I would imagine a 454 4L80E combo could get it running. You’d have to adjust injector size and if I remember, there’s a displacement constant that can be adjusted. It’s been years since I’ve messed with it, so I don’t remember that well. It’s a fun learning experience for sure.
93 3500 Regular Cab - 502/Accel-Ram Swap
- Thread starter amsterdam96
- Start date
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Christian Steffen
I'm Awesome
It would have to be a pcm from a 96+ 454 truck i would imagine, since your engine appears to have multi port injection? I've never tuned a TBI computer but I'm guessing that it wouldn't run MPFI.
The issue with going to a 96+ pcm (might as well go all the way to 0411), is that your old sensors might not play well with a newer computer. Just something you may want to look into if you're really considering computer.
amsterdam96
OBS Enthusiast
I'll double check that it's MPFI but I can't go as far as taking out the injectors. Isn't the fact that it has two fuel rails, enough indication that it's indeed MPFI, like you said? Suppose I'm willing to swap to a 0411, (because it seems there's a lot of info on how to do this) & I find one that'll run a 502+4L80E setup, what would I have to buy? The PCM itself (0411), software, cables, sensors & potentially new wiring for the sensors? or are the old cables fine?
amsterdam96
OBS Enthusiast
Christian is under the impressions that PCMs prior to '96 would not run an multi-port fuel injected engine but a regular throttle body instead.
I'm super eager to play with the all the info that I hope to get from hooking up to my on-board comp, I'm just not sure if I've got the right stuff on the way. I just bought what I need for a physical connection and ProTuner installed on a laptop, So I'm gonna give that a shot. But in the meantime I'm trying to come up with a contingency plan.
You're suggestion as to the 4L80E + 454 solution still stands if I end up going with a carburator out of despair. But in the meantime I'd like to try everything to put this injection system to use.
Christian Steffen
I'm Awesome
It would be quite a bit of work, just a heads up, but the easiest route would probably be to get a harness and computer out of a vehicle with the 0411, since youd need to switch it to OBD2. One other thing I'm not sure about is if there is a crank position sensor in your engine. If not one would need to be added for a newer computer, which isn't easy. The next issue is the price of tuning software, for example hp tuners is about $400 ( I think?) Plus credits.
I would definitely call this a back up plan. If you can get the truck running on the old computer, I'd probably stick with it.
I think the confusion here is batch fire vs sequential. Batch fire will activate each bank of injectors twice per crankshaft revolution. Back in the day GM hadn’t figured out sequential port injection. That is where each individual injector fires at the corresponding time.
All the early EFI was like this until the LT1 came out. Performance wise, there isn’t much to be gained. I’m guessing GM never bothered with sequential port injection until the government squeezed them for better emissions.
If you didn’t have the 4L80E, the go to ECM is the ‘730. These were found in early 90s port injected vehicles. F bodies, FWD cars, ect.
The next step would be GMs first PCM, and the preferred one here is the ‘427. This has been pretty well hacked.
While a much better PCM, I think the ‘411 would be my last choice for this setup. It’s going to require some parts that I’m not sure exist. The MkVI BBC has the required timing set with 4x crank wheel and cover with the crankshaft position sensor. I don’t know enough about BBCs to know if these parts can be swapped over.
For my money, I’d use the equipment you have. Use TunerPro to find out if you can any faulty sensors. It seems like you are still guessing about your fuel pressure. Invest in a test kit. If you plan to stay EFI, you will always need it. It sounds like you have verified with a noid light that the injectors should be pulsing. Depending on how long this has sat for, maybe the injectors are gummed up. They may need to be removed and an ultrasonic cleaning. Worst case, a new set of injectors won’t set you back too far.
This truck is simple. You can get it running. Don’t give up on it.
All the early EFI was like this until the LT1 came out. Performance wise, there isn’t much to be gained. I’m guessing GM never bothered with sequential port injection until the government squeezed them for better emissions.
If you didn’t have the 4L80E, the go to ECM is the ‘730. These were found in early 90s port injected vehicles. F bodies, FWD cars, ect.
The next step would be GMs first PCM, and the preferred one here is the ‘427. This has been pretty well hacked.
While a much better PCM, I think the ‘411 would be my last choice for this setup. It’s going to require some parts that I’m not sure exist. The MkVI BBC has the required timing set with 4x crank wheel and cover with the crankshaft position sensor. I don’t know enough about BBCs to know if these parts can be swapped over.
For my money, I’d use the equipment you have. Use TunerPro to find out if you can any faulty sensors. It seems like you are still guessing about your fuel pressure. Invest in a test kit. If you plan to stay EFI, you will always need it. It sounds like you have verified with a noid light that the injectors should be pulsing. Depending on how long this has sat for, maybe the injectors are gummed up. They may need to be removed and an ultrasonic cleaning. Worst case, a new set of injectors won’t set you back too far.
This truck is simple. You can get it running. Don’t give up on it.
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After rereading it definitely sounds like the injectors may needed to be cleaned or rebuilt. Until you are certain that you have at least 40psi of fuel pressure under load, we are all just guessing.
Post some pics of the missing or disconnected sensors and damaged wiring. We can help get it back together.
Christian Steffen
I'm Awesome
I agree with this, it would be a lot of messing around. There is a guy on ls1tech that made a mark IV run off an 0411, but it took a good deal of work.
amsterdam96
OBS Enthusiast
Thanks for giving me hope regarding the PCM trouble.
amsterdam96
OBS Enthusiast
The engine is only running on two cylinders (Cyl 1 & Cyl 3), we have spark, we have plenty of fuel pressure & the injectors aren't blocked. However if we swap them over to the other side (Cyl 2 & Cyl 4) she doesn't run. We decided to do a compression test because we were worried about the condition of the engine, the compression test showed fine results however.
The spark plugs on the left hand side were wet however (I was worried we were 'flooding' the combustion chamber). It took my friend one look at the fuel cell to realise that there's a compression tank added in after the first fuel pump and another fuel pump after the compression tank. Since this car has had some kind of 'sports' history. I'm assuming that the fuel pressure is what it used to be when it still had a higher voltage spark & dry sump oil rig. The culprit right now is that we PROBABLY have something like double the amount of fuel pressure that we need. So hopefully later this week we'll be able to borrow a fuel pressure test kit & we'll find out how excessive the pressure really is.
We're intent on fixing the mechanical issues first and then focussing on the processor. (I do however have a serial 9 pin adapter on the way and TunerPro rt installed) Let's see if I can get a data-log with no experience and a pre OBD computer.
I'll keep you all posted! Thanks again for the support!
The spark plugs on the left hand side were wet however (I was worried we were 'flooding' the combustion chamber). It took my friend one look at the fuel cell to realise that there's a compression tank added in after the first fuel pump and another fuel pump after the compression tank. Since this car has had some kind of 'sports' history. I'm assuming that the fuel pressure is what it used to be when it still had a higher voltage spark & dry sump oil rig. The culprit right now is that we PROBABLY have something like double the amount of fuel pressure that we need. So hopefully later this week we'll be able to borrow a fuel pressure test kit & we'll find out how excessive the pressure really is.
We're intent on fixing the mechanical issues first and then focussing on the processor. (I do however have a serial 9 pin adapter on the way and TunerPro rt installed) Let's see if I can get a data-log with no experience and a pre OBD computer.
I'll keep you all posted! Thanks again for the support!
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