I have a 1989 trans am with a 305 5 speed trans with 1406 carburetor and a accel distributor. The problem I am having is that the car is not getting gas to the carburetor when the car is running. The car primes and I tested the prime with a test light and can hear it when I turn the key. I jumped the wires to test prime and I jumped the wires to test the fuel pump. Both of these tests sent fuel to the carb. However when the relay is plugged in the car will prime sometimes and then the fuel pump wont come on when the car is running. The car has a new fuel pump relay and new oil pressure sensor. The car has a replacement ECM the previous owner installed. The wiring was played with for the carb swap at the distributor, electric fans, and fuel pump relay but I went over the wiring and made sure the wiring for the fuel pump fuse was solid at the connector. The car has 15, 22, 42, 54 codes on the SES light. What am I missing here to get this car fuel?

 

If the stock distributor was replaced with an aftermarket, the ECM will need to receive reference pulses from that aftermarket replacement just like the stock configuration. Without that, the fuel pump relay will operate for only two seconds and shut down.

The rest of the codes are the result of similar oversight in the removal of the EFI system.

 

Could you maybe let me know how to do that? Its strange because the car never had this problem until now. However the previous owner kept the stock distributor but I changed it because the car was running funky and it was really old and crusty. The author of the EFI to carb swap article picked up an accel so I followed that but maybe I messed up on the fuel delivery part of the swap. I did NOTHING to the fuel pump wiring for the swap I only added a regulator for the fuel pressure so I believe I need to do what your suggesting I'm just not sure how. I could be wrong but my block doesn't seem to have support for a mechanical fuel pump as far as I can tell but I could be wrong.

 

The '89 block probably does not have the fuel pump mounting provision machined, but just left as cast. As a result, a mechanical pump bolted to the engine may not be a practical option. The regulator installed can work just fine so long as it reduces pressure to around 3-5 PSI. The problem is that the fuel pump needs to run, and the pump wil only run if the ECM receives reference pulses from the HEI module in the distributor. The exception is the two-second prime cycle initiated by the ECM when the ignition is first turned on.

The fact that the ECM also has a "42" error code also points to a missing signal from the distributor. There should be a purple/white wire from the distributor to the ECM carrying the reference signal.

The code "15" is likely also the result of disconnected/failed/missing coolant temperature sensor.

The code "54" is probably due to incomplete wiring from the fuel pump or its inability to fuction during a run cycle.

 

I found the wire you are talking about. Right now the car is using the white wire for the tach and the red for the power to the distributor and that's it. That whole connector with the purple wire in it is hanging out dangling there. Where can I connect the purple wire to so I can get the pulses I need? Would I have to go back to a stock distributor if getting the pulses is not possible? I still have everything so I can "undo" the swap but Id rather not if possible.

 

Im thinking maybe I can steal power off another wire from the car to power the fuel pump? My understanding is that all the pump needs to run is 12 volts to the tan/white wire. I know I can jump it off the orange wire and just have the fuel pump operate on a switch and then "problem solved" but I would prefer to try a more stock or more elegant solution. Im not to afraid of cutting up the harness a little because the previous owner got busy installing a crappy autozone fan relay switch and cut a bunch of stuff doing that so the wiring harness isnt exactly in good shape anyway. I tried getting power from the thick pink wire which I thought only had power when the key was in and turned to the tan/ white wire at the fuel pump relay connector and it worked until I turned off the car and pulled out the key and the motor was still running. As of right now Im kind of confused on how to get the purple wire what it needs to work or if that's even possible. Im not even 100% sure if that will fix it because that purple wire has been unplugged for a while now and the car has been running like a top before I got hit with this fuel delivery issue. I also still dont understand how the connector can get jumped and run the pump but with the relay connected it wont work. My thought process is that the relay lets the car prime by connecting the green wire and then once the car runs the relay switches to connecting the orange and tan. Is it the ecm once it gets those distributor pulses switching over the relay? Would I be able to recreate what the relay needs to switch? Could I connect the purple to something to get the pulses if that is possible like the wire for the tach??? Not very good with electrical at all but trying my best here. I can take a bunch of pictures if that helps.

 

I recommend acquiring a shop manual / wiring diagram and fully understanding the system you are working with before sending power every which way.

Assuming the fuel pump relay sends power to the fuel pump, I'd retain this functionality. If the ecm grounds a wire to do this, use another relay to send a ground and activate it from a key on source.

 

I'm confused. I thought the ECM looked for oil pressure after the initial start from the pressure switch (not to be confused with the sender for the gauge)? If it did not have oil pressure it would not let the engine start, going by how my TPI was. Why I ask, is he says that it ran fine before. He then changed the fuel pump relay, dizzy, and oil pressure sensor. Now it will prime (new relay-check), Dizzy not wired up correctly (unchecked) and evidently this will cause a no start issue also, and did you replace the oil sending unit or sensor (one goes to gauge, one is for the ecm)? Sound like possibly the oil switch has an issue (IE - bad, wrong one, etc.) and the dizzy wiring just needs addressed.

