kawaslut

Need advice on PSI (1989 LB9). Car will not start cold after putting new Bosch III #19 injectors (original injectors ohm’s where out of spec, rough idle, etc so I replaced from Southbay), I also replaced the stock regulator. Now when I turn the key on (no start) the psi will jump to 42 then after the fuel pump stops (2 secs) if will fall immediately to 30 then 20 then very, very slowly reach zero. I followed the manual and found that when I pinch off the return line I can get the psi to hold so the book say it’s the regulator. Now when I do get it started the PSI runs around 35psi at idle but when I pull off the vacuum hose from the regulator it jumps to 46-47 and holds. My question is should the PSI at all times be running between 40-47 and not 35?

vinny R

Your pressure numbers seem to be within spec. It should be about 35 @ idle and 45 @ WOT. Give or take a few lbs. Pressure fall off seems to vary but yours sounds like it should not be an issue. The fall off could be in your EVAP system and you may a small leak somewhere but that should not affect on how the car runs. There has been countless threads on here about those Bosch 3's. To lean, to rich, it just seems that everyone who uses those need some sort of tune. I think this is your issue and you probably need one yourself. There are some good tuners on this site.

GeneralDisorder

iTrader: (1)

You may need a tune to properly run the Bosch III's. I agree with vinny R - you're fuel pressure is within normal range and what you describe would be considered acceptable to run. The regulators rarely seal perfectly so bleed down when you shut it off is normal. The vacuum signal reduces fuel pressure according to manifold vacuum and 35 while idling is normal.

The Bosch III 19lb injectors need to be tuned at about 17.5 lb and need the voltage offsets changed to run properly without high BLM's. It sounds like you may not be getting enough cold enrichment which is not related to the injector size constant in your tune so you may also need to increase the cranking fueling by adding to the "Crank PW multiplier vs. Reference Pulse" table.

You should also do a minimum idle speed and TPS adjustment since you got in there and changed injectors. Check your IAC steps when hot, check for vacuum leaks, etc.

GD

kawaslut

Thanks for the info. When you say change the injector to 17.5 do you mean here as shown in the picture? I found the offsets on the form for voltage and inputted them when made a difference on the BLM.

Tuned Performance

iTrader: (92)

GeneralDisorder

iTrader: (1)

Yep you got it. Check your BLM's with those settings.

GD

LiquidBlue

Thanks for the thread. I'm fixin to do this same thing in hopefully the near future. Keep us posted.

kawaslut

I tried to upload the XDL file but this site doesn't allow XDL files to be uploaded. Anyway in the two xls files one is Bosch III with factory offsets and the other is Bosch III with adjustment offset based on forums. Let me know what you think. It runs much better than the factory injectors however the cold start up is not the same. If i crack the throttle just a bit it starts right up. This is a completely stock car with all the emissions.

Thanks I added the zip file.

Tuned Performance

iTrader: (92)

kawaslut

Thanks I did see the IAC was low at idle but when you set the mini idle should you unplug your est (single brown wire)?

Tuned Performance

iTrader: (92)

LiquidBlue

Where did you find the injector pulse with correction -vs- battery voltage numbers? Are these correct and working? I'm trying to locate a source and found
https://www.thirdgen.org/forums/diy-...or-sticky.html

But numbers are all over the map. The closest I could find to these numbers was from RBob in post #4 of the sticky thread.

Tuned Performance

iTrader: (92)

kawaslut

It was tough to find the correct offsets after using the search field. After searching it looks like Rbob had something to start with for the 19# injectors in post #4. It would of been helpful to have a sticky with offsets for the Bosch III 19# and 22# etc.

LiquidBlue

Thanks, at least I wasn't talking to myself! so post #5 are much higher than what was posted here. interesting and confusing...... and I know nothing about tuning ECM's - but have burnt software into chips before, just not for cars, nor do I have the equipment at present time..... happen to know if the Delphi's are true plug and play?