Goumba T

Ok, so quick background. About seven months ago my FPR called it quits, and I hadn't had the time to replace it. Just getting around to it now.

Replaced the FPR, put everything back together. New battery.

Before I bolted everything back up, ran the lines to a container and ran the pump a bit. Don't know if this was enough to clear crud, but I was hoping so.

Turn the key to run, hear fuel pump. Check pressure, pressure's good, holding.

Turn the key to start, and the engine struggles to crank. It turns maybe one full revolution at best, and very slow. The voltage gage drops, and then it quits. Give it a few seconds, repeat.

I have spark, as best as I can check it with this condition, checked with a checker and timing light. Hand turn crank to match timing marks, distributor's pointing where it should be for #1 TDC, if I put the cap on it's (roughly) pointed at the #1 tower. Shouldn't be enough to cause trouble, at least.

What am I looking for next? I was thinking the starter, but that had been replaced last summer (putting it out of warranty), so I'm hoping it's not dead.

Any suggestions welcome.

aliceempire

iTrader: (14)

Start with checking the starter and the battery cables. How much voltage is at different spots? If you have a bad ground or bad cable you should see it with a voltage drop

Goumba T

Well, the cranking turned out to be the starter. Somehow it had managed to crack the nose (this starter was only 6 months old, and replced one that had the nose crack as well... odd).

It still won't fire though.

I connected the laptop, not hoping for much. Using TunerPro it seems to be getting its reference pulse. TPS appears to be functioning correctly to the ECM (.67v closed, 4+v wide open).

One thing I noticed, and don't know if it means anything, but while cranking, should the ECM be getting engine speed data, or does the ECM only pass it on while the engine is running? Just asking as it stayed 0 the whole time while cranking.

GeneralDisorder

iTrader: (1)

Did you check for spark after you got it cranking?

IIRC, you will not get RPM data till the engine fires up, only reference pulses. The ECM fires the injectors by reference pulse count during cranking so I don't think it generates an RPM signal.

GD

Goumba T

I have spark.

One thing I failed to notice last time, OI guess focusing on the cranking, is that I'm losing pressure. It drops to 20psi after a minute after the pump shuts off.

I can't seem to find the thread again, but what is the acceptable pressure drop over time? I know there's a recent thread on here mentioning it...

Goumba T

Nevermind, erroneous post.

Goumba T

Well, here's about where I'm at, and with the weather getting colder may stay that way for a while.

- Cranking well now. Turned out the new (!) starter wasn't acting so new, replaced.
- Have spark. Unfortunately I don't have help so I can't get close enough to note color, but it's there. Besides, my understanding is color really isn't that important. Checked several with a tester as well.
- Module tests fine.
- New cap, rotor, coil just because they weren't that expensive and due for replacement anyway.

- Getting proper pressure, and holding nicely.
- Getting fuel, it seems. If I open the throttle blades after trying to start it, I can small fuel.
- Injectors test at the high end of the range, 14.5-15 ohms, but still within range.

I guess the next thing, which I really don't want to do, is to pull the fuel rails off and check that way. Waste of a buttload of new gaskets..

- All fuses intact.

- IAC functioning, removed it, gave it power, it closed (pintle shot off like rocket - forgot about that).

- TPS within range. At 0.7 closed, ~4.5 when fully open.

- CTS within range.

Tuned Performance

iTrader: (92)

Have you checked injector pulse with a noid light ?
Vats or bad icm if you don’t have injector pulse.

Goumba T

Thanks for the reminder, did it today.

ICM, as in Ignition Control Module? Brand new, I know that doesn't quite disqualify iut, but the ECM is getting the reference pulse.

Correct me if I'm wrong., but would it fail to crank if VATS was interfering? My GP sometimes acts up and I get a steady Security light with no crank.

The noid light indicates I get no pulse on any injector. If anyone's familiar, I picked one up from Harbor Freight, using the GM PFI light,

Tuned Performance

iTrader: (92)

Your right icm ignition control module. If this is your 90 lb9 it has a 1227730 ecm. You can check to see if the ecm is getting a passkey hz signal at pin f10 of the ecm.
With a volt ohm meter you would see 2.5-5v at this blue wire of the ecm .
If you don’t have voltage the passkey (vats) system is not working correctly.
http://tpiparts.net/1227730_pinout_diagram
Your right vats does have a starter enable relay. This can still work and you have a hz signal failure to the ecm.

Goumba T

Finally got some time off from work, though the weather still sucks

Recap:
Have spark on multiple wires. Tested by spark tester and visually by grounding a plug and checking for spark (yellowish, but there).

New ICM and coil (regardless of issue looked like they could use the replacement).

New:

Getting a signal on F10

Still no pulse with noid light or simply the test light.

With a 12V test light, solid light at each injector lead (both on each connector) to ground.

All injectors test to 14.5-15.5 ohms.

Per the service manual tested 467/468 (C11/C12). Solid light with connection to ground, key on, both with and without all injectors disconnected. From here it suggests the ECM is at fault. Anything I can test before plonking down a couple of hundred bucks to find out it's not the issue?

Tuned Performance

iTrader: (92)

You can find ecms on eBay just use your memcal
https://m.ebay.com/itm/1991-camaro-2...IAAOSwo3tasuuo
https://m.ebay.com/itm/1987-1993-Che...cAAOSwyXFarAZw

Goumba T

Thank you for reminding me! I knew there was another question I wanted to ask.

What are the chances that the memcal has somehow failed?

Tuned Performance

iTrader: (92)

The memcal rarely fails.