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Frustrating 454 XL TBI Issue

390Express

Regular Contributor
Chased my ass for a month last year, and figured out that the top half of my STBD TBI was not operating properly, swapped my PT TBI to the STBD motor, and it ran perfectly. I rebuilt the damn thing before I put it on the STBD motor, which already was running poorly. Over the winter I completely disassembled the upper end of the Port motor, found a bent push rod and three leaky valves. Fixed all that nonsense, put it back together, and had the same intermittent stall issue that the STBD motor had the year prior. Re-swapped out the upper TBI (that had been rebuilt with new gaskets, and new injectors), and BOOM, ran perfect...

So, now I know that I have an issue with one of my TBI units, but I can't figure out what it could be. The unit was rebuilt with new injectors and new fuel pressure regulator (diaphram and spring), and still won't stay running. Motor runs for 30-45 seconds, then starves for fuel, as fuel pressure stays constant.

I'm at a loss... could there be something wrong with the casting? I leave the base of the TBI in place, and all sensors, fuel lines, filters, etc., and swap only the upper part of the TBI with the two injectors, with brand new injectors, and brand new regulator, the thing still acts up.

Any idea what could be causing the issue? Is there a breath hole somewhere that should be cleared out? Some casting issue or passage issue that I should be aware of?
 
Here's an update for anyone that comes across this issue... I got it figured out.

My initial TBI rebuild was with factory Borg Warner/GM injectors, and worked great. The issue is, Borg Warner stopped producing the GM TBI injectors, and Partscraft (or whomever supplies Partscraft) bought them out. There are two model injectors, one for the high PSI TBI, and one for the low PSI TBI. At O'Rielly Auto Parts the part numbers are TJ17 and TJ11. The TJ17 injectors are for the high PSI system, and the TJ11 are for the low PSI system. My issue was, they don't have the proper info for the injectors, and O'Rielly gave me TJ17s for my engines, but they needed TJ11s... Brand new injectors, for a 454, as described through their system and others, did not work... It was only a hope and prayer, and a strong desire to not put it back together the exact same way that I took it apart, that caused me to give the TJ11s a try. Put the TJ11 injectors in the boat, BOOM fired right up and ran perfect.
 
Thank you for your input. By chance was your 454 from 1996 or 1997. My understanding is it was different for those two years.

Mine is a 1996 vintage. Be careful basing your analysis off of the engine year only. I'm sure there is going to be some mid-year turnover, with marine engines.

The best way to tell which injector you need, is to determine which PSI your system is supposed to run off of, nominally. My system, nominally, runs off of 12-14 PSI. The newer "high pressure" style TBI (high pressure in quotes, because even the "high" pressure mid-90s TBI systems are fairly low PSI) systems run off of approximately 25 PSI.

Initially I was told that both systems use the same injector, and that the only difference is the rate of fire. Apparently, that information is incorrect.
 
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