Cascade Crew

d00012 · Posted: Thu Jul 16, 2009 6:39 pm Post subject: ECM issue?

Can the ECM shut off the ignition? If so, what would cause it to do that? Haven't worked on my car recently, but I was thinking on how everything works (tested and bought new sensors) yet it keeps dying on me intermittenly, like it's being shut off. I've tested and replaced everything that could be bad and shut it off, but still won't run. Is my ECM fried? It's an 88 305 ECM but is a 350 motor that had a 700r4 swapped in and the fan grounded (appears always hot).

sheltonw3 · Posted: Thu Jul 16, 2009 8:26 pm Post subject:

sounds like your ECM may need to be swapped!...a 305 ecm may not be set to run a 350?...programming maybe different?....you could trying pulling a used one out of a junked car and see if that makes a difference?

just keep in mind ,brand new ecm 's are not cheap!

Al Hasse · Posted: Thu Jul 16, 2009 9:16 pm Post subject:

The ECM in itself isn't that expensive, last time I checked was $90 or so, but that was a couple of years ago. They come without a chip which is the pricey part.

d00012 · Posted: Fri Jul 17, 2009 9:05 am Post subject:

Without a chip? That's lame! Would a GM dealer include everything? How much would that cost me to go to the dealer? Autozone, Napa, and Schucks all have the L05 ECM for around $120, remanufactered.

On another note, what happens if the ECM detects no oil pressure?

blue89 · Posted: Fri Jul 17, 2009 9:13 am Post subject:

I believe without oil pressure the fuel pump won't run.

d00012 · Posted: Fri Jul 17, 2009 9:27 am Post subject:

Ok, just making sure the ECM doesn't do anything else. Fuel pump works, but I'm thinking it has a bad ground. I'm going to test it's voltage first before I get a new ECM (I will need one anyways as this is a 350).

blue89 · Posted: Fri Jul 17, 2009 9:37 am Post subject:

I'd also look into getting a different ecm. You could save more than a few bucks by buying a used one from kurfird.

d00012 · Posted: Fri Jul 17, 2009 9:56 am Post subject:

Think he'll have an L05 ecm from a 89-91 Caprice? It's the only one that I know of that hooks up pin for pin for my set up.

Twilightoptics · Posted: Fri Jul 17, 2009 11:31 am Post subject:

HOLD ON guys.

You've got a 350 engine and a 305 ECM?

305/350 ecms are the same. The Chips are different, injectors are different, and knock sensors are different. The rest on the whole TPI motor are the same.

TBI, 350 trucks got larger throttle bodies and injectors, and a different chip and different computer.

Need to have the right chip for the right motor.

Is this car TBI or TPI?

Remanned ECMs from a parts store are around $100 and when I bought a prom from GMpartsdirect.com it was about $80.

blue89 · Posted: Fri Jul 17, 2009 11:47 am Post subject:

HOLD ON again.

If the preliminary problem is that the car shuts of like you pulled the key you should at least verify that the ignition isn't faulty before you go spending money on an ECM. ECM's do go bad but not that frequently. Not to mention the ignition acts on it's own, the only way the ECM can kill the engine is to leave the fuel injectors off. If you can verify that you have spark when it won't run then look again at the ECM.

iansane · Posted: Fri Jul 17, 2009 3:13 pm Post subject:

HOLD ON TO YOUR BUTTS!

...Yeah. That's it. Laughing

Before swapping crap out, what is this thing? TPI? TBI? Is the induction stock and just the block/heads swapped or was the induction swapped too? Did you do the swapping (as in, can you verify it's a really a 350?)

d00012 · Posted: Fri Jul 17, 2009 5:07 pm Post subject:

It's a 350 TBI from a truck. I didn't do the swapping.

d00012 · Posted: Fri Jul 17, 2009 5:12 pm Post subject:

It will run shortly if I throttle it, but it bogs out, and has a major hesitation after hitting the gas. Have to constantly tap it to get the RPMs up, then after about 10 seconds it dies anyways. Which makes me think the fuel pump, low voltage or bad hose in the tank? The fuel pump wires do look bad.

The wire for the fan was grounded (read always hot), could that have damaged the ECM at all?

Twilightoptics · Posted: Fri Jul 17, 2009 5:45 pm Post subject:

If it's a full 350 TBI setup with the stock thirdgen 305 computer... it's dumping fuel in like a mad mother. You need to re compute it. I think the 7747 ECM is a direct pin out setup. They're in the 350 trucks/vans with TBI.

Think about it. You've got larger injectors... The computer thinks it's got the small ones.

TBI is pretty tempermental to big swaps.

d00012 · Posted: Fri Jul 17, 2009 6:10 pm Post subject:

So the 747 works, and the one for the L05 Caprice, right?

Just tore the fuel lines off, the inlet line looks clogged with a bunch of gunk and only the outlet line has fuel in it.

Large one is the inlet, right?

Twilightoptics · Posted: Fri Jul 17, 2009 6:55 pm Post subject:

Correct. Large is the in, small is the return.

Don't know anything about the caprice stuff.

Check TGO's tuning/prom section.

Need to try and ID the throttle body and injectors too. Sometimes they have a color under the electrical connectors.

d00012 · Posted: Fri Jul 17, 2009 8:02 pm Post subject:

I checked TGO and they said the L05 Caprice from 89-91 for the ECM, or a 350 tbi truck (747).

My dad has a '90 GMC 2500 Suburban with a 350 TBI, know if that one is a 747?

I'll try to ID the throttle body. Is the 220 the one used on the 350 trucks?

Twilightoptics · Posted: Fri Jul 17, 2009 11:17 pm Post subject:

I don't know numbers of TBs. Might need to pull it off and measure.

Only way to know what ECM is what is to look at the tag and see if it says 1227747 I think that's the full number.

d00012 · Posted: Sun Jul 19, 2009 1:46 pm Post subject:

Tested the voltage for the fuel pump... (reddish pink wire is the power wire for the pump, right?)... was only getting 2.24 volts. Isn't it supposed to be around 12 volts? The pump sounds like it's struggling. How do I get it to work, work a new ground, what about the pink wire?

Twilightoptics · Posted: Sun Jul 19, 2009 2:35 pm Post subject:

Get to a w iring diagram and make sure you have the right wire. Think it's a purple or grey At the connector at the tank