My Trans Am has been sitting for a long time. It wouldn't produce any fuel pressure, despite a working Walbro so I spent most of Saturday dropping the tank and replacing the pump/sending unit(a job I did not want to ever do again -- seriously, GM? have to drop the diff just to replace the pump?!)


Well, there's yer prollem! Ethanol can go to hell.

Fuel pressure returned after fixing the above, but the engine still cranks without firing. I checked spark with one of these lights - and it blinked, though I'm not sure how reliable that is.
Checked that the ecm was pulsing the injectors with a noid light, and it was.

The exhaust doesn't smell like gas and there's not even a hint of firing, just cranking air. Gas is over a year old so who knows, maybe it's that bad - though I would expect to smell it at least.

Confounding variables: one of my radiator fans is stuck on -- I'm guessing that the coolant switch between 6 and 8 is shorted, but haven't tested yet due to the location. yep. fan temp switch wire was shorting to the header.
I never know when the old 730 has given up the ghost due to some random electrical spike/bad ground/30 year old capacitors/whatever it is that kills these ECMs

 

You put in a new fuel pump , and then used gas over a year old

 

I noticed the following in another thread: I'm willing to believe these injectors are trash, but it seems implausible that they all became complete trash (ie, not even a little bit of fuel flow in any of them sufficient for a pow) instantly, when they all worked a year ago(which was many years after it had been sitting in the garage).

A friend suggested eliminating the fuel system as a variable by trying to start it on starter spray. Something I've never considered on an injected engine. Is that really doable/advisable with TPI?

 

Yes; it can be a viable troubleshooting tool. Disconnect the air filter housing at the throttle body, open the butterfly and shoot in a short burst of starter spray; have an assistant then immediately try to start the engine. If it fires and runs for a second or two, that's an indicator that you have spark at the plugs but no fuel delivery.

Be careful with the spray; it's highly volatile. Keep it far away from sparks/flames, and use just a small amount while trying to get the engine to fire.

 

If you have spark and air and it won't start you have a fuel problem it is that simple.

OK you replaced the sending unit that's good.

Did you also:
inspect & clean the fuel tank
replace the fuel filter
inspect & clean the fuel lines (compressed air and carb cleaner)
inspect and clean the fuel rails (see above)
inspect/clean or replace the fuel injectors.. the injectors you can try to soak in diesel / kerosene to loosen up any varnish
add fresh fuel (top tier fuel and add some injector cleaner (lucas, seafoam, or marvel mystery oil)

 

I'm fairly confident that the lines aren't gummed up for a few reasons:
- the old filter flowed just as well as the new
- 40ish psi at the Schrader valve (where before there was 0 because of that trashed in-tank fuel hose. once again: screw you, Ethanol/farm subsidies)
- Also to test I put a length of clear hose in line so I could visually confirm fuel flow and priming is near instant

Unfortunately, all signs do point to a problem between the fuel rail and the heads... I'm going to try it on starter fluid (any more tips on that appreciated - it makes me a bit nervous) to confirm before dismantling my intake to get at them.

As evidence of my mental sickness, I did just consider replacing the intake on a nonfunctional car with a Miniram "since I'm taking the intake apart anyway."

 

Don't be nervous , here's how to do it safely ;

Disconnect the rubber boot connected to the throttle body , open the throttle plates , spray a 1/2 second burst into the TB and then put the boot back on (doesn't need to be tightened , speed is of the essence here because the starting fluid evaporates very quickly) and crank the engine over . The only time it's dangerous is if you try spraying it into an open TB while cranking the engine , this can produce a flame out of the TB which of course could be a disaster .

 

OP you understand the alcohol in the fuel is not really an issue, the issue is you let the fuel go bad.

Alcohol evaporates leaving no gum/varnish
Alcohol is hydroscopic meaning it can absorb water. The water could corrode materials that would normally corrode if exposed to water (steel, cast iron) but the water would have no effect on plastic, rubber, stainless, etc.
If left sitting for very long period alcohol blended fuel can go thru phase separation. The alcohol (and any moisture it absorbed) can settle to the bottom of the fuel tank. The water could corrode materials that would normally corrode if exposed to water but not the alcohol.
Alcohol will not freeze. Back in day people used to add those little yellow bottles of "HEET" to their fuel to keep their fuel lines from freezing in the winter. We were adding alcohol, now because of blended fuel frozen fuel lines are not talked about.

Your picture tells a tale of fuel that has turned to varnish.
Old gasoline (pure gas or blended gas ) does exactly that. I see varnish all other the sock, fuel pump body, & even the electric harness. Not to mention the rubber line on the sending unit is cracked/ruined from old age.

When gasoline oxidizes the lighter solvents evaporate, the heavier compounds are left behind as varnish.
If you want to preserve /extend the life of any fuel you add a fuel stabilizer. The chemicals in the stabilizer slows down the oxidation process, which will keep the fuel preserved for 12-18 months.

Don't blame the fuel, that is like blaming chemistry for following the laws of chemistry... blame yourself for not storing the car/fuel properly.

 

Thanks for the helpful reprimand - consider me properly flagellated. You are of course correct that the fuel in the tank was nasty. The deteriorated rubber line on the sending unit is actually what I was blaming on ethanol since it disintegrated in the tank with maybe 10 miles on it, and I've heard rumors (unsubstantiated?) that ethanol is a solvent for rubber fuel lines. As soon as I can get a helper for cranking I'm going to give starter fluid a shot then start taking things apart again (hopefully not another period of months/years for which I'll again have to blame myself!) so I can get closure on this 20+ year project.

 

Alcohol can breakdown certain materials, yes certain rubber materials are on the list. Hopefully the new sending unit you installed has soft line material that is compatible with today's blended fuels.

still assuming 10 gallons of fuel E10 has 1 gallon of alcohol E15 1.5 gallons. 10 -15% alcohol blend is not going to hurt modern fuel system components.

 

I use either brake cleaner or carb cleaner as a test fluid instead of the highly volatile ether in starting fluid..

 

In news that will shock nobody given the evidence at hand, she fires right up on starter fluid. Guess I have a SouthBay order incoming.

 

Fires up instantly with a new set of 30lb injectors from SouthBay. Runs substantially more smoothly than it did last time it fired up. Presumably the injectors were getting pretty gummy by then. Now I just need to update the rom with the new injector constant.... and fix 42 other issues

 

30lb injectors from SouthBay????? What engine do you have in there??? 19lb for 5.0....22lb for 5.7

 

I have a 350, but I'm running boost and would like to eliminate the FMU. 30lb injectors aren't that large - they should result in a very slight reduction in duty cycle under vacuum and ideally a more reasonable max cycle under boost.

 

Gotcha. Seen that in your sig after the fact

 

sounds like you are heading in the right direction.. nicely done. now just don't let it sit for too long... if you have to mothball the project for a long time (past 18 months) drain the fuel and remove/clean/store the injectors.

I used to religiously pull my carb drain it, fog the bowls, metering blocks, & boosters with WD-40 and store it. then I switched to stabil and run the car for 5 minutes before I put it away. I still make sure I turn on the fuel pump every month to re-fill the bowls when I bump start the engine to alternate tension on the valve springs.