My '87 302 Bronco will not fire. My timing is correct and the only Key on Engine off code is an out-of-spec TPS reading. The reading is 1/2 volt lower than it should be with a closed throttle. As I open it up, the reading goes to 4 volts. It isn't a WOT condition. I don't think this is my primary problem. I don't have a puff of smoke or a pop to indicate that it's getting fire and gas in any cylinder at the same time. The timing is correct and the plug wires are correct. The ignition module tested ok and I see spark if I lay the plugs against the frame. I know this isn't a perfect test, but keep reading...

The engine will turn over a few times rather slowly, but not so slowly that it shouldn't crank...then it'll hang. If I let it sit a few minutes, it will turn over a few more times....and it'll hang again.

I took the serpentine belt off thinking an accessory was locked up and it made no difference. I didn't hear any noise that would make me think I'd broken a cam or timing chain. I removed the spark plugs to see if I could find a particular cylinder causing the problem. The hanging continued as I removed plugs 1-7. These plugs were completely dry. When I removed plug 8, the engine spun freely, but it spewed gas out of the #8 cylinder. I think the "hanging" I've seen is occurring on the compression stroke on the 8th piston. It's trying to compress several ounces of liquid gas. Is it possible that a fuel injector has failed so that it offers no resistance to fuel flow? Can it be effectively blown open so that it gets all the gas while the others are starved? The engine can't run because the only cylinder with gas is completely flooded.

My next step is to drain the oil/gas mixture, fill it with new oil, and remove/inspect/replace the fuel injector from the #8 cylinder. Unless...one of you has a better idea. Does this make any sense? Can you think of another failure that could cause these symptoms?

 

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pull vac line off of pressure regulator if gas is present that part is bad. also check fuel pressure at the rail. do you hear the fuel pumps come on when you turn the key on? you might also make sure the battery is good an charged and the terminals are clean and tight.

 

As Kem said, check fuel pressure at the rail. If the #8 injectior is leaking down (as your description would suggest) it will be obvious by the significant drop in pressure a short time after having the key "ON". Fuel system leak down from normal (about 35-45 psi, key on engine off) should take a few hours. If the injector is holding and the pressure remains normal at the rail, the injector may be openiong but sticking when its supposed to be closing. Either way it sounds like an injector-related problem but the condition could feasibly cause the FPR to fail as well.

There is nothing in the system to keep fuel pressure from the pump from reaching all of the injectors equally at the rail.

 

Several of you suggested I take a look at the fuel pressure regulator. A gentleman on the F150 site posted that he'd seen the identical symptoms (#8 cylinder filling up with gas) caused by a bad fpr. When I pulled the vacuum line off the fpr with the ignition on, gas poured out of it. I replaced the fuel pressure regulator, drained almost 3 gallons of gas out of the oil pan, refilled it with cheap oil, and it ran fine. I let it warm up to operating temp for a while and changed the oil again and it seems to have suffered no ill effects. Thanks to all who posted and solved a puzzling problem for me. I still don't understand why the problem only appeared on the #8 cylinder...but I'm back on the road.