rmjohns

I've got an 1985 that I've had for a couple years that I've been struggling with over the last few weeks. In a matter of a week or 2 it went from start immediate, to takes a couple turns of the key to get it to start, to now it won't start at all. Interestingly it did take turns of the key, you couldn't just hold the key on. If it didn't start in the first 2 seconds, it wouldn't, but you could turn it off and try again and it would start in the first 2 seconds of the next crank. or maybe the 3rd crank. Now I've discovered that if I hit it with ether, it pops right up and runs just fine. I've driven it around after starting it this way, and I don't get any codes, it seems to run just fine.

I've checked the usual suspects. The TPS is set at .53 volts. Using WINALDL, I can see the MAT is about right, the coolant temperature looks about right. I checked the ohms of the fuel injectors, they all are in range, and actually were all replaced just after I got the car. I do get good fuel pressure on the rail at start, and I can hear it start for the 2 seconds.

Putting a noid on a fuel injector wire, I don't see a pulse during starting. It obviously lights just fine once the car is started on ether.
I did the 12volts to 430 on the ignition module, and I do see the noid pulse then, but that is taking power from the battery and using that as a signal to the ECM. I had the ignition module checked at the local autoshop, and it checked out OK.

I'm thinking of replacing the ECM, the thought being maybe something is haywire in it's starting mode and it's not driving the ignition module?

I hate just replacing parts. So far, I've done the EGR as it wouldn't hold vacuum, and the Idle control valve, as it was all crudded up.

Any thoughts or suggestions?
Thanks
Rob

Muffin

Cold start injector?

rmjohns

I thought about the cold start injector, though I honestly haven't checked it. My understanding on the cold start injector was that it really came into play when it's really cold, but it wasn't needed for our 97 degree summer days? Maybe I need to go back and check that.

I understand it's hard to find those valves.

Rob.

jfb

The ECM controls the start up sequence and it appears that is your problem, no noid pulses when cranking and startup with starting fluid. The only way I know to prove this is to try a known good ECM.

pletzvet

Check your fuel pressure - is the pump coming on for about 2 seconds when you first hit the key? Is the system holding pressure at about 39 psi after the initial prime?

rmjohns

The initial prime gets me 38 psi, and although I can't see the gauge while cranking, it's still at 38psi when I'm done. I think I read somewhere that the 85 took slightly less pressure than the 86 and later models, not sure why. Hopefully I'm within the acceptable range.

Thanks for the feedback!
Rob

jfb

It takes more than fuel pressure, the injectors have to be pulsed too.

rmjohns

Yep, the not pulsing is baffling to me, espcially since it pulses fine once the car is started. I picked up a new ECM on the way in to work that I'll try tonight. I'm running out of things to try so I'm hoping that the ECM is the problem.

Thanks
Rob.

pletzvet

oops - my bad...it might have helped if I'd read your initial post a little more carefully - I now see that you already noted that you had good pressure at the fuel rail and the pump was priming the system. Considering the basic needs of air, fuel, spark and compression happening in the right order and ratio, it sounds like this is happening fine once the car starts so it tells you that something is happening with this combination at start up, specifically. I note that you have WINALDL and it might be helpful to trace back to any settings that you might have changed with the ECM rather than conclude that the ECM itself is malfunctioning. It'll be interesting to see if the replacement ECM makes a difference.

rmjohns

Actually, I got WinALDL going hoping it would help me debug this no-start problem. Some of the fields make sense to me, like the MAT and coolant temperature are about the same as the current air temperature, The TPS reads .53, etc. It displays a bunch of data that I don't know what the valid ranges should be. I don't have access to it at work, so I can't off the top of my head remember what they are.

So far as I know, I can't change anything with WinALDL, it's a display only utility.

Rob.

rmjohns

I took a couple weeks off on this to bang my head against the wall.
I've tried a replacement ECM without success. I've tested the wires from the ignition module back to the ECM, I don't seen any high resistance or grounding.

I've read where VATS can cause this problem. I also read that the chip can be removed and if it's a VATS problem, the car will start in limp home mode. I've tried this and nada.

With all the parts I've replaced so far, the car runs like a champ. I just can't get it to start without the aid of ether. Actually, that's not exactly true. I found I could run a test light from the 430 circuit to 12 volts while cranking and pulse the signal manually. I won't say it popped to life, but I could get it to start using this method.

So I'm back to being baffled as to why the ECM won't pulse the injectors during startup. The typical culprit to this condition seems to be either VATS or the ignition module, but I don't think either of those two are in play here.

Any other thoughts?
Thanks
Rob.

KM1959

If you haven't already checked the previously-mentioned cold-start injector you might want to. Spray some starter fluid into the throttle body and try a cold start. If it starts, then I'm pretty sure that it's your injector or perhaps its control signal. A friend's car had the exact same symptom.

FWIW, I don't think it's used based on cold outside air temperature (how would the ECM know or care), it's used when the engine is "cold". Good luck!

rmjohns

Thanks for the feedback. I actually had a breakthrough on this last night. I have been running WINALDL while cranking the car to see what the various sensors look like and everything seemed fine. I discovered last night that although the ECM was working, it wasn't getting enough voltage to kick the injectors. Running a voltmeter to the ECM power showed the volts drop from 12.5-13 to only 7ish volts while cranking. I ran a power line straight from the battery to the ECM and got that up to right at 9-10 volts which was just enough to get it to catch a few times and finally start. Something it hasn't done on it's own in weeks.

I didn't get any further on it last night, as I hooked a battery charger up to it to let it charge for a while. I'm sure all my testing has drained it quite a bit. It does seem a little strange in that the starter turns the engine just fine, least to my ear.

This weekend I'll run some tests and see if it's some lose connections or if the starter is sucking too much juice. I'm guessing it's starter related as this car has headers that are pretty close to the starter and I imagine it must get pretty hot. I might need to construct a heatshield of some sort.

Thanks
Rob.