dannysauter

I have a 1991 Z28 It had a 305 TPI and I recently upgraded to a chevy 350. The other day I was driving it and it sputtered and then died. After waiting about ten minutes I tried agian and the car made it home. Ever since the car will start right up and run for about three seconds and then die. It fires up great every time and then dies consistantly. I have replaced the coil, destributor and I have good fuel pressure. If i shoot starting fluid into the intake the motor it will run longer leading me to believe that it is fuel related. The computer does not give me any codes and I need to know where to start. Any ideas would be great.

jmiller

One item to check is the oil pressure switch on the back of the block under the intake manifold. If it reads zero oil pressure, it shuts the fuel pump off. However this problem would always shut the motor down in a few seconds after starting the motor.
You should also check the fuel pump relay which is related to the above sender.

jichniow

Try the Idle Air Control valve. Actually just pull off the throttle body and clean the whole thing. It's very easy and should probably be the first thing you look at for idle problems.

dannysauter

I tried replacing oil pressure sending unit and it still did the same thing it fires right up and then dies immediately. I also replaced the throttle body and nothing changed. I know it is fuel related because when i shoot starting fluid in the intake it keeps running. I am stumped. Any ideas would be great

jmiller

Danny,
You're probably correct about it being a fuel problem. First, keep in mind your motor has 2 oil pressure senders, one for your gauge, usually near the oil filter and the one I mentioned at the back of the block which shuts off the fuel pump if it senses no oil pressure. It is ignored while startup, but after a few seconds running it starts monitoring the pressure.
What you need to do is check the entire circuit including the fuel pump relay and the wiring.
An easy way to check this and your fuel pump is to borrow or buy a fuel pressure gauge that attaches to the schreader valve on the fuel rail. With this gauge installed you can easily determine if this circuit and your fuel pump are causing the problem by watching the fuel pressure. You must disconnect the vacume line to the fuel pressure regulator when doing this test. You should have a minimum of 40 lbs. steady pressure.
Good Luck

ULTM8Z

Also, check your fuel pump relay. It might be on the fritz.

dannysauter

I checked the fuel pump relay and the fuel pump continues to run when the car starts and then dies. I also checked the fuel pressure before the fuel rail with a guage and it was good. What else could be the could it be. Would the computer or a bad sensor cause it to shut off like this?

ULTM8Z

When you start the car, do give it a little throttle? Can you keep it running if you give it some throttle?

dannysauter

when i give it gas the car will cut out and die quicker. pressing on the gas just kills it.

dannysauter

The car still starts and then dies. I have about 39 psi at the schrader valve. When i plug off the return line the max i get is 45 psi. could this indicate fuel pump? Im so confused

jmiller

Danny,
If your fuel pressure is app. 40 lbs WHEN IT DIES, I don't think that the fuel pump is your problem.
You swapped out the motor: Did it ever run OK after the swap?

ULTM8Z

Sounds like there's something making the computer run really lean.

Disconnect the coolant temperature sensor and then try to start the car. It'll start and probably run bad, but if there's any kind of a short in the sensor, it may cause the computer to pull out too much fuel.

Also, check your TPS voltage. Probe the blue and black wires and see what your voltage is at idle (key on, engine off).

cronsformula350

Dude I bet your fuel pump is taking a ****, I've seen alot of them, that work at first and for a few seconds, then they get slower, and stop working until a break again, indicating that they are old and tired of pumping fuel . Replace your fuel pump, and filter while your there.

redrummer

I've recently gone through the same problem.
1) Reset your IAC according to the tech article
2) Probe your TPS and adjust accordingly
3) Check your distributor. #1 plug should be pointing at the #1 cylinder (driver's side front).
4) Check your timing. Set it at 6 degrees before top dead center.
Resetting the IAC will affect your TPS reading, so do them in the order I listed. When you reset your minimum air (IAC), shoot for around 650 rpm. The article says 450, but on my car, it stalled and died at anything below 650.

