TommyFox

Not ecm, Module in distributor. Check if you have a weak spark by taking an old spark plug and pulling say number one plug wire, plug it in and lay it against the block. Start engine, you should have a nice blue spark. If it is yellow then chances are module is toast.

pecosbilly

I knew that...but it seemed most posts indicated ECM replacement solved their problems. Even that seemed as remote as ignition module going bad sitting in my garage for 2 months while I replaced the injectors. More likely is something I either didn't reconnect correctly, or dislodged during re-assembly. If it didn't run or didn't run well before the injector replacement, I'd think some elec part might be at fault...but just sitting with the batt disconnected doesn't seem logical for elec parts to suddenly fail. Of course, logic doesn't always enter into automotive problems. I'll check the spark tomorrow for intensity, thanks for suggesting it. I did notice that the fan comes on when key is turned on & while cranking the fan slows, indicating a draw on the juice. I'd better check for a bad ground. The fan shouldn't come on until motor has warmed up, don't you think?? I've also had to keep the batt charger on slow (2Amp) charge while all this testing is going on & one post said this was dangerous to the ECM. Could I have already damaged it??

pecosbilly

Back in June of '03 The CorvetteKid wrote: "Hey blackvette89, the temp sensor that controls when the fan comes on and off is the one on the intake manifold on the front of the engine (just below the throttle body). It feeds the information to the ECM; it's the ECM that turns the fan on and off." Perhaps the ECM is turning on the fan at startup, (erroneously) drawing much needed amps from the injectors, preventing them from firing correctly. I do notice the fan slows somewhat during cranking, which shows there is a drawdown of voltage and/or amps. I'll try to unplug that sensor & see if it makes a difference, in addition to checking the spark & the ground connections. Bad grounds are one of the most common problems with all things elec.

indianavette

FWIW....I've been fussing for months with slow-start, no-start issues when my '84 is hot. Changed wires, TB injectors, relays. Situtation got progressively worse. Pulled fuel sending unit to replace pump, found a small rupture in the one-inch long rubber hose connecting pump to line. Replaced the hose. Problem solved.

pecosbilly

Thanks Indianavette, but I think not relevant in my case. I've good fuel pressure (42lbs) at the rails. Drops a little when cranking to the 30's, & spark seems good. Haven't checked the individual injectors for firing with a test light yet. Intended to do that today, but was too busy. I'm still thinking I did something wrong when installing the new injectors.

pecosbilly

While re-reading "ALDL" codes info I found this little gem:
"Clearing the Codes: To clear the codes from memory, remove the negative battery cable for a minimum of 10 seconds. Remember to remove the shorting device from the connector after you have read the codes. Disconnecting the battery will clear all stored codes and any stored memory (radio button presets, clock, trip odometer, average gas mileage memory, power seats). "Your ECM/PCM computer will also have to relearn timing/mixture/exhaust emissions."
So, I'm wondering how long is it going to take to "relearn" the timing/mixture/exhaust emissions??? Maybe that's why it won't start...after the battery was disconnected for 2 mos...it's not yet re-learned how to do it!!!! Anyone have any new ideas?? (The ignition wasn't on when I re-connected the batt, so harming the ECM/PCM wasn't a factor)

TommyFox

Mine stays disconnected for four months. Starts right up.

pecosbilly

Thanks, Tommy...
Then it's something I did or didn't do when replacing the injectors. I've rechecked all the fuel connections, no leaks. Checked all the vac connections, all seem to be correct. Still haven't had time to test-light the individual injector connectors. And I haven't located the ALDL plug, it's well hidden amongst what looks like a explosion in a spaghetti factory...in case it might lend me a clue. Spark is good & pump pressure at the Schrader on the fuel rail is 42 then down to mid 30's when cranking. It may have to wait 'til fall as I'm trying to get stuff done to leave FL for my summer home in AZ.

pecosbilly

All the wires to the ALDL plug have been cut & all taped together in a big wad. Suppose this was done by ignorantjackass that installed the stereo or alarm sys or remote starter sys, or all three, so I've got to undo all that mess & try to figure out which wires go where! In re reading the troubleshooting guides, I see that #6) "Engine starts, but stops immediately" #3 is "Vacuum leak at gasket between intake manifold/plenum & throttle body." & since I had this apart to replace the injectors, seems like a good place for me to have left a leak. I'll check it out as soon as I can.

TommyFox

Vacuum leak? Car will for sure not run right. I always put a little tack adhesive and let it sit for a few hours on the gasket's so they have no chance of moving during reassembly.

pecosbilly

That's what I thought, might run lean, but it would run. I sprayed some WD-40 at the joint of plenum & risers, no diff. Still haven't had time to check inj's with a test lite, maybe this eve. after dinner.

Cliff Harris

The best way to clear the error codes in the ECM is to open the ECM power connector. This requires no tools and doesn't affect the other stuff:



The connector only has to be open about 1 second to do this. This clears the error codes and the BLMs (Block Learn Multipliers). The BLMs will be reset to the default value of 120. Driving in a "normal" manner for about 15 minutes will allow the ECM to readjust the BLMs. The ECM uses them to calculate the fuel injector pulse width so your AFR will be off a little until they get tuned. The ECM must be in closed loop mode to adjust BLMs, so the engine needs to warm up first.

pecosbilly

Thanks, Cliff. Gives be something more to check out...that ECM harness connection to the pos batt might not have a good connection & I needed to check the ground connections as well. I'm sure it's something simple, just haven't found it yet. All the wires to the ALDL have been cut & bundled together & all taped with elec tape into a big wad under the dash...I guess it was some fools way to keep everything from hanging down when the remote start, alarm sys & stereo were installed, but it's a real mess to untangle & locate the "A & B" wires so I can check any codes. The A & B wire remnants still at the block appear to be a black w/thin white lines & a white w/thin black lines. Still haven't found them in the "Wad" yet, still looking. I'm 6' 230lbs & it's tight for me to get under the dash for any length of time.

gasman3

Pecos, it runs! The fuel filter was definitly clogged. While replacing it I created another prroblem that I will have to attend to later. Thought I would be clever and drop the X cross memeber where it connects to the frame near the filter to give me more working room. This worked well but 3 of the captured nuts in the frame rail broke loose as I was re-attaching cross member so now only have one bolt holding it in at this location. Will have to use nut serts or something similar to fix this issue. Anyway after installing new filter and cranking over engine I still had no pressure at fuel rail ( have bought injector pressure gauge tool from Harbor Freight). I then pulled the pump relay and checked it out and it checked okay with voltmeter. I then hard wired pump at relay base and pump lit off and I now had 40# at the injector rail. I set up my meter today to test for pump relay signal from ECM with pump relay removed. Turned key to on and saw voltage at the relay base for a few seconds which meant I was getting a signal from the ECM. For the hell of it I turned key to start to see if I got a steady signal from the ECM during cranking and the damned thing started with out the pump relay installed. So I removed my testing equipment and installed the pump drive relay and car starts right up. The only thing strange at this time is the cooling fan comes on right away and cycles on and off. It used to only come on when engine temp reached 235 degrees. I don't know if I should be concerned about this now or not. Cleared all the stored codes and am going to drive it tomorrow to see if service engine soon light comes on again.