Any SBC TBI gurus out there?

[jlhollowx13]

Hi all, hoping someone on here knows more about these engines than I do or knows of a good forum for them.

I have an early 90s chevy 350 TBI in my 60 that I'm having issues with. Recently the inline fuel pump went out. I got a new one per fuel pressure specs at the auto parts store and installed it. It sounds different than my old one but could be a different design. The main thing I noticed was wierd throttle response, it didn't seem to like lower rpms and the engine would sort of seem to cut out if trying to accelerate hard, something like more than quarter throttle or so.

Then yesterday my wife was driving, stopped on a slight incline and was talking to me while it idled. The idle seemed to be a little sporadic, would idle a little high, drop back down for a bit, then back up, etc. She then went to take off and it was extremely low on power, sputtering and wouldn't accelerate up the hill and would die without feathering the clutch. We finally got it up the hill to the house. So today I took it for a spin. If I mash the throttle it cuts out and almost dies, then will eventually rev up. Lower rpm driving has it low on power amd even higher rpms it seems to lack the power it once had but its hard to tell as it's slight. I stopped on a slight hill and tried to go, again very weak under load and was sputtering and wouldn't accelerate. Pushed the clutch in and it would rev up without the load. None of these issues I can recall on the old fuel pump, except for a trip to moab where around 75mph It felt like it was cutting out, when we got home from that trip the fuel pump went out shortly after.

There was no fuel filter before the fuel pump (unless there is one in the tank). I added one between the tank and fuel pump today, I do seem to see one between the pump and engine.

I'm wondering if a higher psi fuel pump with a pressure regulator is what I need, or if there may be some other factors I should look at. Or possibly I got a bad, new fuel pump. I appreciate any insight!

 

[gnob]

Is there a screen filter at the TB?
Otherwise it sounds like you could have a MAP or TPS wierding out

 

[jlhollowx13]

Is there a screen filter at the TB?
Otherwise it sounds like you could have a MAP or TPS wierding out

What I have is my fuel line coming up from under the truck from the fuel pump, runs along the firewall, goes into what I assume is a plastic inline fuel filter, then goes into the throttle body. I don't see anything else, is there possibly something inside the TB where the fuel line enters?

I read about the MAP and that it can be unplugged to see if it helps. I need to locate it and try that.

I'll also mention I have always noticed a bit of surging when on the throttle at a constant spot cruising on the highway. Maybe that's TPS related. Do the TPS in these need to be calibrated or anything? I know some vehicles I have had you had to set them and it was annoying.

I have a 1993 chevy pickup that i got for free that has a bad transmission sitting in the woods on my property. I wonder if parts are the same, if so I can rob from that.

 

[gnob]

Iirc the tps and map are both on the base.
You should be able to trade parts.

 

[jlhollowx13]

I'm reviving this thread as I'm having some similiar issues again. I replaced the fuel pump again when this last happened and it ran fine since, minus some light inconsistency at idle. Yesterday I had it randomly die on me. I pulled over, couldn't hear the fuel pump again. Waited awhile and tried again and the fuel pump kicked on and it started. Did some testing and it seems ill have a hard hot start issue, almost like vapor lock. I've got a new fuel pump to put in if needed, just need a new filter. I cleaned my cap and rotor, cleaned/greased some of the connections, etc. Currently waiting for it to cool to put in a coolant temp sensor in from my parts truck as one of the times it wouldnt start I quickly unhooked that when it wouldn't start and it fired up.

I thought maybe vapor lock because I removed my fan shroud this winter. I reinstalled it but not sure if it's making that much of a difference. Going to keep troubleshooting, hopefully get a second set of hands to check for fuel/spark when this issue happens.

 

[aztoyman]

I had an 88 Suburban with a TBI 350. I had bad gas plug the fuel filter. Filter was on the frame rail. I always carried a spare after that.

I've had issues with the wire connectors at the throttle body/injectors and stuck injectors after sitting a long time. We had an ex GM dealership tech working with us that told me to quickly zap it with 12 volts and it worked to unstick it.

My brother had one that ran weird and it was vacuum leak at worn out throttle shaft. He also had a bad coolant temp sensor cause issues.

It needs the proper flow and pressure so I wouldn't substitute a different pump.

Any codes? I thought it flashed the CEL and you counted the flashes.

Sorry, it was a LONG time ago so all I have. Good luck with it, I hope you figure it out.
Please post up what you find.

 

[jlhollowx13]

I had an 88 Suburban with a TBI 350. I had bad gas plug the fuel filter. Filter was on the frame rail. I always carried a spare after that.

I've had issues with the wire connectors at the throttle body/injectors and stuck injectors after sitting a long time. We had an ex GM dealership tech working with us that told me to quickly zap it with 12 volts and it worked to unstick it.

My brother had one that ran weird and it was vacuum leak at worn out throttle shaft. He also had a bad coolant temp sensor cause issues.

It needs the proper flow and pressure so I wouldn't substitute a different pump.

Any codes? I thought it flashed the CEL and you counted the flashes.

Sorry, it was a LONG time ago so all I have. Good luck with it, I hope you figure it out.
Please post up what you find.

One problem I have is I'm not exactly sure what fuel pump I need. We matched the psi (around 12) at the auto parts store, those were the last 2 I had and they did work until they quit pumping all together. Mine is an inline style on the frame, I added a fuel filter before it as there wasn't one before, just one between pump and throttle body. I'd rather not replace the fuel pump if it's not that, but have one ready to go. Just got my filter so I might swap that out and see how it does this week. And also swap the other one as I've never done that. Seems to be fuel related to me, but I have not 100% confirmed as I haven't had someone there to turn it over when I'm having issues. Next time, I'll have a bottle of starting fluid ready and see if that gets it going. If so I'll know. At least until then I'll have fresh fuel filters. Thanks for all the input. I'll try those as well this week if it persists and update.

