I have a few questions for those of you familiar with these EEC-IV EFI systems! Long-time lurker, first-time poster!

I've been up and down pinout charts and block diagrams, but it would appear I am still missing something. I have a 1988 F-250 equipped with a 351w and ZF5 manual transmission. The powertrain is being swapped into another truck with another fuel management system, but for the time being, I am trying to get the truck to run under its own power so that I can move it into my shop.

The truck was purchased not-running due to a bad wiring harness. It was originally equipped with a Speed Density, Batch-Fire ECU. The ECU is fried. I had a spare harness and ECU out of my 1987 Crown Victoria (5.0), which is Speed Density BUT it is sequential-injected, not batch fire.

The harness swapped over fairly easily, although the O2 sensor setup is different, and so it was left unplugged. From what I understand, this should force the ECU to run in open-loop all the time, avoiding the O2 sampling issue between banks (due to the different firing order). This is fine, as I just need the truck to run well enough to move under its own power; it does not need to run "well."

Given that the 351w has the 13726548 firing order whereas the 302 had the 1542638 firing order, I swapped the injector pins at the harness connector for injectors 3/5 and 4/7. On the 302 SD harness, this was pins 12/14 and 13/42, respectively. From what I understand, this should fix the difference in injector timing to coincide with the firing order.

I have good fuel pressure, power at the coil, and spark from the distributor. The engine will cough and spit here and there, but it won't bust off completely. Are there more differences between the two EEC-IV applications that I am not already aware of? i.e. injector flow rate (I assume the 351w has the same 14lb/hr rate as the Crown Vic?), TFI module, coil, etc?

Another thought I had was to "trick" the ECU into operating in batch-fire mode, perhaps by linking injectors 1, 4, 5, and 8 together as well as 2, 3, 6, and 7 at the harness. By firing all four injectors whenever any of the corresponding injector pins are activated, would this be the same operation as batch-fire? Would I need to use only two triggers per batch instead of all four per batch? Or would this just nuke my ECU's injector drivers?

I know this post was extremely long-winded, but any insight that anyone can provide me would be much appreciated! My alternative to this would be to just purchase another ECU and either repair or replace the original 351w harness, but I'm trying to not spend any additional money, as this "fix" is only temporary to just simply drive it from the parking lot up into the shop. Thanks in advance!!

 

Sounds like you're on top of things. You did make sure the distributor firing order was correct too?
But what about the chance it's had a cam swap? Maybe just for giggles you can do the old finger-over-the-hole trick to find out for sure which piston follows number one in the compression sequence.

There is another difference in the computes between manual and automatic versions. Is the ECM/ECU/Thingy that you're using to try to light off the engine the same one that it came with? So that the transmission type and the ECU match currently?
Mismatching the two will more often than not result in a fried trace inside the computer. Fixable, but deadly from a "get it running now" perspective.

Can you rent a noid-light set to make sure that the injectors are firing?
Is the fuel pump firing up for a second or two each time you turn the key?
Have you checked fuel pressure yet? Pumps don't like sitting with modern fuels it seems, but not sure where you're located and what type of fuels are being run.

That's all I've got at the moment. Other than to say welcome to the forum too!

Good luck.

Paul

 

All I can add is that injection timing's nothing like ignition timing- if you get the order wrong, the engine
might idle a bit worse, but it'll certainly run well enough for 'move it around' duty.

t

 

Would not hurt to see what the computer knows, check the codes.
Sounds like you have spark.
Have you proved that you are getting enough fuel into the cylinders?
Try using a spray bottle with fuel into the Throttle body.

 

You could manually activate the injectors by shorting the colored wire side of the injector conector to ground (key on) for a tenth of a second (for the ones you can reach).
This would put some fuel into the intake as well.
I'm assuming all the 12v wires to the injector connectors are Red.

 

The 5.8L engine has orange topped 19 lb/hr injectors. Hard to say how that is going to work on a computer programmed for 14 lb/hr. The engine should at least start and run under low power conditions.

 

Are you using a complete harness(engine to PCM) for the CV 5.0 or just the engine portion? You cannot mix portions of an SD and MAF harnesses that won't work at all, and you cannot use an SEFI PCM with an SD wiring harness that won't work either.

 

Thanks for all the insight thus far, everyone!

Actually, I've not checked that the distributor is stabbed correctly, so that's a good theory that the plug wires are wrong. I'm going to confirm that #1 cylinder matched the #1 cylinder on the distributor, as well as use some starting fluid to try and get it to bust off that way -- at least that'll confirm that my spark is all correct. I'm using the Crown Vic harness & computer, both the harness and ECU that originally came with the F250 were burnt up. I have the fuel pump wired to constantly run with key power, and am getting pressure at the rail. I've not hooked up a gauge to verify pressure level, however. The truck's been sitting a few months with about 1/8 of a tank of gas in it, and I'm in Houston TX.

This is what I believed as well. I had figured that even with cylinders 3/5 and 4/7 not being swapped it still would've wanted to run at least a little.

I am smelling fuel, so I am getting at least /some/ fuel into it. A few weeks ago I was able to run the truck on brake cleaner with the SPOUT connector disconnected and no injector harness, so I know the truck "runs." I'm going to try this again to ensure that I got the spark wires at the dist correct.

Aha! This very well might be the problem. I know first hand that a set of 19 lb/hr injectors wouldn't run at all on my Crown Vic back when the Crown Vic was still 302-powered. I'm going to swap the 14 lb/hr injectors over from the Vic onto the truck, hopefully we're on to something here!

I'm using both the harness AND computer from the 5.0 Crown Vic. The Crown Vic was SEFI, but *not* MAF. These cars were still speed-density despite being sequentially-injected.

 

Yes the same setup was used in Mustangs and other Fords as well, so as long as you have a complete harness and matching computer it should work. But that means your batch fired trick won't work either because the computer only fires injectors 1 or 2 once per sequence instead of every second pulse.
So make sure injectors and plugs are setup for the HO firing order, and make sure the distributor is stabbed correctly for #1 cylinder on the compression stroke. And just because we don't know your level of familiarity with these motors, #1 is passenger side front and the cylinders are numbered 1-4 front to back on the passenger side and 5-8 front to back on the drivers side, distributor turns counter clockwise.