PDA

View Full Version : Little help, please


etduc
06-27-2009, 09:38 PM
Just did rebuild on Rochester TBI, (1994 Indmar 350). Same fuel pods. Gasket for gasket. Just basic stuff.

Now, pumping WAY to much fuel. On cranking, it imediately goes to 3000 rpm. I guessing something with the fuel pressure diapham. I used the existing spring, as the replacement spring was a little soft.

But everything looks,ok. If some has a Rochester/holley rebuild instructions. I'd appreciate a link, or copy.

Also, how is the proper way to clear the computer.
Thanks

JimN
06-27-2009, 11:26 PM
Just did rebuild on Rochester TBI, (1994 Indmar 350). Same fuel pods. Gasket for gasket. Just basic stuff.

Now, pumping WAY to much fuel. On cranking, it imediately goes to 3000 rpm. I guessing something with the fuel pressure diapham. I used the existing spring, as the replacement spring was a little soft.

But everything looks,ok. If some has a Rochester/holley rebuild instructions. I'd appreciate a link, or copy.

Also, how is the proper way to clear the computer.
Thanks

Check the IAC. If the throttle plates are in their normal closed position (you didn't mess with the set screw, did you?), adding fuel will make it run rich, not go to 3000RPM.

You can use a scan tool or diagnostic computer.

Why would Holley rebuild instructions help?

etduc
06-28-2009, 08:31 AM
Check the IAC. If the throttle plates are in their normal closed position (you didn't mess with the set screw, did you?), adding fuel will make it run rich, not go to 3000RPM.

You can use a scan tool or diagnostic computer.

Why would Holley rebuild instructions help?

Jim

Throttle plates are closed. Didn't mess with set screw. Fuel is back splashing out of tbi, alot
Spray pattern, looks like the fuel pressure regulator is not functioning.

Didn't want to buy a scan tool, but may have to.

Looking for tuning touble shooting instructions. The two tbi are very simular.
Thanks.

André
06-28-2009, 10:06 AM
If the air plates are close,i don't understand how the engine gets sufficient air to rev 3000 rpm...
Softer spring in a regulator will give you less pressure.Did you measure the pressure?

First time i read about my 94 TBI engine beiing call a Rochester ...

JimN
06-28-2009, 10:56 AM
If the air plates are close,i don't understand how the engine gets sufficient air to rev 3000 rpm...
Softer spring in a regulator will give you less pressure.Did you measure the pressure?

First time i read about my 94 TBI engine beiing call a Rochester ...

If the IAC opens far enough, it'll do 3000RPM easily. Another place to look is the PCV hose. If that leaks badly enough, it creates a big vacuum leak and won't draw the fuel into the throttle body.

JimN
06-28-2009, 11:03 AM
Jim

Throttle plates are closed. Didn't mess with set screw. Fuel is back splashing out of tbi, alot
Spray pattern, looks like the fuel pressure regulator is not functioning.

Didn't want to buy a scan tool, but may have to.

Looking for tuning touble shooting instructions. The two tbi are very simular.
Thanks.

I still suspect a vacuum leak, as I posted in the reply to Andre. If the motor goes to 3K and the fuel is splashing, there's not much vacuum below the throttle plates- it's being relieved somewhere else. Look for the IAC and make sure it's secure and there isn't a leak at the gasket. Spray some carb cleaner next to it and if you see an increase in RPM, it's leaking. Also, look at where the end of the IAC is, in the roughly triangular hole. If you don't see the conical end (it's called the pintel), shut it off and remove the IAC to make sure it's still there at all. If the IAC was not installed and teh key is turned ON, the pintle can be ejected.

etduc
06-28-2009, 03:46 PM
I still suspect a vacuum leak, as I posted in the reply to Andre. If the motor goes to 3K and the fuel is splashing, there's not much vacuum below the throttle plates- it's being relieved somewhere else. Look for the IAC and make sure it's secure and there isn't a leak at the gasket. Spray some carb cleaner next to it and if you see an increase in RPM, it's leaking. Also, look at where the end of the IAC is, in the roughly triangular hole. If you don't see the conical end (it's called the pintel), shut it off and remove the IAC to make sure it's still there at all. If the IAC was not installed and teh key is turned ON, the pintle can be ejected.

BINGO! Base plate gasket. Remember, I said Rochester/ Holley are simular. Well, the base plates ARE different. I had gotten a new base plate gasket from local car parts house, and just put in on. (I know, forgot the first rule of mechanicing... measure, compare, confirm.) HUGE air gap.

Put old gasket back on.... Viola! idles great.

Thanks, JimN. You too, Andre.

André
06-28-2009, 08:54 PM
Glad you're running!:)
I have a MEFI manual for our engines if you ever need it for troobleshoothing your EFI system let me know!