90Camaro4ever

iTrader: (2)

I have read this forum for several weeks, and cannot find a post that fits my problem. I am looking for more help. I bought the car new, and plan to keep it forever J

I have a 1990 3.1 MPFI Camaro that will not start. The car has 175,000 miles. No major engine work has ever been required. Every 5 years or so I end up replacing the ECM (not the prom). Besides oil and antifreeze changes, cap, rotor, wires, plugs, brakes, air pump (1), alternator (1), water pump(1), exhaust(many) and battery(many), the car is all original. I only mention this as the fuel injectors are original.

In June, the car was hit in the driver side, and I drove it 3 miles home. The next day I took it out for a ride and it lost power and then died. The first thing I did was to replace the ECM. No Start. After some troubleshooting, I determined the fuel pump was bad and replaced it.

I now have 42 psi on the fuel rail. The car will turn over, so I do not believe it is a VATS issue. I pulled a plug and turned the engine and found an orange spark at the plug. Both sides of the engine spark plugs have an orange spark. Many of the post on this site recommend replacing the coil. I also noticed that all the plugs were carbon fouled which also indicates that the coil could be bad. I decided to replace the coil, cap, rotor, wires and spark plugs since the car had been sitting for 5 months.

Still, no start. I replaced the ECM that I put in two months ago with a different ECM. Still no start. If I spray starter fluid in the intake, the car will run for 2-3 seconds. This is where I get confused. I have 42psi of fuel, I have spark, and I have air. What am I missing???

I do not see any fuel on the spark plugs after trying to start the car. I have a Haynes manual, and it does not have a really good troubleshooting guide. Many post on this site reference an “A-3 chart”, but I cannot find that on the web. Can you recommend a book that has the chart?

I also read that the injectors should have between 12-14 ohms of resistance. Can anyone recommend how to check these without taking off the plenum? I also though I read that a shorted injector will leak. My issue seams to be that the injector is not opening. Is there a way I can test the injectors to see if they actually open any allow gas to flow? Does anyone know what else may cause the injector to not open? How can I check the signal going to the injector? I verified both fuses for the injectors are good.

Should I get a scanner? Would this help me troubleshoot a no start condition?

Any suggestion are welcome J

enswrob

noid light will help with the injectors.. definatly not fireing.. could be a ground issues or injector power issue. also check the injector fuses under the dash.

SageMoonblade

I would check all the wiring in the injector system, this can usually be done with a person turning over the engine while the harness ends are probed with a volt meter. If you find good voltage then its time to replace the injectors, they are only built to last a few years anyway. If you don't find good voltage you will have to look into the wiring o the system better.

REMEMBER: when using a volt meter for this task with the engine turning over the number will flash through quickly.

90Camaro4ever

iTrader: (2)

Thanks guys. I will use the VM this weekend to see if I have a signal to the injectors when cranking (I will watch for the flash on the VM). This will verify the signals from the ECM. I will wait to but the noid based on if I need to take apart the plenum.

Until I looked at the wiring diagram, I always thought that only one injector fired at a time per cylinder. If I am reading the schematic correctly, it looks like 3 injectors fire at the same time because they are wired in parallel. Am I thinking correctly? It looks like there are only two command "ground signals" that are applied from the ECM to ground (fire) the injectors (C11 and C12). Can someone confirm this? Could I simply measure the resistance at the connector plug near the fuel rail to see if I get a resistance around 4 ohms (1/12+1/12+1/12 = 1/RT ~ 4ohms) for parrallel resistance? If at least one resistor is bad -4ohms, I would read around 2 ohms 1/12 + 1/12 + 1/4 = 1/RT.

project89

iTrader: (1)

u are correct, the ecm has 2 common grounds.,the ecm fires all 3 injectors per bank alternating sides.

89' RS/blue

Im having a similar problem with my camaro, v6, 5 speed, 130K. Well i was driving and it just died. So i replaced cap, rotor, plugs, wires, ign module, coil. It has a excellent bright BLUE spark. it has 42psi at the fuel rail, so i checked that the injectors were getting the pulsed ground signal from ecm, they all are. so that means its firing fuel and spark. So now its either a timing or compression issue. if u dont have a noid light, to test injectors, just touch a screwdriver to the injector and put ur ear on it, have someone crank it. You should hear a clicking noise from each of the injectors, if u dont, well it could be the ecm, or wiring. you'll probably have to take off the intake plenum to get to the injectors though, well i did. So good luck man.

Maverick H1L

iTrader: (8)

Just about EVERY GM injector I have tested that was GOOD has 12.6 ohms resistance. If you have one that is outside of 10% (1.2 ohms high/low) of your highest resisting injector, replace it.
MPFI-- Multi Port Fuel Injection, aka Tuned Port Injection (with runners that are actually "tuned" for length to the engine, similar to headers for exhaust) fires one BANK of injectors at a time, aka batch feed.

Check your timing, as was suggested above. Where on the car did you get nailed?

90Camaro4ever

iTrader: (2)

I took the plenum off and measured the resistance to each injector.
#1 - 12.3 ohms
#3 - 7.5 ohms -- bad ???
#5 - 12.5 ohms

#2 - 2.2 ohms -- BAD!
#4 - 12.3 ohms
#6 - 12.3 ohms

Looks like I have two bad injectors. The ecm is firing, and I smelled gas in the intake 5 minutes after I attempted to start the car.

Has anyone ever tried to start a car using only 2 good injectors per side? I would like to try this, but only if others think this is a GOOD idea?

Can any one recommend a place to by injectors? What I have read is that most folks think you should replace all injectors and just not the ones that appear bad. I am in Maryland.

Dakine858

Yeah it's good policy to replace all of your fuel injectors at the same time. Check out Summit Racing for a set of Accel injectors.

http://store.summitracing.com/partde...5&autoview=sku

dodger65

if the injectors are your only problem, then you can unhook those 2 and it should start. electricity follows the path of least resistance, so if you have 1 or 2 injectors bad, they'll get all the juice and it won't start if it's got batch fired injectors...

zs&tas

i would be very suprised if your car will run on four cylinders, ive herd accel are not good, if i was you id go to the scrappy and pull a set, test them and get six working injectors.

90Camaro4ever

iTrader: (2)

I replaced two of the fuel injectors (received them from from Dave MC), and the car is running now. Thanks!!!