 

This is why a shop manual and/or good schematics are important. The oil pressure switch is a redundant path for power to the fuel pump as a backup to the ECM and relay. The ECM does not have any input from an oil pressure switch for any purpose.

The primary system for fuel pump power is the relay. The ECM energizes the relay for two seconds when the igniton switch is turned on. This primes the system and builds the required pressure for the injectors to operate. Without that, an engine would have to be cranked long enough to build oil pressure, whereupon the fuel pump would receive power through the closed oil pressre switch and finally allow the injectors to deliver fuel to the engine. The RELAY is intended to carry the full load (current) of the fuel pump. The auxiliary oil pressure switch can operate the pump, but will have a lot shorter service life than the relay if it is always carrying the fuel pump load.

Fast-forward to the point in time where the system is downgraded to a carburetor with a bowl, the engine will start and operate with the fuel that is retained within the bowl and therefore does not need the ECM to prime the system. Once the carbureted engine is started the fuel pump would operate the in-tank electric pump via the oil pressure switch - for a while. Eventually, as mentioned before, the oil pressure switch will fail from carrying the full currnet of the fuel pump. That seems to be where we are at today, and the ECM fuel pump voltage input is now low enough to set a code "54" from the anticipated degradation of the oil pressure switch from constant use. Without distributor reference pulses being sent to the ECM, the relay will never close when the engine is running.

 

The Accel distributor should have a 5V output to signal the ECM. If not, it is the wrong distributor for your system. If you want to have centrifugal and vacuum advance on the distributor and not use the ECM for timing control, a 8360 distributor MIGHT work but the tach output of the distributor will also have to be routed to the ECM ignition reference input through a resistor, probably about 22-39KΩ, to feed the appropriate signal.

 

The distributor is wired up correctly as far as I can tell. I followed the carb swap How To on the site. The tach works and the car ran great up until now. I changed the oil pressure sensor above the oil filter. I installed Duralast Oil Pressure Switch PS207. I thought the sensor by the distributor and the one by the oil filter were exclusive. If I do have both I cant find the one by the distributor though which is weird. If I find it I will replace it and update here.

 

I got the car with the 1406 on it and put the accel on myself (Part # 59107C) on holly's website. If I cant end up solving the problem would the best course of action be swapping it back to TPI? Id prefer not to because the previous owners hacked up the wiring so im not sure if I would even be able to swap it back.

 

The oil pressure switch behind/left of the distributor would typically be used as the backup for the fuel pump relay. That changed in 1990, IIRC.

If the wiring has been hacked it would be possible to rewire the fuel pump relay to get its operating coil power from the pink/black ignition wire, coil ground to chassis ground, and power and pump connections in the stock configuration. This would operate the pump relay in RUN or START on the ignition switch, but not in the ACC position.

As long as the tan/white wire for the pump is still also connected to the ECM pin B4, that should prevent the code "54" from setting.

Make sure the coolant temperature sensor which was originally at the front corssover of the TPI intake is connected to the ECM harness, and that should eliminate the code 15. It is likely there is a port in the aftermarket intake to mount the sensor, or it can be installed in one of the unused ports in one of the heads.

The solution to eliminate the code "42" was described earlier.

 

The oil pressure switch by my distributor doesn't exist I dont think.

This a picture of my distributor hole and Im not seeing any oil pressure switch. Im sure I have the completely wrong intake but also im not seeing a connector for the switch as well. Maybe its tucked somewhere. There was a nest of wires shoved behind the engine that I found today I never realized it until now. I took a wire and spliced it into the wire for the tach, soldered in 35k ohms resistors and plugged it into the purple wire and it worked. Im not sure if it is 100% fixed I will do more investigating tomorrow.



This is a little off topic but I would like to thank you guys for your help. After taking everything you guys said into consideration I got the car running on its own with the fuel relay. I work par time at a school and they were having a trunk or treat. For anyone who doesnt know a trunk or treat is where people decorate their trunks and park in the school parking lot and give out candy to the students. I decorated the car with my gf and we gave out so much candy. I got so many compliments on the car people loved it and we gave away so much candy to the kids. Thank you so much guys for your help. Couldnt have done it without your suggestions. (I tried to dress the car up as a ghost lol)

 

Nice. Right On, for being a giver... The OPSU should be down by your oil filter then. Good job figuring it out, and great help as usual from Vader!

 

Ops can go here or above oil filter if block is tapped

 

what is ops? Im confused because earlier in the thread some one mentioned there was a oil sending unit or sensor. Are they the same thing? if not how can one go by the distributor or by the oil filter. I have the one by the oil filter but I think maybe that one is for the gauge only and not the ecm? Do I need both?

 

Early years had a oil pressure switch and gauge sender separate.
later a all in 1.