Ordered cabin and engine bay fuse boxes to try as well. I've read that sometimes these can be culprits? They're easier to find than BCU/ECU pairs at this point so figured it was worth a shot.

Cabin fuse box is a brand new unit, $170.
Engine fuse box is pulled from a parts truck, was only $30.

Soooo many engine bay units on eBay, but only like three cabin boxes were available, all for that $150 range.

 

Too bad about new coils not fixing it. Is there spark? Pulses don't matter except that they make spark or squirt fuel.

Fuel pump should be energized just long enough (some seconds) to pressurize the fuel line when the key is first turned on, but should be energized again during both cranking (with starter motor) and running. Other wires are at the fuel pump for the tank level gauge, so make sure measuring the right wires. Can be difficult to hear fuel pump running if garage is noisy, but should be able to hear initial key on seconds of operation, then not be able to hear during cranking. Is there fuel pressure?

Trying to pin down the basics to keep from re-tracing steps, frustrating I know.

 

Not to derail the thread but I might give that a try, it was super frustrating to have to swap for that little problem. Don't suppose you took pics?

 

Well generally I am not in favor of firing the parts cannon at problems but then again if you don't have spares now you will. Anyway, need to get back to basics:

1. Confirmed fuel pressure while cranking, so that is not it.
2. No spark, so that is a clue. You have voltage at the coils though, so the power feed is not it.
3. Tried multiple coil sets, no love. 99.99% chance not every coil pack is bad, maybe one, but not four.
4. You need a ground pulse from ECU to coils to fire them. You can check that but unclear on if you would see it with a DVM, it is going to be short. You would likely need an old analog meter and mostly only us old guys have those. Easier to test with a known good ECU (on the way).
5. You also need injectors to pulse, which requires a good working CPS. Known good/working is the best way to confirm. Not that I recommend it, but I have removed the injector manifold and cranked the truck to see if I get a squirt. Fire hazard, so I do not recommend. One lasts time: I DO NOT RECOMMEND DOING THAT

I would recommend stop throwing parts at it until you can test with known good set of ECU/BCU.

 

1. This needs to be amended actually. I'm going to get a pressure tester on the fuel rail again today to verify this. I think me thinking the fuel pump was spraying was a false positive generated by me using the Nanocom to force the fuel relay on (to test the fuel pump itself was operational) but I need to test pressure while cranking still.

And totally agreed, I'm not a huge fan of the parts cannon approach either haha. Parts are thankfully cheap for these relatively speaking, and this being one of our daily drivers, at this point I figure any parts I throw at it will replace very old parts and only increase reliability, OR as you mention, just add to the spares inventory, which is also fine since we plan on having this truck forever and as we all know... some parts are becoming pretty scarce.

Thanks again for loaning me the ECU/BCU. Any leads on a place I can purchase a set of my own too? Even just to have on-hand for testing in the future.

 

This is the easiest and safest way to test the ECU pulsing the injectors. For the coil you would use a "screwdriver-style" test light connected to the positive on the battery.

https://www.harborfreight.com/11-pie...set-97959.html

 

For the noid light kit - it looks like I'm taking off the intake manifold to get down to those connectors, yeah? Would I need to reassemble in order to safely crank it over or just crank it with the manifold off?

 

I'm unclear on the state of the fuel pump at the moment , but pulling the pump fuse would prevent fuel delivery (as long as you bleed the pressure off first), but I would also disconnect the coils and then you're free to crank away.

 

Oh oh oh, I'm such a moron lol. I totally misunderstood how this works. I'm just testing that the ECU is sending a pulse to the injectors... like you very clearly said haha. Clearly need more caffeine (and less toddler tantrums) this morning. Appreciate the patience haha.

 

In theory you could backprobe the harness at the ECU pins to connect the noid light there, since you'll have the ECU area open anyway. It would take some custom wiring as the noid lights just have pins that you stick in the injector plug, alligator clips or something. I'm not sure which is more of a hassle but taking the manifold off can be a PITA.