mooch56

I am at my end with this i've ohmed all the injectors and they all ohm good so none are shorted. I have fully bypassed the vats with a module so they should be getting siginal. I have replaced the ecm still same results. The im getting code 21 which is for the tps and i checked it and its reading 5.2 volts DC which is wot (wide open throttle) when the key is in the on position which I think it would still fire even if the tps is out idk. The only thing i havent checked is the iacv. I just need some insite on how to go about checking it and how to tell if it is good or bad. oh yea almost forgot replaced all wires, all plugs,and distributor.

thanks

vetteoz

iTrader: (13)

Wrong.
IF ECM sees TPS volts over a certain amount when cranking it thinks you have throttle open to clear a flooded engine and shuts down the injectors.
The code 21 is telling you exactly what the problem is;
the ECM is seeing the wrong TPS voltage while cranking
Reset TPS to factory spec 0.54 Volts

IAC plays no part in start up ; only idle control

mooch56

how do you reset it since it reads wot on the connection with the key in the on position? I mean your telling me to reset a wire b/c that is where the the 5.2 DC is. I know what the specs are for a correctly functioning tps. Basically you are telling me to get a new one or somehow reset it. need more insite

el_muerte

You won't be able to adjust the TPS to .54VDC if it's reading 5V right now... unless it's on upside down and backwards lol. Sounds like you need a new one.

John 89 Formula

make sure your probing the correct wires on the tps, the gray wire will read 5v that's the referance signal from the ecm, the dark blue wire is the signal wire that should be at .54 with the throttle closed and between 4 and 5 volts at wot.

mooch56

All right thanks ill check it

mooch56

on the siginal is .39 vdc. I think the range should be between .54 and .46 correct?

ASE doc

.45-.55 is the correct range. .34 volts would not set a code 21. You probably have an open TPS signal circuit to the ECM. Clear the code by disconnecting the batt- terminal for 30 seconds. Turn the key on and try starting the car a few times. Did the code 21 come back? If so you need to check for TPS signal at the ECM. Youll need a good wiring diagram and a DVOM.

You should also have a scanner for this type of diag. A scanner would tell you right now what TPS voltage the ECM is seeing or if there is any other signal missing that would prevent injector pulse.

mooch56

adjusted tps siginal is correct now even to the ecm no more code 21, but its still doing the same thing. it fires but instantly shuts off. It maybe the ecm but ive tried just about everything. I have fuel pressure 42psi. at the rail. maybe its the regulator. any suggestions?

racethesunlive

sounds similar to a no start issue i was having (it eventually stopped starting hot or cold)

see: This thread

mooch56

replaced icm same results

John 89 Formula

unplug the maf see if it runs, sounds like a maf related problem.

mooch56

unplugged maf still no go did same thing

ASE doc

Hey Mooch56, It sounds as if your fuel pump control may not be functioning correctly. The fuel pump relay, provides power to the pump durring start up. Power is then routed thru the oil pump pressure switch located just above the oil filter.
check fuel pressure while starting the car, see if it comes up durring cranking, and then drops off immediately after start up. You may have a bad oil pressure switch, wiring, or simply low oil pressure.

Drac0nic

Have you hooked a fuel pressure gauge up in general? That would be my course of action. If you have an oil pressure safety switch that's gone out and the relay that's gone out it could do this. Left me stranded beside the road once in my heap. Besides that, it could be a pump wiring etc. if it's not getting fuel. You can feel the injectors tick if someone is cranking. If they don't tick it could be a bad ignition module or pickup

mooch56

i have oil pressure its around 35psi. it has constant pressure 42psi when cranking and when the key is in the on position but it will only run for a second or two idk if i would get an accurate reading if its only like two seconds. ive replaced the icm and the pickup coil already as well as 4 injectors the only reason i didn't do all 8 is because of funds and the other 4 ohmed correct. i just dont know the range they have to be between one another. the new ones are 16.3 and the others are 15.9. all within operating means but will they not fire if they are .4 ohms off from one another? i think its the ecm it has to be i have that remaned 16195289 you know the one that if there is a falt in a circuit the ecm automatically shuts that circuit down to prevent damage to it that could be the prob thanks for all yall's help ill give it a spin

Drac0nic

"should" work. what resistances were the 4 injectors you replaced, and were they all on a single bank? Besides that it may be time to find some noids. What about VATS even though I think someone already mentioned that. I would try to see if they tick like I mentioned. It may be bad drivers from the dead injectors.

mooch56

zero ohms, I've already fulling bypassed VATS with the VATS module from Hawks. It seems like it may not be as minor of a problem as I thought or it may be the oil pressure switch or relay but it's pumping oil and it has pressure but it may need some more TLC or looking into, I will give it a try, thanks

ASE doc

VATS was a very simple theft deterent system. It only prevents starter function and has no effect on the ECM or any other system, only the starter.

ASE doc

The oil pressure switch will cause fuel pressure to drop immediately when you realease the key from start to run. Watch for this when checking fuel pressure. If either of your injector drivers were bad, its unlikely the engine would start at all. If it did it would be running on 4 cylinders.

Another system that could cause this symptom is the EST. The ECM supplies a 5 volt "bypass" signal across the EST(electronic spark timing) circuit during cranking. This 5v signal places the ignition module in bypass mode where timing is fully retarded for easier starting. When the ECM sees 400rpm, it drops out of bypass mode and goes into EST mode. A fault in the EST circuit can cause the system not to go into EST and can cause a start and stall complaint. You may want to test the EST circuit, the tan/black wire that you disconntect to set timing, for correct function. There should be 5v on this wire while crankng. The signal should switch to about 2.5 volts when engine reaches 400 rpm. The signal, with engine running is actually a digital pulse. It will read as about 2.5 volts on a digital meter.

ASE doc

I need to repeal my remark on the VATS system. I am completely off base on this. Its been so long since I dealt with a VATS issue and I was going off a quick scan of the factory wiring diagrams. On closer view, I realize that the VATS system is indeed tied directly into the ECM. It allows, or doesnt, fuel injector pulse as well as starter actuation. I apologize for this misinformation.

mooch56

yea its cool. the ecm sends a 30hz 5v signal to allow the injectors to fire but that system is bypassed i know this because it has ran with that module in it but it just decided it doesnt want to start now

mooch56

hey guys didn't know to uplug the est siginal wire when i dropped in the new distributor then set timing its a rookie mistake i just need to know one more thing i have an advance in timeing during startup is it susposed to retard during startup right let me do some voltage checks and see if it is the est. also i need to know what voltage needs to be at the plug for the oil pressure sensor. i have no oil pressure now one more thing fml

evilemokid94

iTrader: (6)

check the fuel pressure reuglator vacum, i had the same problem, it would start and run on fluid but not by itsself, turn out my fuel regulater vacum was melted shut, i replaced that and BOOM, fired right up.

ASE doc

The dash gauge oil pressure sending unit will test at 12v with key on if the gauge fuse and circuit are okay. The fuel pump oil pressure switch will test at 12v at all times if the fuel pump fuse is okay. If in doubt about oil pressure, the best bet is connect a mechanical gauge and verify.