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1988 Firebird Formula 5.0 TBI will not start

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Old Dec 19, 2018 | 08:14 PM
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xbazzarex's Avatar
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From: Mohnton, PA
Car: 1985 T/a, 1988 Formula
Engine: LB9 and LO3
Transmission: 700R4 and 700R4
Axle/Gears: 9 bolt 3.27, unknown
1988 Firebird Formula 5.0 TBI will not start

Good evening i have an 88 firebird formula with the 5.0 tbi engine, i had just gotten home, pulled into the garage and was revving the car abit (my two year old loves the sound), kicked it up to around 3000 rpms or so and the rpms then dropped and the car shut off. i was not redlining the car or even revving it long maybe 10 seconds. now the car sounds like its going to start but dosent actually fire up. so far ive checked all fluids, re charged the battery as it was low, replace the alternator(had a new one just hadn't gotten around to it yet). at this point i am thinking it could be the fuel filter is clogged. ive had the car around a month and it was not to well maintained before i picked it up. any thoughts on this let me know, i have quite a few new parts ive picked up for it and haven't gotten around to installing so im not to worried about changing some stuff out.
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Old Dec 19, 2018 | 08:46 PM
  #2  
TheFryer's Avatar
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From: Nocona Texas
Car: 1988 Iroc-Z
Engine: 5.0L LB9
Transmission: rebuilt 700r4
Axle/Gears: 2.73
Re: 1988 Firebird Formula 5.0 TBI will not start

being a TBI, pull the air filter assy off it and have someone turn it over and see if you have fuel spraying out of the two injectors. if not then cycle the key on and off a few times and listen for the fuel pump to kick on and off. if its not then look at the relays and fuses, if it is then look at the filter. if your getting fuel to the injectors the next thing would be to check for spark.
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Old Dec 20, 2018 | 01:56 PM
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Re: 1988 Firebird Formula 5.0 TBI will not start

Originally Posted by xbazzarex
...... and was revving the car abit (my two year old loves the sound), kicked it up to around 3000 rpms or so and the rpms then dropped and the car shut off. i was not redlining the car or even revving it long maybe 10 seconds.......
Check the timing .

As in , rotate the crankshaft till it's a few degrees before top dead center on cylinder number one's firing stroke , and then make sure the distributor's rotor is in fact pointing at the spark plug wire leading to cylinder number one's spark plug .

I'm telling you to check this because free revving a high mileage not well maintained engine can make a worn and loose timing chain jump a tooth or few .......

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Old Dec 22, 2018 | 12:07 AM
  #4  
xbazzarex's Avatar
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From: Mohnton, PA
Car: 1985 T/a, 1988 Formula
Engine: LB9 and LO3
Transmission: 700R4 and 700R4
Axle/Gears: 9 bolt 3.27, unknown
Re: 1988 Firebird Formula 5.0 TBI will not start

thanks for the input so far, fuel is getting to the injectors so no issue there. Timing is adjusted, it was off. but still not firing up. the battery was low again and i dont have an explanation for that. any other ideas please let me know.
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Old Dec 22, 2018 | 12:20 PM
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Re: 1988 Firebird Formula 5.0 TBI will not start

Originally Posted by xbazzarex
.........Timing is adjusted, it was off. but still not firing up........
I think you misunderstood my post .

If the distributor timing was off , and off by an amount that an engine that ran before the free revving incident still won't run now , it's a high probability that your timing chain has in fact jumped , and no amount of adjusting the distributor is gonna fix that . How much did you have to move the distributor to get the rotor to point at cylinder number one's spark plug wire , with number one set to TDC of it's firing stroke ?

If your 100% certain you have spark , an injector pulse (you did do a noid light check on both injectors , yes ?) and proper fuel pressure to the TBI unit , your next check will need to be a compression test of all eight cylinders , and report back the results here . I realize you won't be able to warm the engine up first as is customary when doing a compression test , but a cold cranking cylinder pressure test will tell us whether your timing chain has jumped or not .

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