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Old 05-14-2009, 05:45 PM   #1
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Default stalls immediately after starting

When I go to start my car it will go to start and then immediately die. I can hear it combusted for a cycle or so just before it dies. The weird part is if I unhook the AFM it will sometimes will then idle, until you hook the AFM back up. I tried swapping my AFM for another working AFM and still nothing.

I will get a code 8 and 10 if it runs without the AFM. No code gets shown when trying to crank it with the AFM still hooked up.

So there is fuel, spark and timing since I can get it to idle AFM-less, but something it causing the car to die the moment an AFM is connected back into the systems.

This just started after I swapped the whole rear subframe from my 91 to a 96. I am starting to doubt it has anything to do with the swap but just in case.

specs of the car:
91 body
1.8 swap
stock ECU
DIY turbo
AFPR but no timing control.
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Old 05-14-2009, 05:58 PM   #2
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do you hear the fuel pump prime when you turn the key to the on position with the AFM installed?
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Old 05-14-2009, 06:15 PM   #3
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Well, we sure get some strange ones here...

Code 08 is Airflow Meter open or short circuit, and
Code 10 is Intake Air Temp sensor open or short circuit.

Both of these are exactly what you'd expect to get when removing the airflow meter.

What I find very puzzling is that you say it runs with the airflow meter disconnected. The reason I say this is that the contact which turns on the fuel pump relay is located within the AFM. Power is supplied to the fuel pump relay during cranking by a separate circuit, but once the starter is disengaged, the fuel pump should shut off unless the AFM is present and giving the appropriate switch closure.

I'd start by investigating the operation of the fuel pump relay (which is called the Circuit Opening Relay) in the wiring diagrams. It's under the dashboard by the steering column, and if I recall correctly it has a brightly colored plug (green or yellow.)

Here's an experiment. With the AFM removed, turn the key on but do not start it. Can you hear the fuel pump running? (open the gas filler and stick your ear against it.) It should be off.

Now install the AFM and check again. Should still be off.

Lastly, stick your finger into the AFM (it'll have to be detached from the airbox for this to work) and manually push the door open. The fuel pump should now turn on.

Do that test, and get back to us.


The only other thing I can possibly think of- did you re-attach the ground strap to the PPF during your swap?
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Old 05-14-2009, 06:41 PM   #4
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Quote:
Originally Posted by Trent View Post
do you hear the fuel pump prime when you turn the key to the on position with the AFM installed?
If the AFM is hooked up yes. And I even checked the hoses in the engine bay and there is pressure in the lines.

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Originally Posted by Joe Perez View Post
Well, we sure get some strange ones here...

Code 08 is Airflow Meter open or short circuit, and
Code 10 is Intake Air Temp sensor open or short circuit.

Both of these are exactly what you'd expect to get when removing the airflow meter.

What I find very puzzling is that you say it runs with the airflow meter disconnected. The reason I say this is that the contact which turns on the fuel pump relay is located within the AFM. Power is supplied to the fuel pump relay during cranking by a separate circuit, but once the starter is disengaged, the fuel pump should shut off unless the AFM is present and giving the appropriate switch closure.

yea that is what puzzles me. But it doesn't start every time, with the AFM unhooked it is kinda random, have yet to find a pattern to it. But once it is running it will die if I give it fuel or re hook up the AFM


I'd start by investigating the operation of the fuel pump relay (which is called the Circuit Opening Relay) in the wiring diagrams. It's under the dashboard by the steering column, and if I recall correctly it has a brightly colored plug (green or yellow.)

Here's an experiment. With the AFM removed, turn the key on but do not start it. Can you hear the fuel pump running? (open the gas filler and stick your ear against it.) It should be off.

if the AFM is unhooked I don't hear the pump, in the cabin(i have a 255 pump now and when the AFM is hooked I can hear a massive whin)

Now install the AFM and check again. Should still be off.

With the key to On and the AFM hooked I can hear the whin of the pump

Lastly, stick your finger into the AFM (it'll have to be detached from the airbox for this to work) and manually push the door open. The fuel pump should now turn on.

Do that test, and get back to us.


The only other thing I can possibly think of- did you re-attach the ground strap to the PPF during your swap?
when I swaped over the rear subframe I left the PFF attached to the car and didn't touch the wiring harness other then to move it out of my way. First thing I checked was the ground at the back of the PPF. I will try play with the AFM now and see if I can get any changes from the AFM and fuel pump.
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Old 05-14-2009, 06:53 PM   #5
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I just got back from playing with the AFM and here is what I found.

With the key to ON and the AFM hooked up. The pump is off now(no whin or pressure in the fuel return line). If I tap open the shutter in the AFM, I can hear the relay click on and pressure builds in the return line, until I closed the shutter.

With the key to On and the AFM unhooked. The pump is off to start with it. Playing with the shutter didn't turn the relay on and no pressure through the return line.

With the key to On, AFM hooked, and the jumper to turn the pump on. The pump was off to start with but as soon as I hit th shutter in the AFM the pump clicked on and stated on until I pulled the jumper out of the diganois box.
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Old 05-14-2009, 09:07 PM   #6
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Originally Posted by wildfire0310 View Post
With the key to On, AFM hooked, and the jumper to turn the pump on. The pump was off to start with but as soon as I hit th shutter in the AFM the pump clicked on and stated on until I pulled the jumper out of the diganois box.
Ok, that's not right. There's some freaky **** going on with your fuel pump circuit.

Will it start and run with the AFM in and the FP terminal at the box jumpered to GND?
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Old 05-16-2009, 04:47 PM   #7
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Ok, that's not right. There's some freaky **** going on with your fuel pump circuit.

Will it start and run with the AFM in and the FP terminal at the box jumpered to GND?
So now that work not running me tired I got back to the car. I got some new freaky things for you Joe.

