I just put a 350 into my 91 z28 (orig 305) and it ran for like a week then one day it just died. Ever since, it will fire up for a second or two then it just dies. I have tried almost every thing ( I think) Any suggestions? I ahve tried running a differetn computer, checkign the wire connections, and harness for visible deformations. Any thoughts woudl eb greatly appreciated

 

Check the fuel pump, fuel filter. The tpi setup will turn the pump on to prime the system. But it takes the oil pressure sending unit/ fuel pump switch to keep the pump on.

 

False. The oil press. switch is merely a failsafe if the relay dies.

Check for a vacuum leak. When I put an AFPR on my bird way back, I had forgotten to re-attach the brake booster vac. line. The car fired, revved and died 2 seperate tries.

Also, make check your minimum air setting (idle speed with the IAC fully seated). Check your TPS voltage, make sure the IAC is still working, too. Just a few thoughts...

 

My Bad!!, so check the relay. Sounds like its getting an initial supply of fuel and then running out. My Old T/A TPI did this, thats why I suggest checking it out.

 

No big deal bud. It's really a very common misconception.
In fact, just a fyi (if anyone cares), the oil press switch jumps (when closed above 5-10psi) the power in (to the relay) to the power out to the fuel pump. Essentially, it bypasses the relay but, the relay is primary power source controlled by the ECM (the ecm grounds the relay). In the event the relay fails to make contact, the oil press switch will supply power to the FP after it reaches X-psi oil pressure.

 

That’s interesting; I was taught that the Oil press switch SHUTS OFF the fuel pump if the oil pressure drops below 5 psi to protect the engine from damage. I wish I had a wiring diagram right now.

 

Thats what i thought as well, didn't think it was a back up for the relay???????

 

try i guys, see if your car will run with the oil press. switch unplugged, i will do it tommorrow, i am pretty sure it will NOT run

 

Feel free to try guys. Your car won't miss the switch at all.


Here's a diagram of the switch wiring.. http://www.deadbird.org/imagesold/tpi3.gif

This is my bud's '72 350 Chevy truck. I put an 88 GTA TPI on it, there is no oil pressures switch because I cut it off (no provision on a '72 block for it)... runs just fine..

 

I just did a search for “fuel pump relay oil pressure”. It came back with over 400 threads.

Here is what I learned:
The fuel pump gets power from 2 sources, the relay and the oil sender switch above the oil filter. The computer triggers the fuel pump relay for 2 seconds. Once 4 psi oil pressure is reached, the switch in the oil sender closes and sends 12 volt to the pump in a parallel path with the relay.
This makes me think the oil switch is bad.

Hey deadbird, Thanks for posting that schematic. The TPI looks sweet mounted inside that P/U. Nice of you to help out your buddy with the swap.
I was wondering if:
1. Did you use the stock GTA wiring harness or aftermarket?
2. Was the ECM PROM stock GTA programming or aftermarket?
This info might help us understand jimmysauter problem. I don’t have a Fuel Injected car so I can’t try to duplicate this problem.
ALSO 91 ECM might be different then 88 as to how it's programed.

 

Well, I realize everyone has their own interpretation of how it works and alot of other are just plain confused due to bad information. This ramble is just mine from a little research and having completely rewired my 'bird and the '72.
The TPI in the truck is a MAF setup running the stock PROM and stock harness. The ECM did work but, not correctly. It would not go into diagnostic mode and it stopped controlling the IAC. It was replaced with one from AZone and now works fine.
The ECM harness also came with the TPI. I simply modified the harness to hide wiring and eleminate the oil press switch since it isn't needed for operation. The interior harness is from 3 different v6 camaro's spliced together to make a complete harness.
What's actually in the engine ? not a clue but, it seems to not irritate the stock programming (because of it being MAF TPI and probably not to wild of a motor). It did run like crap (rough.. as if it had a fairly large cam) initially but, after some general tuning and paying attention to hand turning the motor, it was found there was a good amount of slack in the timing chain causing enough retard to the cam to make it run rough (the chain had enough slack to touch the block). After a double roller chain swap, it runs very smoothe.
I have also modified the stock tank to accept a OEM type in tank pump.

As far as the ECM & fuel pump goes, they are all wired the same.
Here's the diagram for a 91 TPI FP
http://www.deadbird.org/z/ecm91.gif

The presence of the switch is irrelevant to the ECM operating the FP relay. Since it is in parallel, once the relay is grounded by the ECM, the circuit is complete. There is no function to the switch once the relay is closed.

It is just the same as having to switches on the positive side of a light bulb, one is pointless once the other is on. Some follow-up feedback from jimmy would be useful to this as well...

 

thanks for the help, We got the car running but it now dies randomly. So, it'll drive around for a while then die. It then won't start for like 5 min to 45 min then it'll run again??? so I'm still trying to figure it out.

 

Try replacing the ignition module in the distributor.

 

we put on a distributor from a different running car ( we put a dfi into that other car) in and it still acts the same. Another condition is that we can keep the car running by squirting starter fluid in the Throttle body, which again could be a faulty module from the distributor ... so we'll try replacing the module in the distributor

 

That sounds like a fuel issue.... did you check your fuel pressure. Maybe your pump is getting hot after driving and cutting out.... just an idea. GM isnt known for having good pumps

 

Bad as I hate to say it....fuel pump.

 

The next symptoms we have is that we can keep the car running by squirting gas in the intake. Also, we pulled off the fuel rails and cranked the car over and only the right bank of injectors were firing. How much Pressure does the fuel rail need to have?

 

we pulled off the fuel rails and cranked the car over and only the right bank of injectors were firing.
That could be a fuse problem. The injector banks are powered independant as the fuse panel. Remove the fuses to inspect, so many times (lazy) people just look at them w/o actually pulling (because you can) and think they are alright. The ECM only controls the ground to them.
It could also be fault in the wiring. Either at the union where the wiring splits to the individual injectors or at the ECM plug.

How much Pressure does the fuel rail need to have?
Absolute minimum (IMO), 35psi. Fuel pressure should rise with throttle/load to the engine as well (or drop in manfold vacuum.. same difference)

 

You have an electrical problem. Do you have a Volt-Ohm meter for troubleshooting?

 

We figured it out-- One of the fuel injectors had an intermitent short in it so it was shutting the left half of the motor off when it would short out.

Thanks for all of the help, I was pretty sure that it wasn't a major problem but we just had a heck of a time narrowing it down. Thanks again. -Jimmy