 to 10 volts or so w/key to start and less than 1.5 volts w/key to on. If you don't have voltage w/key to start then the ECU will defer to the AFM for the fuel amount used on start up which is rather small as compared to the amount used when the ECU does receive the start signal. This might not be the cause of your problem but that you don't have any signal is odd and the previous time you checked this pin you stated you had 3 volts or so.

Now w/key to start the Black/White wire that runs to the starter solenoid splits off and runs to the connector which mates the Front and the Emission harness together and at this connector the Black/White wire gets mated to a Black/Blue wire that runs to pin 3B. There are two Orange connectors located above and to the right of the ECU and one of them is FEM-02 which is the connector that has the B/W wire on the Front side of the connector and B/L on the Emission side. If you truly have no signal on B/L w/key to start then you need to see if the B/W wire that mates to it has any voltage w/key to start.

 

You also need to check to see if the fuel pump is wired properly and not cutting out. At the rear of the car by the driver side shock tower and under the carpeting is the connector which mates the Rear harness to the fuel pump. It has a Blue wire, Black wire, a White/Red wire and a White/Green wire and the Blue wire should have less than 12 volts w/key to start. Also, make sure the Black wire that serves as a ground wire has 0 volts as well. If the Blue wire does not have the proper voltage then you need to check the voltage on the Blue/Red wire coming out of the Circuit Opening relay w/key to start.

 

i checked and double checked again and i have nothing to 3b with the key to start
i found the plug and the B/W wire with black and blue wire on the emissions side. 0 volts with key to start. checked it three times to make sure.

 

Did you just check the B/L wire at this connector or the B/W wire that feeds it?

 

checked b/w

 

If the B/W wire does not have voltage w/key to start then you need to find where the B/W wire splits in two. At the starter is where you will find the B/W wire. Follow this wire upwards and you will find a connector where the wire splits in two where one wire runs to the starter solenoid and the other runs to the Orange connector near the ECU. So check at the condition of the connector where the B/W wire splits and see why the B/W wire that goes to the starter solenoid has voltage but the other wire does not.

 

ok... i got under the car and checked the b/w wire and it was pretty loose on the starter. so i put a new end on it. got a new batt. as well. tested pin 3b again and now i have the proper voltage. tested the fuel pump and the blue wire was around 7.5 volts with the key to start. so i then tested the blue/red wire in the circuit opening relay for kicks. which tested around 9 volts


now car wont start at all

so i put a jumper on the fuel relay and the connector under the hood again to see what happens.

nothing... car wont even start like that now

 

Perhaps the engine is flooded. What do the spark plugs look like? Are they wet/dry or have a buildup and if so what is the color of the build up?The fuel pressure should be about 30 or so when running and a bit higher than that at start up. If the fuel switch internal to the AFM is perhaps not working properly then one of the jumpers will be necessary and the relay jumper is a good place when choosing between the two possibilities. Another thing to check possibly is the Black/White wire in the top row far left position of the Circuit Opening relay as it should read voltage w/key to start.

 

i will have to bring a sparkplug socket home from work tomorrow. cant seem to find a suitable socket. i tested the black/white wire and it has voltage with key to start.

 

so i just tried to start it again a few times and it fired right up. revs to about 3k and dies with a big backfire each time. pop! pulled the plugs and they were clean but wet with fuel.