TBI 350 issues

[_Auzzy_]

So tonight I checked voltage and it seems to be staying consistent. I also swapped the fuel filter.

Still running like dog poo... LS swap seems like a likely candidate. I'll throw a few more nights at this and see what I can figure out.

Do these TBI motors have any sensors that would cause this issue. Also it wouldn't idle with or without the fan on tonight.

The engine coolant temp sensor can cause issues, also the throttle position sensor too. Have you checked for vacuum leaks? The smallest disturbance throws these simple systems into fit.

Here's a link I've held on to that helped me with mine.

TBI Sensor Testing 101 - Third Generation F-Body Message Boards

TBI - TBI Sensor Testing 101 - After spending many days searching and compiling a list of different resistances and volts needed to test the various sensors on a TBI engine I have finally found some of the stuff I was looking for. I wanted to share it so maybe a moderator will make it a sticky...

www.thirdgen.org

 

[mbryson]

If you do pull it, I’d be interested in it if it has good compression. Mine is a bit long in the tooth

 

[skippy]

I am only getting 6 PSI of fuel pressure right before the throttle body. I dropped the tank and everything looked 100 years old so I'll refresh that. The hose connecting the fuel pump to the pickup was broke down bad I pulled it apart with out undoing hose clamps...

How are these fuel systems regulated? Is there a pressure regulator in the throttle body?

I am throwing a new fuel pump in it along with new lines and stuff.

 

[I Lean]

I am only getting 6 PSI of fuel pressure right before the throttle body. I dropped the tank and everything looked 100 years old so I'll refresh that. The hose connecting the fuel pump to the pickup was broke down bad I pulled it apart with out undoing hose clamps...

How are these fuel systems regulated? Is there a pressure regulator in the throttle body?

I am throwing a new fuel pump in it along with new lines and stuff.

There is a pressure regulator in the throttle body, which sends excess fuel back through the return line.

 

[skippy]

There is a pressure regulator in the throttle body, which sends excess fuel back through the return line.

Are those a common failure? I found one on oreilly website but it said operating pressure was 55+ PSI. I was under the impression these motors ran on 12-15

 

[mbryson]

FWIW, I run my YJ in-tank pump and I think it runs at about 40-50 psi? I think the regulator just circulates fuel that's unneeded back to the tank?

 

[I Lean]

Are those a common failure? I found one on oreilly website but it said operating pressure was 55+ PSI. I was under the impression these motors ran on 12-15

Post #3 and #4 here make it sound like it's a common deal. Post #1 might describe your symptoms exactly? https://www.hotrodders.com/threads/help-troubleshooting-89-350-tbi-problem.108268/

 

[_Auzzy_]

Are those a common failure? I found one on oreilly website but it said operating pressure was 55+ PSI. I was under the impression these motors ran on 12-15

You are correct. The diaphragm is a common failure. If it ends up being your culprit I'd also suggest jumping the spring rate up to a 14psi spring to help reduce the low end hesitation

 

[Mouse]

There also used to be kits you could buy to turn the pressure regulator on the TB to an adjustable one. I converted a 77 blazer I had and used a dedicated gauge to maintain proper pressure. That engine ran better with a touch more pressure than the stock setting.

 

[Hickey]

Post #3 and #4 here make it sound like it's a common deal. Post #1 might describe your symptoms exactly? https://www.hotrodders.com/threads/help-troubleshooting-89-350-tbi-problem.108268/

Lots of great tech in that thread.

 

[Pile of parts]

Post #3 and #4 here make it sound like it's a common deal. Post #1 might describe your symptoms exactly? https://www.hotrodders.com/threads/help-troubleshooting-89-350-tbi-problem.108268/

Great article. My engine runs well but I have been trying to solve a similar issue of the idle going up and down that he describes in Post #1. Might be worth a shot. Thanks for having an issue @skippy , it might help me solve mine too.

 

[N-Smooth]

Great article. My engine runs well but I have been trying to solve a similar issue of the idle going up and down that he describes in Post #1. Might be worth a shot. Thanks for having an issue @skippy , it might help me solve mine too.

I still wish you had a helicopter

 

[skippy]

Oreilly stocks the diaphragm kit and new fuel pump so Ill knock those out tonight. Im trying to decide if I need/want to get the adjustable regulator from JET...

JET Performance 61500: Adjustable Fuel Pressure Regulator 1987-95 GM Truck 4.3L/305/350/454 TBI - JEGS

Adjustable Fuel Pressure Regulator

www.jegs.com

 

[N-Smooth]

It's shiny so I say do it

 

[skippy]

So I pulled the fuel pressure regulator apart tonight and everything looked kosher. But since its apart I threw a rebuild kit in it anyways. I didn't have time to get the fuel pump and tank put back in so we will wait to see if it runs better tomorrow night.

 

[skippy]

CJ seems to be good to go, I don't know if it was the pressure regulator or the fuel pump. But it's got good fuel pressure and runs like a champ again!