2.3L ('83-'97) 1990 2.3L No Start and I'm baffled

[Ceej]

In the two areas where you see the copper trace, there was damaged coating. where the break is, it was completely covered in burnt coating. The trace was burnt in two, and the ends curled up. Unless the component completely burned up, there was nothing there. The photo is after cleaning the surfaces. I just ordered a loaded ECM, as without a schematic, it will be very difficult to troubleshoot the board. This appears to be tied to a common trace leading to several devices across the board, one of which is a small SMD populated daughter board of six conductors soldered at an angle off the motherboard. There is an 8pin SMD on the daughter board along with other components. My electronics background is a bit aged, so I've not been able to identify what many of the SMD's are. They don't seem to follow the tables I find online, as the numbering scheme doesn't match up, (Where I can read them.) I can tell which are caps, diodes and resistors, but some of the other surface mount parts are outside my experience. It's no longer worth the time to fiddle with it. Thanks for trying to help!
CJ

 

[Ceej]

Looks like my reply didn't go in. Sorry for the delay. That area was covered with burnt conformal coating. No SMD there. Unless it completely vaporized. In any event, the foil was burnt in two there, and was curled back. This photo is after I cleaned the area, and trimmed the remains of the trace away.

Unless I can find a schematic, I'm not going to be able to repair this. I am not well versed in SMD components. I'm an old Navy ET, but we didn't have SMD's back then. Magnetic tape computer storage, Discrete components, and lot's of tubes. I can't read the numbers on these things. Gonna be a chore for me to fix it.

CJ

 

[pentode]

I haven't found a schematic here but all I can say is that it looks like you jumped the right points... since that didn't bring it back to life, must be that the short took out some other component in that circuit.

Re: SMD components, I feel your pain. I'm not even sure my 20-year-old eyes could have seen the markings on these things but the markings are so cryptic that it'll take you an hour to figure out what you're dealing with anyway.

 

[SenorNoob]

We keep a set of these:

at work for things like that. They make all the difference sometimes. I've used them when soldering small parts like that just so I could tell one contact from the other.

 

[Ceej]

Well, back at it. Been buried at work. The "New" ECM didn't end in the same letters. It's an AA, rather than an A2A.

The truck starts, then immediately dies. If I fiddle with the accelerator pedal, I can keep it running, intermittently. I have to wind it up, and as soon as it gets rolling it fires, then dies, then hits again. Switching on and off. When I quit messing with the go pedal, it dies. Thought maybe the ignition switch, but I have constant 12volts with the key on at the injectors. One of the vacuum lines was off that plugs in under the upper manifold, but it acted the same way once reinstalled. TPS?

I'm going to guess that the AA isn't the same ECM, though it escapes me what could be that different. None of my FAPS lists the E9T-12A650-A2A

CJ

 

[tomw]

Not up on newer trucks like this one... If you have a gray ignition module, it has both START and RUN circuits. The START gets juice when the switch is in the START position, increasing dwell in the coil, shuts off after engine start and the switch released back to RUN.
If you have one, I would put a spark tester where visible and watch its activity when you start the engine. If it quits showing spark, it might be the ignition switch is failing(mind did in an 85 2.3) and it loses power to the ignition module unless you hold your mouth just right, and the key in the exact correct angle in the ignition switch. Mine was column mounted and was moved by a rod conneted to the back side of the key cylinder. Cheap to replace. It was coming out of position as the contact board was not being held in place any more by the bent over 'fingers' that kept it attached to the pot metal housing. Easy to replace. Take a file and make flats on either side of the fasteners and use a small adjustable to remove. The original fasteners have 'break off' heads, so a wrench won't work. They say drill, etc, but filing the flats for a wrench is quicker and easier, IMO. No longer had to hold the ignition key in THAT position to keep it running.
If not that, check the MAP sensor and any codes. A blown MAP may not indicate the engine is running, and the ECM will cut fuel flow when the manifold falls to zero(I think). Had that where a Vulcan would start and die start and die.... start and die. Finally checked the MAP... 87 model Sable/Taurus. I think it had codes for a failing MAP. I had been starting like a WW-I airplane engine huffin and a puffin on one or more cylinders and finally hitting on all 6. I ignored that... until it would no longer start. MAP was cheap and it worked. Bought the cheapest I could find and viola - it runs.
tom

 

[Ceej]

Something I wasn't aware of, as most of my vehicles have been carbureted. This pickup came in MAP or MAF flavors. Pretty simple thing to miss. Mine is MAP. Rebooting...

 

[scotts90ranger]

Yeah, '90 was a split year, early versions had a MAP sensor in the cowl on the passenger side, later had a MAF at the air filter housing... my '90 was early as well, I see you're localish, I have the stock ECM off mine in the garage if somehow that helps any... if you're close I might be able to come over and help at some point...

Oh, another thing that happened mid '90 is 3 wire vs 4 wire oxygen sensors, early was 3 later was 4, found that one out the hard way... same connector annoyingly just one has the heater ground in the engine harness the other is just a grounded body...

 

[Ceej]

I'm down in the south valley a bit over sixty miles away. I take it if I unplug the O2 sensor, it would have three pins rather than 4? Good to know.
The MAP sensor I have is shaped differently than most of the ones that come up in a search. It bolts to the firewall, and the hose fitting sticks straight out rather than pointing down. Build date is '89. Thanks for the reply! I might take you up on the help!

 

[Ceej]

It lives! Got an A2A computer, and it lept back to life! Now runs awesome. And winter sets in. Paint next year?

A buddy came over with his daughter to help with it. She learned to drive a manual transmission in the back yard once it was running. Lots of fun!

Thanks for the replies folks! I think I'll have this old pickup ready for a quick primer coat and back on the road.

CJ

 

[scotts90ranger]

Nice, capacitors have a lifespan and some will just die... it was sounding like that was it.

I have a '92 here that I'm pretty sure might be the same issue...