EST wire connected issue

**budweiser_man** · 09-24-2013

1974 chevy K5 blazer truck
1991 Chevy K5 blazer 350TBI motor
SM465 and 205
Wiring from same truck
EGR deleted from wiring harness

Problem: truck will start and run for about 1 second than die with EST wire connected. truck will start and run with wire disconnected.

things I have noticed or tried:
tach drops as soon as it starts, fires and dies right away connected. I have back probed the ECM with a fluke meter and I have the pin out with the voltages I need and from what I can tell they are all correct. grounds where they belong and voltage where it belongs.

When trying to start I tested the wires going to the distribtior and got the voltages i needed from the 4.5 across the EST wire, 1.5 on one of the other wires, black/red wire is ground and it ohms out to ground with less that 20 ohms when key is on and about 2-3 ohms when key is off.

Wiring harness looks good no breaks or ground issues.

I have tryed a different ESC and spark advance inside of the dizzy.

next when the truck is running with the EST wire disconnected and I plug it back in the truck will contune to run just fine.

Idea:
Is it ok to have 20+ ohms on the black/red wire when starting, I did try to ground out this wire and no difference when trying to start.
it is acting like the truck does not know it has started and is ok to run.

**Six_Shooter** · 09-24-2013

What are the injectors doing when the truck stalls, do they stop before the engine stops or as it's stopping?

20 ohms is fine, you will never see 0 ohms on that wire, due to how it's connected through the ECM to the vehicle.

**budweiser_man** · 09-24-2013

the injectors counuine to fire for a split second after it sounds like power was cut to it.

**EagleMark** · 09-24-2013

Check wire A6 that it has power from key on, to crank and back to key on always till key off.

Check wire B1 and C16 have power always, key on and key off.

**budweiser_man** · 09-24-2013

ok thanks! I will give this a try tonight

**budweiser_man** · 09-25-2013

A6 is on when key is on and cranking, B1 and C16 are always on key off on crank

really dought timing issue due to it starts so nice when disconnected.

would the computer be trying to advanve the timing too much for it to start. and what does the computer use for a reference to 0 or ground on the EST wire

**JP86SS** · 09-25-2013

Also check your engine to firewall ground wire is intack.
The fender to the battery one to while your checking.
Jp

**budweiser_man** · 09-25-2013

check all grounds, look good test light from battery to computer good ground and hot. what tells the computer the truck is running? like a spark signal?

tell me if im too far off;
when sire is connected it is giving the computer a voltage and I might have a poor connection somewhere and the voltage from the EST wire is putting it over the edge.

I messed with the timing a little. I turned the distribitor clockwise a bunch and it kind of started with the wire connected and dieda few seconds later. ran like crap. but with the wire disconnected I timed it right at 0 earlier. I will be putting it back at 0 with wire disconnected

just tried, turned distribtor clockwise, it started with est wire connected. ran like crap turned distrubitor back to about where I had it with EST wire disconnected and and ran pretty good. shut truck off and now back to orignal problem.

**jim_in_dorris** · 09-25-2013

Try this. Start the truck with the wire unplugged. Verify timing is at 0 with a timing light. With truck running, plug wire back in. Check timing with timing light. What is it reading now?

**EagleMark** · 09-25-2013

And if it retards instead of advances? The wires on pickup coil are reversed!

**jim_in_dorris** · 09-25-2013

You picked up on that pretty quick Mark ;)

**budweiser_man** · 09-25-2013

ok I will check that today, I thought the wires on the pickup coil only plug in one way though? so remove them from there plug and reverse them? It is worth a shot.

**EagleMark** · 09-25-2013

Only if the timing retards instead of advances when EST bypass is plugged in!

**budweiser_man** · 09-26-2013

So started truck with wire disconnected. Let it warm up. Timing is at 0.

Also just so it is know I am using a non adjustable timing light if that maters.

I plugged in EST wire while running and no difference. Reved it up and it retared a little. So mark went right when you are standing in front of truck. So would this mean my pickup coil is backwards or ok?

Went ahead and switched the pickup coil leads (the 2 wires inside of the distribitor cap) and it did not run at all and it Did not want to start with EST connnected so I switched it back.