Author Topic: Fuel line size for TBI / Runs rough / Stalls.  (Read 211 times)

Offline 87_Rado

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Fuel line size for TBI / Runs rough / Stalls.
« on: May 20, 2020, 01:42:55 PM »
How is everyone doing. Been a while since I've posted anything but I'm running into an issue with my 87 with the 350 TBI set up. I'm having trouble with it lacking power in take off and will want to stall on idle and when put into gear. I put a new pump and sending unit in the tank when I first started the project. From my understanding is that the fuel feed should be 3/8, the return should be 5/16 and then then vent. I recently rebuilt the throttle body with all new gaskets and seals and cleaned everything very well. Still no help on the sluggish power and stallling issue. The truck is throwing a code 44 which is a lean code. 02 sensor was replaced maybe a year ago. I checked all around the base gaskets and vacuum lines with carb clean to look for a possible vacuum leak. Still no help. Egr and solenoid replaced not to long ago with all new lines as well. New PCV valve. I've done slot of work to it to try to figure this out. I'm remembering that I sprung a leak in the hard fuel lines coming from the tank that run along the bottom of the cab, in-between the cab and the bed. I replaced it with soft runner line that run to the frame rails but I used all 5/16 lines for Feed, return and vent... Do you guys think this could be my issue!? Will 3/8 on the feed/pressure side make that big of a difference over 5/16? Let me know what you guys think please any little bit of advice or other suggestions would help! Much appreciated in advance 👍🤘

Offline Mike81K10

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #1 on: May 20, 2020, 07:37:51 PM »
I think it could make a difference and a kick or blockage can further complicate things. Make sure your tanks are clean of rust and debris (ethanol can mess up the fuel system - it did mine anyhow) , filters clear, and I would install a 3/8 line, some say 1/2 lines.
« Last Edit: May 20, 2020, 07:57:02 PM by Mike81K10 »

Offline JohnnyPopper

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #2 on: May 20, 2020, 08:37:49 PM »
Sounds like blockage of some sort.

Remove your doubt by installing correct size lines.
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Offline 87_Rado

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #3 on: May 21, 2020, 10:57:42 AM »
Thank you guys for the response 👍 I'm going to add the 3/8 FI rated fuel line today and make sure the line is free of any kinks. I just added a new inline filter so I know that is not the cause. I'm really hoping this line does me justice because I've been chasing this issue for quite some time. I'm also going to throw a new NTK 02 sensor In if napa has one. Just to remove the doubt like Johnny popper said. I will check back after the job is done. Any other suggestions is still much appreciated thanks again guys  🤘

Offline 87_Rado

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #4 on: May 21, 2020, 07:53:55 PM »
Well I guess it's back to the drawing board fellas. Yet another attempt with no success.. I spent the better have of my day dropping the fuel tank and plumbing in the correct size lines. Pulled the pump, Cleaned the screen, which looked good anyways. Ran fresh fuel lines, 3/8 for feed, 5/16 for return and 1/4 for vent. No blockage or kings anywhere in the line, and put another brand new filter In line. I'm stumped again I took it for a ride and it's made absolutely no difference at all. Any other suggestions fellas? Cap and rotor is new, plugs and wires are new, coil is new. Ignition control module was just replaced. All parts less than two weeks old due to no spark. But the truck is just running like crap and I would love to get this figured out. Any other advice is much appreciated.

Online bd

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #5 on: May 21, 2020, 08:19:05 PM »
What is the measured fuel pressure?  Do you have a scan tool?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline 87_Rado

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #6 on: May 22, 2020, 10:46:38 AM »
BD, thanks for the responses. I do not have a scan tool. I would like to get one and I spoke with another member about it but I'm not sure of a decent model for a decent price.. I just ordered the guage and adapter from cfm technologies. Going to install that when it comes in to verify fuel pressure. It seems like it runs leans and then adjust the fuel trim to compensate and feels like it's dumping fuel. I'll have to feather the gas at idle and coming to a stop to try and keep it running.

Online bd

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #7 on: May 22, 2020, 10:57:36 AM »
Other than increasing susceptibility to engine ping, does unplugging the vacuum line from the EGR valve improve the symptoms?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline 87_Rado

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #8 on: May 22, 2020, 11:56:28 AM »
I have tried unplugging those and it didn't make a difference. I went ahead and replaced the egr and the solenoid and the vacuum lines anyways, just to remove the doubt. Im actually taking a drive right now and I read somewhere on the forum to try and unplug the CTS and MAP sensors and see if that makes a difference and it's seems have to significantly improved my drivability. Haven't had to feather it coming to stops and idle seems to have smoothed out after driving and coming to a stop. Still a little rough on start up but overall it's much better than it was with the sensors plugged in. Any ideas why this may be / what would cause this? I appreciate the quick responses 👍

Offline VileZambonie

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #9 on: May 22, 2020, 12:36:20 PM »
Lot's of parts changing and guess work here. You could have low fuel pressure, faulty TPS, yadda yadda. You should get a scan tool and fuel pressure gauge. It would save you time and money!
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Offline 87_Rado

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #10 on: May 22, 2020, 12:44:36 PM »
Fuel pressure gauge is on order and will be installed as soon as possible. The scan tool I am looking for a recommendation you can still purchase that is decently priced, so if you have an option there let me know. I'm just a diy guy. I've been trying to solve it myself but countless fails has led me to ask for advice on the forum. As I said before the recommendations or suggestions is always helpful and appreciatied thanks again 👍

Online bd

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #11 on: May 22, 2020, 01:18:00 PM »
87_Rado, when the sensors are disconnected the ECM defaults to a fixed program with limited dynamic input. 

I totally agree with Vile.  You need a scanner, a DVM, and a fuel pressure gauge to diagnose elusive TBI issues.  Typically, the more you spend on a scanner the greater its functionality.  If you need to purchase in a hurry your options may be more limited than when there is ample time to be selective with no pressure.  As Vile posted elsewhere, there are many options with a broad range of prices and functionality.

I use a Bosch OBD 1300 available from O'Reillys Auto Parts because of its ready availability and OBD 1 and OBD 2 functionality.  Other options are available (Innova, Actron, et al).  Bear in mind that no single scanner is perfect.  And, they become quite pricey as capabilities increase.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline 87_Rado

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #12 on: May 22, 2020, 01:24:03 PM »
Okay sounds good I will look into the Bosch because I would love to get this figured out once and for all. As of right now I'll be leaving the sensors unplugged because it runs 10x better that way. Fuel pressure gauge is on the way so I will keep you posted on that. What is a dvm?

Offline VileZambonie

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #13 on: May 22, 2020, 01:35:30 PM »
Digital Volt Meter
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Offline 87_Rado

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Re: Fuel line size for TBI / Runs rough / Stalls.
« Reply #14 on: May 22, 2020, 10:06:53 PM »
Ohh okay lol yeah I'm good with a volt meter. I'm fully capable of doing any trouble shooting/testing I just don't have the knowledge of these trucks, as to what to test and why that's all.