maroguy1

I did the same exact swap into my 85 tpi. I can keep it running by flipping the throttle but as soon as it gets below 1000rpm it just kills. I blocked off all emissions ports on the intake. I don't hear a vacuum leak and my fuel pressure is 50 without it running. If I don't give it gas it will run for about 3 seconds and slowly just die.

cronsformula350

If you think its a vacuum leak, get a propane torch, remove the nozzle end, attach about 2.5 ft of hose to the torch end, then add a piece of 1/8" tubing with a bend on it to the end, and leave it about a foot long. What you can use this for, is to check for vacuum leaks, your not going to blow up your engine or anything, the rpm will go up and then fall if you come upon a vacuum leak with the homemade tool, phr and other magazines also use a similar tool to this.

redrummer

Why go through all that trouble when you could just spray carb cleaner around the intake?

the gtaman

hi check your coil wires to see if any are broken ,this might help.

maroguy1

My timing is on my fuel pressure is constant and it is not running rich. Also it is kinda hard to set th iac if it doesn't idle at all. Computer doesn't show any codes. This tpi is pissing me off time for a carb!!!

eric305TPI

For dannysauters problem. It sounds like the ECM is losing the reference pulse from the distributor and of course quits firing the injectors.

C20T/A

Hope this helps.
1. Reset your computer if you havn't already.
2. Did you also change your chip to the 350 program.
3. make shure your sensors are correct for your engine as well.
4. If it is fuel realated it has to be injectors because you have ruled everything else out.
Find out if it is rich or lean death. (Probably lean)

the gtaman

hi a friend of mine bought a ta with the same problem,iv'e been messing with this car for about 3 days now. it will start up and shut off ,over and over again.if you try to give it gas it dies fast.we've been pouring gas in the throttle body ,that is the only way it will run. this car came with a 305 ,but now has a 88 350 in it. the lady that had it said that it would start huming and then shut off while driving ,10 min later it started up . she said it did this off and on for a couple of month's until it finally died !sounds like the fuel pump,well it now has a new pump,filter,regulator ,43lbs of pressure in the line ,we have changed every sensor we could find. the cold start injector is good .computer is good i 've tried it in my gta ,also massair too. i think this is everything .:

1991tealRSt-topGuy

check for reference pulse between the distrib and ECM

dannysauter

check for reference pulse between the distrib and ECM


How is the best way to check that?

antoine

unplug the tps so the computer will go in bypass mode and see if that works.

eric305TPI

To check for the reference pulse you need to check circuit 430 (distributor reference) which is ECM terminal D8(purple with white stripe) that comes from Pin C on the ignition module in distributor for a 5volt square wave voltage while the engine is turning. Hope that helps.

cronsformula350

Get a service manual from chiltons or clymer for the car, and check the coil module and cap. My 87, back before I bought it, stopped running, because the coil module took an s. It also took out the coil because of it. I bet your not getting any spark, and your pressure regulator may have also failed, giving the motor too much gas at start up, and may also hinder its starting ability by flooding it.

dannysauter

I puled my fuel rail and when I turn over the motor the passenger side bank of injectors squirt fine but the drivers side bank does not squirt at all. This explains why it runs for a second and then dies. How can i go about troubleshooting the drivers side bank of injectors.

cronsformula350

You may have a fusible link, or a wiring harness problem, it is doubtful that all the injectors on one bank failed at the same time.

eric305TPI

First check the inj1 fuse and if that is ok check to see if you have power on each injector plug (WITH A VOLTMETER) between the pink wire and ground with the key on. If you do have power then check to see if the ground side(dark blue wire) is being pulsed while cranking(may be difficult to see without a graphing voltmeter or a scope).

cronsformula350

you could use some noid lights to see if there firing, but inorder to get a test light to show anything, someone will need to crank the motor over, the injectors don't fire when the ignition is just on.

dannysauter

I finally found it. All the fuel injectors were within resistance specs except one which read .07 ohms. They are supposed to be 11-15 ohms. I replaced this and now that side works. i just have to get another injector and put it together. That injector was shutting down the whole bank. thanks

eric305TPI

Glad you found it. I totally forgot about the current limiter that shuts down the circuit if the resistance is too low.