In Need of Help with 1989 PROM Chip

[Jonald]

Hello - I’ll try to make this post not too long-winded. For many years I’ve been trying to get my 1989 Chevrolet c3500 7.4l to pass emissions. Sometimes it passes, most of the time it does not. Much diagnosis and many parts thrown at her. Discovered through this forum it’s had the wrong PROM chip (ANTY). Bought a few blank chips and a programmer, and burned a new chip(AKUN). When I installed the new chip, the truck started and sounded like it was running on less than eight cylinders, then it died and will not start again. Diagnosis tells me no fuel. Through testing, my fuel pump does not run when I turn on the key, but I can apply 12v through the wire harness and it comes on. Injectors fire when voltage is applied through the harness, just not getting the fuel. I understand this is a by-pass system and by-passes the ECM until the parameters are met. Does that mean it doesn’t use the ECM at all until those parameters are met? Or does it use a base tune to start? I broke the original ANTY chip when trying to release it from the holder, so I cannot put the old chip in to see if that was the issue. There is also the possibility that I bought and burned the wrong chip. I used a M2732A 21v and the AKUN tune from this forum. Before the chip swap the truck had no issues starting or running. At this point any advice is good advice. Thanks.Questions:
1.) Did I use the correct chip for the tune?
2.) Is the ECM/PROM completely “by-passed” during starting.

[In-Tech]

Very common smog problem with ANTY.

Double check chip orientation. Dimple in chip needs to match dimple in holder.

[stew86MCSS396]

I can vouch that inserting the PROM in backwards caused the fuel pump to not operate. The owner of the vehicle jumped the gun and changed the fuel pump only to be disappointed by the outcome. This kinda stemmed from installing a zif adapter with the handle away from pin 1 due to some kind of interference issue with the handle and the emulation cable.

[Jonald]

Thanks for getting back to me. I checked the orientation of the chip. I believe it to be in correctly. Also, the ANTY chip was the one with the wrong tune for my truck. Curious if there is a "smog" or "87oct" tune for AKUN? Thanks.

[stew86MCSS396]

Can't speak for the M2732a 21v but which burner do you own and do you know if it's able to program those PROMs???

[Jonald]

I used a Willem Prog PCB6e-2019. I had to resurrect an old desktop pc to be able to use it. But pretty sure it programed the chip. At least it said it did after a conformation. Anyways, not sure if the chip is the issue. I pulled a chip (ACLX) from the salvage yard over the weekend. It should be similar to the ANTY chip I took out, it is for a 1987 7.4l 3-speed Truck. But it's still not getting fuel. Going to do more diagnosis this week. Problem started only after the chip swap with the "burned" AKUN chip. -

[TriumphR3]

Maybe faulty oil pressure sensor/switch. Typically there is 2. One for gauges, one for fuel cutoff.

[Jonald]

Those were my next items to check off.