I think when I did this test I may not had the pin in all the way or something:

With the key to On, AFM hooked, and the jumper to turn the pump on. The pump was off to start with but as soon as I hit th shutter in the AFM the pump clicked on and stated on until I pulled the jumper out of the diganois box.


Cause I rejumped the system and the pump turned on once the Key turned to On.

Either way. New test.

Jumper pin forcing the pump on, AFM hooked up. Still died when trying to start

Jumper pin forcing the pump on, AFM UNhooked. Car started immediately and even was able to apply about 10-15% gas, would break up at about 3K RPM in neutral and the motor tried to die if I gave it more then 10-15% gas but it would recover and reidle.

So what ever is messed up is either with BOTH the two AFM I have or there is something with the wiring. Any ideas almighty Joe .
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Old 05-17-2009, 06:08 PM   #8
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Bump::

Anyone any ideas.

Also I been trying to look and see if I can find the wiring diagram for the AFM and all. See if I can trace the lines, but not such luck.

On a side note. I am in the middle of building a MS for my car. Planning to run it in parallel at first. Question is could I run a parallel step-up and not run the AFM??
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Old 05-17-2009, 06:23 PM   #9
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Your car is possessed. You must drive a wooden stake through its heart.

Here are the relevant diagrams:













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Old 05-17-2009, 11:32 PM   #10
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thanks joe. Now I need to start reading and checking relays and grounds.
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Old 05-18-2009, 02:12 AM   #11
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Have you checked for massive vacuum leaks at all? I ask because your AFM is acting properly by your description. With the key in the on position, and no jumpers in the box, the fuel pump will only turn on once the flapper moves. It relies on the vacuum through intake manifold while the car is turning over to move the flapper, thereby starting the fuel pump. It's a safety thing, so that if you get into an accident and your motor turns off, your pump isn't just pissing fuel everywhere. When jumpered, the fuel pump will turn on whenever you put the key to the on position. I'm thinking vacuum leak because it runs when you force fuel at it, but it runs like crap. I would say it's letting in a bunch of air somewhere and isn't metering properly.
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Old 05-18-2009, 03:40 AM   #12
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Quote:
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Have you checked for massive vacuum leaks at all? I ask because your AFM is acting properly by your description. With the key in the on position, and no jumpers in the box, the fuel pump will only turn on once the flapper moves. It relies on the vacuum through intake manifold while the car is turning over to move the flapper, thereby starting the fuel pump. It's a safety thing, so that if you get into an accident and your motor turns off, your pump isn't just pissing fuel everywhere. When jumpered, the fuel pump will turn on whenever you put the key to the on position. I'm thinking vacuum leak because it runs when you force fuel at it, but it runs like crap. I would say it's letting in a bunch of air somewhere and isn't metering properly.
What is really bad about the whole thing is that the car ran fine. i parked the car worked on the rear end. And then it didn't start again. I haven't touched anything in the engine bay.
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Old 05-18-2009, 04:07 AM   #13
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People park their cars, don't do anything to it, and it doesn't start the next time they try. Doesn't seem too odd to me.

I would check for vacuum leaks, as that seems to make sense.

How the car even starts without a AFM connected is beyond me, unless there is still some sort of pressure left over in the rail.
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Old 05-18-2009, 04:14 AM   #14
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People park their cars, don't do anything to it, and it doesn't start the next time they try. Doesn't seem too odd to me.

I would check for vacuum leaks, as that seems to make sense.

How the car even starts without a AFM is beyond me, unless there is still some sort of pressure left over in the rail.
I am thinking that is why it was random when the AFM was unhooked without jumping the fuel pump there maybe just enough pressure in the line for it to be able suck enough fuel for it to start. so far it has started every time with the afm unhooked and the pump jumped. So for some reason when the AFM is hooked up something is shorting out or the ecu is getting a bad signal and causing it to die ASAP.
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Old 05-30-2009, 05:16 PM   #15
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So i finally made some progress on my car. It still isn't running correctly yet but I have completely ruled out the fuel system.

I have ruled it to be dealing with one pin off the AFM. It has to do with pin C off the AFM. So either something in the wiring, the ecu, or the TPS. Need to do some more search and all.
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Old 05-31-2009, 03:07 PM   #16
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OK I am totally stumped and need some real help here.

Here is what i have learned/ruled out.

No matter what I do the car will not start if I have the AFM plugged in..

If I ground out Pin C from the AFM the car rev up and then stall.

If I unhook the TPS sensor and AFM, start the car I can then rehook up the AFM and the car will idle fine. I can even remove the jumper from the Diag box. If I re hook up the TPS the rev climb for a sec hold and then the car stalls.

I have ruled out being anything Fuel related. Since I can jump the two pins on the AFM and the car with start.

I have tested the TPS using:

Quote:
The test for the TPS requires looking for continuity between the "IDL" and "TL" terminals when the accelerator pedal is fully up, and no continuity when pedal is any other position. Also, there should be no continuity between any of the three terminals when off-idle, except when the pedal is fully down. For that case, there should be continuity between the "POW" and "TL" terminals.

"POW" is the top terminal, "TL" is the middle, and "IDL" is the bottom terminal.

If adjustment is needed, loosen the TPS mounting screws and rotate the TPS housing in whichever direction gives the correct responses.

(The 1990 manual says that a .016" feeler gauge between the throttle stop screw and the flange on the throttle pulley should show continuity from IDL to TL, and a .027" gauge should show no continuity between any two terminals.)
The only thing I didn't test was the feeler gauge as I don't have a feel gauge, but it did pass all three test.

I have tried a different AFM and a different ECU. Any ideas please I am at a lose here. If I can't figure this out soon, my car is magically going to catch on damn fire...ahhh
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