how to accurately test ECM?

**MQQN28** · 05-02-2018

Tyree

Something to check. I see that you think it may be a fuel problem. When I put the efi on the flathead I had a problem that came and went not all the time and was noticeable when I went around corners.
At first I had no CEL no way of data logging and I hooked up a monitor to the o2 sensor and saw it was running rich.
I finally figured out it happened when I filled the tank. I thought it was a good idea at the time to hook up the purge line to the emission outlet on the tank. This was a straight link without a purge canister. So full tank going around corners vac line sucked fuel and caused flooding. FIX.... disconnect this line.
It maybe a long shot but check if your problem occurs when the tank is at a particular level, it could be a pick up level?
I had people telling me all sorts of things, wrong octane rating, timing, coil, spark plugs, my age, wiring, it just wasn't going to work, put carbies on it, fuel filter, fuel pump.......

MOC

**Tyree** · 05-02-2018

MOC, I appreciate this reply.. my tank is an aftermarket under bed tank.. brand new from LMC truck. It only has an inlet for for fuel pump supply through sender and a single return line.. at this point, I am open to all suggestions at this point. :(

**MQQN28** · 05-04-2018

Originally Posted by Tyree

MOC, I appreciate this reply.. my tank is an aftermarket under bed tank.. brand new from LMC truck. It only has an inlet for for fuel pump supply through sender and a single return line.. at this point, I am open to all suggestions at this point. :(

Tyree
Some other things to check.
I had forgotten that I had to change a coil in both the hot rod and daily driver. The daily driver would crap its self coming home from work and the first time felt like it was running out of fuel. The next two times were more violent and I figured it was a coil pack. Replaced and all was fine. The coil in the hot rod was less obvious but died in the drive way and was easy to diagnose.
I also had the battery deteriorate in it and it also gave indications of fuel problems.
It may well be worth checking Coil, battery, and alternator as these can fail slowly with intermittent symptoms that the ECM tries to correct and give the impression that there is a fuel problem.
The alternator can develop problems that the ECM sees as falling battery voltage and try to compensate giving an impression that something else is happening.
At this stage you may have to eliminate devices before you find the problem. Going back to carbies may not fix the problem.
It is very hard to find an intermittent problem when it fails outright and you get to it you know.

MOC

**tamperedchevy** · 05-09-2018

do you have catatlytic converters?

**Tyree** · 05-09-2018

no converter

**Tyree** · 05-10-2018

I somehow, someway came up with the hypothesis that my coil or some component within the ignition system was not performing under load. This was my best guess at this point because I was confident in the mechanics of the engine and the fuel system/wiring harness was working properly. This was really tricky because the symptoms would not reveal themselves consistently. I pulled the ignition module off the distributor and the pins connecting to the pickup coil were rusted and had green corrosion. I also decided to replace the coil as well. Took it for a test drive and it ran great. No issues. I cannot say specifically which component was failing. I ran the truck through city blocks and also on interstate without a single hiccup. I hope that this has resolved my phantom issue. I will know more after a few more test drives. Again, thank you to all of the contributors and suggestions on this post.