I've been doing some searching but figured I'd ask a question here to see if there is a more specific response to save me time and money.

I recently purchased a 1991 305 tbi camaro. It was in pretty bad cosmetic shape, but mechanically seems pretty solid. It may or may not have been sitting for 1+ years, (based on pack rat turds etc in the engine bay), but I have checked things out, done a bit of work on it, and have been driving it the past two months and have had very little issues.

The reoccurring issues I am having deals with engine stalling/not starting intermittently.

The symptoms are:

1) Random rough starting
- Takes too long cranking to turn over occasionally
- Turns over but immediately stalls (usually after its been warmed up)

2) Stalling on sudden deceleration (from off ramps on highways etc)

3) Recently today, I couldn't get it to start and run for about 15 minutes. It just kept either cranking, starting then stalling immediately, or starting and idling for a few seconds, then stalling. On the way back when I finally got it started, it would randomly stall on the road (no change in throttle.)


Based on these symptoms, there are a few things I take that could be causing this.

-Bad Fuel pump
-Bad Pickup coil
-Bad Ignition control module
-Bad TPS
-Clogged EGR


I was initially thinking fuel pump, but when it was running, I didn't have a loss in power, and when flooring it, it behaved normally and drove well. I have not yet checked the EGR valve, but I don't think that would cause hard start/no start.

The things I've done within the past two months are:

-New plugs/wires/cap/rotor and oil change
-New Fuel filter
-New O2 sensor
-New PCV Valve
-Checked and replaced many vacuum lines to get rid of leaks (vacuum gauge reads good vacuum)
-Sea foamed engine
-New valve stem seals (it was smoking on startup but not anymore)

Also, the previous owner (who only had it for about a month before me, just didn't have time ot work on it) said he replaced

-Coolant temperature sensor
-Thermostat

(I checked and they both seem new)
Also, I have no engine codes.


So based on all the new stuff and work, I believe the issue is coming from either the Pickup coil, Ignition Control Module, or Fuel pump.


Does anyone have any more input on what they think it is? And if it is the pickup coil, should I replace the entire distributor instead, or is it not too bad to replace the pickup?

 

Unfortunately I haven't had time to work on my car, but the problem hasn't come up often except for yesterday afternoon.

With this time, the car would start and stall immediately, not start, or only idle for a few seconds then stall (pressing the gas would do nothing to keep it from stalling if it was idling.)

However, I was in a quieter place this time and was able to listen to the fuel pump priming. I didn't hear the fuel pump prime every time, and the times I did not hear it prime, it wouldn't start.

When it did start, but die soon after, I would hear it prime, but the priming noise was not a constant whine like I'm used to with my truck. The wine from the pump almost sounded as if it were "losing charge" or if the battery was dying when the pump was priming (which it wasn't dying). It would wine normally at first, then get lower pitched before it shut off (about 2 seconds each time.)

When it did finally start, the whine from the fuel pump was a constant, normal pitch.

I was going to rent a fuel pump tester (I have one that screws into a fuel rail, but the TBI units need a special adapter that I don't have), but my local parts store only has the kit, which is $110 to rent which I didn't want to throw down right now.

Does this sound like the fuel pump may be the culprit now (and not my pickup coil?) I would love to test the pressure, but I don't know where to get the adapter unless probably somewhere online, and I'll probably have to wait over a week to get it and then test it. It also seems like any adapter I've looked at that I can get is also around 30-60 dollars, and since the fuel pump is only 50, it would be better just to replace it instead of spend more to test if it's bad.

I hope taking down the fuel tank isn't too hard. I'm sure there is a writeup somewhere if I do a search. I may wait to replace the pump though because I need to replace my throw-out bearing soon, and I figure it may more convenient to take the tank out while I'm taking the transmission out.

 

Based on your description, you should investigate the wire harness from battery to fuel pump relay to fuel pump, INCLUDING the wiring in the tank, which is known to corrode. Some fuel pumps ship with the in-tank harness included. If not, the in-tank harness is typically about $20.

IF (big IF) the wiring is OK, then the in-tank pump is failing. You'll want to replace the pump and the strainer on the end of the pump. CLEAN OUT THE FUEL TANK. Rust and dirt particles are known killers of the replacement pump.

First Guess: The fuel tank job and the transmission job are pretty much non-related except that both require you to be under the car. You might as well verify the wiring and if needed, drop the tank now.

 

Thank you for the reply! I should have a chance to check some of the wiring today and see if that is the issue.

I thought when dropping the tank, I may have to have the rear axle hanging as low as it can be, and when taking of the transmission, I read that you need to have the rear axle hang and take off the torque arm bar (or whatever it is called.) I have to do a little more reading on how to proceed in both situations, but I've changed fuel pumps and transmission before in other vehicles so it shouldn't be too hard.

 

Just an update, I ended up getting an adapter to test the fuel pressure so I could use my own equipment and it didn't leak like the one I borrowed. The fuel pressure test about 10psi when the engine was cold and idling.

Apparently this is in the acceptable range, but I already had almost everything out of the way to take down the fuel tank.

I decided that since my pump was probably good now, I would return the precision pump I bought and buy an AC-delco one to put in its place.

I took everything down, the inside of the tank look quite clean, and the pump inside was a Carter pump. The pump sock/strainer was quite brittle and looked like it was filled with loose deteriorating paper. Also, the rubber line connected the pump to metal line was quite brittle and starting to crack. The wiring to the pump seemed good though so I left that alone.

After replacing the pump, the PSI with the AC-delco pump was at 11.

So the pressure increased slightly, but I don't think that was this issue in the first place. However, at least I know I have a good pump now so I won't have to deal with this for a long time. I believe the issue I was having is either from the ignition control module, or the pickup coil. Either way, I'll be replacing my distributor next if I still have the main problem after I get my transmission work done..

Unfortunately, I just found my input shaft on my T5 transmission is heavily worn because the pilot bearing was completely chewed up... Hopefully this will be a semi-quick and semi-cheap fix since I pulled the input shaft out already.