1989 TPI MAF formula
Rebuilt 355, pretty stock stuff eg: cam, compression, oil system, heads, etc.
Parts changes: 1.6 roller rockers, 30" valve seats ( Vizard ) Stock injectors cleaned and flowed by Kinsler=good
Replacement MAF ( Advance/Microtech)

Vats operational, bypased lock cylinder with resistor

Ran fine, besides lower idle vacuum/slightly rough idle.

Swapped out stock FPR for BBK adj unit, ( damn BBK, I can't adjust the psi any lower than 44psi running,) BLM is at about 124, but exhaust smells slightly rich.

Anyway, crank and fire engine as normal cold and it starts runs fine, but let it run for a minute and shut it off and try and restart and it does not even seem like it want's to fire.

Parts swapped/replaced with no change:
Coil
P/U coil
HEI module
Fuel pressure=good ( checked w/gauge)
Bypass fuel pump relay, same as above
No vats issue per dash light and scan tool
RPM signal checked w/scan tool cranks at 200 RPM ( shown on dash tach as well.)
Checked injectors w/ noid light=good
Pulled ECM ( aftermarket NAPA unit) tapped/shook while cranking...no start.
All fuses checked=good
Unplugged MAF=same no start
Intake and Coolant temp sensors checked via scan tool=good
Throttle position makes no difference (as to bypass a bad IAC motor)
TPS voltage at .54V

Pulled a plug and it appears slightly wet ( have not sprayed starting fluid in intake to verify fuel possibility.)

Spark present w/ spark tester.

Slightly stumped....could use some direction....inspiration. I realize that that I've changed before this problem was the FPR, but this issue has happened before and now it is just more consistent. It has to be electrical...something warming up and going open.....etc.

During crank mode, is it correct for no inj. Pulse width to be given/read on a scan tool? I have zero pulse width while cranking...though that was weird.

I appreciate any help.

Rob

 

Fabbed up a spacer plate which allows FPR adjustment, although it has no effect on the no start.

Narrowed down the no start cause...fuel pressure. Didn't do it at 30psi, or at 34 psi, but when I got up to about 36psi I could run the engine, shut it off and it will not start after that.....unless I release fuel pressure ( via my gauge,) and then it will start fine. I could of sworn I read of someone who had injectors that would stick shut unless he tapped on them, etc. Being that this happens when fuel psi increases eliminates a vapor lock type problem. The injectors are stock as far as I can tell, I just didn't think all 8 would stick shut ( maybe it's due to injectors with mileage, combined with a little heat and ta da....no injector opening.)

That's it for now.

Rob

 

Had the EXACT same problem, it's the injectors. Put in some Ford Motorsport injectors and kiss your problem goodbye. Or find the bad injector(s) and replace them. But, preferably buy new ones.

 

I do have a set of stock 19lb injectors from an 01 Mustang GT, so in theory I could run those ( albiet at a higher FPR setting, 45 -50 PSI) on a stock engine. The 4.6 2V that year was rated at 260hp and 19lb'ers can support up to 300HP. With the mods on my 5.7, I don't see how I could be getting more than 250 HP as it is. I don't want to risk buring a stock engine for $225 in injectors.....I just can't spend $225 right now...or really anytime soon.

Any thoughts??

Rob

 

Installed OE Mustang injectors. Runs good, thanks TGO.