I’m gonna pick up a test light today. Made post right after work lol, I don’t even remember what I was thinkin.
Is the check engine light on? Have you tested for stored trouble codes? I presume this truck is OBD I. Do you know how to check for stored trouble codes on this truck? The folks at GM kindly put diagnostic tests into the ECM, and you paid for them, so you might as well take advantage of this feature. Might be a shortcut to a solution.
As mentioned prior, that fact that the injectors are not squirting gas doesn’t necessarily mean there is anything wrong with the injectors, the ECM, or the wiring from the ECM to the injectors. Just make sure everything is properly powered up. (If something important wasn’t powered up, there would probably be a DTC and the CEL would be on.)
The ECM won’t pulse the injectors unless it senses that the engine is turning. This is to prevent flooding situations. It appears on your truck, there’s a distributor reference signal called the Distributor Ignition reference pulse. That is what the ignition system uses to determine engine RPM and crankshaft angle. It doesn’t appear your engine has a crank sensor, the crank angle is implied from the distributor angle. In any event, that signal isn’t active unless the engine is cranking or running. Without that signal, say the wire becomes grounded, the control module won’t fire the injector.
wow did not know that. I while back when things were still shaky with it the light did come on before dying out. Might just see about a cheapo reader next paycheck.
Make sure the “cheapo reader” does OBD1 (and has the adapters you need) before you plunk down the cash
A scan tool capable of complete live data might help you solve the no start, but a plain old code reader won’t help you at all. Find the 12-pin ALDL connector under the steering column, use a paper clip to connect terminals A and B, and turn the key on. Watch the service engine light for how it flashes. 3 long flashes and 2 short flashes is code 32 for example.
@db4690 indeed. I’ll look into them tomorrow.
@asemaster do you have a link that has all the meanings
No, but there are only a handful of codes, and I honestly can’t think of any that would make you not have injector pulse or power. From what I can remember:
14 and 15, Coolant temp sensor
21 and 22, Throttle position sensor
32 EGR
35? MAP sensor
42 Electronic Spark Control
44 and 45, Oxygen sensor
55 internal ecm error
Don’t hold me to these.
But lets not get ahead of ourselves. You have spark, right? I assume you have a running fuel pump when cranking? Injectors not operating, check for power, check for ground.
I concur w/ @asemaster , a code reading tool isn’t what it needed at this point. OBD I is used on early 90’s cars, up to around 1995. There was no little to no standard on what OBD I did, and the connectors were not standardized either, so purchasing code reading tools for OBD I is risky unless you know that particular one has the proper adapter and will work on your particular car. Plus you really don’t need a tool, the number of codes are very limited. OBD I DTC’s can usually be read in a special test mode (apparently enabled on your truck as mentioned above by asemaster) by counting blinks on the check engine light. I do this w/ little to no difficulty on my early 90’s OBD I Corolla.
If the CEL did come on, I expect you’ll find a DTC stored about the ESC (electronic spark control) module.
I’ll give it a go w/o a test tool with just the paper clip. With work and college I have not had much time to get around on this.
Have you actually verified yet whether or not there is battery voltage present at and through the ECM fuse with the key in both the run and start positions?
It’s very easy sometimes to overthink a problem with the end result being a huge waste of time and money.
A long overdue update once again…used a test light on the injectors to ground and had a person crank the engine, the light did come on. So what does this mean?
So that proves that power is getting to the injectors but apparantly the ECU isn’t turning them on by pulsing the ground connection to them for some reason. It could because of the security system has an issue or the ECU is bad.
OK, so with your test light attached to ground you have good power to the injectors. Now with your test light attached to battery positive check the other wire to the injector while cranking. It should flash, this is the ECM “pulsing” the injector. If it doesn’t, my next test would be for good spark at the distributor.
Has the crank sensor signal been checked yet? Another good thing to do would be to see if the engine will fire up by using a little starter fluid sprayed into the intake.
Checked injector to pos battery terminal it showed signal but while cranking went dead or very little. Checked spark when it was towed home, it was good.
So it appears the ECU may be the cause of the problem since the light fades out.
So from your test with a noid light you know it doesn’t flash when you crank it, right? With your test light (not as good as a voltmeter but if it’s all you have…) you know you have battery voltage at the injectors but no ground (flashing ground, or pulse), right?
Are you doing this with both injectors unplugged?
You’re 100% sure you have good spark?
Does the service engine light come on with the key on?
I’m trying to think what the next step should be without the proper test equipment.
Long time on not getting up on this while missing with Escort. 100% sure of spark, I think today I’m going to aim at the oil pressure switch after doing some research this morning. Thinking back to another post and doing some research it maybe the oil pressure switch causing this.
Another update, went out to give her a go before getting some rest, started up and ran just fine around the block (SHOCKED). Check engine light did not come on at all. Pulled her back into driveway and 3 out of 13 times she gave a little hesitation but started fine after turning back the key and giving it another go.
Well maybe whatever area you worked on last had a connection problem and by moving things around the problem got corrected. At least you now know the ECU is okay and the trouble is most likely due to a simple bad connection somewhere.