Cascade Crew

[kutison]

My "new" 89 305 TBI Camaro won't start unless primed

When cranking the engine while starting, the injectors won't spray.
However, if I pour a bit of gas into the throttle and crank it over, the pistons fire, and it gets the injectors spraying.

I replaced the fuel pump, (it was burnt out) and the fuel pump relay.
The fuel pump still won't work through the relay, I have it bypassed at the moment.

All of the fuses are good.

When cranking I can hear the fuel pump running, but only because it is hotwired from the stereo power wire

but even then the fuel still isn't spraying out of the injectors. unless I put gas in the throttle to get it going...

I have hear people say that it could be a bad ECM, ICM or the oil pressure sensor.

Any advice would be much appriciated.

[Dewey316]

I would check the pickup coil in the dizzy.

[Twilightoptics]

THE Oil Pressure Sender could be the culprit but I don't think so.

Sounds like ECM or the signal to the ECM.

[iansane]

[Dewey316]

But he said his pump is going...the injectors fire based on the signal from the pickup. Something isn't telling the computer to start firing off the injectors. The only other thing I could think of is VATS.

[Twilightoptics]

I thought Vats disabled the starter relay?

[blue89]

You could confirm the pickup coil by checking spark? But if he had a bad pickup coil, no spark, so it wouldn't start with fluid? I wonder what codes he's throwing.

[Twilightoptics]

True dat.

Maybe the injector driver board?

[kutison]

I should clarify about the fuel pump.

Ive replaced the fuel pump and the relay and it is still not getting power to the fuel pump at the sending unit. So I have temporarly ran power to the pump from an accessory wire

as for the injectors, noone thinks it could be the ignition control module?

I have another thread running about this same thing at

http://www.automotiveforums.com/vbulletin/showthread.php?t=930930&highlight=kutison

[Twilightoptics]

Module has nothing to do with the injectors/pump.

You might start checking that the ECM is getting proper power.

[kutison]

alright, ill start there. was I hearing something about a fuse in the connection to the ECM, from the battery itself?

and I hate to ask......where is the ECM exactly?

[Twilightoptics]

[Xophertony]

[chevymad]

Ah, I'll have to disagree with paul here a bit. The ignition module has to be good to get injector fire. The way the system works the ignition pickup sends a signal to the ignition module. The module then amplifies this signal. If the engine is cranking less then 400rpm(as in not running yet, but cranking) then the module triggers the coil directly. The amplified signal from the module is also sent to the ECM. The ECM then fires the injectors based on this signal. If the rpm is over 400, then the ECM also sends a timed ignition signal back to the module, which amplifies it again and triggers the coil. The EST wire you disconnect to time the engine is a 5v signal wire that the ECM uses to tell the ignition module whether to trigger the coil directly or to trigger it using the timing modified signal from the ECM.

Now that that's clear LOL.

If your ignition module gets weak the signal won't be strong enough to trigger both the ECM and the coil. So you'll have spark but no injector pulse. If its in this state, usually disconnecting the EST wire will drop the load enough on the module to allow the engine to start on its own.

That said i'd say its either module or ECM. If you had a scope you can check the ignition signal strength at the ecm to determine which. Without it.. take a guess.

I actually just had a tbi truck in a few weeks ago that had a module acting this way. New module cured it.

[kutison]

alright, that pretty much falls in line with what ive been hearing. I won't be able to do anything for a couple of days, so ill get back to you guys this weekend with what I find out.

[chevymad]

OH, one more thing. Be sure to take an ohm meter and measure the resistance of the injectors. Make sure they're the same. If you have an injector short out, it will hurt the injector driver in the ecm. I doubt this is your problem since you can make it run after adding fuel, but its a fairly easy check.

And the reason it runs after you add the fuel. Once the engine is started your alternator kicks in and you now have 14.4 volts or so. This compares to the maximum of 12, and more likely 9.5-10 when you're cranking the engine. More voltage means it amplifies the signal better. Fuel pumps sometimes do the same. They wont pump enough when cranking.. but once started the extra voltage makes them work.

[kutison]

heh, Now to find a friend with an ohm meter

[aaron_sK]

$20 for a multimeter at Schucks. You will need one if you're going to be working on your own car.

[Al Hasse]

[Quasi-Traction]