 

[jlhollowx13]

Also as a side note, I try to run 91 octane ethanol free as much as I can. Maybe 75% of the time it gets 91 ethanol free, the other times it gets low grade ethanol (can't remember if 83 or 85 here in the mountains, not E-85 or whatever of course).

 

[trainbufftony]

Tbi 350, last I checked wanted about 60psi of fuel.
Verify that, but 12 isn't going to do it.

Check your fuel pressure regulator which is in your throttle body assembly.
If it's stuck, you'll never get correct fuel pressure from any pump, it will all return to the tank.
Best of luck.

 

[jlhollowx13]

Tbi 350, last I checked wanted about 60psi of fuel.
Verify that, but 12 isn't going to do it.

Check your fuel pressure regulator which is in your throttle body assembly.
If it's stuck, you'll never get correct fuel pressure from any pump, it will all return to the tank.
Best of luck.

I thought 50-60 for the newer engines, post 95ish, and 9-15 for TBI, but i may be wrong and if I'm wrong hopefully someone will chime in as that will make a massive difference! Will check out info on the regulator for sure. Thanks!

 

[55guy]

This what i have works great ,

Walbro GSL395 Inline Fuel Pump 130LPH Low Pressure / TBI (universal external pump

 

[55guy]

Need more info ??? Do you have a fuel return Line , Engine temp gauge ? , Sorry to say I would only put new sensors back in , Try one fix at a time , ,and yes check the code light , You tube shows you how to read it ,

 

[jlhollowx13]

Need more info ??? Do you have a fuel return Line , Engine temp gauge ? , Sorry to say I would only put new sensors back in , Try one fix at a time , ,and yes check the code light , You tube shows you how to read it ,

Yes I have a fuel return line, stock fj60 temp guage, which shows normal temps. Sorry, might have forgot to mention before I did check codes but didn't have any, just the usual '12'.

 

[jlhollowx13]

This what i have works great ,

Walbro GSL395 Inline Fuel Pump 130LPH Low Pressure / TBI (universal external pump

Just did a quick search on this one. Looks identical to the new one I have ready to put in. The only reason I went with this one was because the parts guy said it pumps differently than my current one and is more reliable in case mine is going out, I forgot the word he used. Otherwise it was the same psi, etc as the one I have on it currently.

 

[jlhollowx13]

A bit of an update. Drove it to work this morning, drove great for the 15 miles into town, nothing odd to mention. Got to town, stopped at the gas station and it wouldn't start when I went to leave.

Sometimes the fuel pump would prime, other times it wouldn't when trying to start it. I then sprayed starting fluid and it seemed to fire a bit, sputter and die.

My battery is old (2015), but it seems to turn the engine over just fine. Could it be the issue if it's turning the engine over good?

When I sprayed starting fluid and it 'started', it sounded a lot like our diesel dump truck at work when it has a hard time starting and some starting fluid gets sprayed in it. It kind of makes me think maybe the fluid ignited in my fj60 because of compression and maybe not spark? Maybe im not getting spark but it still ignited? Is that possible? Still haven't had a 2nd pair of hands to help check for spark when this happens so going off what in able to do on my own.

A little insight on the starting fluid deal would be helpful, not sure if it definitely seems like fuel issue or not. I don't want to install the $150 fuel pump if that's not the problem, would rather return it and buy the right parts if my fuel pump is fine.

Appreciate any insight.

 

[gnob]

if the pump doesn't come on in that key on, you have pump or wiring issues.
gm ignition modules are a common fail as well.
pretty unlikely the motor was compression igniting the ether.

 

[trainbufftony]

Get in the habit of using the key in run position to prime the fuel system. Don't crank the engine until your fuel pump stops running.
Could simply be a weak battery.
If you have fuel pressure when you start to crank you will start it.
If you're cranking at the same time you're trying to build fuel pressure then you may never get sufficient fuel pressure/volume to start the engine. On a TBI application the fuel pump will turn on, run for a few seconds then stop. At that point, start the engine.

 

[jlhollowx13]

Get in the habit of using the key in run position to prime the fuel system. Don't crank the engine until your fuel pump stops running.
Could simply be a weak battery.
If you have fuel pressure when you start to crank you will start it.
If you're cranking at the same time you're trying to build fuel pressure then you may never get sufficient fuel pressure/volume to start the engine. On a TBI application the fuel pump will turn on, run for a few seconds then stop. At that point, start the engine.

Thanks for confirming that. Yes that is my starting procedure and what I have taught my wife who drives it more. Always let it prime, only start it after it has stopped. Has always started reliably doing this. Wierd thing is, this morning when it WOULD prime, I still couldn't get it started. Turn key to on, hear fuel pump prime, what til it stops, turn it over and it would just crank. But when spraying the ether it would do as described. I thought maybe with the ether it would bridge a gap of no fuel if the pump was stopping while cranking, but didnt seem to help. Maybe weak battery factoring in, as in it will prime, but then won't keep pumping as the starter is activated? I'm not sure.

 

[jlhollowx13]

if the pump doesn't come on in that key on, you have pump or wiring issues.
gm ignition modules are a common fail as well.
pretty unlikely the motor was compression igniting the ether.

Thanks, I thought it would be unlikely for the compression to ignite it as well but wasn't sure. As for the pump priming, right now it seems hit and miss, but currently it still won't start even with the pump priming.

 

[trainbufftony]

Put a vise grip on the return line if you can find a rubber section of it.
Force maximum pressure, by blocking the outlet to the regulator.
Then start it.
If it starts perfectly, put a new fuel pressure regulator in the throttle body.

Fuel pressure regulators fail intermittent like that if they bind or stick.